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Species of Rastrelliger in the Java Sea, their taxonomy, morphometry and population dynamics Sudjastani, Tatang 1974

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\ c THE SPECIES OF RASTRELLIGER IN THE JAVA SEA, THEIR TAXONOMY, MORPHOMETRY AND POPULATION DYNAMICS by TATANG SUDJASTANI B.Sc. Academy of Agriculture Bogor, Indonesia, 1962 A THESIS SUBMITTED IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE in the Department of Zoology We accept this thesis as conforming to the required standard The University of Br i t ish A p r i l , 1974 Columbia In presenting t h i s thes is i n p a r t i a l f u l f i l m e n t of the requirements f o r an advanced degree at the U n i v e r s i t y of B r i t i s h Columbia, I agree that the L ibrary s h a l l make i t f r e e l y a v a i l a b l e f o r reference and study. I fur ther agree that permission f o r extensive copying of t h i s thes is for s c h o l a r l y purposes may be granted by the Head of my Department or by h i s representat ives . I t i s understood that copying or p u b l i c a t i o n of t h i s thes is f o r f i n a n c i a l gain s h a l l not be allowed without my wri t ten permission. Department of ZOOLOGY The U n i v e r s i t y of B r i t i s h Columbia Vancouver 8, Canada Date 9 APRIL 1974 ABSTRACT Rastrelliger i s a mackerel genus which i n h a b i t s the Indo-P a c i f i c Regions. T h i s genus i s c h a r a c t e r i z e d by l o n g , numerous and f e a t h e r l i k e g i l l r a k e r s , and anal f i n without s p i n e s . Two s p e c i e s , Rastrelliger braahysoma and R. kanagurta, are r e c o g n i z e d . These are i d e n t i f i e d by the d i f f e r e n c e s i n the r a t i o s o f the g r e a t e s t body depth and the le n g t h of i n t e s t i n e to f o r k l e n g t h , and the appearance of the c e p h a l i c l a t e r a l l i n e canal systems. Synonymies, d e s c r i p t i o n s and morphometric ranges are g i v e n . The morphometric c h a r a c t e r s of the two s p e c i e s e x h i b i t some i n t r a s p e c i f i c d i f f e r e n c e s due to sexual dimorphism and strong a l l o -m e t r i c growth, R. braahysoma e x h i b i t s i n t r a s p e c i f i c g e o g r a p h i c a l v a r i a t i o n i n i t s d o r s o v e n t r a l depth, g r e a t e s t body depth, and i n t e r -o r b i t a l d i s t a n c e ; w h i l e R. kanagurta e x h i b i t s v a r i a t i o n o n l y i n i t s d o r s o v e n t r a l depth and head depth. Both speci.es a t t a i n t h e i r maximum growth increments before they reach sexual m a t u r i t y . The v i t a l parameters f o r y i e l d p r e d i c t i o n are as f o l l o w s : the c o e f f i c i e n t o f growth r a t e K=0.19, 0.23; the length-weight exponent b=2.88, 3.19; the maximum le n g t h 1.^=22.92 cm, 23.89 cm; the na t u r a l m o r t a l i t y c o e f f i c i e n t M=0.38, 0.37; and the t o t a l m o r t a l i t y c o e f f i c i e n t Z=0.82, 1.20 f o r i ? , braahysoma and R. kanagurta r e s p e c t i v e l y . Rastrelliger f i s h e r i e s i n the Java Sea have not y e t i i reached maximum e x p l o i t a t i o n which suggests the p o s s i b i l i t y of i n c r e a s -ing p r o d u c t i o n by i n c r e a s i n g f i s h i n g i n t e n s i t y . i i i TABLE OF CONTENTS Page ABSTRACT i TABLE OF CONTENTS i i i LIST OF FIGURES v LIST OF TABLES v i i ACKNOWLEDGMENTS ..... x I. INTRODUCTION 1 I I . MATERIALS AND METHODS 2 I I I . RESULTS AND DISCUSSIONS 7 1. Systematics Study 7 D e s c r i p t i o n o f the genus Rastrelliger ... 7 Key to the s p e c i e s o f Rastrelliger . . . . 8 S p e c i f i c D e s c r i p t i o n s 8 Rastrelliger braahysoma 8 Rastrelliger kanagurta 9 Nomenclature 12 Di a g n o s t i c Characters 23 2. Morphometric Study 25 Sexual Dimorphism 30 A l l o m e t r i e Growth 30 Geographic V a r i a t i o n s . 33 3. M e r i s t i c C h a r a c t e r s 45 4. Q u a l i t a t i v e Characters . . . . . . . . . . . 49 5. P o p u l a t i o n Study Rastrelliger F i s h e r i e s . . . P o p u l a t i o n Parameters . . . Sexual C o n d i t i o n s .... Longevity Environmental T o l e r a n c e Competitor and Predator . P a r a s i t e s Growth Behaviour Age Length-weight R e l a t i o n s h i p s Recruitment S u r v i v a l Rates ' M o r t a l i t i e s . Dynamics o f P o p u l a t i o n s . . Beverton and H o l t Model R i c k e r Model , IV. GENERAL DISCUSSIONS V. CONCLUSIONS LITERATURE CITED APPENDICES . . . V LIST OF FIGURES Figure Page 1. Bathymetric Chart o f the Java Sea 3 2. R a t i o o f Body Parts to Fork Length 16 3. R a t i o o f Fork Length to Body Depth 17 4. Sexual Dimorphisms o f Rastvelligev bvachysoma 32 5. Geographical V a r i a t i o n s i n R. bvachysoma 32 6. Geographical V a r i a t i o n s i n R. kanaguvta 44 7. F i r s t Occurrence o f Haemal Brace 47 8. C e p h a l i c L a t e r a l L i n e Canal System o f Rastvelligev . . 52 9. D i g e s t i v e T r a c t s o f Rastvelligev 53 10. Sexual M a t u r i t y Stages Composition o f R. kanagurta . . 61 11. Sexual M a t u r i t y Stages Composition o f R. bvachysoma . . 62 12. Growth Curve o f R. bvachysoma 69 13. Growth Curve o f R. kanaguvta 70 14. R e l a t i o n Between T o t a l E f f o r t and Catch Per Un i t o f E f f o r t o f Rastvelligev kanaguvta 75 15. Length Frequency D i s t r i b u t i o n of R. kanaguvta 86 16. Length Frequency D i s t r i b u t i o n o f R. bvachysoma .... 87 17. Catch Curve o f R. kanaguvta 97 18. Catch Curve o f R. bvachysoma 98 19. Y i e l d I s o p l e t h Diagrams of R. kanaguvta 106 20. Y i e l d per R e c r u i t as a Function of F of R. kanaguvta; f o r t = t = 4.0 months 107 21. Y i e l d per R e c r u i t as a Function o f F of R. kanaguvta; f o r t = 4.5 and t = 4.0 months .... 108 v i F i g u r e Page 22. Y i e l d I s o p l e t h Diagrams of R. braahysoma 109 23. Y i e l d per R e c r u i t as a Function of F o f R. braahysoma; f o r t = t p = 3.0 months . . . 110 24. Y i e l d per R e c r u i t as a Fun c t i o n o f F o f i?. braahysoma; f o r t = 4.0 and t = 3.0 months I l l v i i LIST OF TABLES Table Page 1. Morphometric Measurements o f Rastvelligev bvachysoma 11 2. Morphometric Measurements o f R. kanaguvta 13 3. Frequency D i s t r i b u t i o n o f the Ratios o f Head-Length to Body Depth 18 4. Frequency D i s t r i b u t i o n o f the Ra t i o s o f Fork-Length to Body Depth ! 9 5. Frequency D i s t r i b u t i o n o f the Ra t i o s o f I n t e s t i n e Length to Fork Length 20 6. Regressions of Sample No. 1 26 7. Regressions o f Sample No. 2 27 8. Regressions of Sample No. 3 28 9. Regressions of Sample No. 4 .' . . . 29 10. Comparisons o f Body P r o p o r t i o n s Between Males and Females 31 11. Comparisons o f Body P r o p o r t i o n s Between C l a s s -Modes o f 16.0 cm FL and 20.0 cm FL 34 12. Comparisons of Body P r o p o r t i o n s Between C l a s s -Modes of 14.0 cm FL and 20.0 cm FL 35 13. Comparisons o f Body P r o p o r t i o n s Between C l a s s -Modes o f 14.0 cm FL and 16.0 cm FL 36 14. Comparisons of Body P r o p o r t i o n s Between Samples No. 1 and No. 2 37 Table v i i i Page 15. Comparisons o f Body P r o p o r t i o n s Between Samples No. 3 and No. 4 . . 38 16. Comparisons o f Body P r o p o r t i o n s Between Samples No. 1 and No. 3 39 17. Comparisons o f Body P r o p o r t i o n s Between Samples No. 2 and No. 4 40 18. Comparisons of Body P r o p o r t i o n s Between Samples No. 2 and No. 3 . 41 19. Comparisons o f Body P r o p o r t i o n s Between Samples No. 1 and No. 4 42 20. Covariance Analyses f o r P a i r s of Rastrelliger 43 21. G i l l Raker Counts o f Rastrelliger 48 22. The Degree o f I n t e r g r a d a t i o n s o f the T o t a l G i l l Raker Counts of Rastrelliger 48 23. Productions of Payang F i s h e r i e s i n the North Coast o f Java 54 24. F i e l d Key of M a t u r i t y Stages (Males) 58 25. F i e l d Key o f M a t u r i t y Stages (Females) 59 26. Von B e r t a l a n f f y Growth Parameters o f Rastrelliger from the I n d o - P a c i f i c Region 71 27. Age-Length-Weight Key o f R. kanagurta 84 28. Age-Length-Weight Key of R. braahysoma 85 29. The Length-Weight Exponential Values o f Rastrelliger o f the Java Sea 90 ix Table Page 30. The Length-Weight Exponential Values o f Rastrelliger from the I n d o - P a c i f i c Region 91 31. S u r v i v a l Rate o f R. kanagurta 95 32. S u r v i v a l Rate o f R. braahysoma 96 33. M o r t a l i t y C o e f f i c i e n t s o f R. kanagurta 100 34. R i c k e r Y i e l d Model o f R. kanagurta 115 35. Ri c k e r Y i e l d Model o f R. braahysoma . 116 36. R i c k e r Y i e l d Model of R. braahysoma ... 117 X ACKNOWLEDGEMENTS I wish to express my deep a p p r e c i a t i o n and thanks to my s u p e r v i s o r Dr. Norman J . Wilimovsky who encouraged me to undertake t h i s study, gave a d v i c e and c r i t i c i s m . My thanks a l s o goes t o Messrs. T.D. l i e s and Stephen Borden, Dr. D.J. R a n d a l l , Dr. J.R. Adams, Messrs. D.E. Wilson, R. S t a n l e y , Ni I-shun and R.S.. Milne f o r g i v i n g u s e f u l s u g g e s t i o n s . I am very g r a t e f u l to Messrs. R.B. Wilson, B.J. Anderson and Miss CM. McAskie from the Canadian I n t e r n a t i o n a l Development Agency f o r c o n t r i b u t i n g i n v a r i o u s ways to t h i s study. F i n a l l y , I wish to extend my thanks to my s u p e r i o r i n the D i r e c t o r a t e General o f F i s h e r i e s , Mr. Moh Unar the D i r e c t o r o f the Marine F i s h e r i e s Research I n s t i t u t e , and to my c o l l e a g u e s i n the Regional F i s h e r i e s S e r v i c e s and the I n s t i t u t e f o r Marine Research i n J a k a r t a f o r a s s i s t i n g i n data c o l l e c t i o n s . i I. INTRODUCTION The Kembung -- the genus Rastrelliger -- c o n s t i t u t e one o f the most important groups of f i s h e s o f the a r t i s a n a l f i s h e r i e s o f Indonesia. On the north c o a s t o f Java i n 1971, the c a t c h was 10,000 ton s , c o n s t i t u t i n g over 10% of the t o t a l marine f i s h e r i e s p r o d u c t i o n o f the area. In the f i v e - y e a r s development program of the Government of Indonesia (1969/1974), which i n c l u d e d i n v e s t i g a t i o n of f i s h e r i e s , t h i s genus with tuna and o i l - s a r d i n e s had p r i o r i t y over o t h e r commercial s p e c i e s . During the l a t e f i f t i e s an experimental canning p r o j e c t f o r t h i s genus was u n s u c c e s s f u l due to m i s c a l c u l a t i o n of the stock abundance and mistakes i n e s t i m a t i n g the economics of the p r o j e c t . Most i n v e s t i g a t i o n s on Rastrelliger are c o n f i n e d to the neighbouring s t a t e s of Indonesia. The most important c o n t r i b u t i o n i n the Indonesian waters was conducted by de Beaufort (1951) and o n l y few o b s e r v a t i o n s have been recorded s i n c e . In c o n t r a s t to the r a t h e r e x t e n s i v e f i s h e r i e s i n v e s t i g a t i o n s as d e s c r i b e d above, the i d e n t i t i e s of the s p e c i e s w i t h i n the genus are s t i l l i n doubt. There are many synonyms because l o c a l races or i n d i v i -d u a l s have been d e s c r i b e d under d i f f e r e n t names. The o b j e c t i v e s of t h i s t h e s i s are: (1) to v e r i f y the s p e c i e s i d e n t i t i e s , (2) to study t h e i r morphometry, and (3) to estimate the p o p u l a t i o n parameters to a i d f i s h e r i e s management. 2 I I . MATERIALS AND METHODS During the 1972 f i s h i n g season ( e a r l y West Monsoon) samples of Rastrelliger were c o l l e c t e d from the two main f i s h i n g areas i n the Java Sea, i . e . , Tanjung S a t a i i n the south west coast o f Borneo and J a k a r t a i n the north coast of Java ( F i g u r e 1). A l l the f i s h were c o l l e c t e d from the same f i s h i n g gear, the shore s e i n e s having s t r e t c h e d mesh s i z e o f about 3.0 to 4.5 cm. The samples were t e m p o r a r i l y preserved i n f o r m a l i n 10% (+ borax, to r e t a r d shrinkage) and t r a n s f e r r e d to 37% i s o p r o p y l a l c o h o l . Measurements were made using d i a l c a l i p e r and a m e t r i c s c a l e . S i x t e e n morphometric, seven m e r i s t i c and some q u a l i t a t i v e c h a r a c t e r s were examined on a l a r g e s e r i e s of specimens. P r o p o r t i o n were c a l c u l a t e d from the numbers o f specimens mentioned i n the d e s c r i p t i o n or appearing on the t a b l e s . M e r i s t i c c h a r a c t e r s were determined from ra d i o g r a p h s . C l e a r i n g and s t a i n i n g were done f o r bone s t r u c t u r e examinations. The measurements and counts used i n t h i s study are those d e f i n e d by Hubbs and L a g l e r (1964) with some o p t i o n s which are d e s c r i b e d on page 4. F i s h e r i e s data were c o l l e c t e d from Regional F i s h e r i e s S e r v i c e s , the Marine F i s h e r i e s Research I n s t i t u t e and the I n s t i t u t e f o r Marine Research i n J a k a r t a . Each morphometric c h a r a c t e r was s u b j e c t e d to r e g r e s s i o n a n a l y s i s . Regression l i n e s were compared by c o v a r i a n c e a n a l y s i s . Other c h a r a c t e r s were t r e a t e d to b a s i c s t a t i s t i c a l a n a l y s e s . 3 F i g u r e 1. Bathymetric shaded part shore where chart of the Java Sea. Depth i n meters, represents an area 30 to 60 miles o f f -sampled R a s t r e l l i g e r were taken. 4/ A l l c a l c u l a t i o n s were performed on IBM 1130 and 360/67 Computers, using programs t h a t are a v a i l a b l e at the U.B.C. Computing Centre. Anatomical Features, Terms jl. FORK LENGTH ( F L ) : i s the d i s t a n c e from the most a n t e r i o r p a r t o f the head (L) to the end of the membranous edge of caudal f i n at f o r k ( F ) . 2. BODY LENGTH (BL): i s the d i s t a n c e from the most a n t e r i o r p a r t of the head (L) to the i n s e r t i o n of the caudal f i n ' s d o r s a l lobe (B). 3. GILL COVER HEAD LENGTH ( L G 1 ) : i s the d i s t a n c e from the most ante-r i o r p o i n t of the snout (head), i . e . , mandibular symphysis L, to the most d i s t a n t p o i n t of the o p e r c u l a r membrane ( p o s t e r i o r membranous edge g i l l cover, G 1 ) . 4. MAXILLARY (sheath) LENGTH (UJ): i s l e n g t h of the upper jaw, which i s taken from the a n t e r i o r most p o i n t of the p r e m a x i l l a r y to the p o s t e r i o r most p o i n t of the m a x i l l a r y . 5. HEAD DEPTH ( Y J 1 ) : i s measured from the m i d l i n e at the o c c i p u t v e r t i c a l l y downward to the v e n t r a l contour o f the head. For the sake o f p r a c t i c a l i t y t h i s head depth i s measured from the g i l l cover notch (Y) v e r t i c a l l y downward to the v e n t r a l contor of the head ( J ' ) . 6. DORSO VENTRAL DEPTH (D1V): or a n t e r i o r d o r s a l depth, i s the d i s t a n c e from the i n s e r t i o n o f a n t e r i o r d o r s a l ( i . e . i n t e r -s e c t i o n a n t e r i o r margin f i r s t d o r s a l s p i n e , f i n held e r e c t , with the contour o f the back) to the i n s e r t i o n o f a n t e r i o r v e n t r a l f i n . 7. DORSO ANAL DEPTH (D2A): i s the d i s t a n c e from the i n s e r t i o n f i r s t ray o f p o s t e r i o r d o r s a l to the i n s e r t i o n f i r s t anal f i n ray, i t i s s l i g h t l y o b l i q u e . 8. GREATEST DEPTH ( h ) : i s body depth, i . e . , the g r e a t e s t dorso-v e n t r a l dimension, e x c l u s i v e of the f l e s h y or s c a l y s t r u c t u r e s which p e r t a i n to the f i n bases. 9. PERPENDICULAR IRIS DIAMETER ( I h ) : i s measured v e r t i c a l l y . 10. PERPENDICULAR PUPIL DIAMETER (Eh): i s measured v e r t i c a l l y . 11. LENGTH OF PECTORAL FIN (Ph): i s the d i s t a n c e from the extreme base o f uppermost or outermost ray to the f a r t h e s t t i p o f the p e c t o r a l f i n . 12. LENGTH OF PELVIC FIN (Vh): i s the d i s t a n c e from the extreme base o f the an t e r i o r m o s t ray to the f a r t h e s t t i p o f the p e l v i c f i n . 13. INTERORBITAL DISTANCE (00): o r i n t e r o r b i t a l width i s the l e a s t bony width t h a t i s measured where the p o i n t s a re pressed t i g h t l y a g a i n s t the bone so as to e l i m i n a t e so f a r as p r a c t i c a b l e the t h i c k n e s s o f the f l e s h o v e r l y i n g the bony rims. 6 14. PECTORAL BREADTH (PP): i s the d i s t a n c e measured from the o r i g i n o f the l e f t p e c t o r a l f i n to the r i g h t p e c t o r a l f i n , i t i s a p r o j e c t i o n . 15. NUMBER OF GILL RAKERS: unless otherwise s t a t e d the count i s t h a t o f the f i r s t g i l l a r c h . The numbers on the upper limb and lower limb a re taken s e p a r a t e l y ; the two f i g u r e s are separated by a plus s i g n . A g i l l r a k e r t h a t s t r a d d l e s the angle o f the arch i s i n c l u d e d i n the count o f the lower limb. A l l the rudimentary r a k e r s a r e i n c l u d e d i n the count. 16. NUMBER OF RAYS OF THE ANTERIOR DORSAL FIN:, a l l spines are designated by roman numerals no matter how rudimentary o r how f l e x i b l e they may be. True spines are unpaired (median) s t r u c t u r e s , without segmentation. S o f t rays a re designated by A r a b i c numerals, a re u s u a l l y (not always) branched and f l e x i b l e , and are b i l a t e r a l l y p a i r e d and segmented. 7 I I I . RESULTS AND DISCUSSION 1. Systematics S t u d i e s D e s c r i p t i o n o f the Genus Rastvelligev Jordan and S t a r k s . Rastvelligev Jordan and S t a r k s , 1908:607 ( o r t h o - t y p e : Soombev bvaahysomus B l e e k e r , 1851). D e s c r i p t i o n -- Ad u l t s m a l l , from 15 to 35 cm. Body f u s i f o r m , moderately compressed; body and cheek covered with small s c a l e s , those o f the b r e a s t l a r g e r than o t h e r s . Eyes with well developed adipose e y e l i d . Mouth moderately l a r g e , m a x i l l a r y r e a c h i n g to a p o i n t n e a r l y v e r t i c a l below p o s t e r i o r edge o f eye. Small t e e t h i n jaws. Vomer and p a l a t i n e s edentulous. G i l l r akers long and numerous, f e a t h e r l i k e : v i s i b l e when mouth i s opened. Two d o r s a l s , the f i r s t spinous. Anal without s p i n e s . Five or s i x f i n l e t s behind d o r s a l and a n a l . Caudal deeply f o r k e d . P e c t o r a l s s h o r t , p o i n t e d with broad base. P e l v i c s with spines and f i v e r a y s . Marine, i n l a r g e s c h o o l s , i n s h o r e . Feeds on both zoo- and phyto-plankton. Rastvelligev i s a t present c o n s i d e r e d to c o n t a i n two s p e c i e s o c c u r r i n g i n abundance throughout the I n d o - P a c i f i c Region: i n t r o p i c a l Indian Ocean and western P a c i f i c Ocean. 8 Key to the Species o f Rastvelligev Jordan and Starks 1. G r e a t e s t body depth i n f o r k l e n g t h 3.1 - 3.7 (x = 3.4); very f i n e l y d e n d r i t i c c e p h a l i c l a t e r a l l i n e system; head l e n g t h s l i g h t l y l e s s e r than g r e a t e s t body depth 0.89 - 1.07 (x = 0.98); l e n g t h o f i n t e s t i n e i n f o r k l e n g t h 2.2 - 3.0 (x = 2.5); d i g e s t i v e t r a c t very convoluted , R. bvachysoma. 2. G r e a t e s t body depth i n f o r k l e n g t h 3.8 - 4.4 (x = 4.0); not f i n e l y d e n d r i t i c c e p h a l i c l a t e r a l l i n e system; head l e n g t h d i s t i n c t l y g r e a t e r than g r e a t e s t body depth 1.01 - 1.19 (x = 1.11); l e n g t h o f i n t e s t i n e i n f o r k l e n g t h 1.3 - 1.4 (x - 1.35); d i g e s t i v e t r a c t l e s s convoluted R. kanaguvta. S p e c i f i c D e s c r i p t i o n s 1. Rastvelligev bvachysoma (Bleeker) Scombev bvachysomus B l e e k e r , 1851:356 ( d e s c r i p t i o n , o c c u r r e n c e ) . Scombev kanaguvta B l e e k e r , 1852:34 (nec. C u v i e r and Va l e n c i e n n e s , d e s c r i p t i o n ) . Scombev neglectus van Kampen, 1907:7 ( d e s c r i p t i o n ) . Rastvelligev bvachysoma Fowler, 1928:132 (morphometric d e s c r i p t i o n ) . Rastvelligev neglectus de B e a u f o r t , 1951:211 ( d e s c r i p t i o n , f i g u r e , o c c u r r e n c e ) . D e s c r i p t i o n -- Body compressed, g r e a t e s t body depth 3.4 (3.1 - 3.7) i n FL a t o r i g i n o f the seventh d o r s a l s p i n e . Head l e n g t h l e s s e r than or a s l i g h t l y g r e a t e r than g r e a t e s t depth 0.98 (0.89 - 1.07); 9 3.5 (3.3 - 3.7) i n FL. Eye about equal to i n t e r o r b i t a l space. Mouth o b l i q u e , m a x i l l a r y reaching to below hind border of eye. A s i n g l e s e r i e s o f f i n e and p o i n t e d t e e t h i n the jaws. P a l a t e edentulous. G i l l r a k e r s 19 (17-21) on the upper limb o f the f i r s t g i l l a r c h ; the l o n g e s t ones equal o r g r e a t e r than the d i s t a n c e between snout and p u p i l . F i r s t d o r s a l spine s h o r t e r than second. Second d o r s a l f i n concave. Anal f i n s i m i l a r to second d o r s a l ; o r i g i n o f anal s l i g h t l y behind t h a t o f second d o r s a l . P e c t o r a l t r i a n g u l a r , l o n g e r than v e n t r a l ; about equal o r g r e a t e r than p o s t o r b i t a l p a r t o f head. S c a l e s c t e n o i d . L a t e r a l l i n e s c a l e s 125 (120-131); s l i g h t l y curved. Measurements o f 117 specimens on Table 1. F i n formulae: XI(X - X I ) ; D 2 12(12 - 13) + 5(5 - 6 ) ; A 13 + 5(5 - 6); P 1 18(16 - 18); P 2 1.5; ve r t e b r a e 31(38 specimens). Colour i n l i f e : B l u i s h - g r e e n i n the back above l a t e r a l l i n e s and s i l v e r y i n the b e l l y and s i d e s below l a t e r a l l i n e s . A row of dark spots along base o f f i r s t d o rsal with dusky i n c o l o u r . P e c t o r a l , v e n t r a l and anal f i n s y e l l o w i s h - h y a l i n e with dusky margins. Caudal f i n y e l l o w i s h . C o l o u r a t i o n s o f preserved specimens g r a d u a l l y fades to b l u i s h grey and d u l l white. Local common name: Kembung Perempuan. L o c a l h a b i t a t : C o a s t a l waters o f Indonesian A r c h i p e l a g o . Range: The range extends from Andaman I s . through Indonesian Arch. to F i j i and Solomon I s . Rarely found i n South A f r i c a n waters. 2. Rastrelliger kanagurta ( C u v i e r ) Scomber kanagurta C u v i e r , 1817:313 ( d e s c r i p t i o n ) . 10 \Scombev loo Lesson, 1829:277 ( o c c u r r e n c e ) . Scomber chrysozonus Ruppell , 1835:10 (occurrence, f i g u r e ) . Scomber microlepidotus R u p p e l l , I bid:37 ( d e s c r i p t i o n , f i g u r e ) . Scomber moluccensis B l e e k e r , 1856:40 ( d e s c r i p t i o n ) . Scomber reani Day, 1870:690 ( o c c u r r e n c e ) . Scomber lepturus A g a s s i z , 1874:tab.2 ( o c c u r r e n c e ) . Eastrelliger brachysomus Jordan and Dic k e r s o n , 1908:610 (nec. B l e e k e r , d e s c r i p t i o n , o c c u r r e n c e , f i g u r e ) . Rastrelliger kanagurta Jordan and S t a r k s , 1917:440 ( o c c u r r e n c e ) . Rastrelliger ehrysozonus Kishinouye, 1923:406 ( c l a s s i f i c a t i o n , synonymy, d e s c r i p t i o n , d i s t r i b u t i o n , f i g u r e ) . Rastrelliger microlepidotus Barnard, 1927:296 ( o c c u r r e n c e ) . Rastrelliger serventyi Whitley, 1944:268 (occurrence, d e s c r i p t i o n ) . D e s c r i p t i o n -- Body moderately compressed; g r e a t e s t depth 4.0 (3.8-4.4) i n FL at the o r i g i n o f the seventh d o r s a l s p i n e . Head l e n g t h d i s t i n c t l y g r e a t e r than g r e a t e s t depth, 3.6 (3.5 - 3.7) i n FL. Eye equal or s l i g h t l y l e s s than i n t e r o r b i t a l space. Mouth o b l i q u e , m a x i l l a r y not reach i n g to a poi n t below hind border o f eye o r not so f a r i n young specimen. A s i n g l e s e r i e s o f f i n e pointed t e e t h i n the jaws. P a l a t e and vomer edentulous. G i l l r a k e r s 21 (18 - 23) on the upper limb and 37 (35 - 39) on the lower limb o f the f i r s t l e f t g i l l a c r h ; the l o n g e s t 11 TABLE 1 Morphometric Measurements o f Rastrelliger braahysoma Bleeker (n = 117) No. Character Mean Standard E r r o r Range 1 Fork Length 15.50 T.39 12.20 - 18.20 2 T o t a l Length 17.40 1.63 13.70 - 20.50 3 Body Length 14.09 1.29 11.10 - 16.50 4 Head Length 4.45 0.43 3.50 - 5.30 5 M a x i l l a r y Length 2.46 0.29 1.80 - 3.10 6 Head Depth 3.54 0.37 2.70 - 4.40 7 .Dorsoventral Depth 4.40 0.48 3.30 - 5.60 8 Dorsoanal Depth 4.17 0.42 3.20 - 5.10 9 G r e a t e s t Depth 4.53 0.50 3.40 - 5.80 10 Perp. I r i s Diam. 0.91 0.09 0.70 - 1.20 11 Perp. P u p i l Diam. 0.49 0.05 0.30 - 0.70 12 P e c t o r a l F i n Length 2.19 0.25 1.60 - 2.70 13 P e l v i c F i n Length 1.90 0.23 1.40 - 2.90 14 I n t e r o r b i t a l Distance 0.94 0.12 0.60 - 1.30 15 P e c t o r a l Breadth 2.10 0.28 1.40 - 2.70 12 equal to d i s t a n c e from p u p i l to snout. F i r s t d o r s a l s p i n e s h o r t e r than second and equal to d i s t a n c e from snout to eye; l a s t spine very s m a l l . A n t e r i o r rays o f second d o r s a l f i n l o n g e s t , s l i g h t l y l e s s than f o u r t h spine o f f i r s t d o r s a l . The edge o f second d o r s a l and anal f i n s concave. O r i g i n o f anal f i n s l i g h t l y behind t h a t o f second d o r s a l ; s i m i l a r i n shape. P e c t o r a l pointed and t r i a n g u l a r . S c a l e s c t e n o i d , l a t e r a l l i n e 130 (125 - 140). Measurements o f 103 specimens on Table 2. F i n formulae: D ] XI(IX - X I ) ; D 2 12(12 - 13) + 5(5 - 6 ) ; A 13 + 5(5 - 6 ) ; P ] 19(19 - 20); P 2 1.5; v e r t e b r a e 31 (40 specimens). Colour i n l i f e : B l u i s h with g r e e n i s h - g r e y str-ipes above and s i l v e r y below l a t e r a l l i n e s . Dark spots along the f i r s t d o r s a l base. P e c t o r a l , v e n t r a l and anal f i n s h y a l i n e . Dorsals and caudal dusky along margins. Colour o f preserved specimens back b l u i s h grey, d u l l s i l v e r y white. Local common names: Kembung L e l a k i , Kembung, Banyar. Local h a b i t a t : A l l over Indonesian waters. Range: The range extends from Durban (South A f r i c a ) , P e r s i a n G u l f , through C e n t r a l I n d o - P a c i f i c a r e a , Ryukyu, Queensland ( A u s t r a l i a ) , F i j i to Hawaii I s . Nomenclature The most important study on Rastrelliger i n t h i s r e g i o n was made by de B e a u f o r t (1951). No other work has been done s i n c e . In s p i t e o f the e x t e n s i v e i n v e s t i g a t i o n s being done i n T h a i l a n d and I n d i a , the nomenclature o f the f i s h i s s t i l l i n doubt. 13 TABLE 2 Morphometric Measurements o f Rastrelliger kanagurta C u v i e r (n = 103) No. Ch a r a c t e r Mean Standard E r r o r Range 1 Fork Length 17.41 2.08 13.90 - 21.90 2 T o t a l Length 19.39 2.35 15.40 - 24.40 3 Body Length 15.98 1.90 12.60 - 20.00 4 Head Length 4.84 0.57 3.90 - 6.20 5 M a x i l l a r y Length 2.48 0.35 1.80 - 3.30 6 Head Depth 3.39 0.43 2.60 - 4.40 7 Dorsoventral Depth 4.27 0.54 3.10 - 5.50 8 Dorsoanal Depth 4.06 0.52 3.10 - 5.20 9 G r e a t e s t Depth 4.35 0.58 3.30 - 5.60 10 Perp. I r i s Diam. 1.03 0.14 0.80 - 1.50 11 Perp. P u p i l Diam. 0.57 0.07 0.40 - 0.80 12 P e c t o r a l F i n Length 2.29 0.33 1,70 - 3.10 13 P e l v i c F i n Length 1.93 0.27 1.20 - 2.60 14 I n t e r o r b i t a l Distance 1.02 0.16 0.70 - 1.40 15 P e c t o r a l Breadth 2.32 0.38 1.60 - 3.20 14 I t s synonymy i s r a t h e r obscure because l o c a l races o r i n d i v i d u a l s have been d e s c r i b e d under d i f f e r e n t names. The taxonomic p o s i t i o n o f the genus Rastrelliger has been accepted s i n c e Jordan and Starks (1908) proposed i t f o r the mackerels having long g i l l r a k e r s . S t a r k s (1921) r a i s e d the subgenus Pneumatophorus as a genus beside the genera Scomber and Rastrelliger. Fraser-Brunner (1950) and C o l l e t t e and Gibbs ( 1963) r e c o g n i z e d only two genera, i . e . , Scomber ( i n c l u d i n g Pneumatophorus) and Rastrelliger. There are s e v e r a l i n t e r p r e t a t i o n s a t the s p e c i e s l e v e l . De Beauf o r t (in de Beaufort and Chapman, 1951) l i s t s t h r e e s p e c i e s , Rastrelliger braahysoma B l e e k e r , R. negleotus van Kampen and R. kanagurta C u v i e r . He noted t h a t R. braahysoma may be a v a r i a n t o f R. negleotus. Manacop (1956) d e s c r i b e d o n l y two sp e c i e s R. braahysoma and R. chryso-zonus R u p p e l l . He f u r t h e r s t a t e d t h a t R. negleotus van Kampen i s a synonym o f R. braahysoma B l e e k e r , and R. kanagurta C u v i e r i s a synonym o f R. ohrysozonus R u p p e l l . Jones and S i l a s ( 1962) r e c o g n i z e d two s p e c i e s and c o n s i d e r e d R. negleotus as a synonym o f R. braahysoma and opposed de Be a u f o r t (1951) d e s c r i p t i o n . T h e i r incomplete evidence caused some c o n f u s i o n among the workers i n Indonesia and ad j a c e n t r e g i o n s who s t i l l r e c o g n i z e d and used de Bea u f o r t ' s works. D r u z h i n i n (1968) supports de B e a u f o r t and s t a t e s t h a t he i s not i n agreement w i t h Jones and S i l a s , however, with no str o n g arguments. Matsui (1967) proposed a new s p e c i e s , R. faughni sp.n., which f o r m e r l y was named Scomber australasicus; and recog n i z e d two o t h e r s p e c i e s , R. braahysoma and R. kanagurta. His proposal i s s t i l l w i d e l y questioned. 15 The c o n t r o v e r s y , thus, r e s t s on whether R. braahysoma and R. negleotus are d i f f e r e n t s p e c i e s . The frequency d i s t r i b u t i o n o f the r a t i o s o f head l e n g t h t o g r e a t e s t body depth f o r Rastrelliger from the no r t h c o a s t o f Java and Tg. S a t a i ( F i g u r e 3, Table 3) i s d i s t i n c t l y bimodal with a s l i g h t over-l a p . The degree o f i n t e r g r a d a t i o n o f the two sympatric samples are 5.6% from J a k a r t a and 2.2% from Tg. S a t a i a r e a . The frequency d i s t r i b u t i o n o f the r a t i o s o f g r e a t e s t body depth t o f o r k l e n g t h i s a l s o bimodal and show no o v e r l a p with 0.0% degree o f i n t e r g r a d a t i o n between these sympatric samples ( F i g u r e 2, T a b l e 4 ) . The r a t i o s o f the l e n g t h o f i n t e s t i n e to f o r k le n g t h show non-overlapping ranges, of which the degree o f i n t e r g r a d a t i o n i s 0.0% (T a b l e 5 ) . Those c h a r a c t e r s t h a t belong to two groups t h a t e x i s t s y m p a t r i c a l l y , with no i n t e r g r a d a t i o n between each o t h e r , and, t h e r e -f o r e , the two groups should be c o n s i d e r e d as two v a l i d s p e c i e s . The f i r s t group i n c l u d i n g samples no. 1 and no. 2 i s Rastrelliger braahysoma and the second group R. kanagurta, c o n t a i n s samples no. 3 and no. 4. De B e a u f o r t (1951) s t a t e d t h a t he r e c o g n i z e d R. negleotus van Kampen (1907) with the f o l l o w i n g arguments "Van Kampen (I.e.) p o i n t e d out, t h a t the two common s p e c i e s o f Rastrelliger i n the Java Sea have been confused by Ble e k e r and o t h e r s . The s p e c i e s t h a t B l e e k e r c a l l e d loo C u v i e r and Vale n c i e n n e s , i s the same as t h a t o f French a u t h o r s , but i t i s a synonym of kanagurta. The ot h e r s p e c i e s i s mentioned by B l e e k e r and o t h e r s as kanagurta, and had t h e r e f o r e to be renamed. Van Kampen c a l l e d i t negleotus" . With regard to braahysoma de Beaufort 16 F i g u r e £, Graphic comparison of observed ranges and means. Ratio of fork length F L to greatest body depth (h) of Rastrel l iger of four samples f r o m two different l o c a l -i t ies . Base line represents range, white bar twice standard deviation, short ver t ical bar mean. 17 No. If- 1 1 I "-70 LG/h 1 I l N-45 5r- . » 1 • N«o4 H 1 -1 N«72 TL/h I 1 i N-45 3f ' I i N-34 N-63 "I 6 I 'iQ i ^ ° , f ^ — 1 ,4 , .6 • £ iL. I I 1 K-72 2f 1 I I n - 4 P 3J. I 1 i N-35 BL/h ' I ' H-67 2 | ' 8 • I '.2 , V , '1 r - ^ , 4 f 0 , .,2 Figure 3. Ratio of head length (LG), total length (TL), and body length (BL) each to greatest body depth (= height, h) of four samples of Rastrelliger from two l o c a l i t i e s . Base l ine represents range, white bar twice standard deviation, short vertical bar mean. TABLE 3 Frequency D i s t r i b u t i o n o f the Ratios o f Head Length to Greatest Body Depth o f Rastrelliger Head Lenqth 0.89 0.92 0.95 0.98 1.01 1.04 1.07 1.10 1.13 1.16 1.19 N ' Body Depth SAMPLE No. 1 x = 0.996 2 1 12 19 . 23 9 6 72 S.D. = 0.055 2.8 1.4 16.7 26.4 31.9 12.5 8.3 100 No. 2 x = 0.970 1 8 7 20 7 2 - 45 S.D. = 0.038 2.2 17.8 15.6 44.4 15.6 4.4 100 No. 3 x = 1.110 1 9 10 8 4 2 34 S.D. = 0.038 2.9 26.5 29.4 23.5 11.8 5.9 100 No. 4 x = 1.117 2 1 16 17 14 7 11 68 S.D. = 0.034 2.9 1.5 23.5 25.0 20.6 10.3 16.2 100 I n t e r g r a d a t i o n : SYMPATRIC: No. 1 - No. 3 : 5.6% OTHERS: No. 1 - No. 2 : 32.8% No. 2 -- No. 4 : 2.2% No. 1 — No. 4 : 6.35% No. 2 — No. 3 : 1,45% No. 3 — No. 4 : 43.4% TABLE 4 Frequency Distribution of the Ratios of Fork Length to Greatest Body Depth in Rastrelliger Fork Lenath Body Depth 3.1 3.2 : 3.3 3.4 3.5 3.6 3.7 3.8 3.9 4.0 4.1 4.2 •4.3 4.4 N SAMPLE No. 1 1 2 14 20 16 13 7 73 x = 3.46 S.D. = .14 cv = 4.05 1.4 2.7 19.2 27.4 21.9 17.8 9.6 100 No. 2 1 3 12 13 12 4 1 46 x = 3.40 S.D. = .13 cv = 3.68 2.2 6.5 26.1 28.2 26.1 8.7 2.2 100 No. 3 6 9 7 7 4 35 x = 3.98 S.D. = .13 cv = 3.20 17.2 25.7 20.0 20.0 11.4 100 No. 4 9 10 17 19 9 2 2 68 x = 4.03 -S.D. = .15 cv = 3.63 13.3 14.7 25.0 27.9 13.3 2.9 2.9 100 _ J Intergradation: SYMPATRIC: No. 1 ~ No. 3 : 0.0% OTHERS: No. 1 — No. 2 : 41.75% No. 2 — No. 3 : 0.0% No. 2 — No. 4 : 0.0% No. 1 — No. 4 : 0.0% No, 3 — No. 4 : 42.2% TABLE 5 Ratios of the Length of Intestine to Fork Length of Rastrelliger SAMPLE Fork- Intestine SAMPLE Fork- Intestine Length Fork Length Length Fork Length No. 1 17.671 2.48 No. 3 20.434 1.38 17.887 2.51 18.028 1.35 18.238 2.56 19.988 1.37 18.524 2.60 19.694 1.35 18.170 2.55 17.609 1.33 x = 18.098 2.54 19.151 1.36 No. 2 17.535 2.95 No. 4 18.147 1.32 16.351 2.22 19.507 1.38 16.207 2.42 18.693 1.36 17.479 2.61 18.802 1.33 18.747 2.80 15.437 2.31 x = 16.959 2.55 18.787 1,35 Intergradation between SYMPATRIC groups: No. 1 - No. 3 : 0.0% No. 2 - No. 4 : 0.0% o 21 (1951) commented: " I t was not 5, as s t a t e d by Bl e e k e r , but 6 f i n l e t s behind d o r s a l and a n a l , and d i f f e r s from the o t h e r I n d o - A u s t r a l i a n s p e c i e s o f Rastvelligev by i t s g r e a t depth " (page 212). In my o p i n i o n , Van Kampen's (1907) d e c i s i o n to name the sp e c i e s with g r e a t body depth as neglectus cannot be accepted, because Bleeker i n 1851 a l r e a d y named i t bvachysoma. His view probably was caused by Bleeker's i n adequate d e s c r i p t i o n s s i n c e i t was d e s c r i b e d from a s i n g l e specimen ( 120 mm long and without a caudal f i n ) . Comparison of Bleeker's (1851), Van Kampen's (1907) and de Beaufort's (1951) data with t h a t o f the present study are as f o l l o w s ( F i g u r e 3): R. bvachysoma Bleeker (1851), de Beaufort (1951). - Height 2.79. T h i s i s w i t h i n the range of g r e a t e s t body depth i n BL of sample no. 1 and no. 2: 2.79 - 3.34 (x 1 = 3.14; x 2 = 3.10). - Head as long as high. T h i s i s w i t h i n the range of the head le n g t h -- g r e a t e s t body depth r a t i o s of sample no. 1: 0.89 -1.07 (x = 0.996) and sample no. 2: 0.89 - 1.04 (x = 0.970). - Head 3.15 i n l e n g t h . T h i s i s w i t h i n the range o f the r a t i o s o f sample no. 1: 2.99 - 3.46 (x = 3.15) and sample no. 2: 3.08 -3.34 (x = 3.20). - G i l l r a k e r s on lower branch 35. T h i s i s w i t h i n the range of sample no. 1: 3 5 - 3 7 (mode = 36) and sample no. 2: 34 -37 (mode = 35). R. negleotus van Kampen (1907), de Beau f o r t (1951). - Height 3.1 - 3.4 i s w i t h i n the range o f g r e a t e s t body depth i n BL. of samples no. 1 and no. 2. - Head as long as high, i s w i t h i n the range o f the head l e n g t h and g r e a t e s t body depth r a t i o s o f samples no. 1 and no. 2. - Head 3.2 - 3.5 i s w i t h i n the range o f head l e n g t h i n BL o f samples no. 1 and no. 2. - Head 3.8 - 3.9 i n l e n g t h with c a u d a l . T h i s i s w i t h i n the range of head l e n g t h i n TL o f samples no. 1 and no. 2, i . e . , 3.74 - 4.08 (x = 3.90) and 3.73 - 4.08 (x = 3.93) r e s p e c t i v e l y . - G i l l r a k e r s on lower branch 29 - 34 a r e w i t h i n the range o f sample no. 2. These d e s c r i p t i o n s suggest t h a t R. negleotus van Kampen i s a synonym o f R. braahysoma B l e e k e r . R. kanagurta C u v i e r (1817), de Beau f o r t (1951). - Height 3.4 - 3.8. T h i s i s w i t h i n the range o f the g r e a t e s t body depth i n BL o f samples no. 3: 3.49 - 3.95 (x = 3.65) and no. 4: 3.46 - 4.17 (x = 3.70). - Height 4.1 - 4.7 i n le n g t h with c a u d a l . T h i s i s w i t h i n the range of the g r e a t e s t body depth i n TL o f sample no. 3: 4.20 -4.79 (x = 4.43) and sample no. 4: 4.15 - 4.84 ( x = 4.49). - Head (somewhat) longer than h i g h , i s w i t h i n the range of the . r a t i o s o f head l e n g t h to g r e a t e s t body depth o f sample no. 3: 1.04 - 1.19 (x = 1.11) and sample no. 4: 1.01 - 1.19 (x = 1.12). 23 - Head 3.2 - 3.3 i n l e n g t h . T h i s i s w i t h i n the range o f head l e n g t h i n BL o f sample no. 3: 3.16 - 3.36 (x = 3.29) and sample no. 4: 3.14 - 3.50 (x = 3.31). - Head 3.9 - 4.3 i n l e n g t h with c a u d a l . T h i s i s w i t h i n the range o f head length i n TL o f sample no. 3: 3.87 - 4.09 (x = 3.99) and sample no. 4: 3.86 - 4.37 (x = 4.01). - G i l l r a k e r s on lower branch 35 - 38, are w i t h i n the range o f sample no. 3: 35 - 39 (mode - 37) and sample no. 4: 35 - 37 (mostly: 37). The above comparisons suggest t h a t a l l the d e s c r i p t i o n s o f C u v i e r (1817) and de Beaufort ( 1951) are i n agreement with the data o f samples no. 3 and no. 4, i . e . , R. kanaguvta. D i a g n o s t i c Characters R a t i o o f Fork Length to G r e a t e s t Body Depth The r a t i o of values o f f o r k l e n g t h to g r e a t e s t body depth ranges from 3.10 to 4.40 (Table 4 ) . The frequency d i s t r i b u t i o n o f sympatric samples show two d i s t i n c t bimodal histograms with no o v e r l a p . The values o f the degree o f i n t e r g r a d a t i o n among samples a r e : Sample no. 1 to no. 2: 41.75% no. 1 to no. 3: 0.0 % ( sympatric, J a k a r t a ) no. 1 to no. 4: 0.0 % no. 2 to no. 3: 0.0 % no. 2 to no. 4: 0.0 % ( s y m p a t r i c , Tg. S a t a i ) no. 3 to no. 4: 42.2 % 24 The above data suggest t h a t these c h a r a c t e r s are u s e f u l i n d i s t i n g u i s h i n g the two s p e c i e s . Ratio o f Head Length to G r e a t e s t Body Depth The average r a t i o s o f head l e n g t h to g r e a t e s t body depth ranges from 0.89 to 1.22 (Table 3). The frequency d i s t r i b u t i o n s o f these r a t i o s f o r sympatric samples (no . 1 and no. 3; no. 2 and no. 4) shows two d i s t i n c t bimodal histograms with modes o f 0.98, 1.01, and two modes o f 1.10. Samples from Tg. S a t a i area have an i n t e r g r a d a t i o n value 5.6% and from J a k a r t a area 2.2%. The degree o f i n t e r g r a d a t i o n between areas a r e : Sample no. 1 to no. 2: 32.8% no. 1 to no. 4: 6.35% no. 3 to no. 2: 1.45% no. 3 to no. 4: 43.4% These c h a r a c t e r s a r e key c h a r a c t e r s t h a t have been used to d i s t i n g u i s h s p e c i e s . The present data show s l i g h t o v e r l a p s , t h e r e f o r e , these c h a r a c t e r s have disadvantages as k e y - c h a r a c t e r s . Ratio o f Other Measurements to E i t h e r Head Length or G r e a t e s t Body Depth The r a t i o o f body length BL, f o r k l e n g t h FL, and t o t a l l e n g t h TL to head l e n g t h , shows a c o n s i d e r a b l e o v e r l o p w i t h degree o f i n t e r -g r a d a t i o n ranging from 13.5 - 34.0% between sympatric samples; w h i l e the r a t i o to g r e a t e s t body depth the degree o f i n t e r g r a d a t i o n ranges from 0.0 - 2.1%, thus, g e n e r a l l y , the r a t i o s o f body p a r t to g r e a t e s t body depth are u s e f u l i n d i s t i n g u i s h i n g s p e c i e s . 25 Ratio o f the Length o f I n t e s t i n e to Fork Length The l e n g t h o f i n t e s t i n e i n FL ( T a b l e 5) between sympatric samples shows no o v e r l a p , the degree o f i n t e r g r a d a t i o n i s 0.0%. The f i r s t group, i . e . , samples no. 1 and no. 2, has r a t i o s 2.2 - 2.95 (x = 2.54); whereas the second group, samples no. 3 and no. 4, has r a t i o s 1.32 - 1.38 (x = 1.35). T h i s r a t i o i s good as key-c h a r a c t e r f o r d i s t i n g u i s h i n g s p e c i e s . 2. Morphometric Study For c h a r a c t e r s s t u d i e d , the r e g r e s s i o n o f each c h a r a c t e r on f o r k l e n g t h FL i s a r e c t i l i n e a r r e g r e s s i o n , with c o r r e l a t i o n c o e f f i c i e n t range from 0.71 - 0.99 (Tables 6, 7, 8, & 9 ) . y = a + bx where: x the independent v a r i a b l e , f o r k l e n g t h y the dependent v a r i a b l e , l e n g t h o f any body p a r t The c h a r a c t e r s were examined f o r p o s s i b l e b i a s caused by sexual dimorphism o r s t r o n g a l l o m e t r i c growth. A n a l y s i s o f c o v a r i a n c e i n d i c a t e d t h a t : 1. l o n g i t u d i n a l measurements and p e l v i c f i n l e n g t h are s i g n i f i c a n t l y d i f f e r e n t (1%) between sexes (Table 10) , 2. p e r p e n d i c u l a r i r i s and p u p i l diameters, p e c t o r a l f i n l e n g t h , and p e c t o r a l breadth show st r o n g a l l o m e t r i c growth ( 1 % l e v e l o f s i g n i f i c a n c e ) (Tables 11, 12, 13). 26 TABLE 6 Regressions o f Sample No. 1 from J a k a r t a , N = 72 y = a + bx, where: x i s f o r k l e n g t h , y i s measurements o f any body p a r t s , r i s c o r r e l a t i o n c o e f f i c i e n t , c v . i s c o e f f i c i e n t o f v a r i a t i o n , T i s Student's t value. C h a r a c t e r a b S.E. o f b r c. v. % T T o t a l l e n g t h -0.2360 1.1420 0.0292 0.9778 1.37 39.05 Body l e n g t h 0.0292 0.9076 0.0234 0.9774 1.36 38.71 Head length 0.0187 0.2880 0.0123 0.9416 2.25 23.40 M a x i l l a r y l n . -0.5541 0.1959 0.0099 0.9203 3.27 19.68 Head depth -0.2071 0.2427 0.0121 0.9225 2.79 19.98 Dorsovent. d. -1.0954 0.3531 0.0188 0.9132 3.51 18.74 Dorsoana. d. -0.7110 0.3138 0.0185 0.8960 3.65 16.88 Gre a t e s t b.d. -1.0948 0.3606 0.0207 0.9008 3.77 17.35 I r i s diam. 0.0716 0.0550 0.0065 0.7078 5.82 8.38 Pupi l diam. 0.0766 0.0270 0.0032 0.7105 5.30 8.44 P e c t o r a l l n . -0.3756 0.1676 0.0092 0.9078 3.40 18.10 P e l v i c length -0.3765 0.1483 0.0165 0.7303 7.04 8.94 I n t e r o r b i t . d. -0.3006 0.0805 0.0053 0.8742 4.59 15.06 Pect. breadth -1.0682 0.2019 0.0152 0.8452 6.00 13.23 27 TABLE 7 Regressions o f Sample No. 2 from Tg. S a t a i , N = 45 y = a + bx, where: x i s f o r k l e n g t h , y i s measurements o f any body p a r t s , r i s c o r r e l a t i o n c o e f f i c i e n t , c.v. i s c o e f f i c i e n t o f v a r i a t i o n , T i s Student's t value . Character a b S.E.of b r c.v. % T T o t a l l e n g t h -0.3889 1.1413 0.0131 0.9972 0.93 86.88 Body l e n g t h -01.711 0.9199 0.0060 0.9991 0.52 152.83 Head length -0.1638 0.2954 0.0071 0.9875 1.99 41.09 M a x i l l a r y I n . -0.6566 0.1996 0.0067 0.9766 3.39 29.77 Head depth -0.5317 0.2621 0.0079 0.9807 2.78 32.88 Dorsovent.d. -0.6542 0.3283 0.0102 0.9807 2.84 32.04 Dorsoanal.d. -0.1514 0.2807 0.0106 0.9704 3.11 26.36 G r e a t e s t b.d. -0.7970 0.3476 0.0105 0.9810 2.81 33.12 I r i s diam. -0.0264 0.0595 0.0029 0.9517 4.00 20.32 Pu p i l diam. -0.1340 0.0413 0.0025 0.9266 6.23 16.15 P e c t o r a l In. -0.3636 0.1626 0.0053 0.9777 3.04 30.52 P e l v i c l e n g t h -0.2306 0.1350 0.0074 0.9409 4.89 18.21 I n t e r o r b i t . d . -0.2462 0.0763 0.0050 0.9163 6.70 15.00 Pect. breadth -0.7629 0.1881 0.0081 0.9619 4.68 23.08 28 TABLE 8 Regressions of Sample No. 3 from Jakarta, N = 35 y = a + bx , where : x is fork length, y is measurement of any body part, r i s correlation coeff ic ient , c v . is coefficient of variat ion, T i s Student's value. Character a b S.E.of b r c v . % T Total length -0.3424 1.1353 0.0302 0.9885 1.23 37.51 Body length -0.2741 0.9318 0.0153 0.9955 0.76 60.59 Head length -0.0060 0.2800 0.0090 0.9831 1.47 30.82 Maxillary In. -0.4448 0.1700 0.0085 0.9610 2.65 19.97 Head depth 0.0842 0.1920 0.0101 0.9567 2.35 18.86 Dorsovent. d 0.3913 0.2229 0.0126 0.9507 2.35 17.60 Dorsoanal d. 0.2400 0.2219 0.0122 0.9533 2.36 18.14 Greatest b.d. 0.1010 0.2460 0.0163 0.9344 2.94 15.07 I r is diam. -0.1854 0.0709 0.0069 0.8713 5.19 10.20 Pupil diam. -0.1016 0.0386 0.0035 0.8832 4.90 10.81 Pectoral l n . -0.3866 0.1555 0.0100 0.9374 3.39 15.46 Pelvic length -0.2247 0.1250 0.0080 0.9382 3.23 15.57 Interorbit .d. -0.0523 0.0606 0.0066 0.8485 5.16 9.21 Pect. breadth -0.9698 0.1916 0.0093 0.9631 3.05 20.54 29 TABLE 9 Regressions o f Sample No. 4 from Tg S a t a i , N = 68 y = a + bx , where: x i s fo r k l e n g t h , y i s measurement o f any body p a r t , r i s c o r r e l a t i o n c o e f f i c i e n t , c.v. i s c o e f f i c i e n t o f v a r i a t i o n , T i s Student's t v a l u e . Character a b S.E.of b r c.v. % T T o t a l length -0.0062 1.1119 0.0124 0.9959 1.21 89.37 Body length 0.1484 0.9090 0.0068 0.9981 0.80 133.03 Head l e n g t h 0.1895 0.2660 0.0051 0.9881 1.99 52.09 M a x i l l a r y In. -0.2823 0.1578 0.0041 0.9778 3.19 37.87 Head depth -0.1805 0.2041 0.0044 0.9845 2.50 45.60 Dorsovent. d. -0.3092 0.2599 0.0065 0.9798 2.92 39.78 Dorsoanal. d. -0.2785 0.2487 0.0057 0.9831 2.65 43.56 Gr e a t e s t b.d. -0.4484 0.2754 0.0071 0.9786 3.09 38.61 I r i s diam. -0.0524 0.0620 0.0030 0.9302 5.52 20.59 Pu p i l diam. 0.0695 0.0285 0.0018 0.8801 6.27 15.06 P e c t o r a l In. -0.3793 0.1526 0.0044 0.9728 3.71 34.10 P e l v i c length -0.2536 0.1253 0.0039 0.9691 3.84 31.91 I n t e r o r b i t . d. -0.2862 0.0752 0.0033 0.9417 6.12 22.74 Pect. breadth -0.5646 0.1642 0.0063 0.9538 5.25 25.79 30 Sexual Dimorphism Rastrelliger braahysoma show sexual dimorphism i n body l e n g t h , m a x i l l a r y l e n g t h , v e n t r a l f i n l e n g t h , and probably caudal f i n l e n g t h (Table 10). The male has a s h o r t e r head, s h o r t e r m a x i l l a r y , s h o r t e r v e n t r a l f i n and s h o r t e r body; and probably has a longer caudal f i n . The purpose of t h i s sexual dimorphisms i s not y e t been s t u d i e d i n t h i s p a r t i c u l a r f i s h . I s p e c u l a t e t h a t t h i s dimorphisms i s more f o r sexual purposes r a t h e r than f o r d i s p l a y ; such as longer v e n t r a l f i n i n female i s probably f o r o b t a i n i n g b e t t e r balance and d i v e r g i n g the eggs w h i l e d i s c h a r g i n g them. T h i s dimorphism i s l e s s l i k e l y to appear i n f i n s which are c r i t i c a l f o r locomotion. The longer body i n female can be r e l a t e d to the need f o r more space i n body c a v i t y f o r eggs, as female gonads are g e n e r a l l y much bigger than male gonads. The longer head and m a x i l l a r y are probably r e l a t e d to the more i n t e n -s i v e and a c t i v e f e e d i n g i n the female than i n the male. The above c h a r a c t e r s should not be used f o r r a c i a l s t u d i e s . A l l o m e t r i c Growth The morphometric data of R. kanagurta suggest t h a t perpendic-u l a r i r i s and p u p i l diameters, p e c t o r a l f i n l e n g t h , and p e c t o r a l breadth show strong a l l o m e t r i c growth (Table 11, 12, 13). These c h a r a c t e r s cannot be used f o r r a c i a l s t u d i e s purposes. 31 TABLE 10 Comparison of Body P r o p o r t i o n s o f Rastrelliger spp. by Covariance A n a l y s i s f o r the Males and Females Taken from Tg. S a t a i . Data Show Variance R a t i o and i t s S i g n i f i c a n c e . Fr i s the v a r i a n c e r a t i o to t e s t the s i g n i f i c a n c e o f the r e g r e s s i o n d i f f e r e n c e , Fb t o t e s t the r e g r e s s i o n c o e f f i c i e n t d i f f e r e n c e , Fa to t e s t the a d j u s t e d mean d i f f e r e n c e . In the case where the r e g r e s s i o n c o e f f i c i e n t d i f f e r e n c e i s s i g n i f i c a n t , the t e s t o f the ad j u s t e d mean becomes i n a p p r o p r i a t e . C h a r a c t e r Fr Fb Fa T o t a l l e n g t h 3.91** 0.14 5.58* Body l e n g t h 6.46*** 0.07 1.97 Head l e n g t h 1.35 7.38** (0.05) M a x i l l a r y l e n g t h 1.36 5.32* 0.51 Head depth 2.11 1.89 0.49 Dorsoventral depth 1.03 0.89 0.36 Dorsoanal depth 1.94 1.52 0.00007 Gr e a t e s t body depth 1.00 1.90 0.33 Perp. i r i s diameter 1.16 2.62 0.02 Perp. p u p i l diameter 1.80 0.87 2.59 P e c t o r a l f i n l e n g t h 2.02 0.17 2.18 P e l v i c f i n l e n g t h 14.88*** 0.001 1.63 I n t e r o r b i t a l d i s t a n c e 1.24 1.10 0.91 P e c t o r a l breadth 1.05 1.04 0.000003 S i g n i f i c a n t a t 5% l e v e l . S i g n i f i c a n t a t 1% l e v e l . S i g n i f i c a n t a t 0.1% l e v e l . Note: The above s p e c i e s was named Rastrelliger brachysoma. 32 R A S T R E L L I G E R B R A C H Y S O M A F i g u r e . 4 Sexual D i m o r p h i s m s . male — — — female F i g u r e . 5 Geographical — —- f r o m f r o m Var ia t ions . the north coast of Java T g . Satai area 33 Geographic V a r i a t i o n s Comparisons were done on head depth, d o r s o v e n t r a l depth, dorsoanal depth, g r e a t e s t body depth and i n t e r o r b i t a l d i s t a n c e s i n c e these c h a r a c t e r s show n e i t h e r sexual dimorphism nor strong a l l o m e t r i c growth i n both s p e c i e s . A n a l y s i s o f c o v a r i a n c e on the data i n d i c a t e d t h a t : 1. between sympatric samples ( h o . 1 and no. 3; no. 2 and no. 4) these c h a r a c t e r s show a very h i g h l y s i g n i f i c a n c e d i f f e r e n c e (0.01%); 2. the d o r s o v e n t r a l depth, g r e a t e s t body depth, and i n t e r o r b i t a l d i s t a n c e have s i g n i f i c a n c e i n t r a s p e c i f i c d i f f e r e n c e ' 5%), showing geographical v a r i a t i o n s in-i?. braahysoma (Table 20). The f i s h from Tg. S a t a i area possess g r e a t e r d o r s o v e n t r a l depth, g r e a t e r body depth, and longer i n t e r o r b i t a l d i s t a n c e than i t s c o u n t e r p a r t from the north c o a s t o f Java. In o t h e r words the R. braahysoma from the north c o a s t o f Java i s more sl e n d e r than t h a t one from Tg. S a t a i ( F i g u r e 5). 3. R. kanagurta shows geographic v a r i a t i o n i n i t s head depth and d o r s o v e n t r a l depth (Table 20). The f i s h from the north c o a s t o f Java possess g r e a t e r head depth and d o r s o v e n t r a l depth. So thus R. kanagurta from Tg. S a t a i i s s l e n d e r and has l e s s e r head depth than the one from the north c o a s t o f Java ( F i g u r e 6 ) . 34 TABLE 11 Comparison o f Body P r o p o r t i o n s o f Rastrelliger spp. by Covariance A n a l y s i s Between Classmodes o f 20.0 cm Fork-Length 17.5 -22.4 cm) and o f 16.0 cm Fork Length (14.5 - 17.4 cm) Taken from Tg. S a t a i Area Data show v a r i a n c e r a t i o and i t s s i g n i f i c a n c e . Fr i s the v a r i a n c e r a t i o to t e s t the s i g n i f i c a n c e o f the r e g r e s s i o n d i f f e r e n c e . Fb to t e s t the r e g r e s s i o n c o e f f i c i e n t d i f f e r e n c e . Fa t o t e s t the a d j u s t e d mean d i f f e r e n c e . In the case where the r e g r e s s i o n c o e f f i c i e n t d i f f e r e n c e i s s i g n i f i c a n t , the t e s t o f the ad j u s t e d mean becomes i n a p p r o p r i a t e . C h a r a c t e r Fr Fb Fa M a x i l l a r y l e n g t h 1.40 6.12* 0.95 Head depth 1.67 1.51 1.25 Dorsoventral depth 1.15 0.09 2.14 Dorsoanal depth 1.35 0.81 1.05 Gr e a t e s t body depth 1.18 1.54 0.65 Perp. i r i s diameter 2.32* 13.97*** (2.54) Perp. p u p i l diameter 1.29 14.34*** (2.84) P e c t o r a l f i n le n g t h 1.58 4.03* 0.68 I n t e r o r b i t a l d i s t a n c e 1.12 1.91 0.53 P e c t o r a l breadth 3.27** 0.81 0.07 S i g n i f i c a n t a t 5% l e v e l . S i g n i f i c a n t a t 1% l e v e l . S i g n i f i c a n t a t 0.1% l e v e l . * ** *** Note: The above s p e c i e s was named Rastrelliger kanagurta. 35 TABLE 12 Comparison o f Body P r o p o r t i o n s o f Rastrelliger spp. by Covariance A n a l y s i s Between Classmodes o f 20.0 cm Fork-Length (17.5 -22.4 cm) and o f 14.0 cm Fork-Length (13.5 - 14.4 cm) Taken from Tg. S a t a i Data show v a r i a n c e r a t i o and i t s s i g n i f i c a n c e . Fr i s the v a r i a n c e r a t i o to t e s t the s i g n i f i c a n c e o f the r e g r e s s i o n d i f f e r e n c e . Fb to t e s t the r e g r e s s i o n c o e f f i c i e n t d i f f e r e n c e . Fa to t e s t the ad j u s t e d mean d i f f e r e n c e . In the case where the r e g r e s s i o n c o e f f i c i e n t d i f f e r e n c e i s s i g n i f i c a n t , the t e s t o f the a d j u s t e d mean becomes i n a p p r o p r i a t e . C h a r a c t e r Fr Fb Fa M a x i l l a r y l e n g t h 1.56 0.67 12.20** Head depth 1.40 0.91 4.86* Dorsoventral depth 1.04 0.52 0.58 Dorsoanal depth 2.03 0.06 0.17 Gr e a t e s t body depth 2.88 0.01 0.12 Perp. i r i s diameter 2.62 2.27 13.87*** Perp. P u p i l diameter 1.07 0.001 21.83*** P e c t o r a l f i n i l e n g t h 1.19 1.49 8.17** I n t e r o r b i t a l d i s t a n c e 1.37 1.55 3.06 P e c t o r a l breadth 2.29 0.10 0.67 * S i g n i f i c a n t a t 5% l e v e l . ** S i g n i f i c a n t a t 1% l e v e l . *** S i g n i f i c a n t a t 0.1% l e v e l . Note: The above s p e c i e s was named Rastrelliger kanagurta. 36 TABLE 13 Comparison o f Body P r o p o r t i o n s o f Rastrelliger spp. by Covariance A n a l y s i s Between Classmodes o f 16.00 cm Fork-Length (14.5 -17.4 cm) and o f 14.00 cm Fork-Length (13.5 - 14.4 cm) Taken from Tg. S a t a i Data show v a r i a n c e r a t i o and i t s s i g n i f i c a n c e . Fr i s the v a r i a n c e r a t i o and i t s s i g n i f i c a n c e o f the r e g r e s s i o n d i f f e r e n c e . Fb to t e s t the r e g r e s s i o n c o e f f i c i e n t d i f f e r e n c e . Fa t o t e s t the a d j u s t e d mean d i f f e r e n c e . In the case where the r e g r e s s i o n c o e f f i c i e n t d i f f e r e n c e i s s i g n i f i c a n t , the t e s t o f the a d j u s t e d mean becomes i n a p p r o p r i a t e . C h a r a c t e r Fr Fb Fa M a x i l l a r y l e n g t h 0.10 0.11 2.32 Head depth 1.18 2.08 1.04 Dorsoventral depth 1.10 0.09 0.11 Dorsoanal depth 1.49 0.003 0.04 G r e a t e s t body depth 2.42 0.02 0.30 Perp. i r i s diameter 1.12 1.07 0.39 Perp. p u p i l diameter 1.20 0.65 0.45 P e c t o r a l f i n le n g t h 1.32 0.89 2.56 I n t e r o r b i t a l d i s t a n c e 1.22 2.61 0.003 P e c t o r a l breadth 1.12 0.05 0.01 S i g n i f i c a n t a t 5% l e v e l . S i g n i f i c a n t a t 1% l e v e l . S i g n i f i c a n t a t 0.1% l e v e l . Note: The above s p e c i e s was named Rastrelliger kanagurta. 37 TABLE 14 Comparison o f Body P r o p o r t i o n o f Rastrelliger spp. by Covariance A n a l y s i s Between Sample No. 1 and Sample No. 2 from J a k a r t a and Tg. S a t a i r e s p e c t i v e l y Data show v a r i a n c e r a t i o and i t s s i g n i f i c a n c e . Fr i s the v a r i a n c e r a t i o to t e s t the s i g n i f i c a n c e o f the r e g r e s s i o n d i f f e r e n c e . Fb to t e s t the r e g r e s s i o n c o e f f i c i e n t d i f f e r e n c e . Fa to t e s t the a d j u s t e d mean d i f f e r e n c e . In the case where the r e g r e s s i o n c o e f f i c i e n t d i f f e r e n c e i s s i g n i f i c a n t , the t e s t o f the a d j u s t e d mean becomes i n a p p r o p r i a t e . C h a r a c t e r Fr Fb Fa Head depth 1.15 1.81 1.26 Dorsoventral depth 1.65* 1.37 3.90 Dorsoanal depth 1.49 2.42 2.36 G r e a t e s t body depth 1.92* 0.31 9.90** I n t e r o r b i t a l d i s t a n c e 1.82* 0.31 1.15 * ** *** S i g n i f i c a n t a t 5% l e v e l . S i g n i f i c a n t a t 1% l e v e l . S i g n i f i c a n t a t 0.1% l e v e l . 38 TABLE 15 Comparison of Body Proportions of Rastrelliger spp. by Covariance Analysis Between Samples No. 3 (Jakarta) and No. 4 (Tg. Satai) Data show variance ratio and i ts significance. Fr is the variance ratio to test the significance of the regression difference. Fb to test the regression coefficient difference. Fa to test the adjusted mean difference. In the case where the regression coefficient difference is s igni f icant , the test of the adjusted mean becomes inappropriate. Character Fr Fb Fa Head depth Dorsoventral depth Dorsoanal depth Greatest body depth Interorbital distance 1.05 1.28 1.05 1.07 1.19 1.20 5.89* 3.80 2.80 3.03 6.51* 1.54 2.23 0.39 0.84 * ** *** Significant at 5% leve l . Significant at 1% leve l . Significant at 0.1% leve l . 39 TABLE 16 Comparison o f Body P r o p o r t i o n s o f Rastrelliger spp. by Covariance A n a l y s i s Between Samples No. 1 ( J a k a r t a ) and No. 3 (Jaka r t a ) Data show v a r i a n c e r a t i o and i t s s i g n i f i c a n c e . Fr i s the v a r i a n c e r a t i o to t e s t the s i g n i f i c a n c e o f the r e g r e s s i o n d i f f e r e n c e . Fb to t e s t the r e g r e s s i o n c o e f f i c i e n t d i f f e r e n c e . Fa to t e s t the a d j u s t e d mean d i f f e r e n c e . In the case where the r e g r e s s i o n c o e f f i c i e n t d i f f e r e n c e i s s i g n i f i c a n t , the t e s t o f the a d j u s t e d mean becomes i n a p p r o p r i a t e . Character Fr Fb Fa Head depth Dorsoventral depth Dorsoanal depth G r e a t e s t body depth I n t e r o r b i t a l d i s t a n c e 1.44 2.21* 2.31** 1.62 1.54 9.41** 28.92*** 14.83*** 17.26*** 5.26* (>D (>D (>D (>D 25.41*** * ** *** S i g n i f i c a n t a t 5% l e v e l . S i g n i f i c a n t a t 1% l e v e l . S i g n i f i c a n t a t 0.1% l e v e l . 40 TABLE 17 Comparison o f Body P r o p o r t i o n s o f Rastrelliger spp. by Covariance A n a l y s i s Between Samples No. 2 (Tg. S a t a i ) No. 4 (Tg. S a t a i ) Data show v a r i a n c e r a t i o and i t s s i g n i f i c a n c e . Fr i s the v a r i a n c e r a t i o to t e s t the s i g n i f i c a n c e o f the r e g r e s s i o n d i f f e r e n c e . Fb to t e s t the r e g r e s s i o n c o e f f i c i e n t d i f f e r e n c e . Fa to t e s t the a d j u s t e d mean d i f f e r e n c e . In the case where the r e g r e s s i o n c o e f f i c i e n t d i f f e r e n c e i s s i g n i f i c a n t , the t e s t o f the ad j u s t e d mean becomes i n a p p r o p r i a t e . Character Fr Fb Fa Head depth Dorsoventral depth Dorsoanal depth Greatest body depth I n t e r o r b i t a l d i s t a n c e 1.31 1.04 1.46 1.09 1.009 43.43*** 31.96*** 7.80** 31.39*** 0.03 (>D (>1) (>1) (>1) 19.82*** * ** *** S i g n i f i c a n t a t 5% l e v e l . S i g n i f i c a n t a t 1% l e v e l . S i g n i f i c a n t a t 0.1% l e v e l . 41 TABLE 18 Comparison o f Body P r o p o r t i o n s o f Rastrelliger spp. by Covariance A n a l y s i s Between Samples No. 2 (Tg. S a t a i ) and No. 3 ( J a k a r t a ) Data show v a r i a n c e r a t i o and i t s s i g n i f i c a n c e . Fr i s the v a r i a n c e r a t i o to t e s t the s i g n i f i c a n c e o f the r e g r e s s i o n d i f f e r e n c e . Fb t o t e s t the r e g r e s s i o n c o e f f i c i e n t d i f f e r e n c e . Fa t o t e s t the a d j u s t e d mean d i f f e r e n c e . In the case where the r e g r e s s i o n c o e f f i c i e n t d i f f e r e n c e i s s i g n i f i c a n t , the t e s t o f the a d j u s t e d mean becomes i n a p p r o p r i a t e . Character Fr Fb Fa Head depth Dorsoventral depth Dorsoanal depth G r e a t e s t body depth I n t e r o r b i t a l d i s t a n c e 1.25 1.34 1.54 1.18 1.18 27.65*** 38.75*** 11.73*** 28.36*** 2.93 ( 1) ( 1) W\ 9.87** * ** *** S i g n i f i c a n t a t 5% l e v e l . S i g n i f i c a n t a t 1% l e v e l . S i g n i f i c a n t a t 0.1% l e v e l . 42 TABLE 19 Comparison of Body P r o p o r t i o n s o f Rastrelliger spp. by Covariance A n a l y s i s Between Samples No. 1 ( J a k a r t a ) and No. 4 (Tg. S a t a i ) Data show v a r i a n c e r a t i o and i t s s i g n i f i c a n c e . Fr i s the v a r i a n c e r a t i o to t e s t the s i g n i f i c a n c e o f the r e g r e s s i o n d i f f e r e n c e . Fb t o t e s t the r e g r e s s i o n c o e f f i c i e n t d i f f e r e n c e . Fa to t e s t the a d j u s t e d mean d i f f e r e n c e . In the case where the r e g r e s s i o n c o e f f i c i e n t d i f f e r e n c e i s s i g n i f i c a n t , the t e s t o f the a d j u s t e d mean becomes i n a p p r o p r i a t e . Character Fr Fb Fa Head depth 1.52 9.84** ( 1) Dorsoventral depth 1.72* 25.61*** ( 1) Dorsoanal depth 2.18** 13.79*** ( 1) Gre a t e s t body depth 1.75* 17.65*** ( 1) I n t e r o r b i t a l d i s t a n c e 1.84* 0.56 54.49*** * ** *** S i g n i f i c a n t a t 5% l e v e l . S i g n i f i c a n t a t 1% l e v e l . S i g n i f i c a n t a t 0.1% l e v e l . 43 SAMPLE NUMBER CHARACTER No.l Head depth Dorsoventral depth -No.2 Dorsoanal depth Greatest body depth * ** I n t e r o r b i t a l distance * No. 2 Head depth ** *** Dorsoventral depth No. 3 Dorsoanal depth Greatest body depth •if*-* i n t e r o r b i t a l distance * **# ** No. 3 Head depth **-•)<• * Dorsoventral depth ** No.4 Dorsoanal depth Greatest body depth * *#* I n t e r o r b i t a l distance *** ##* Fr Fb Fa Fr Fb Fa Fr Fb Fa Table 20.Covariance analyses f o r pairs of R a s t r e l l i g e r . Fr, Fb and Fa are the variance r a t i o s used to t e s t the si g n i f i c a n c e of difference i n regression l i n e , regression c o e f f i c i e n t and adjusted mean r e s p e c t i v e l y . * : S i g n i f i c a n t at 5 7* l e v e l . ** : " 1 io " *** : 11 0.1 fo " R A S T R E L L I G E R K A N A G U R T A Geographical Var ia t ions . • f r o m T g . Satai area - f r o m the north coast of Java 45 3. M e r i s t i c Characters  Number o f Vertebrae T o t a l numbers o f v e r t e b r a e appeared to be cons t a n t as a l l specimens examined had 31 v e r t e b r a e . 26 specimens o f 7 - 9 cm FL possessed 31 v e r t e b r a e . There i s no d i f f e r e n c e i n vertebrae number between R. braahysoma and R. kanagurta. F i r s t Haemal Spine The f i r s t haemal s p i n e appeared c o n s t a n t on the tenth v e r t e b r a e i n Rastrelliger. Sample no. 1, i . e . , R. braahysoma from the north c o a s t o f Java have a mean o f the f i r s t haemal s p i n e l o c a t i o n o f 9.9 (0.3 S.D.) with c o e f f i c i e n t o f v a r i a t i o n 3.1%. Sample no. 2, no. 3, and no. 4 appeared c o n s t a n t on the tenth v e r t e b r a e . F i r s t Dorsal Spine The f i r s t d o r s a l f i n s p i n e counts appeared v a r i a b l e between 10.6 (0.5 S.D.) to 11.0 (0.0 S.D.). A n a l y s i s o f v a r i a n c e i n d i c a t e d h i g h l y s i g n i f i c a n t d i f f e r e n c e s (1%) between R. kanagurta from the no r t h c o a s t o f Java and the one from Tg. S a t a i a r e a . The f i s h from the former area has e l e v e n spines on i t s f i r s t d o r s a l f i n , whereas the one from the l a t t e r area i s v a r i a b l e , 46 e i t h e r p o s s e s s i n g e l e v e n o r ten spines (x = 10.6, S.D. = 0.5, n = 20). Dorsal F i n Rays and F i n l e t s The second d o r s a l f i n rays plus f i n l e t s counts appear to be l e s s v a r i a b l e . The c o e f f i c i e n t o f v a r i a t i o n ranged from 0.0 to 2.9%. There i s no s i g n i f i c a n t d i f f e r e n c e between s p e c i e s . The f i n - r a y s vary from 12 to 13 and the d o r s a l f i n l e t s from 5 to 6. Anal F i n Rays and F i n l e t s The counts o f anal f i n rays and anal f i n l e t s appeared c o n s t a n t , i . e . , 18. The f i n - r a y s are 13 and the anal f i n l e t s v a r y between 5 and 6. F i r s t Occurrence o f Haemal Brace The f i r s t haemal brace o c c u r r e d as a s t r u c t u r e on ver t e b r a e as d e s c r i b e d by Roedel (1952) ( F i g u r e 7 ) . He suggested t h a t t h i s c h a r a c t e r i s good f o r d i s t i n g u i s h i n g race i n Pneumatophorus. The f i r s t occurrence o f haemal brace i n Rastrelliger appeared on e i t h e r the t h i r t e e n t h o r the f o u r t e e n t h v e r t e b r a e . The c o e f f i c i e n t o f v a r i a t i o n range from 2.2 to 3.6. The means range from 13.7 (0.5 S.D.; n = 20) to 13.9 (0.3 S.D.; n = 20). Figure 7. F i r s t Occurence of Haemal Brace on Vertebrae ( a f t e r Roedel, 1952). 1. P a r t i a l l y Formed Brace 2. Haemal Brace 48 TABLE 21 G i l l Raker Counts o f Rastrelliger Species Name Part o f G i l l Arch Mean S.D. C o e f f i c i e n t o f V a r i a t i o n s N R. braahysoma Upper 19.0 1.0 5.47 14 Lower 35.8 0.9 2.46 25 T o t a l 55.0 1.0 1.82 15 R. kanagurta Upper 20.6 1.3 6.27 28 Lower 36.6 1.0 2.73 30 To t a l 57.2 1.9 3.27 28 TABLE 22 The Degree o f I n t e r g r a d a t i o n o f the T o t a l G i l l Raker Counts o f the F i r s t L e f t G i l l Arch o f Rastrelliger G i l l Raker Count 54 55 56 57 58 59 n Species R. braahysoma 40 26.7 26.7 6.6 - - 100 R. kanagurta 14.3 7.1 10.7 21.4 25 21.4 99.9 I n t e r g r a d a t i o n = 19%. 49 A n a l y s i s o f v a r i a n c e i n d i c a t e d t h a t t h e r e i s no s i g n i f i c a n t d i f f e r e n c e between and w i t h i n s p e c i e s . T h e r e f o r e , t h i s c h a r a c t e r cannot be used i n r a c i a l s t u d i e s o f Rastrelliger spp. G i l l Raker The g i l l r a k e r counts on the f i r s t l e f t g i l l a rch show c o n s i d e r -a b l e v a r i a t i o n s . The c o e f f i c i e n t o f v a r i a t i o n o f the g i l l r a k e r counts on the lower limb i n R. kanagurta was 2.7, and the mean was 36.6 (S.D. = 1.0); i n R. braahysoma was 2.5 and 35.8 (S.D. = 0.9) r e s p e c t i v e l y . Those values o f the upper limb were 6.3 and 20.6 (S.D. = 1.3); and 5.5, 19.0 (S.D. = 1.0). The t o t a l g i l l r a k e r counts on the f i r s t l e f t g i l l arch show o v e r l a p between s p e c i e s ; the degree o f i n t e r g r a d a t i o n was 19% (Tables 21, 22). 4. Q u a l i t a t i v e Characters  C o l o u r a t i o n No d i s t i n c t d i f f e r e n c e s e x i s t i n body c o l o u r a t i o n among samples. The dark spots or s t r a y spots below the f i r s t d o r s a l and on the t i p and o u t e r margin o f the f i r s t d o r s a l f i n show a s l i g h t d i f f e r e n c e i n the degree o f darkness between fi. braahysoma and R. kanagurta. The former s p e c i e s possesses darker c o l o u r on i t s t i p and o u t e r margin o f the f i r s t d o r s a l f i n , whereas the second one has c l e a r e r l o n g i t u d i n a l bands above the l a t e r a l l i n e s . 50 C e p h a l i c L a t e r a l L i n e Canal There i s an apparent d i f f e r e n c e i n the appearance of the c e p h a l i c l a t e r a l l i n e system between the two s p e c i e s . R. braahysoma possesses a very f i n e l y d e n d r i t i c canal system; whereas R. kanagurta has a l e s s f i n e l y d e n d r i t i c one ( F i g u r e 8). T h i s c h a r a c t e r i s u s e f u l i n d i s t i n g u i s h i n g s p e c i e s , and can be used as a key c h a r a c t e r s . D i g e s t i v e T r a c t The d i g e s t i v e t r a c t i n R. braahysoma i s much more convolut-ed than t h a t o f R. kanagurta. T h i s d i f f e r e n t appearance i s r e l a t e d t o the longer i n t e s t i n e i n the f i r s t s p e c i e s . The shape of the stomach d i f f e r s o n l y i n the presence o f a small f l a p p y t i p at the bottom o f the stomach o f R. kanagurta ( F i g u r e 9 ) . 5. Po p u l a t i o n Study Rastrelliger F i s h e r i e s Rastrelliger i s f i s h e d i n p r a c t i c a l l y a l l c o a s t a l areas o f Indonesia; and i s caught m a i l y by payang-net. The payang net i s an e n c i r c l i n g s u r f a c e s e i n e with a bag, and have the upper l i n e s . s h o r t e r than the lower ones. The fishermen u s u a l l y use a l u r e t h a t i s c a l l e d rumpon to a t t r a c t the f i s h and conc e n t r a t e them. The payang-net i s 51 dragged passing underneath or a l o n g s i d e the rumpon and i s hauled up to the v e s s e l . The o p e r a t i o n takes p l a c e during the day. Thousands of such rumpons l i e s c a t t e r e d over the Java Sea. Several f i s h i n g gears such as shore s e i n e , g i l l net, and tr a p s are u t i l i z e d along the c o a s t a l a r e a s . In the l a t e p a r t of 1971, the purse s e i n e was intro d u c e d i n the Bay of J a k a r t a . I t has operated economically s i n c e 1972 i n the c o a s t a l areas of the north coast of Java. The f i s h caught c o n s i s t of two s p e c i e s , R. brachysoma or Kembung Perempuan which i s caught mainly i n the c o a s t a l zones; and R. kanaguvta or Kembung L e l a k i o f the o f f s h o r e areas. The major p a r t o f lan d i n g s comes from the Sunda S h e l f a r e a , i n p a r t i c u l a r the north coast of Java, the south and the south west coasts of Borneo (Kalimantan) and the east c o a s t of Sumatra. The p r o d u c t i o n i n the north c o a s t of Java i s estimated as exceeding 10,000 tons per y e a r , of which the g r e a t e r p a r t of the l a n d i n g c o n s i s t s of R. kanaguvta (Table 23). In the e a s t e r n p a r t o f Indonesia the f i s h i n g a c t i v i t i e s are not y e t developed. P o p u l a t i o n Parameters The present study of Rastrelliger p o p u l a t i o n dynamics i n Indonesian waters begins with a n a l y s i s of v a r i a b l e s or parameters o f i t s p o p u l a t i o n s . D e t a i l e d analyses o f v a r i a b l e s a f f e c t i n g y i e l d have been attempted i n the G u l f o f T h a i l a n d and Indian waters. 52 Figure 8. Cephalic L a t e r a l Line System of R a s t r e l l i g e r . R» brachysoma II . R. kanagurta Abbreviations: CL, cephalic l a t e r a l i s ; ' F, f r o n t a l ; 10, i n t e r o r b i t a l ; LL, l i n e a l a t e r a l i s ; POC, postocular commi-sure; SO, supraorbital; ST,supratemporal. 53 Figure 9 . Dimension of measurement of the digestive tract of Rast re l l iger . 1. stomach; 2. pylor ic ; 3. intestine. I. ths stomach of R. brachysoma II. the stomach of R. kanagurta 54 TABLE 23 Production o f Payang F i s h e r i e s i n the North Coast o f Java o f R. kanagurta 1969 1970 1971 Month (tons) (tons) (tons) I 210 275 535 II 203 358 521 III 408 528 863 IV 849 1,093 1,156 V 547 645 1,003 VI 499 528 934 VII 431 562 739 VIII 438 424 588 IX 551 593 869 X 725 735 1,011 XI 802 774 1,033 XII 509 584 906 T o t a l 6,172 7,099 10,158 Sources: (1) The Sea F i s h e r i e s S e r v i c e o f Jakarta-Raya i n J a k a r t a , (2) " of the Province o f West Java i n Bandung, (3) " o f the P r o v i n c e o f Middle Java i n Semarang, (4) " of the Pr o v i n c e of East Java i n Surabaya. 55 The i n f o r m a t i o n a v a i l a b l e does not meet the data requirement of modern management models. Moreover, some d i f f i c u l t i e s such as un-d e t e c t a b l e growth r i n g s on s c a l e s and o t h e r s k e l e t a l s t r u c t u r e s , v a r i a -b i l i t y i n growth r a t e s , i n d e f i n i t e spawning p e r i o d s and the p a u c i t y o f c a t c h s t a t i s t i c s l e a d to a t b e s t , approximate e s t i m a t i o n s of parameters. However, the r e s u l t s r e p o r t e d here compare f a v o u r a b l y with the r e s u l t s obtained by v a r i o u s i n v e s t i g a t o r s from the adjacent r e g i o n s . Sexual C o n d i t i o n s  M a t u r i t y The importance o f age at sexual m a t u r i t y f o r management purposes i s obvious. N i k o l s k i i (1969) s t a t e s t h a t because o f d i f f e r -ences i n growth r a t e s , young hatched at the same time w i l l reach m a t u r i t y at d i f f e r e n t ages. Sexual m a t u r i t y may be governed by attainment of a c e r t a i n s i z e r a t h e r than age. The s i z e a t m a t u r i t y i s t h e r e f o r e an important parameter i n management, e s p e c i a l l y f o r t r o p i c a l s p e c i e s , wherein e x p l o i t a t i o n should allow an adequate number o f spawners, i . e . , l a r g e r than o r equal to the s i z e at sexual m a t u r i t y , to assure a continued supply o f young f i s h . The data suggest t h a t Rastvelligev kanaguvta i n the Java Sea a t t a i n s i t s sexual m a t u r i t y at 19.0 (18.0 - 20.5) cm TL or at about 7 months of age ( F i g u r e 29 i_n Appendices, T a b l e 27). Chidambaram and Venkataraman (1946) found the minimum s i z e at sexual m a t u r i t y of R. kanaguvta i n Indian waters to be 20 cm. 56 In the same waters Pradhan (1956) suggested 22.4 cm TL at m a t u r i t y . P a t h a n s a l i (1966) rep o r t e d that R. kanagurta caught a t Pangkor I s . , M a l a y s i a , a t t a i n e d sexual m a t u r i t y a t 17.5 - 19.8 cm. The s i z e a t ma-t u r i t y o f the same f i s h i n waters o f the P h i l i p p i n e was recorded as 21.0 - 21.9 cm ( P h i l i p p i n e s F i s h e r i e s Handbook, 1952). Tiews (1958) g i v e s 18.0 cm f o r t h i s f i s h i n the same r e g i o n . No rec o r d s are a v a i l -a b l e from the o t h e r r e g i o n s o f the I n d o - P a c i f i c area. R. braahysoma a t t a i n s i t s sexual m a t u r i t y at 17.3 (17.0 -17.5) cm TL or about 7.5 months o l d ( F i g u r e 11, Table 28). The o n l y other comparable data f o r t h i s s p e c i e s were obtained i n M a n i l a Bay, The P h i l i p p i n e s , where the s i z e at m a t u r i t y was 15.0 -16.9 cm ( P h i l i p p i n e s F i s h e r i e s Handbook, 1952); Tiews (1958) g i v e s 16.5 cm. Beverton (1963) s t u d i e d the age at m a t u r i t y o f c l u p e i d s and e n g r a u l i d s and s t a t e d t h a t f i s h with high K value (von B e r t a l a n f f y growth parameter) mature at an e a r l i e r age than f i s h with low K. The data suggest that Rastrelliger f o l l o w t h i s p a t t e r n . R. kanagurta with a higher K value (= 0.23) mature at a younger age (= 7 months) than R. braahysoma with a lower K value (= 0.19) that mature at 7.5 months o l d (Table 26, 27, 28; F i g u r e 11, 29 i_n Appendices). Gonads Several i n d i c a t o r s o f the m a t u r i t y stages are a v a i l a b l e e i t h e r f o r the f i e l d or l a b o r a t o r y . These keys have been d e s c r i b e d by Indian workers and were developed from The Key to the Stages o f Sexual M a t u r i -57 t y of the Herring by the I n t e r n a t i o n a l Council f o r the E x p l o r a t i o n of the Sea (Pradhan and P a l e k a r , 1956). In t h i s study the f i e l d keys were employed (Table 24, 25). No f e c u n d i t y study has been c a r r i e d out. Devanesan and John (1940) estimated an average of 94,000 eggs per female R. kanaguvta i n Indian waters. Boonprakob (1966) estimated 86,000 eggs per female f o r advanced group eggs and 479,000 eggs per female f o r t o t a l ova of the same s p e c i e s caught i n the G u l f of T h a i l a n d . For R. bvachysoma he estimated 100,000 - 166,000 eggs per female f o r advanced group and 200,000 - 500,000 eggs per female f o r t o t a l ova. Furthermore, he w r i t e s t h a t R. kanaguvta r e l e a s e d 20,000 eggs per batch and R. bva-chysoma between approximately 20,000 and 30,000 eggs per batch. Spawning The mature gonads of R. kanaguvta are found mostly i n January and May ( F i g u r e 10), but t h e r e i s evidence t h a t stage IV (mature) gonads are found i n September. The data suggest t h a t i n the Java Sea t h e r e are two spawning seasons, the f i r s t d u r i n g the West Monsoon probably from October to February and the second during the East Monsoon from June to September. P a t h a n s a l i (1961) assumed t h a t the spawning season of R. kanaguvta on the west coast of M a l a y s i a i s from October to A p r i l . Jones and Rosa (1962) s t a t e d t h a t the spawning season of t h i s f i s h i n Indian waters appears to be from March to September. 58 TABLE 24 F i e l d Key o f M a t u r i t y Stages o f Rastrelliger (Males) Extent o f Testes i n Body C a v i t y General Appearance o f Testes Stage and S t a t e Less than 1/2 length o f c a v i t y Very small t r a n s l u c e n t o r w h i t i s h s t r a n d v i s i b l e I Immature S l i g h t l y more than 1/2 length o f c a v i t y D i s t i n c t o v o i d o r elongate f l a t body v i s i b l e ; mostly t r a n s l u c e n t ; w h i t i s h II Maturi ng About 2/3 or over length o f c a v i t y Opaque; white and f l a t ; some-times creamy I I I Maturing Much over 2/3 to f u l l l e n g t h o f c a v i t y Opaque; white; s o f t ; sperm e x t r u s a b l e IV Mature Much reduced i n s i z e , about 1/3 o f c a v i t y Bloodshot and f l a b b y , p a r t l y t r a n s l u c e n t V Spent Note: For Fresh M a t e r i a l . 59 TABLE 25 Field Key of Maturity Stages of Rastrelliger (Females) Extent of Ovary in Body Cavity General Appearance of Ovary Stage and State About 1/3 length of cavity Translucent; redish to pink-ish in colour; ova inv is ib le I Immature About 1/2 length of cavity Translucent; pinkish in colour; ova inv is ib le II Maturing About 2/3 length of cavi ty Pinkish yellow colour; granular, opaque in appearance III Maturing Over 2/3 to f u l l length of cavity Orange to pink in colour; superficial blood vessels conspicuous; translucent eggs v i s i b l e ; ripe eggs are extrusable IV Mature Shrunken to about 1/2 length of cavity; walls loose Remnant of disintegrating opaque and ripe ova v i s i b l e ; may be dark red or translucent V Spent Note: For Fresh Material. 6 0 R. bvachysoma from Tg. S a t a i appears to have a long spawning season t h a t l a s t s from May to October. T h i s c o n c l u s i o n i s based upon the m a t u r i t y stages data ( F i g u r e 11) and the disappearance o f t h i s f i s h f o r s e v e r a l months during which time they migrate from the area to spawn. In the G u l f o f T h a i l a n d , Boonprakob (1966) r e p o r t e d t h a t the spawning season of R. braohysoma i s from January to August. Druzhi-n i n (1968) s t a t e s t h a t i n Burma waters the same s p e c i e s has a spawning season t h a t l a s t s from September to May. Jones and Rosa (1962) s t a t e t h a t Rastrelliger spawn i n s u c c e s s i o n over a prolonged p e r i o d and o n l y a small p o r t i o n o f ova mature each time g i v i n g a " s p e c k l e d " appearance stage. P a t h a n s a l i (1966) s t a t e s t h a t there i s c o n s i d e r a b l e d i f f e r e n c e i n the m a t u r i t y stages of R. kanagurta o v a r i e s w i t h i n f i s h of the same school and i n the same s i z e range. T h i s r e s u l t e d i n p e c u l i a r modes of egg r i p e n -ing and spawning. As the spawning of any one batch o f ova i s not simultaneous i n a l l f i s h , a number of broods are produced during each r e p r o d u c t i v e season. Boonprakob (1966) suggested t h a t a spawner of R. braohysoma a f t e r r e l e a s i n g the f i r s t batch of eggs probably r e l e a s e s subsequent batches of eggs at s h o r t i n t e r v a l s o f time. Evidence of repeated spawning i s not unusual i n the f a m i l y Scombridae. Fry (1936) i d e n t i f i e d repeated spawning i n Scomber japonicus which he says may spawn two or more times a season. The spawning season i s from A p r i l to August and occurs o f f the C a l i f o r n i a Coast. 61 40-20 40-20 0-4G-2G C-UC 2G C-4C 2C C 4C 2C Nov.71 Dec.71 Jan.72 Feb.72 May.72 Jun.7? Jul.72 Aug.72 Ser>.72 i nniy/T 1 I f f l l T Y Figure 10. Sexual Maturity Stages Com-oosition of R. kanagurta from the north coast of Java, 62 Sexual Maturity Stage 17 18 19 20 21 TL (cm) Figure n Length end Sexual Maturity Stage Compositions of R. brachysoma from Tg. S a t a i , on March 1°72. 63 I f the number of batches can be determined, the time taken by each batch to develop could be determined which i n t u r n would a l l o w one to measure the l e n g t h of the breeding season. Without knowledge o f a d e f i n i t e breeding season i t i s d i f f i c u l t to determine annual r e -cruitment and to r e l a t e r e c r u i t s to the broods of young i n one y e a r . Repeated spawning w i t h i n a year c r e a t e s sub-year c l a s s e s , possessing d i f f e r e n t growth r a t e s , which causes o v e r l a p s i n the l e n g t h frequency d i s t r i b u t i o n making the d i f f e r e n t age groups d i f f i c u l t to i d e n t i f y . Fry (1936) s t a t e s t h a t Scomber scombrus spawns i n water deeper than 70 meters, with a temperature range of 16.7 to 20.6° C. He found p e l a g i c eggs of s. japonicus f l o a t i n g at o r near the sur-f a c e i n the open sea. Bigelow and Welch (1925) found eggs i n water temperature ranging from 4 to 17.8° C with s a l i n i t y from 31.9 to 33.0 °/oo. The s u r f a c e ( < 10 m) temperature i n the Java Sea and adjacent areas i n January, February, and March ranges from 27.5 -29.0° C, and the s a l i n i t y ranges from 32.0 - 33.0 °/oo. In A p r i l , May, and June the temperature i s approximately 29.0°C and the s a l i n i t y approaches 33.5 °/oo ( i n the e a s t e r n p a r t of Java Sea i t i s 34.25 °/oo). These c o n d i t i o n s continue throughout J u l y , August, and September, except i n the e a s t e r n p a r t o f the Java Sea where s a l i -n i t y i s s l i g h t l y higher. In October, November, and December the temperature' and s a l i n i t y decrease to 27.5° (the western edge of the Java Sea: 27.5 - 29.0°) and 32.5 °/oo (the e a s t e r n part of the Java Sea ranges from 33.5 - 34.5 °/oo) ( B a r k l e y , 1968). 64 The sa l in i ty in the coastal areas is generally lower than that of the offshore due to the inflow of r ivers. This condition might prevent egg development as they need water of high density for the osmotic requirements of the eggs. If Rastrelliger spawns in the same depth as Scomber they must migrate to deeper waters from the Java Sea area (where the depth does not exceed 50 m). These areas could be the South China Sea, the Indian Ocean or the eastern part of the Java Sea adjacent to the Flores Sea. I suspect that the West Monsoon population spawns in the South China Sea or the Indian Ocean, and the East Monsoon population in the Flores Sea. Egg and larval studies in the above areas and in the Java Sea might help elucidate the spawning behaviour of Rastrelliger. Sex Ratio The males and females of R. kanagurta in the commercial catches exist in approximately equal proportions with a ratio of 1.0 to 1.1. The unpublished data of the Institute for Marine Research in Jakarta show that in the West Monsoon (1971/1972) the ratio is 1.0 to 1.2 and in the East Monsoon (1972) i t is about equal. In Indian waters, Jones and Rosa (1962) observed a ratio of 1.0 to 1.0. In R. braahysoma the rat io is 1.3 to 1.0 (1972); whereas Druzhinin (1968) recorded a ratio of 1.0 to 1.7 between males and fe -males in Mergui Arch. , Burma. 65 ! Longevity The data suggest that R. kanaguvta in the Java Sea can attain 24.0 cm TL or 3 years of age (Table 26, 27). In unpublished data of the Marine Fisheries Research Ins t i - ' tute in Jakarta, Kadir (1966) recorded a specimen of 26.5 cm caught in the south west of Borneo. The largest specimen caught in Indian waters was 27.0 cm (Jones and Rosa, 1962). De Beaufort (1951) record-ed a length of 37.0 cm. R . bvachysoma can reach 23.0 cm TL or 3 years of age (Table 26, 28). In the Gulf of Thailand i t is recorded as 21.0 cm and de Beaufort (1951) recorded 21.9 cm. Environmental Tolerance Although there is no def ini t ive study concerning the hardi-ness of these f i s h , some information.is available from various investigations.. Pradhan (1956) writes that R. kanaguvta can withstand low sa l in i ty of 2.04 °/oo but without stating the duration. Jones and Rosa (1962) write that the f ish are known to enter estuarine water of Kali River, India, and ascend along the t idal current to a distance of more than 2 km during the month of Apri l and May when the range of s a l i -nity is 29.7 - 34.6 °/oo. Moreover, they stated that the genus Ras-tvelligev is distributed in the Tropical Indo-West Pacif ic Faunistic Region only; i t does not extend eastward to the East Pacif ic Barrier. Oceanographically the former region possesses a high surface tempera 66 t u r e which does not f a l l below 17°C i n any season and a t the 200 m i s o b a t h the temperature i s 15°C. Pradhan and Gangadhara (1962) s t a t e t h a t R. kanagurta appears to be more s u c c e p t i b l e to changes i n temperature than s a l i n i t y . The t o l e r a n c e to these f a c t o r s depends upon the s i z e o f the f i s h i n t h a t l a r g e r f i s h are more r e s i s t a n c e to a higher temperature and s a l i n i t y . Competitor and Predator The scads (Decapterus spp.) and the o i l - s a r d i n e s (Sardinella . spp.) seem to be the most important competitors f o r food. . The f i s h e s , l i k e Rastrelliger, are plankton f e e d e r s . The tuna and t u n a - l i k e f i s h e s (Katsuwonus spp. and Euthyn-nus spp.), sharks and porpoises a r e Rastrelliger p r e d a t o r s . P a r a s i t e s U n i d e n t i f i e d nematodes were recovered from the body c a v i t y of R. kanagurta but none from R. braahysoma. Several Indian i n v e s t i g a t o r s recorded trematode, cestode, and copepode p a r a s i t e s i n R. kanagurta ( S i l a s , 1962). Growth Growth i s manifested as an i n c r e a s e i n the s i z e of an organism. The best measurement i s weight. However, s i n c e a c c u r a t e weighing i s not e a s i l y done at s e a , growth can be determine from l e n g t h data; t h e r e f o r e , the length-weight r e l a t i o n s h i p i s necessary. The methods used i n growth s t u d i e s are g e n e r a l l y i n v o l v e d : 67 J tracing the seasonal or annual increase in mean or modal length of successive age groups in the population; - the back calculation method of Petersen (1891), i . e . , by taking measurement of skeletal structures, usually scales (Lea, 1910) or otol iths (Hickling, 1933); - by tagging, i . e . , by measuring the increase in length of tagged f ish between capture and recaptures. The f i r s t method gives the average growth characteristics of a population and the last two methods give growth data for i nd i v i - . dual f i s h , or the last one can also be used to provide data to supple-ment the other methods. George and Bannerji (1964) used the f i r s t method to study the age and growth of Rastrelliger kanagurta in India and Hongskul (1972) combined the f i r s t and the third methods to study the population dynamics of R. braohysoma in the Gulf of Thailand. In this study the modal progression method as described by George and Bannerji (1964) was employed. The main d i f f i cu l t y in deter-mining length frequency distributions was caused by the prolonged and fractional spawning season. Another important consideration involves determining the age of f i r s t appearance. To obtain an accurate estimation, larval and juvenile studies must be conducted. Larval collections have been done in India, but did not involve growth and age studies. Growth Model 68 The well known Von B e r t a l a n f f y ' s (1934) model was employed. The method o f f i t t i n g has been d e s c r i b e d by Beverton and Holt (1957), R i c k e r (1958), and o t h e r s . In t h i s study a computer program developed by A l l e n and mo-d i f i e d by Wilimovsky (1972) was used ( F i g u r e 12, 13). The l e n g t h at any time t i s g i v e n by: l t = L (1 - e " K ( t " V ) where: l t the l e n g t h at time t L the asymptotic l e n g t h t h a t i s the v a l u e of 1 assum-ing age i n c r e a s e s i n d e f i n i t e l y K the c o e f f i c i e n t of growth r a t e at which a f i s h approaches i t s maximum le n g t h t the h y p o t h e t i c a l time at which the l e n g t h of a f i s h would have been zero. Von B e r t a l a n f f y growth parameters obtained i n the Indo-Paci-f i c Regions show c o n s i d e r a b l e v a r i a b i l i t y (Table 26). The i n c o n s i s -tency among the e s t i m a t i o n s from v a r i o u s i n v e s t i g a t o r s may p a r t l y d e r i v e from the v a r i a b i l i t y of samples, average modes employed, and probably the o v e r l a p p i n g lengths i n the l a t e ages, as growth s i g n i f i -c a n t l y decreases c r e a t i n g poly-age groups. The l a s t reason may have r e s u l t e d i n an over estimate of the growth r a t e . Hongskul (1972) s t a t e s t h a t those parameters o b t a i n e d from tagging data and modal p r o g r e s s i o n method a n a l y s i s are n e a r l y the same. ITTING OF VON EERTALANFFY GROWTH EQUATION KEM3LNG PEREMPUAN (RASTRELLIGER BRAGHYSOM/ 20.0 , 0.0 0.9 1.8 2.8 3.7 4.6 5.5 6.4 7.3 8.3 9.2 10.1 11.0 (month) F i g u r e 12 Growth Curve of R. braohysoma. Abscissa-age i n months; ord i n a t e - ! e n g t h i n cm. (IBM 1130, CALCOMP 565) FITTING OF VON BERTALANFFY GROWTH EQUATION KEMBUNG LELAKI (RASTRELLIGER KANAGURTA) 22.4 + Figure 13 Growth Curve o f R. kanagurta. Abscissa-age i n months; o r d i n a t e - l e n g t h i n cm. (IBM 1130; CALCOMP 565) 71 TABLE 26 Von B e r t a l a n f f y Growth Parameters o f Rastrelliger from Various Authors and L o c a l i t i e s i n the I n d o - P a c i f i c Region Species A u t h o r - Y e a r - L o c a l i t y K *o (month) L oo (cm) R. kanagurta George and B a n e r j i (1964) - Cochin 0.43 21.77 - C a l i c u t 0.26 23.26 - Karwar 0.36 22.40 Pooled 0.30 22.84 R. kanagurta S u d j a s t a n i (1973) - Java Sea 0.23 0.92 23.89 (0.02) (SE) (.13 SE) (.52 SE) R. negleotus (braahysoma) Hongskul (1972) - the G u l f o f T h a i l a n d 0.28 -0.03 20.91 R. braahysoma S u d j a s t a n i (1973) - Java Sea 0.19 0.10 22.92 (0.02) (SE) (.18 SE) (.76 SE) 72 The estimated parameters of the Von B e r t a l a n f f y model o f from the Java Sea are: R. kanagurta R. braahysoma K *0 L 0.2316 (0.0176 S.E.) 0.9182 (0.1294 S.E.) 23.8886 (0.5186 S.E.) 0.1885 (0.0187 S.E.) 0.0993 (0.1817 S.E.) 22.9170 (0.7638 S.E.) month cm The Poi n t o f I n f l e c t i o n on the Growth Curve T h e o r e t i c a l l y a s t a b i l i z e d f i s h p o p u l a t i o n has i t s maximum y i e l d i n f l u e n c e d by the nature of growth and depends on the r a t e s o f natu r a l and f i s h i n g m o r t a l i t y ( T e s t e r , 1952). As i t i s known t h a t a f i s h has maximum change i n weight at the i n f l e c t i o n p o i n t , then, i t i s necessary to know the p o s i t i o n of the i n f l e c t i o n p o i n t on the growth curve. T e s t e r d e s c r i b e s t h r e e types of growth c u r v e s , the growth curve with the i n f l e c t i o n p o i n t i n the e a r l y of l i f e , about m i d - l i f e , and l a t e i n l i f e . R a t i o n a l management and e x p l o i t a t i o n o f a f i s h s p e c i e s r e q u i r e s knowledge of the i n f l e c t i o n p o i n t p o s i t i o n i n the growth curve p r i m a r i l y i n i t s r e l a t i o n s to the age at sexual m a t u r i t y . Ssentongo (1971) generated a formulae t h a t d e r i v e d from the Von B e r t a l a n f f y ' s growth equation to determine the age a t the i n f l e c t -i o n p o i n t . I t i s : 73 t . n = 1/K In b + t i . p . o where: t . is the age at the inf lect ion point. I • [J • b is the length-weight exponent The inf lect ion point of Rastrelliger kanagurta is at the 5.9 months (17.8 cm TL), whereas for R. braahysoma i t is at 5.7 months (15.1 cm TL). Both species have inf lect ion points early in l i f e , meaning they attain their maximum growth increments before they reach the age at sexual maturity (7.0 and 7.5 months of age for R. kanagurta and R. braahysoma respectively). Thus, the exploitation of the Rastrelliger should be beyond the inf lect ion point to allow suff ic ient spawners (certain age classes). The natural mortality coefficient of the f ish is high, about 0.4, so that kind of exploitation could mean a loss of biomass. However, the results of the Ricker Yield Model suggest that at the present conditions where the age at f i r s t capture ( t £ ) is 3.0 months for R. braahysoma and 4.0 months for R. kanagurta, the exploitation w i l l hot endanger the populations since the stocks exhibit strong 7.0 - 8.0 months age classes (Tables 34, 35 and 36). Behaviour Hardenberg (1938) states that Rastrelliger are pelagic and migrate. Their migration in the Java Sea follows the migration pattern of the scad (Deoapterus spp.) one of their competitors for food, but is generally later by one or two weeks. He describes that at the end of 74 the West Monsoon a stock o f o c e a n i c Rastrelliger i s p r e s e n t . At the beginning o f the East Monsoon the water o f the Java Sea begin to flow i n a w e s t e r l y d i r e c t i o n and the Rastrelliger moves o f f i n a w e s t e r l y d i r e c t i o n and d i s a p p e a r s . A f t e r some weeks a new stock e n t e r s the Java Sea through i t s e a s t e r n entrance. At the end o f the East Monsoon the r e v e r s e happens and two new stocks e n t e r the Java Sea, one from the north west out o f the South China Sea and one from the south west out o f the Indian Ocean. An attempt was made to prove t h i s h y p o t h e s i s . As was d e s c r i b e d i n the previous s e c t i o n , there i s geographical v a r i a t i o n i n R. kanagurta i n head depth and d o r s o v e n t r a l depth. I suspect t h a t these d i f f e r e n c e s suggest t h a t the two samples might come from two d i f f e r e n t p o p u l a t i o n s . Secondly, there are two spawning seasons i n t h i s a r e a , i . e . , from October to February ( i n the West Monsoon) and from June to September ( i n the East Monsoon). Moreover, the c a t c h per u n i t o f e f f o r t and t o t a l e f f o r t r e l a t i o n s h i p ( F i g u r e 14) suggests t h a t there are two d i f f e r e n t p o p u l a t i o n s i n v o l v e d i n one c a l e n d a r y e a r . The f i r s t p o p u l a t i o n was present i n the months o f January, February, March, and reappeared i n September, October, November and December; while the second p o p u l a t i o n was present i n A p r i l , May, June, and J u l y . These evidences support the hypothesis o f Hardenberg (1938). In a d d i t i o n to these m i g r a t i o n s , Rastrelliger appears to e x h i b i t l o c a l movement. Pradhan (1956) w r i t e s t h a t i n Karwar, I n d i a , during a n o r t h - e a s t e r l y wind, R. kanagurta schools e n t e r i n s h o r e waters. Jones and Rosa (1962) s t a t e t h a t s c h o o l s o f t h i s f i s h u s u a l l y move 75 CPUE |-2001 i 1 \ i 1 1 1 5 10 15 20 25 TOTAL (X 1000 ) EFFORT Figure. 14. Relation^between T o t a l E f f o r t (Total Catch/Catch per unit of e f f o r t ) and Catch Per Unit of E f f o r t of R. kanagurta from the north coast of Java, i n 1971 (arable-numbers represented months).-West Monsoon E a s t Monsoon 76 with the c u r r e n t o f water a t high t i d e . When there i s a s t r o n g e a s t e r l y wind the schools come c l o s e to the shore through deeper l a y e r s o f water. The m i g r a t i o n o f R. braahysoma was observed i n Tg. S a t a i a r e a . T h i s f i s h always disappears d u r i n g the months o f May to October. I t seems they migrate to somewhere nearby t h i s area to spawn, s i n c e t h e i r gonads i n A p r i l are mostly mature. The l o c a l movement has a l s o been observed i n the G u l f o f T h a i l a n d area (Hongskul, 1972). The reason f o r t h i s phenomenon i s not y e t c l e a r , but Harden-berg (1955) s t a t e s t h a t t h i s f i s h tends to f o l l o w the h i g h e s t d e n s i t i e s o f p lankton. Age The a b i l i t y to determine the age o f f i s h i s an important t o o l i n f i s h e r i e s b i o l o g y and management. The e v a l u a t i o n o f age a l l o w s one to understand the age composition o f a f i s h p o p u l a t i o n and to determine the r o l e o f p a r t i c u l a r age c l a s s e s i n the f l u c t u a t i o n s . The e x i s t i n g p r i n c i p l e o f age d e t e r m i n a t i o n i s based on the r e c o g n i t i o n o f seasonal changes i n the form and composition o f s k e l e t a l s t r u c t u r e s o r o t h e r hard p a r t s which have been named growth marks o r growth checks. Those marks are a r e s u l t o f f l u c t u a t i o n s i n the growth o f the. f i s h . The ease and accuracy i n a p p l y i n g the p r i n c i p l e depends upon i t s e x i s t e n c e and r e g u l a r i t y . Research on t h i s problem s t a r t e d almost 77 a hundred years ago. R e i b i s c h (1899) was among the e a r l y i n v e s t i g a t o r s t o use o t o l i t h s , Heincke (1904) used bones and Dahl (1909) has d e s c r i b e d the method of age de t e r m i n a t i o n i n d e t a i l . I t i s known t h a t the growth r a t e o f f i s h i s not uniform, even when t h e . e n t i r e l i f e c y c l e takes p l a c e i n an almost steady s t a t e environmental c o n d i t i o n such as t h a t found i n t r o p i c a l waters. There i s a l s o the s o - c a l l e d seasonal v a r i a t i o n i n growth r a t e . This v a r i a t i o n w i l l be expressed i n the hard p a r t s o f the f i s h such t h a t periods o f r a p i d growth w i l l be i n d i c a t e d by wide zones and slow growth by narrow zones. G e n e r a l l y , i n the temperate zone, where i n w i n t e r the growth r a t e i s a t i t s minimum, the f l u c t u a t i n g p e r i o d i c i t y i s annual; whereas i n t r o p i c a l waters i t i s completely d i f f e r e n t . As e a r l y as Hoffbauer's (1898) work on carp s c a l e s , the use o f s c a l e s f o r age det e r m i n a t i o n has depended upon the appearance o f re c o g n i z e a b l e y e a r l y growth r i n g s c a l l e d a n n u l i . A n n u l i have a d i f f e r -ent appearance i n d i f f e r e n t s p e c i e s . In many sp e c i e s f a l s e a n n u l i o r acce s s o r y marks have been observed and sometimes they are d i f f i c u l t to d i s t i n g u i s h from true a n n u l i . Van Oosten (1957) s t a t e s t h a t these f a l s e a n n u l i can be a t t r i b u t e d to growth c e s s a t i o n caused by d i s e a s e , p a r a s i t i s m , i n j u r y , s t a r v a t i o n , o r a temporary drop o r r i s e i n tempera-tu r e or some ot h e r s i m i l a r unfavourable environmental changes. However, the c a u s a t i v e f a c t o r s i n the formation o f these growth checks have not y e t been determined. As has been s t a t e d b e f o r e , s c a l e s and o t o l i t h s w i l l be used f o r age det e r m i n a t i o n . On the s c a l e the f a s t growing zones are represented by wider s c l e r i t e s o r c i r c u l i i and the slow growing zones 78 by narrow scler i tes arranged close together in the form of bands or rings. The l i terature which deals with temperate f ish species describes that these rhythms of growth are seasonal and that there is a close relation between periodic structure of the f ish hard parts and the growth of the f i s h . In several instances those hard parts show the secondary rings or false annuli described above in addition to the normal annual rings. Some doubts have been raised as to the qual i fy -ing characters of an annual and a secondary r ing. This leads to the some uncertain assumptions in the quality of the causative factors that are responsible for the formation of the growth checks of a f ish in tropical waters. The classic theory that growth rate is greater during the period of higher temperature is well known. Cutler (1918) states that temperature was a controll ing factor of sc ler i te width in the scale of Pleuroneotes. A higher temperature produce wider scler i tes correspond-ing to the summer zone and lower temperatures produced narrow scler i tes or the winter zone. Dannevig's (1925) experiments gave the contrary results , that i s , that the sc ler i te width was greater at lower temperature and lower feeding. Dannevig (1925), and Graham (1929) state that there is a marked correlation between sc ler i te width and growth rate caused by an inherent rhythmical response. The narrow zones on the scales and otoliths of cod (Dannevig, 1933) and the transparent zones in the otol iths of hake (Hickling, 1933) have been observed to be found during the last part of the summer and autumn in the majority of the specimens; whereas in several other 79 f i s h e s these growth checks are l a i d down du r i n g the p e r i o d o f lowest temperature. T h i s c o n t r a d i c t i o n i n the r e l a t i o n o f temperatures to the formation o f the annual growth checks throws doubt on the p o s s i b l e i n f l u e n c e o f temperature i n the phenomenon o f p e r i o d i c i t y o f the s t r u c t u r e o f the hard p a r t s o f f i s h (Menon, 1950). Gray and Setna (1931) found t h a t Salmo irideus [S. gaivdnerii) which had been f e d c o n t i n u o u s l y throughout the y e a r d i d not show any well d e f i n e d summer and w i n t e r zones Brown (1946) observed t h a t i n specimens kept under c o n t r o l l e d temperature, food, l i g h t , flow o f water, and amount o f l i v i n g space, composition and a e r a t i o n o f water, the annual p e r i o d i c i t y i s markedly v i s i b l e on the s c a l e s . Fage and V e i l l e t (1938) suggest t h a t the maturation o f gonads was g e n e r a l l y f o l l o w e d by a decrease i n the growth r a t e . Menon (1950) s p e c u l a t e s t h a t an i n h e r e n t p h y s i o l o g i c a l rhythm i s a more probable c a u s a t i v e f a c t o r i n the formation o f the growth checks. Chidambaram e t a l . (1952) s t a t e t h a t there i s a decrease i n the r a t e o f f e e d i n g and the amount o f food consumed d u r i n g the maturation o f gonads. Food i s an important f a c t o r i n the growth o f a f i s h and maturation o f gonads i s a momentous p h y s i o l o g i c a l event i n the growth h i s t o r y o f the animal. The simultaneous occurrence o f reduced f e e d i n g and gonad maturation may p l a y an e f f e c t i v e p a r t i n the p e r i o d i c formation o f the growth checks." Schneider (1910) suggests t h a t the decrease o f f e e d i n g a t the spawning time, a s s o c i a t e d with the d r a i n on the r e s e r v e s to supply m a t e r i a l to the gonads, i s a heavy excess of output over input o f m a t e r i a l s ( i n / H i c k l i n g , 1933). 80 The growth checks s i m i l a r to those found i n temperate f i s h e s have been r e p o r t e d i n the t r o p i c a l f i s h e s by H o r n e l l and Naidu (1924), Devanesan (1943), N a i r (1949) and o t h e r s . However, the v a l i d i t y and i n t e r p r e t a t i o n o f these checks remains u n c e r t a i n . A d e t a i l e d study o f the l i f e h i s t o r y o f the o i l - s a r d i n e (Sardinella longioeps) by H o r n e l l and Naidu (1924) gives i n t e r e s t i n g d e t a i l s on the q u e s t i o n o f the age and growth r a t e o f the f i s h . They s t u d i e d the growth r a t e by s i z e a n a l y s i s and computed the age by Petersen's method i n a d d i t i o n to s c a l e r e a d i n g . T h e i r works l e a d s e v e r a l Indian s c i e n t i s t s to determine age and growth o f Rastrelliger kanagurta. Seshappa (1958) s t a t e s t h a t R. kanagurta g r e a t e r than o r equal to 23 cm TL e x h i b i t c l e a r r i n g s on the s c a l e s . He b e l i e v e s t h a t these are spawning marks, and thus c o u l d be u s e f u l i n age s t u d i e s . Since t h i s f i s h reaches sexual m a t u r i t y a t 20 cm TL (Chidambaram e t a l . , 1946) or a t 22.4 cm TL (Pradhan, 1956) there i s no reason why the r i n g s only e x i s t a t s i z e 23 cm or above i f the causal f a c t o r i s spawning. More s t u d i e s must be conducted to decide whether those r i n g s are u s e f u l f o r age d e t e r m i n a t i o n o f t h i s f i s h . In g e n e r a l , the a b s o l u t e age determina-t i o n o f t r o p i c a l s p e c i e s has not y e t proven to be s u c c e s s f u l . A review o f the l i t e r a t u r e suggests t h a t not enough work has been done on the p h y s i o l o g i c a l f a c t o r s r e s p o n s i b l e f o r the formation o f growth r i n g s . At p r e s e n t , very l i t t l e i s known o f the b a s i c chemistry and h i s t o l o g y o f t h i s phenomenon. As has been s t a t e d above i t i s not y e t p o s s i b l e to determine the a b s o l u t e age o f t r o p i c a l s p e c i e s , i . e . , Rastrelliger, using the 81 growth checks. In s p i t e o f the i n a c c u r a c y , the s t a t i s t i c a l method demonstrated by Petersen (1891) and others remains the best technique to o b t a i n the r e l a t i v e o r the s t a t i s t i c a l age o f t h i s f i s h . T h i s method has been observed to be s a t i s f a c t o r y f o r f i s h e r i e s work i n v o l v -ing lower age c l a s s e s p r o v i d e d there are r e l a t i v e l y l a r g e samples. In t h i s study the s t a t i s t i c a l age o f Rastrelliger was d e t e r -mined by the modal p r o g r e s s i o n method as d e s c r i b e d by George and Ban n e r j i (1964). By f o l l o w i n g , f o r s e v e r a l seasons, the modal p r o g r e s s i o n o f the average length from the time o f f i r s t appearance i n the f i s h e r y , von B e r t a l a n f f y growth parameters can be estimated and the age-length key can be generated. Rastrelliger kanagurta e x h i b i t the f o l l o w i n g c h a r a c t e r i s t i c s : 1. the length frequency d i s t r i b u t i o n data i n d i c a t e s t h a t a mode o f 14.5 cm appeared i n June and mode o f 14.0 cm appeared i n November ( F i g u r e 16); 2. the m a t u r i t y stages data show t h a t the l a r g e s t percentage o f s e x u a l l y mature i n d i v i d u a l s was found i n January and May (F i g u r e 10) ; these data suggest t h a t the 14.5 cm mode which appeared i n June and the 14.0 cm mode which appeared i n November must r e p r e s e n t the broods t h a t hatched i n about February and June r e s p e c t i v e l y . T h e r e f o r e , the R. kanagurta o f 14.0 - 14.5 cm le n g t h are about 5 months o l d . 82 R. braahysoma: 1. the l e n g t h frequency d i s t r i b u t i o n data o f November e x h i b i t modes o f 10, 11, 12, and 16 cm ( F i g u r e 15); 2. the m a t u r i t y stages data o f March and A p r i l i n d i c a t e mostly s e x u a l l y mature where 100% o f i n d i v i d u a l s were found i n mature gonad c o n d i t i o n s ( F i g u r e 11); 3. t h i s f i s h always disappears i n May and reappears a t the end o f October and i s never caught during t h i s i n t e r v a l ( i n Tg. S a t a i ) These evidences suggest t h a t the polymodal p o p u l a t i o n was a r e s u l t o f a prolonged spawning season t h a t l a s t s from May to September. T h e r e f o r e , the s m a l l e s t mode must come from the l a t e s t hatched brood, v i z . , the 10 cm R. braahysoma has to be 3 months o l d . The Von B e r t a l a n f f y growth parameters from both s p e c i e s have been d e s c r i b e d i n the previous s e c t i o n . By employing those parameters and u s i n g the age-length formulae d e r i v e d from the Von B e r t a l a n f f y e q u a t i o n a s : t = 1/K ( -In (1 - l t / L ) ) + t Q the age length key can be generated (Tables 27 and 28). The r e s u l t s f o r R. kanagurta i n d i c a t e t h a t the c a l c u l a t e d lengths have h i g h e r value than the observed modes i n younger groups but are approximately equal i n oTder age groups. In R. braahysoma, however, a very s l i g h t d i f f e r e n c e e x i s t s . 83 Age and S i z e Composition E. kanagurta o f 10 months age c l a s s (21 cm TL) were dominant i n the 1972 catch (Table 39 j_n Appendices). The f i s h o l d e r than 18 months (23 cm TL) were r a r e l y r e p r e s e n t e d . The range o f the samples was from 4 - 2 4 months o f age (12.5 - 23.5 cm T L ) ; g e n e r a l l y the commercial catch i s from 6 to 12 months o l d (17.0 - 22.5 cm T L ) . George and B a n n e r j i (1964) s t a t e s t h a t the commerical f i s h e r i e s f o r t h i s f i s h i n India depend mainly on f i s h ranging i n s i z e from 18 -22 cm TL, i . e . , the f i s h which are i n the 0-year completing i t s f i r s t y e a r o f l i f e through the f i s h e r y . Manacop (1955) s t a t e s t h a t R. kanagurta caught i n the P h i l i p p i n e has an average l e n g t h o f about 25 cm. D r u z h i n i n (1968) recorded the f i s h caught i n Burma waters con-s i s t s mainly o f 19.1 - 21.0 cm FL ( o r 21.2 - 23.3 cm TL, converted; whereas D r u z h i n i n and Myint (1968) recorded a range o f 15.6 - 22.5 cm FL ( o r 17.3 - 25.0 cm TL, converted) i n t h e i r samples i n the same a r e a , Mergui Arch., Burma. In t h i s study E. braahysoma o f the 9 months age c l a s s (18.5 cm TL) were dominant i n 1971/1972 c a t c h ; f i s h o l d e r than 18.0 months o f age (22 cm TL) were r a r e l y caught (Table 38 j_n Appendices). The range of the samples was from 4"- 21 months of age ( 10.0 - 22.5 cm TL ); but g e n e r a l l y the f i s h i n the commercial c a t c h range from 7 to 12 months o l d (17.0 - 20.0 cm T L ) . Hongskul (1972) observed a range o f 10.0 - 23.0 cm TL i n the G u l f o f T h a i l a n d f i s h e r y ; however, the f i s h caught were g e n e r a l l y w i t h i n the 14.0 - 22.0 cm TL range. Manacop (1955) recorded an average 84 TABLE 27 Age-Length-Weight Key o f B. kanagurta from the Java Sea Age (Month) Computed Length (cm) Observed Mode (cm) Computed Weight (g) 1 4.93 - .99 2 8.85 - 6.39 3 11.96 - 16.71 4 14.43 - 30.43 5 16.38 14.5 45.60 6 17.93 16.8 60.87 7 19.16 18.2 75.23 8 20.14 19.3 88.22 9 20.91 20.8 99.45 10 21.53 21.2 109.17 11 22.02 21.6 117.30 12 22.41 22.0 124.07 18 23.52 - 144.77 24 23.79 - 150.15 36 23.88 - 151.97 85 TABLE 28 Age-Length-Weight Key o f R. braohysoma from Tg. S a t a i Age (Month) Computed Length (cm) Observed Mode (cm) Computed Weight (9) 1 3.93 _ 1.33 2 7.19 - 7.56 3 9.89 10.0 18.94 4 12.13 12.0 34.09 5 13.98 13.5 51.31 6 15.52 15.7 69.97 7 16.79 16.3 86.95 8 17.84 17.9 103.55 9 18.71 18.5 118.76 10 19.44 19.5 132.60 11 20.03 20.0 144.53 12 20.53 - 155.16 18 22.15 - 193.10 24 22.67 - -36 22.89 - -F i g u r e 15. Length-Frequency D i s t r i b u t i o n of R. braohysoma from Tg. S a t a i i n the 1971/1972 f i s h i n g season. 87 2a. a. 40 20-o -•40.. 20-• a. 4 0 - -20-Q. 40-20 a. 40-20-0 H 1 1 1-0ct.71 Nov\71 / \ Dec,71 Jan.72 Feb.72 \ Mar. & Apr.72 I t 16 18 20 $2 tk H 1 1 l -May.72 Jun.72 Jul.72 Aug.72 Sep.72 Oct.72 — i 1 1— -—i \ i — i 1 4 1 6 1 8 2 0 2 2 2 4 TL( cm Figure 16 Length-Frequency D i s t r i b u t i o n of R, kanpgurtn from the north copst of J P V B in the 1 9 7 1 - 1 Q 7 2 f i s h i n g sepson. 88 o f about 18.0 cm TL i n the P h i l i p p i n e s waters and Dr u z h i n i n (1968) recorded a dominant group o f 18.1 to 21.0 cm FL (20.3 - 23.6 cm TL, converted) i n Burma waters. In the same l o c a t i o n D r u z h i n i n and Myint (1968) recorded a range o f 16.6 - 22.0 cm FL (18.6 - 24.7 cm TL, con-v e r t e d ) i n t h e i r samples. The above data suggest t h a t the Rastrelliger f i s h e r i e s i n the I n d o - P a c i f i c Regions a l l i n v o l v e the same s i z e range o f f i s h and i t can thus be concluded that these f i s h e r i e s depend on a s i n g l e y e a r c l a s s , i . e . , one y e a r o l d s . Age and S i z e a t F i r s t Capture The age and s i z e a t f i r s t capture o f R. kanagurta was 4 months o f age (12.5 cm TL) and f o r R. braohysoma i t was 3 months o l d (10.0 cm TL) ( F i g u r e 15, 16). ' Jones and Rosa (1962) s t a t e t h a t the s m a l l e s t dominant group was 12.0 cm TL f o r R. kanagurta i n I n d i a ; w h i l e Hongskul (1972) uses age a t f i r s t capture 4 months as a parameter i n h i s study o f R. braohysoma p o p u l a t i o n dynamics i n the G u l f o f T h a i l a n d . No o t h e r r e c o r d o f t h i s parameter i s a v a i l a b l e i n the I n d o - P a c i f i c Regions. Age and S i z e a t M a t u r i t y The importance o f t h i s parameter i s r e l a t e d to the need f o r adequate spawning stock to assure a continued supply o f young. The d i s c u s s i o n has been conducted on pages 59 and 71. 89 Maximum Age and S i z e In t h i s study the maximum length o f R. kanagurta was 23.89 cm TL (0.52 cm S.E.) and f o r R. braohysoma i t was 22.92 cm TL (0.76 cm S.E.). Both being over 3 years o f age (Table 26, 27, 28). Comparison w i t h i n the I n d o - P a c i f i c Regions were d e s c r i b e d i n the previous s e c t i o n . The Length-Weight R e l a t i o n s h i p In f i s h e s the length and weight r e l a t i o n s h i p can be adequately represented by: W = a L b where b i s an exponent with a value between 2 and 4. I f b = 3.0 i t i n d i c a t e s isometric growth, w h i l e b values o t h e r than 3.0 are i n d i c a t i v e o f a l l o m e t r i c growth. The length-weight r e l a t i o n s h i p o f R. kanagurta was determined s e p a r a t e l y f o r males and females, s e x u a l l y mature, immature and u n d i f f e r -e n t i a t e d . The t o t a l length TL o f samples ranged from 10.0 to 22.5 cm. The b values o b t a i n e d are l i s t e d i n Tables 29 and 30. Comparisons w i t h i n the I n d o - P a c i f i c Regions, i . e . , Indian waters and the G u l f o f T h a i l a n d show t h a t the b values o f t h i s f i s h from the Java Sea area are lower. I t i s w e l l known t h a t t h i s c o e f f i c i e n t d i f f e r s between s p e c i e s and a l s o o f t e n d i f f e r between p o p u l a t i o n w i t h i n s p e c i e s . The d i f f e r e n c e s TABLE 29 The Length-Weight E x p o n e n t i a l (b) Value of R. kanagurta from the Java Sea I d e n t i f i c a t i o n B V a r i a n c e a (In) Variance (In) ANC0VA (the S i g n i f i -cance o f F Value) Male Female 3.134 3.013 0.0068 0.0072 -12.15 -11.49 0.1930 0.0332 F(c.v.) = -F(b) = -F(a) = * Sex U n i d e n t i f i e d Sex Immature (mixed) 3.175 3.189 0.0013 0.0062 -12.38 -12.44 0.0332 0.1776 F(c.v.) = -F(b) = -F(a) = -Sex U n i d e n t i f i e d Sex Mature (mixed) 3.175 3.010 0.0013 0.0037 -12.38 -11.48 0.0332 0.1063 F(c.v.) = -F(b) = * F(a) = ** Female, M a t u r i t y Stage < I I I Female, M a t u r i t y Stage > I I I 2.933 3.078 0.0073 0.0687 -11.08 -11.82 0.2084 0.0199 F(c.v.) = -F(b) = -F(a) = ** A l l Mixed o f R. kanagurta 3.193 0.0004 -12.46 0.0106 A l l Mixed o f R. braahysoma 2.880 0.1266 -10.29 0.3325 Note: * i s 5% l e v e l o f s i g n i f i c a n c e . ** i s 1% l e v e l o f s i g n i f i c a n c e . ^ o TABLE 30 The Length-Weight Exp o n e n t i a l (b) Values from Various Author i n the Indo P a c i f i c Region o f the Rastreliger I d e n t i f i c a t i o n Author (Year) b Variance a V a r i a n c e R. kanagurta: Male Female Rao, K.V.N., (1962) W a l t a i r , I n d i a 3.2628 3.2785 - .004983 .004874 -R. kanagurta: Pradhan, L.B., (1956) Karwar, I n d i a 3.1737 - .005978 R. kanagurta: Male Female V a n i c h k u l , P. and V. Hongskul (1963), G u l f o f T h a i l a n d 3.7633 3.0375 - -6.7081 (log ) -5.0244 (log) -R. neglectus Male Female V a n i c h k u l , P. and V. Hongskul (1963), G u l f o f T h a i l a n d 3.1463 3.1235 - -5.2417 (log ) -5.1819 (log) -| R. braohysoma Jones and S i l a s (1962) Andaman I s . , I n d i a 3.5779 - -6.0421 -R. kanagurta Jones and S i l a s (1962) Andaman I s . , I n d i a 3.3087 - 5.5390 ( l o g ) -vo 92 may be due to sex, m a t u r i t y and season. Vaznetsov (1953) s t a t e s t h a t during development f i s h pass through s e v e r a l s t a n z a s , each o f which may have i t s own b value. Tesch (1968) s t a t e s t h a t w i t h i n any stanza the b value w i l l o f t e n be n e a r l y constant throughout the y e a r or throughout a s e r i e s o f d i f f e r e n t environments, whereas the a_ value w i l l vary s e a s o n a l l y , and between h a b i t a t s . The a n a l y s i s o f c o v a r i a n c e i n d i c a t e s t h a t b d i f f e r s s i g n i -f i c a n t l y ( 5 % ) , i n R. kanagurta, between s e x u a l l y - u n i d e n t i f i e d and sex-u a l l y - i d e n t i f i e d (mixed) specimens (Table 29). There i s no d i f f e r e n c e o f b values due to sex or sexual m a t u r i t y stages. The c o e f f i c i e n t a_, by c o n t r a s t , show s i g n i f i c a n t d i f f e r e n c e s due to the above evidences (Table 29). These two c o n d i t i o n s suggest t h a t the f i s h e x h i b i t s at l e a s t two stanzas during i t s l i f e ; the f i r s t i s w h i l e i t i s young and s e x u a l l y u n d i f f e r e n t i a t e d . The second stanza begins as soon as i t s sex can be i d e n t i f i e d which i s probably a few months before i t reaches m a t u r i t y . In many s p e c i e s s e v e r a l stanzas are completed during embryonic and l a r v a l l i f e , and a l l subsequent growth comprises a s i n g l e s t a n z a (Tesch, 1968). Hecht (1916) s t a t e s that i n f i s h the body form i s l a i d down very e a r l y i n l i f e and i s maintained w i t h i n narrow l i m i t s throughout the p e r i o d o f growth, and thus has uniform but indeterminate growth. Ssentongo (1971) says t h a t t h i s kind of growth a p p l i e s o n l y to e x t e r n a l s u r f a c e s f o r K e l l i c o t (1908) shows t h a t i n a dog f i s h the b r a i n and v i s c e r a d i f f e r i n t h e i r growth r a t e s i n much the same way as i n h i g h e r v e r t e b r a t e s . To obey Hecht 1s law Ssentongo s t a t e s t h a t the b 93 value should be w i t h i n a 2.5 - 3.5 l i m i t , otherwise the b value cannot apply over a wide range o f l e n g t h without causing profound changes i n body form. Furthermore, he suspects t h a t these values came from b i a s e d samples. Recrui tment Recruitment i s g e n e r a l l y d e f i n e d as the number o f f i s h o f a s i n g l e y e a r group e n t e r i n g the e x p l o i t a b l e phase o f a s t o c k , o r , as the number o f f i s h o f a s i n g l e y e a r group a r r i v i n g on a f i s h i n g grounds. I t i s important i n f i s h e r i e s management as an index o f abundance t h a t i s used f o r p r e d i c t i o n , and has been d i s c u s s e d i n d e t a i l by R i c k e r (1954 , 1958), Beverton and H o l t (1957), Gushing (1973), and o t h e r s . ' 1 Recruitment i n Rastrelliger has not y e t been s t u d i e d . Whether i t occurs e a r l y o r l a t e i n l i f e i s determined by the r e l a t i v e p r o x i m i t y of the nursery grounds to the f i s h i n g grounds. T h i s r e l a t i o n s h i p i s not y e t understood. However, to determine the age a t r e c r u i t m e n t ( t r ) the most d i r e c t i n f o r m a t i o n a v a i l a b l e i s t h a t obtained from l a n d i n g samples. The estimated t w i l l not be h i g h e r than the t r u e v a l u e , s i n c e r e j e c t i o n o f the s m a l l e s t f i s h w i l l not o c c u r . T h i s i s caused by the nature o f the market and f i s h e r i e s systems i n the a r e a , where n e i t h e r mesh s i z e nor l e g a l f i s h s i z e r e g u l a t i o n s e x i s t , and a l l s i z e s o f f i s h are marketable. The data suggest t h a t the t f o r R. braahysoma was 3.0 months o f age (10.0 cm TL) and f o r R. kanagurta was 4.0 months o f age (12.5 cm TL) ( F i g u r e 15, 16). 9 4 The change in recruitment seems to exert more influence than does f ishing pressure on stock fluctuations of Rastrelliger as this fishery depends on a single 0-year class. The stock recruitment relationship which is necessary to relate the abundance of pre-recruit phase to age class strength is not yet established. Therefore, the increase in fishing intensity should be conducted cautiously. Survival Rates The method of a single catch curve analysis as described by Robson and Chapman (1961) was employed (Figures 17 and 18; Table 31 and 32). This method has been shown by Bayl i f f (1966) to be better in estimating this parameter than other methods. The survival rates of R. kanagurta for three different fishing seasons were calculated in monthly periods. In West Monsoon 1971 the survival rate was 0.3348 (variance = 0.0010); in the East Monsoon 1972 was 0.7154 (variance = 0.0020), and in the West Monsoon 1972 was 0.3540 (variance = 0.0020). A marked difference between the survival rates in the West and East Monsoon suggests that they are two different populations, which again supports Hardenberg's hypothesis (1938). Assuming that the fishing and natural mortalities are constant, then there was an increase in the recruitment of 5.47% in the 1972 West Monsoon's population. The survival rate of R. braahysoma from Tg. Satai in 1972 fishing season was 0.4411 (variance = 0.0002). Hongskul (1972 reported that the average of the instantaneous 95 TABLE 31 E s t i m a t i o n o f S u r v i v a l Rates o f R. kanagurta i n the Java Sea by the Method o f Robson and Chapman (1961) 1. November 1971 Age-Month Frequency Coded Age C a l c u l a t i o n 7 8 . - - T = 10+2(7)+3(2) = 30 n = 41+10+7+2 = 60 m = 2 9 18 - s = T - 3 0 = 0 34 5 n-m+T 60-2+30 10 41 0 11 12 10 7 I II v a r i a n c e = s^" s^ = 0.0026 n ( l - s 3 ) 18+ 2 I I I 2. December 1971 Age-Month Frequency Coded Age C a l c u l a t i o n 7 8 18 - T = 14+2(5)+3(2) = 30 n = 51+14+5+2 = 72 m = 2 9 36 - „ _ 30 _ n ~n 72-2+30 10 51 0 11 12 14 5 I II v a r i a n c e = • 3 0 ^ " , 3 ^ 2 = 0.0021 72(1-.30^) 18+ 2 III 96 TABLE 32 E s t i m a t i o n o f S u r v i v a l Rate o f R. braohysoma i n Tg. S a t a i Area (1972) Age (Month) Frequency Coded Age C a l c u l a t i o n 9 450 0 T = 786 10 327 I n = 998 11 206 II m = 2 12 13 III s = 0.44 18+ 2 IV v a r i a n c e = 0.0002 0.8185 0.5589 I 1 1 1 1 1 1 1 1 1 1 1 1 1 K 5 6 7 8 9 10 11 12 H 16 18 AGE Figure 17. Catch curves f o r R. kanagurta of the n o r t h coast of Java, A. West Monsoon 1971; B. Ea s t -Monsoon 1972: C. West Monsoon 1972. A b s c i s s a -age l n months; o r d i n a t e - l o g a r i t h m o f the %-frequency. 98 l n %f 3 f 2+ It 01 -14-k 5 6 7 8 9 10 11 12 14 16 18 AGE Figure. 18. Catch curve for R. brachysoma of Tg. Satai i n 1971-1972 f i s h i n g season. Abscissa- age i n months; ordinate- logarithm of the % -frequency. 99 t o t a l m o r t a l i t y (Z) d u r i n g 1962-1968 o f R. braohysoma i n the G u l f of T h a i l a n d v a r i e d between 0.7028 - 1.3470, with an average value o f 1.0124 along the western c o a s t and the i n n e r G u l f ) . Assuming the n a t u r a l m o r t a l i t y r a t e s o f t h i s s p e c i e s i s equal then the lower instantaneous m o r t a l i t y (Z = 0.8185) i n the Tg. S a t a i area i s probably due to a much lower f i s h i n g p r e s s u r e as compared with the G u l f o f T h a i l a n d . M o r t a l i t i e s There are a number o f approaches t h a t can be taken to estimate m o r t a l i t y o f e x p l o i t e d f i s h populations.. Tagging o f f i s h and subsequent r e c a p t u r e s i s the best f i e l d technique t h a t can be employed i n the c a l c u l a t i o n o f m o r t a l i t i e s and o t h e r p o p u l a t i o n parameters. M o n i t o r i n g o f the c a t c h and f i s h i n g e f f o r t i s another u s e f u l technique s i n c e catch per u n i t o f e f f o r t i s approximately p r o p o r t i o n a t e to stock abundance. T o t a l m o r t a l i t y can a l s o be i n f e r r e d from the age compositions o f the c a t c h . T h i s approach was employed i n t h i s study by u t i l i z i n g the method d e s c r i b e d by Robson and Chapman (1961). The s e p a r a t i o n o f t o t a l m o r t a l i t y i n t o i t s components, nature and f i s h i n g m o r t a l i t i e s , i s d i f f i c u l t i f f i s h i n g r e p r e s e n t s o n l y a small f r a c t i o n o f the t o t a l m o r t a l i t y (Cushing, 1968). Assuming t h a t n a t u r a l m o r t a l i t y o f R. kanagurta i s c o n s t a n t throughout the y e a r , Gull and's (1969) method can be used to estimate these parameters (Table 33). He s t a t e s t h a t i f the amount o f f i s h i n g 100 TABLE 33 Estimates o f M o r t a l i t i e s o f R. kanagurta by the Method o f Gu l l a n d (1969) November 1971 December 1971 s = 0.34 = 0.30 i = 1.0789 ( o r Z) = 1.2040 f = 5,853 ( t o t a l e f f o r t ) = 6,923 Gulland's e q u a t i o n Z = q f + M 1.0789 = q x 5,853 + M 1.2040 = q x 6,923 + M then: q = 0 00012 M = 0 37 ( n a t u r a l m o r t a l i t y ) f i s h i n g m o r t a l i t y = 0.70 f i s h i n g m o r t a l i t y = 0.83 101 changes t h i s w i l l r e s u l t i n a change i n t o t a l m o r t a l i t y . He shows t h a t p l o t t i n g estimated t o t a l m o r t a l i t y Z a g a i n s t f i s h i n g e f f o r t ( f ) values y i e l d s a s t r a i g h t l i n e with a slope q(= the c o e f f i c i e n t o f c a t c h a b i l i t y ) , and an i n t e r c e p t M on the y - a x i s . The e s t i m a t e d s u r v i v a l r a t e o f R. kanagurta i n November 1971 was 0.34 (rounded v a l u e ; v a r i a n c e = 0.0026) gives an instantaneous t o t a l m o r t a l i t y Z o f 1.08. In December 1971 i t was 0.30 (rounded v a l u e ; v a r i a n c e = 0.0021) with a corresponding Z of 1.20. The t o t a l e f f o r t f (= t o t a l c a t c h d i v i d e d by c a t c h per u n i t o f e f f o r t ) were 5,853 and 6,923 u n i t e f f o r t s f o r November 1971 and December 1971 r e s p e c t i v e l y ( T a b l e 41 i n Appendices). By employing G u l l and's method d e s c r i b e d above, those data o f R. kanagurta g i v e an estimate o f q = 0.00012, F = 0.70 i n November 1971 and F = 0.83 i n December 1971, and an instantaneous n a t u r a l m o r t a l i t y M of 0.37. The n a t u r a l m o r t a l i t y and growth r a t i o (M/K) o f R. kanagurta o f the Java Sea then was 1.6. B a n n e r j i (1970) suggests t h a t t h i s r a t i o f o r R. kanagurta p o p u l a t i o n i n the e a s t e r n c o a s t o f India ranged from 1.5 to 2.5 (with v a r i o u s values o f K and an estimated value o f M = 0.65). The M/K value o f t h i s f i s h from the Java Sea compared f a v o u r a b l y with the M/K values obtained by Bannerji i n Indian waters. Hongskul (1972) estimates the M/K r a t i o f o r R. braohysoma i n the G u l f o f T h a i l a n d to be 2.0. I f the R. braohysoma p o p u l a t i o n from Tg. S a t a i has the same M/K value as i n the G u l f o f T h a i l a n d , the n a t u r a l m o r t a l i t y M and f i s h i n g m o r t a l i t y F values w i l l be 0.38 and 0.44 r e s p e c t i v e l y (K was 0.19; and Z was 0.82). 102 These estimated parameters w i l l be used l a t e r i n p o p u l a t i o n dynamics s t u d i e s . Dynamics o f P o p u l a t i o n s The r e s u l t s obtained as mentioned i n the previous s e c t i o n s i n d i c a t e the c h a r a c t e r i s t i c s o f the Rastrelliger p o p u l a t i o n s i n the Java Sea. They possess high values o f growth and n a t u r a l m o r t a l i t y r a t e s . The stock r e c r u i t m e n t r e l a t i o n s h i p cannot be determined i n t h i s study, thus o n l y the y i e l d per r e c r u i t model has been used. The model i s based on the assumption t h a t c a t c h obtained from a y e a r c l a s s throughout i t s f i s h a b l e l i f e span i s p r o p o r t i o n a l to i t s i n i t i a l numbers when r e c r u i t e d . Beverton and H o l t (1957) have d e r i v e d a y i e l d model t h a t i s very u s e f u l f o r e v a l u a t i n g the p o t e n t i a l y i e l d o f a f i s h e r y . T h e i r equation i s : Beverton and H o l t Y i e l d Model Y/R = FW e-^W 3 Z n=0 ; - n K ( t c - t 0 ) ,-(F+M+nK)(t x-t c) (1-e F+M+nK The b a s i c assumption i s t h a t growth i s i s o m e t r i c . Y y i e l d i n weight, R number o f r e c r u i t s e n t e r i n g the f i s h e r y a t age t maximum weight o f an i n d i v i d u a l f i s h , W oo h y p o t h e t i c a l age of zero l e n g t h , o r t p i s age a t time o f r e c r u i t m e n t , o r t p , i s age a t f i r s t c a p t u r e , age o f e x i t from the f i s h e r y , 103 K the Von B e r t a l a n f f y growth parameter, U i s 1,-3, 3, and -1 f o r n = 0, 1 , 2 , and 3 r e s p e c t i v e l y . I t i s well accepted t h a t the growth o f many f i s h i s not i s o m e t r i c . For such growth the c a l c u l a t i o n o f y i e l d can be conducted by u s i n g the Incomplete Beta F u n c t i o n t h a t was d e s c r i b e d by Jones (1957) and the equation was expressed by Wilimovsky and Wicklund (1963) as: Y = F/K R W e 2 ^ " ^ ) { [x, P, Q]-[X r P, Q] } where: Z instantaneous t o t a l m o r t a l i t y , X e ~ K ( t c - t 0 ) X i e - K ( t - t 0 ) P Z/K Q 1 + b; b i s the length-weight exponent. Wilimovsky and Wicklund (1963) prepared a t a b l e f o r t h i s f u n c t i o n . Employing the Beverton and H o l t (1957) model, the y i e l d s were c a l c u l a t e d and i s o p l e t h diagrams were c o n s t r u c t e d ( F i g u r e s 19, 20, 21, 22 and 24). R. kanagurta: tn = 0.92 months, o t r = 4.0 months, t = 4.0 months, t = 18.7 months, K = 0.2316 Wm = 152.0 grams 104 R. braohysoma: t Q = 0.10 months t = 3.0 months r t = 3.0 months t = 21.3 months K = 0.1887 = 213.0 grams. The model was simulated with v a r i o u s parameter v a l u e s , the f i s h i n g m o r t a l i t y F ranged from 0.1 to 1.5 with 0.1 increments; the n a t u r a l m o r t a l i t y M ranged from 0.1 to 1.0 with 0.1 increments; and t from 4.0 months f o r R. kanagurta and 3.0 months f o r R. braohysoma to 12.0 months with one month increments. D e t a i l e d d i s c u s s i o n on the concept o f y i e l d models have been given by Beverton and H o l t (1957), R i c k e r (1958), S c h a e f e r and Beverton (1963), Gulland (1969), and o t h e r s . In an e x p l o i t e d f i s h p o p u l a t i o n the f i s h are r e c r u i t e d to the f i s h e r y a t age t but are not caught u n t i l the age a t f i r s t c a p t u r e , t . In Rastrelliger f i s h e r i e s i n the Java Sea, where t h e r e i s no f i s h i n g r e g u l a t i o n such as l e g a l mesh o r f i s h s i z e , the t i s equal to t . T h i s c o n d i t i o n o f the f i s h e r y i s named a "knife-edge" f i s h e r y . Observation on y i e l d o f R. kanagurta as r e v e a l e d by the i s o p l e t h diagrams are given below ( F i g u r e s 19, 20 and 21). The g r e a t e s t y i e l d o f R. kanagurta can be ob t a i n e d i f the s i z e o f f i r s t capture i s 15.5 cm TL with a f i s h i n g m o r t a l i t y o f 1.4 105 (the n a t u r a l m o r t a l i t y was 0.4). The y i e l d i n weight per r e c r u i t i n t h i s c o n d i t i o n i s 22.4 g; and a t pr e s e n t where the f i s h i n g m o r t a l i t y i s 0.8, the y i e l d i n weight per r e c r u i t i s 21.5 g. The age a t f i r s t capture a t present i s 4.0 months (with F = 0.8) and the y i e l d per r e c r u i t i s 21.3 g. The f i s h i n g i n t e n s i t y can be i n c r e a s e d without a f f e c t i n g the f i s h e r y u n t i l the maximum y i e l d per r e c r u i t i s reached a t a f i s h i n g m o r t a l i t y o f 1.3. T h i s means th a t a t maximum f i s h i n g p r e s s u r e , the i n c r e a s e o f 62.5% f i s h i n g m o r t a l i t y w i l l cause the y i e l d per r e c r u i t to i n c r e a s e by 1.6%. A g r e a t e r i n c r e a s e o f f i s h i n g m o r t a l i t y or f i s h i n g pressure o f 75% t h a t g i v e s a y i e l d per r e c r u i t i n c r e a s e o f 4.2% can be achieved i f the f i s h e r y s t a r t e d to ca t c h the f i s h a t 15.5 cm TL (or 4.5 months o f age). An estimated n a t u r a l m o r t a l i t y o f 0.38 and f i s h i n g m o r t a l i t y o f 0.44 (see the previous s e c t i o n ) were employed i n c o n s t r u c t i n g the i s o p l e t h diagram o f R.. braahysoma o f Tg. S a t a i ( F i g u r e s 22, 23 and 24). Under the present c o n d i t i o n where the f i s h i n g m o r t a l i t y i s 0.44, the n a t u r a l m o r t a l i t y i s 0.38 and the s i z e a t f i r s t capture i s 10.0 cm TL, the y i e l d i n weight per r e c r u i t i s 18.0 g. The h i g h e s t y i e l d per r e c r u i t o f 20.8 g can be obtained i f the length o f f i r s t capture i s 12.0 cm TL and the f i s h i n g m o r t a l i t y i s 1.5. The f i s h i n g pressure can be doubled without harming the stock s i n c e R. braahysoma has an asymptotic y i e l d per r e c r u i t to f i s h i n g m o r t a l i t y r e l a t i o n s h i p diagram f o r n a t u r a l m o r t a l i t y g r e a t e r than 0.4. Under t h i s c o n d i t i o n the y i e l d per r e c r u i t w i l l gain an i n c r e a s e o f on l y 15.6%. 106 I 1 1 1 1 1 1 > 1 1— 1 1 1 1 )—— .1 .2 .3 .4 .5 .6 .7 .8 .91.0 .1 .2 .3 .4 .5 F F i g u r e 19. Y i e l d i s o p l e t h diagram of R. kanagurta. Y i e l d i n weight per r e c r u i t (Y w/R) was at an i n t e r v a l s o f 2 grams; natu r a l m o r t a l -i t y (M) was 0.4, t c = 4.0 months. The f i s h i n g m o r t a l i t y F = 0.8 was i n 1971. 1 1 1 1 1 1 1 1 —| 1-- 1 * 2 « 3 '«5 .6 .7 .8 .9 1.0' .1 .2 .3 .4 .5 F F i g u r e 20. Y i e l d per r e c r u i t as a f u n c t i o n of f i s h i n g m o r t a l i t y of R. kana-gurta. The n a t u r a l m o r t a l i t y M range from 0.05 to 1.0; t = t = 4.0 months. The f i s h i n g m o r t a l i t y F = 0.8 was i n 1971. c r F i g u r e 21. Y i e l d per r e c r u i t as a f u n c t i o n of f i s h i n g m o r t a l i t y of R. kana-gurta; the nat u r a l m o r t a l i t y (M) range from 0 . 0 5 - 1 . 0 : t = 4 5 and t = 4.0 months. c 109 I 1 1 1 1 1 1 : i 1 1 1 1 1 1 1 -I 1 .2 .3 .4 .5 .6 .7 .8 .9 1.0 .1 .2 .3 .4 .5 F Figure 22. Yield isopleth diagram of E. bvachysoma. Yield in weight per recruit (Yw/R) at an interval of 1.0 gram. The natural mortal i ty (M) = 0.4 and the age at f i r s t capture t = 3.0 months. F i g u r e 23. Y i e l d per r e c r u i t as a f u n c t i o n of f i s h i n g m o r t a l i t y (F) o f R„. braahysoma from Tg. S a t a i ; with t = 3.0 and t = 3.0 months, the n a t u r a l m o r t a l i t y (M) ranged from 0.1 to 1.0: F i g u r e 24. Y i e l d per r e c r u i t as a f u n c t i o n of f i s h i n g m o r t a l i t y of R. braahysoma. The natu r a l m o r t a l i t y M range from 0.1 to 1.0; t = 4.0 and t = 3.0 months. 1 1 2 As has been s t a t e d above, the h i g h e s t y i e l d per r e c r u i t i n c r e a s e can be o b t a i n e d by i n c r e a s i n g the s i z e a t f i r s t capture from 1 0 . 0 cm to 1 2 . 0 cm TL. However, s i n c e the e s t i m a t i o n o f parameters were drawn from the H. braahysoma s i t u a t i o n i n the G u l f o f T h a i l a n d (Hongskul, 1 9 7 2 ) , these p r e d i c t i o n s need v e r i f i c a t i o n with o r i g i n a l data from these a r e a s . The Incomplete Beta F u n c t i o n gives unbiased y i e l d e s t imates f o r f i s h with a l l o m e t r i c growth. I t was d e s c r i b e d by Jones ( 1 9 5 7 ) and an e q u a t i o n was generated by Wilimovsky and Wick!und ( 1 9 6 3 ) from the Beverton and H o l t Y i e l d e q u a t i o n . The d i f f e r e n c e s i n y i e l d a b s o l u t e v a l u e s o b t a i n e d are caused p a r t l y by l o g t r a n s f o r m a t i o n s and probably the rounded f i g u r e o f the instantaneous t o t a l m o r t a l i t y Z. However, the a b s o l u t e y i e l d value i s not o f primary importance i n t h i s study but i t responded to the changes o f parameters. R i c k e r Y i e l d Model R i c k e r ( 1 9 5 8 ) g i v e s a y i e l d model which i s based on an e m p i r i c a l growth r e l a t i o n s h i p . I t permits s i m u l a t i o n o f growth and m o r t a l -i t i e s when they cannot be expressed i n a s i n g l e f u n c t i o n o f time. T h i s model i s probably the best y i e l d model a v a i l a b l e t h a t can be a p p l i e d t o t r o p i c a l s p e c i e s which possess a s h o r t l i f e span, seasonal growth, and v a r i a b l e f i s h i n g i n t e n s i t y over a f i s h i n g season. T h i s 113 has been demonstrated by B a y l i f f (1966) f o r a n c h o v i e t a , Cetengvaulis mysticetus, i n the G u l f o f Panama. The equation i s : ( P T * W 1 + e 9 T " 1 T ) i T = T R R where: Y£ e q u i l i b r i u m y i e l d under given c o n d i t i o n s , g instantaneous r a t e o f growth, i instantaneous r a t e o f t o t a l m o r t a l i t y , p instantaneous r a t e o f f i s h i n g m o r t a l i t y , q instantaneous r a t e o f na t u r a l m o r t a l i t y , T time i n t e r v a l (months), T^ the f i r s t p e r i o d under c o n s i d e r a t i o n , T the l a s t p e r i o d under c o n s i d e r a t i o n , W weight o f an i n d i v i d u a l f i s h d u r i n g t h a t p e r i o d . The assumption o f the model a r e : 1. growth and m o r t a l i t y r a t e are independent o f po p u l a t i o n s i z e ; 2. c a t c h a b i l i t y i s constant throughout f i s h i n g season; 3. the p o p u l a t i o n i s s t a b l e . A computer program by Wilimovsky (1972) was used. The r e s u l t s appear on Tables 24, 35 and 36. 114 The t o t a l e q u i l i b r i u m y i e l d o f R. kanagurta f o r an i n s t a n t a n -eous f i s h i n g m o r t a l i t y o f 0.8 and n a t u r a l m o r t a l i t y o f 0.42 was 1.35 g per gram r e c r u i t . The f i s h i n g m o r t a l i t y 0.0 f o r age c l a s s e s 11, 12, 13, and 14 months o l d i s r e l a t e d t o u n a v a i l a b i l i t y o f these groups as they were l e a v i n g the f i s h i n g ground i n the East Monsoon ( f o r West Monsoon pop u l a t i o n ) and were being r e p l a c e d by another new stock t h a t e n t e r the f i s h i n g ground. T h i s s i t u a t i o n l i k e l y serves as a " n a t u r a l " c l o s e d f i s h i n g season f o r the f i s h e r y , which w i l l strengthen the incoming stock on the f i s h i n g ground. The same s i t u a t i o n occurs with R. braahysoma i n Tg. S a t a i area where the f i s h are u n a v a i l a b l e during the months o f May to October. The t o t a l e q u i l i b r i u m y i e l d f o r a f i s h i n g m o r t a l i t y o f 0.48 and a n a t u r a l m o r t a l i t y o f 0.34 was 1.96 g per gram r e c r u i t . I f the f i s h i n g i s doubled, the y i e l d w i l l i n c r e a s e to 2.98 g per gram r e c r u i t with a decrease i n the mode le n g t h o f the biomass f r o m 21.3 cm TL to 20.9 cm TL. The i n c r e a s e i n f i s h i n g pressure tends to decrease the mean s i z e ( l e n g t h ) o f the biomass. Y T F l r> VQDFL = AR 1 Tr-iVFT I C r.SA.'i AGE MEAN LENGTH MEAN WEIGHT G 0 P G-P-Q WEIGHT CHANGE STOCK MEAN BICMASS YIELD V 4,00 144. C. 0. 40 0.0 3 0.C60 C.29S 1.347 1C00. 1173. 93. > — 5.00 6.C0 164. 179. 0. 0. 0.23 0.03 0.030 C.174 1.190 1347. 1604, 1475. l i s . i 7.CO 192. 0. 0.21 0.15 0.03 0.02 0.030 0.0 = 0 0.103 0.042 1.114 1.04 3 1737. 1696. 1S26. 135 . .146. 6.00 9.00 2C1 . 209 . 0. 0. 0. 11 0.C3 o.oeo 0.2 09 1.009 ISo:.. 16S2. 1374.' " 149. 10.00 21 = . 0. 0. 09 0.07 0.03 0.02 o.oeo 0.000 -0.016 0.041 0.953 1.0-2 1852. 1567 . 1B91. 149. 0. , 11.CC 12.00 22C. 224. c. 0. 0.05 0.03 coco 0.C26 ' 1.026 1921. 19S2. 1936. 0. 13.00 227. c. 0. C4 0. 04 0.02 0.03 O.CCO 0.000 0.012 0.010 1.012 1.010 2C07. 1994. 2017." 0. 0. 14.00. 15.CC 2 30. 232. 0. c. 0.0 2 0.0 3 0.030 -C.032 0.920 2023. 1S67. 1947. 155 . ! 16.00 233 . 0. 0.01 0. Oi ~0"f03~ 0.02 ~67b so ~ o.cso -0.C96 -0.093 0.903 0 . 9 1C 1696. 1732. 1620. 14 2. 129. i 1 i 17.00 13.00 234. 233 • 0. 0. 0.01 0.03 0.020 -0.096 0.903 1544. 1402. 1473. 117. r—-— 1 i TOTAL 1.56 0.42 0.50 0.343 TOTAL YIELD = 1245. TABLE 34 Instantaneous r a t e s o f growth (q). natural m o r t a l i t y "(a) and f i s h i n a m o r t a l i t y (p) f o r R. kanagurta o f the Java Sea. The f i s h i n g and n a t u r a l m o r t a l i t y i s d i v i d e d evenly through the y e a r , except during the months which where i t migrates Trom the Java Sea and, t h e r e f o r e , u n a v a i l a b l e to the fishermen, g - p - q i s equal to g - i . Instantaneous r a t e s of growth (g) d i s t r i b u t e d according to t h e i r observed seasonal "Incidence. The computdliun uT e q u i l i b r i u m y i e l d , i n successive, ribhiny seasons, from 1 ,000 w e i g h t - u n i t s at age 4.0 months. :  Y I r L ! ) ? •on"!. A 3 I Tr> r T T T " F A N r A G E M E A N LENGTH M E A.N WEIoHT G 0 P C - K - Q A'E I oHT C n A M G E STOCK MEA.^I 6 1 C r ' .AS S Y I E L D 3 . 0 0 9 9 . 0 . 1 0 0 0 . r• 4 . 0 0 1 2 1 . 0 . 0 . 5 3 0 . 3 9 0 . 0 2 0 . 0 2 0 . 0 4 0 0 . 0 4 0 0 . 5 2 5 0 . 3 3 2 1 . 6 9 0 1 . 3 9 4 1 6 9 0 . 1 3 4 3 . 2 0 2 3 . 5 3 . 3 0 . 5 . 3 0 1 3 9 . -". Z C 0 . 0 . 0 . 3 1 0 . 0 2 0 . 0 4 0 0 . 2 5 7 1 . 2 9 3 2 3 5 6 . 3 0 < - 9 . 2 7 0 2 . I C S . • 7 . 0 0 1 6 S . 0 . 0 . 2 2 0 . 1 7 0 . 0 2 0 . 0 2 0 . 0 4 0 0 4 C ' L 0 0 . . 6 3 0 . 1 1 2 1 . 1 3 3 1 . 1 1 9 3 6 0 7 . 3 3 2 3 . 3 8 2 3 . 1 3 3 . 1 5 2 . S . 0 0 9 . 0 0 1 7 S . 1 S 7 . 0 . c. 0 . 1 3 0 . 0 2 0 . 0 4 0 0 . 0 7 7 l . O S C 4 0 3 9 . 4 3 6 3 . 4 2 0 1 . 1 6 3 . i n .-\ r\ + v • w v 1 9 4 . c. C . i l C O S 0 . 0 2 0 . 0 2 c.coo coco 0 • 0 9 C . C . 0 6 6 1 . 0 9 4 1 . 0 6 c 4 7 7 5 . 4 5 6 9 . 4 9 3 = . C . 0 . 1 1 . C C 1 2 . 0 0 2 0 0 . 2 C 5 . 0 . o.. 0 . 0 7 0 . 0 2 0 . 0 0 0 0 . C 5 1 1 . 0 5 2 5 1 0 1 . 5 3 6 3 . 5 2 3 4 . 0 . 1 3 . 0 0 ' . 2 0 9 . 0 . 0 . 0 5 0 . 0 4 . 0 . 0 2 0 . 0 2 coco 0 . 0 0 0 n <J * s, J ^ C . 3 2 9 . 1 . C 3 7 1 . 0 2 9 5 5 7 0 . 5 4 6 9 . 5 6 5 2 • 0 . c. 1 1 4 . C O 1 5 . 0 0 2 1 3 . 2 1 6 . 0 . 3 . 0 . C 4 0 . 0 2 0 . 0 4 0 - 0 . 0 1 9 0 . 9 S 0 5 7 3 4 . 5 6 2 2 . 5 6 7 3 . 2 2 7 . -... — 1 6 . 0 0 2 1 3 . 0 . 0 . 0 2 0 . 0 2 0 . 0 2 0 . 0 2 0 . 0 4 0 C . 0 4 _ 0 " 0 • 03 2 - 0 . 0 3 3 C . 9 6 7 0 . 9 6 6 5 4 3 7 . ; p i J . 5 3 4 7 . 2 2 1 . 2 1 3 . 1 7 . 0 0 . I t . 0 0 2 2 0 . 2 2 2 . 0 . 0 . 0 2 0 . 0 2 - 0 . 0 3 3 C 9 6 6 5 2 5 7 . 5 0 3 2 . 5 1 6 9 . 2 0 6 . 1 9 . C C 2 2 3 . 0 . 0 • Z x 0 . 0 1 0 . 0 2 0 . C 2 C . 0 ' , 0 C . C 4 0 - 0 . 0 4 7 - 0 . 0 4 7 • 0 . 9 5 4 C . 9 5 3 4 5 4 5 . 4 9 6 ; . 4 7 3 7 . i i c i 1 3 9 . 2 0 . 3 0 2 2 4 . 0 . 4 6 2 5 . T O T A L 2 . 3 6 0 . 3 4 C . 4 S 1 . 5 4 0 • T O T A L Y I E L D = 1 9 6 2 . TABLE 35. Instantaneous r a t e s ' o f growth ( g ) , nat u r a l m o r t a l i t y (q) and f i s h i n g m o r t a l i t y (p) f o r R. brachysoma from Tg. S a t a i area. As i n TABLE 34, except t h a t the computation of e q u i l i b r i u m y i e l d from 1 ,000 w e i g h t - u n i t s a l aye 3.0 inuriLlis. : ; — — — — . s i r * - * Y f - i n r 1 , AGE 3 .CO MEAN LENGTH 99. MEAN WEIGHT 0. G 0 p G - P - Q WEIGHT CHANGE STOCK, 1000. MEAN BIC.v.ASS YIELO • t 4. CO 121. 0. 0.58 0.39 0.02 0.02 0. C30 0. C 8 0 0.4i-5 0.292 1.624 1.339 1624. 1512. 1399. 104. 1 T i • 1 1 5. CC 6. CO 139. 155. 0. 0. 0.31 0.02 0.C3O 0.217 1.242 2175. 2704. 2439. 195. I i i i 7.00 168. 0. 0. 22 0. 17 0.02 0.02 0.030 0. 030 0.12S 0.072 1.136 1.075 3074. 2 5 59. 3190. 2 3 i . 25 5 . S .00 9.CO 173. 137. C . 0. 0. 13 0.02 0. 0 3 0 0.027 1.037 3307. 3432. 3269 . 269 . • 10.00 • 194. 0. 0.11 0.0 3 C.C2 0.02 0. GOO 0. CCO 0.090 0.066 1.C94 1.06 3 3756. 3 594. 33S4. °» 0. 11. C C 1 2 .CO 2 CC . 2C5 . o. • 0. 0.07 C O 2 O.OOO 0.051 1.C52 4 012. 4222. 4 i l 7 . 0. 13.CO' • 209. 0. 0.05 0.04 0.02 __C_02_ 0. OCC _0.COO 0. C 2 6 0.029 1.037 1.029 4331. 4302. 4446 . 0 • 0. 14.00 15.00 213. 216 . 0. 0. 0. 04 0.02 o.oac -0.059 0.942 4511. 42^9. 433C. 350. 1 6 • G C 218. 0. . 0.02 0. C2 0.02 0.02 C C 3 0 _C_C80 _ _ ^ ~- ~i i — w . U / Z ^0 J LC7 3 0.929 0.92 3943 . 4099 . 3 303. 327. 20^ - . 17.CO 15.00 220. 222 . 0. 0. 0.02 0.02 0 . C 5 0 -0.07 2 0 • v 2 S 2665. 3406. 3537. 232 . 19.00 223. 0. 0.01 0.01 . C.C-2 0.02 . 0. 030 0.030 -0.037 -0.03 7 0.916 0.916 . 3122. 2 992. 261. 239. 20. CO 224. 0. 2 6 6 2 . ! : : TOTAL 2. 36 0. 34 0.96 1.060 ' TOTAL YIELD = 29S3. TABLE 36. Instantaneous r a t e n f g r o w t h ( g ) , n a t u r a l m n r t a l i t y (q) anH f i c h j n g m o r t a l i t y (p) of R. braohysoma from Tg. S a t a i a r e a , as i n TABLE 35, except tha the f i s h i n g m o r t a l i t y (p) was doubled. ~ ; " : 118 IV. GENERAL DISCUSSION >* The genus Rastvelligev has been accepted s i n c e the time Jordan proposed i t (Jordan and S t a r k s , 1908). There are two s p e c i e s w i t h i n the genus t h a t have caused c o n t r o v e r s y , namely Rastvelligev bvachysoma B l e e k e r (1851) and R. neglectus van Kampen (1907). Some re c o g n i z e them as two v a l i d s p e c i e s and others t h i n k t h a t R. neglectus i s a synonym o f the former s p e c i e s . T h i s problem probably e x i s t s because past systema-t i c s t u d i e s of marine f i s h e s i n v o l v e d too few specimens and were l e s s a n a l y t i c a l than the s y s t e m a t i c s t u d i e s of f r e s h water f i s h e s (Hubbs, 1943). Natural populations are almost always d i s t i n g u i s h a b l e by d i f f e r e n c e s i n t h e i r morphology. The general method used to i d e n t i f y populations at any rank i s by determining the d i f f e r e n c e s o f t h e i r morphological c h a r a c t e r s . These c h a r a c t e r s can be d i v i d e d i n t o two k i n d s , q u a l i t a t i v e and q u a n t i t a t i v e c h a r a c t e r s . Any o f the l a t t e r can be expressed e i t h e r as a count ( m e r i s t i c c h a r a c t e r ) or as a measurement (morphometric c h a r a c t e r ) . Two c l o s e l y r e l a t e d s p e c i e s u s u a l l y d i f f e r i n s e v e r a l c h a r a c t e r s . Sometimes the d i f f e r e n c e s between them are not pronounced, thus the c h a r a c t e r s employed should be those t h a t e x h i b i t the g r e a t e s t divergence. The degree of d i f f e r e n t i a t i o n i s d i f f i c u l t to determine, e s p e c i a l l y from small samples, but, as Hubbs (1943) s t a t e d , i t i s the t r u e s t measure one can o b t a i n of the stage of s p e c i a t i o n . In search f o r d i s t i n c t i v e c h a r a c t e r s , one seeks those which r e f l e c t i n h e r i t a b l e g e n e t i c d i f f e r e n c e s r e g a r d l e s s o f sex, s i z e , and environment. 119 Determining whether two c h a r a c t e r s do o r do not i n t e r g r a d e i s a main problem i s s y s t e m a t i c s . The degree o f i n t e r g r a d a t i o n as d e s c r i b e d by Ginsburg (1938) and Royce (1957) was employed. As has been s t a t e d i n the previous s e c t i o n s each morphometric c h a r a c t e r was su b j e c t e d to r e g r e s s i o n a n a l y s i s . Regression technique was chosen because o f i t s value i n morphometric study i n t h a t the s i z e or growth o f one c h a r a c t e r i s r e l a t e d i n a p a r t i c u l a r way to the s i z e o r growth o f another c h a r a c t e r . A n a l y s i s o f c o v a r i a n c e was used to compare r e g r e s s i o n l i n e s ; t h i s provides answers as whether two o r more samples d i f f e r more than would be expected from chance. The f a c t o r s such as the d i s t i n c t n e s s o r the s i z e o f the gap, the e v o l u t i o n a r y r o l e o r the nature o f the a d a p t a t i o n zone and the degree o f d i f f e r e n c e must be weighed before any d e c i s i o n on the sys t e m a t i c s t a t u s i s to be made. The g r e a t e r the d i f f e r e n c e o r the gap between two c l u s t e r s o f s p e c i e s , the g r e a t e r the j u s t i f i c a t i o n f o r r e c o g n i z i n g both c l u s t e r s as se p a r a t e t a x a . The d i f f e r e n c e i s measured not only i n terms o f phenetic d i s t a n c e but i n terms o f b i o l o g i c a l s i g n i f i c a n c e . The e x i s t e n c e o f a gap i m p l i e s r e p r o d u c t i v e i s o l a t i o n and t h i s d i f f e r e n c e may be used f o r taxonomic r e c o g n i t i o n o f the s p e c i e s . The d i f f e r e n c e i n the u t i l i z a t i o n o f the environment i s r e s p o n s i b l e f o r the s i z e o f gap between taxa. The data o b t a i n e d d u r i n g t h i s study suggest t h a t i n the Java Sea there are only two species o f Rastvelligev, R. bvachysoma and R. kanaguvta; other s p e c i e s a re reduced to synonyms. Rastvelligev i s d i s t r i b u t e d abundantly i n the Indonesian waters. T h i s genus i s caught i n the Java Sea and c o n t r i b u t e s s i g n i f -120 i c a n t l y to marine f i s h e r i e s p r o d u c t i o n . The problem o f whether o r not t h i s Rastrelliger i s composed o f a number o f p o p u l a t i o n s has not y e t been analysed. Hardenberg's hypo t h e s i s (Hardenberg, 1938) based on Decapterus m i g r a t i o n p a t t e r n s d e s c r i b e s the Rastrelliger s t o c k s i n the area and i s the only p o p u l a t i o n study t o have been attempted. In o r d e r to approach the above problem and to v e r i f y the h y p o t h e s i s , morphometric s t u d i e s have been conducted. Four samples from two d i f f e r e n t f i s h i n g grounds were compared. The r e s u l t s o f the comparisons o f R. braahysoma sub-samples from Tg. S a t a i area suggest t h a t l o n g i t u d i n a l measurements and p e l v i c f i n l e n g t h a r e s i g n i f i c a n t l y d i f f e r e n t (1%) between sexes ( T a b l e 10). These c h a r a c t e r s were d e l e t e d from f u r t h e r morphometric a n a l y s e s . To a v o i d p o s s i b l e b i a s due to a l l o m e t r i c growth, comparisons among R. kanagurta sub-samples from the north c o a s t o f Java were done by length-groups. The r e s u l t s are t h a t the p e r p e n d i c u l a r i r i s diameter and the p e r p e n d i c u l a r p u p i l diameter, p e c t o r a l f i n l e n g t h , and p e c t o r a l breadth are s i g n i f i c a n t l y d i f f e r e n t (1%) among the groups (Tables 11, 12., 13). These c h a r a c t e r s e x h i b i t s t r o n g a l l o m e t r i c growth and thus, should be d e l e t e d f o r f u r t h e r a n a l y s e s . The c h a r a c t e r s t h a t do not e x h i b i t e i t h e r sexual dimorphism o r s t r o n g a l l o m e t r i c growth are compared among samples and the r e s u l t s are shown on Table 20. The data suggest t h a t R. braahysoma e x h i b i t s geographical v a r i a t i o n i n the d o r s o v e n t r a l depth, g r e a t e s t body depth, and i n t e r o r b i t a l d i s t a n c e , R. kanagurta i n the head length and the 121 dorso v e n t r a l depth. T h e r e f o r e , from the sta n d p o i n t o f morphometry there are two d i f f e r e n t p o p u l a t i o n s o f Rastrelliger spp. i n the Java Sea area which supports the Hardenberg hypothesis f o r R. kanagurta s t o c k s . The m e r i s t i c c h a r a c t e r s examined do not e x h i b i t i n t e r - o r i n t r a s p e c i f i c d i f f e r e n c e s . The q u a l i t a t i v e c h a r a c t e r i n d i s t i n g u i s h i n g s p e c i e s i s the appearance o f the c e p h a l i c l a t e r a l l i n e canal system. The l a n d i n g s o f Rastrelliger mostly come from the Sunda S h e l f a r e a . In t h i s study, as has been s t a t e d b e f o r e , two s p e c i e s o f Rastrelliger are r e c o g n i z e d , R. braahysoma or Kembung Perempuan and R. kanagurta or Kembung L e l a k i . Kembung L e l a k i i s caught mostly by payang-net i n the o f f s h o r e r e g i o n s , w h i l e Kembung Perempuan i s caught i n the c o a s t a l areas by s e v e r a l kinds o f f i s h i n g gears such as g i l l -n e t s , s h o r e - s e i n e s , and t r a p s . The data i n t h i s study suggest t h a t the Rastrelliger f i s h e r i e s depend mainly on the 0-year c l a s s which i s completing i t s f i r s t y e a r o f l i f e i n the f i s h e r i e s . The f i s h are immature o r j u s t mature. The success o f t h i s kind o f f i s h e r y w i l l depend on the s t r e n g t h o f the incoming 0-year c l a s s which i s dependent on the seasonal s u r v i v a l r a t e o f the young, and the c o n d i t i o n s o f the environment t h a t i n f l u e n c e m i g r a t i o n o f the f i s h to the f i s h i n g grounds. The change i n r e c r u i t -ment seems to have a s t r o n g e r i n f l u e n c e than f i s h i n g pressure on the f l u c t u a t i o n o f the stock. The study o f s t o c k - r e c r u i t m e n t r e l a t i o n s h i p s are a n e c e s s i t y and must be undertaken to r e l a t e the abundance of the 122 p r e - r e c r u i t phase to age c l a s s s t r e n g t h f o r f i s h i n g success p r e d i c t i o n . The data suggest t h a t the Kembung f i s h e r i e s i n the Java Sea have not y e t reached maximum e x p l o i t a t i o n which suggests the p o s s i b i l i t y o f i n c r e a s i n g p r o d u c t i o n by i n c r e a s i n g f i s h i n g i n t e n s i t y . S i n c e the p a r e n t - r e c r u i t r e l a t i o n s h i p i s not y e t e s t a b l i s h e d the i n c r e a s e should be undertaken c a u t i o u s l y to av o i d causing a d e c l i n e i n r e c r u i t m e n t s u f f i c i e n t enough to hurt the f i s h e r i e s . However, the " n a t u r a l " c l o s e d f i s h i n g seasons i n the Java Sea are l i k e l y to keep the f i s h e r i e s i n good c o n d i t i o n . 123 V. CONCLUSIONS Analyses o f morphometric data suggest t h a t there are two sp e c i e s i n the genus Rastrelliger, Rastrelliger braahysoma and R. kanagurta. R. negleotus i s c o n s i d e r e d to be a synonym o f R. braah-ysoma. Both s p e c i e s e x h i b i t i n t r a s p e c i f i c geographical v a r i a t i o n s i n the d o r s o v e n t r a l depth, the g r e a t e s t body depth and the i n t e r o r b i t a l d i s t a n c e i n the former s p e c i e s ; and i n the d o r s o v e n t r a l depth and the head depth i n the l a t t e r ones. A n a l y s i s o f ca t c h curves i n d i c a t e s a v a r i a t i o n i n the i n s t a n -taneous t o t a l m o r t a l i t y c o e f f i c i e n t ; f o r i ? , kanagurta i t i s 1.08 i n November 1971 and 1.20 i n December 1971. I t a l s o i n d i c a t e s v a r i a t i o n i n the s u r v i v a l r a t e s o f the West and Ea s t Monsoon Rastrelliger kanagurta p o p u l a t i o n s , t h a t i s o f 0.34 and 0.72 r e s p e c t i v e l y . The s u r v i v a l r a t e s o f the West Monsoon p o p u l a t i o n i n 1971 and 1972 are n e a r l y the same. The estimated n a t u r a l m o r t a l i t y M was 0.40. R. braahysoma had a s u r v i v a l r a t e o f 0.82 i n the 1971/1972 f i s h i n g season, with an estimated n a t u r a l m o r t a l i t y M o f 0.40. The f i s h i n g m o r t a l i t y F o f R. kanagurta i n the north c o a s t o f Java area was 0.83 (December 1971) and i t was 0.44 f o r R. braahysoma i n Tg. S a t a i area (1971/1972 f i s h i n g season). In o r d e r to determine the p o t e n t i a l y i e l d o f the f i s h p o p u l a t i o n s , the y i e l d per r e c r u i t models o f Beverton and H o l t (1957) and o f R i c k e r (1958) were employed. The data suggest t h a t y i e l d can be i n c r e a s e d by 124 i n c r e a s i n g the f i s h i n g p ressure more than 60% f o r R. kanagurta and can be doubled f o r R. braahysoma o f Tg. S a t a i area. The g r e a t e s t y i e l d f o r both s p e c i e s can be achieved by extending the age or s i z e o f the f i r s t capture to 4.5 months o f age (15.5 cm TL) and 4.0 months o f age (12.0 cm TL) r e s p e c t i v e l y . The f l u c t u a t i o n s of the catch d u r i n g past y e a r s was probably caused by f a i l u r e or success o f r e c r u i t m e n t r a t h e r than by the i n c r e a s e i n f i s h i n g p r e s s u r e . The f i s h p o p u l a t i o n s do not appear to be i n a s t a t e o f over-e x p l o i t a t i o n , t h e r e f o r e , the f i s h i n g a c t i v i t i e s should be i n c r e a s e d to gain more food and to i n c r e a s e employment. 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A Key to the F a m i l i e s o f Marine F i s h e s o f the West Coast. C a l i f o r n i a S t a t e F i s h and Game Comm. Fish. Bull., 5: 16 pp. Tesch, F.W. 1968. Age and Growth. j_n W.E. R i c k e r ( e d . ) , Methods f o r Assessment o f F i s h P r o d u c t i o n i n Fresh Waters. IBP, London, 313 pp. Tiews, K. 1958. Report to the Government of the P h i l i p p i n e s on Marine F i s h e r y Resources. Phil. J. Fish., 6 ( 2 ) : 107-208. V a n i c h k u l , P. and V. Hongskul. 1966. Length-weight r e l a t i o n s h i p s o f chub-mackerel {Rastrelliger spp.) i n the G u l f o f T h a i l a n d . Proo. Indo-Pacif. Fish. Coun., 11(2): 20-23. 135 van Kampen, P.N. 1907. Uber Zwei Scomber - Are tn des indischen Archipels. Bull. Dept. Agric. Indes. Neerl., 8 ( Z o o l . 2): 1-8. Van Oosten, John. 1957. The s k i n and s c a l e s . Jto M.E. Brown e t a l . , The P h y s i o l o g y o f Fi s h e s New York, Academic P r e s s , 1957. von B e r t a l a n f f y , L. 1934. Untersuchungen uber d i e G e s e t z l i c h k e i t des Wachstums, Arch. Entw. Mech. Org. Berlin, 131: 613-652. . 1938. A q u a n t i t a t i v e theory o f o r g a n i c growth. Hum. Biol., 10: 181-243. . 1957. Q u a n t i t a t i v e laws i n metabolism and growth. Q. Rev. Biol., 32: 217-31. Wilimovsky, N.J. and E.C. Wicklund. 1963. Tables o f the incomplete Beta f u n c t i o n f o r the c a l c u l a t i o n o f f i s h p o p u l a t i o n y i e l d , Vancouver, Univ., B r i t i s h Columbia, I n s t i t u t e o f F i s h e r i e s , 291 pp. . 1972. Lec t u r e s on F i s h e r i e s B i o l o g y and Management and Icht h y o l o g y , U n i v e r s i t y o f B r i t i s h Columbia, Vancouver, B.C., Canada. Whitley, G.P. 1944. New Sharks and f i s h e s from Western A u s t r a l i a . Australian Zoologist, 10: 252-73. 1 3 6 a c A P P E N D I C E S Body measurements of Rastrelliger. CO 137 5 10 15 20 25 TOTAL (X 1000) EFFORT Figure 14 a. Rela t i o n between T o t a l E f f o r t and Catch Per Unit of E f f o r t ; and between T o t a l E f f o r t and T o t a l Catch of R. kanagurta from the north coast of Java i n 1971. This i s the s i m p l i -f i c a t i o n of Fi%ure 14; f i t t e d by eyes. Catch I (X 10tons! 40 30 28 26 24 22 20 18 16 14 12 10 8 6 4 2 0 140 •i 1 1 » 1 —I** 1 \ 1 1 r 2 3 4 5 6 7 8 9 10 11 12 1971 28. Monthly productions of the north coast of Jev in 1971. A. R. kpnpgurta; B. Decautprus snn.t C, Euthynnus snn. 141 % 40 •• 30 . . 20 + 10 1 o • ' 1 1 1 1 1 — 17.0 > 5 18.0 > 5 19.0 5 Figure 29.Frequency dis t r ibut ion Java Sea (1972) . I J I I I 1=3= 20.0 > 5 21.0 < 5 22.0 > s 23.0 TL (cm) of mature R. kanagurta from the 142 T w/R 1.0 tc R. kanagurta. R. brachysomp. Figure 30. Y i e l d per r e c r u i t es a function of t 0 with f i s h i n g mortality F ranged from .1 to 1.5. 143 TABLE 37 Rastrelliger braahysoma Productions o f Tg. S a t a i Area Month 1968 (ton) 1969 (ton) 1970 (ton) I 357 360 600 II 398 373 712 III 303 511 584 IV 143 136 281 V 55 64 120 VI 7.5 9 56 VII - _ VIII - • - _ IX - - _ X •• - - _ XI 70.6 120 85 XII 287 592 239 T o t a l 1,621.1 2,165 2,678 Source: The Sea F i s h e r i e s S e r v i c e of the Province of West Kalimantan (Borneo) i n Pontianak. 144 TABLE 38 Age D i s t r i b u t i o n o f R. braahysoma i n Tg. S a t a i Area i n 1971/1972 F i s h i n g Season Age (Month) Frequency % In % 4 12 .75 .2914 5 27 1.7 .5195 6 190 11.8 2.4707 7 263 16.4 2.7958 8 116 7.2 1.9773 9 450 28.0 3.3329 10 327 20.4 3.0136 11 206 12.8 2.5515 12 13 .81 .2114 13+ 2 .13 2.0832 145 TABLE 39 Age Distribution in the Catch of R. kanagurta in the Java Sea Age (Month) West Monsoon 1971 (f) East Monsoon 1971 (f) West Monsoon 1972 (f) 4 - 4 -5 - 16 -6 - 32 1 7 24 33 5 8 22 27 8 9 70 23 24 10 n o 22 52 11 30 21 14 12 15 16 7 13+ 6 9 4 146 TABLE 40 Average E f f o r t o f a Payang-Boat i n 1971 i n the North Coast o f Java n = 8 boats; power = 20 H.P.; crew = 16 Month F i s h i n g Day F i s h i n g T r i p I 22 4 II 10 2 I I I 22 4 IV 14 3 V 17 3 VI 14 3 VII 13 3 VIII 12 2 IX 16 4 X 18 4 XI 13 2 XII 16 4 T o t a l 187 38 Average 15.6 3.2 147 TABLE 41 i?. kanaguvta S t a t i s t i c s i n 1971 i n the North Coast o f Java Month T o t a l Catch (kg) Catch/Boat/Day (CPUE) E f f o r t = T o t a l C a t c h C/B/D I 535,004 19.2 27,865 II 520,879 26.6 19,582 III 863,163 65.4 13,198 IV 1,156,411 51.9 22,282 V 1,002,515 78.2 12,820 VI 934,393 125.2 7,463 VII 739,127 148.3 4,984 VIII 587,734 25.6 22,958 IX 869,431 38.8 23,626 X 1,010,473 62.6 16,142 XI 1,032,547 176.4 5,853 XII 905,458 130.8 6,923 

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