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Factors affecting timing and size of runs of hilsa shad (Hilsa ilisha) in Bangladesh and Pakistan Das, Nitya Nanda 1985

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Factors Affecting Timing and Size of Runs of Hilsa Shad (Hilsa ilisha) in Bangladesh and Pakistan by Nitya Nanda Das  A t h e s i s s u b m i t t e d i n p a r t i a l f u l f i l l m e n t of t h e r e q u i r e m e n t s f o r t h e d e g r e e of Master of Science in T h e F a c u l t y of G r a d u a t e S t u d i e s ( D e p a r t m e n t of Z o o l o g y ) We accept t h i s t h e s i s as c o n f o r m i n g to t h e required standard  The  U n i v e r s i t y of B r i t i s h  Columbia  A p r i l 1985  © N i t y a Nanda D a s , 1985  In p r e s e n t i n g  t h i s t h e s i s i n p a r t i a l f u l f i l m e n t o f the  requirements f o r an advanced degree a t the U n i v e r s i t y of B r i t i s h Columbia, I agree t h a t the L i b r a r y s h a l l make it  f r e e l y a v a i l a b l e f o r reference  and study.  I further  agree t h a t p e r m i s s i o n f o r e x t e n s i v e copying o f t h i s t h e s i s f o r s c h o l a r l y purposes may be granted by t h e head o f my department o r by h i s o r her r e p r e s e n t a t i v e s .  It i s  understood t h a t copying o r p u b l i c a t i o n o f t h i s t h e s i s f o r f i n a n c i a l gain  s h a l l not be allowed without my w r i t t e n  permission.  Nitya Nanda Das  Department o f  zoology  The U n i v e r s i t y o f B r i t i s h Columbia 1956 Main Mall Vancouver, Canada V6T 1Y3 Date  22 April 1985  ABSTRACT D a t a w e r e g a t h e r e d i n 1983 a n d 1984 on t h e H i l s a f i s h e r y i n t h e M e g h n a River  in  Bangladesh,  including  effort  as  and  on  factors  estimated  by  related  weekly  to  counts  its of  seasonal fishing  variation, boats,  l a n d i n g s as e s t i m a t e d b y c o u n t s of f i s h o f f l o a d e d at C h a n d p u r . d a t a were also a n a l y z e d c o n c e r n i n g  and  Historical  factors influencing annual variations  in  H i l s a l a n d i n g s f r o m t h e Padma R i v e r of t h e G a n g e s (1967-1974) a n d f r o m t h e I n d u s R i v e r of P a k i s t a n ( 1 9 6 8 - 1 9 8 2 ) . of  landings.  Hilsa  No  landings  significant  and  fishing  maximum a i r t e m p e r a t u r e  relationship intensity.  years  variation River. and  earlier of  a  significant  Hilsa l a n d i n g s ,  may  be  that  to t h e f i s h e r y ,  observed  good  indicators  between  mean  water  riverine  level  in  both this  Hilsa  negative the  1  +  and the s u r v i v a l  y e a r s when t h e r e i s a v e r y h i g h r a i n f a l l .  relationship  Padma R i v e r  negative  are  and  i n f l u e n c e on a n n u a l v a r i a t i o n s  in t h e Padma r i v e r of t h e G a n g e s .  Mechanisms regulating  rainfall  recruited  had  was  Rainfall,  h a d no o b v i o u s  s e a s o n a l t i m i n g of H i l s a r u n s two  Rail shipments were  and  association  year  old  of e g g s  Rainfall  with in  they  and f r y  annual  the  between  when  Indus  landings are  first  is minimum i n  In t h e G a n g e s a n d I n d u s  rivers,  a n n u a l l a n d i n g s w e r e not c l o s e l y c o r r e l a t e d , a n d a p p e a r to be d e p e n d e n t part  on e a r l i e r  rainfall conditions  within  each  region.  This  - ii  -  in  dependency  o f f e r s a means of r o u g h f o r e c a s t of a n n u a l h a r v e s t on t h e b a s i s of rainfall data.  in  previous  TABLE OF CONTENTS  ABSTRACT LIST OF TABLES LIST OF FIGURES  i i V vn  ACKNOWLEDGEMENTS  viii  1. INTRODUCTION  1  2. STUDY AREAS  3  2.1 2.2  Ganges River Indus River  3. KNOWN FEATURES OF BIOLOGY OF H i l s a i l i s h a 3.1 3.2 3.3 3.4 3.5 3.6 3.7 3.8 3.9  Migration Maturity.and reproduction Spawning season Factors influencing spawning Spawning grounds Eggs Larval history Age and growth Food  3 7 10 10 16 17 19 20 21 22 23 23  4. SEASONAL VARIATIONS IN H i l s a IN THE PADMA AND MEGHNA RIVERS IN BANGLADESH  24  4.1  Description of fishery  24  4.2  Relations of landings to effort 4.2.1 Method of estimating effort 4.2.2 Method of estimating landings 4.2.3 Marine versus freshwater landings 4.2.4 Results and discussion Relationship of landings to environmental factors 4.3.1 Sources of data 4.3.2 Relationship of landings to r a i n f a l l 4.3.3 Relationship of landings to mean water level 4.3.4 Relationship of landings to minimum discharge 4.3.5 Relationship of landings to maximum a i r temperature 4.3.6 Discussion  32 32 36 36 40 43 43 49 52 57  4.3  57 60  5. ANNUAL VARIATIONS IN Hilsa IN THE PADMA AND MEGHNA RIVERS OF BANGLADESH AND IN THE INDUS RIVER OF PAKISTAN  67  5.1  Sources of data  67  5.2  Results 5.2.1 Relationship of landings to r a i n f a l l in the Padma River of the Ganges at Goal undo in Bangladesh 5.2.2 Relationship of r a i n f a l l to maximum water level in the Padma River of the Ganges at Goal undo in Bangladesh . . . 5.2.3 Relationship of landings to r a i n f a l l in the Meghna River at Chandpur in Bangladesh 5.2.4 Relationship of landings to r a i n f a l l in the Indus River of Pakistan 5.2.5 Correlations between the Ganges and the Indus Hilsa landings with a two-year lag in r a i n f a l l 5.2.6 Relationship of landings to mean a i r temperature in the Padma River of the Ganges at Goal undo in Bangladesh . . . 5.2.7 Relationship of landings to mean a i r temperature in the Indus River of Pakistan  70  5.3  Discussion  70 77 77 80 80 85 85 90  6. CONCLUSIONS  94  LITERATURE CITED  96  APPENDIX  104  LIST OF TABLES  TABLE  1.  Number of different types of Hi 1sa fishing gear/day that were in operation during different months of the year, the Meghna River between Chandpur and Nilkamal from January 1984 to August 1984. The values reported are the mean and t h e i r standard e r r o r s . Each monthly mean is based on four observations 34  TABLE  2.  Mean catch/day of Hi 1sa (kg) by two types of gear in different months in the r i v e r stretch from Chandpur to Nilkamal of the Meghna River (after Bangladesh Fisheries Resources Survey System, 1984)  35  Monthly freshwater landings of Hilsa and fishing intensity (calculated as described in text) for the River Meghna at Chandpur during the period of January to August 1984. Monthly freshwater landings are calculated from eight daily observations. Regression s t a t i s t i c s shown below  37  Rail trans-shipment records, and observed riverine and marine Hi 1sa landings in metric tonnes for the Meghna River at Chandpur from January 1984 to August 1984. The values reported are the mean and t h e i r standard e r r o r s . Each monthly mean of freshwater and marine water Hi!sa is based on eight observations and trans-shipment on 30/31 days of observation  41  Estimated y i e l d (y-j) in tonnes and effort in thousands of man-hours (g-j) of Hilsa i l i s h a in Godavari River by d r i f t g i l l nets in the monsoon months of the years 1963-69 (after Rajyalakshmi et a l . 1972). Regression s t a t i s t i c s shown below  42  Monthly trans-shipment of Hilsa through Goalundo Railway Station (1967-74) in metric tonnes  48  Landings of Hilsa i l i s h a from 1967 to 1974 of the Padma River at Goalundo, with r a i n f a l l and mean a i r temperature of Faridpur from 1962 to 1974  68  Annual landings of Hilsa and r a i n f a l l the period 1933-1940  69  TABLE  TABLE  TABLE  TABLE TABLE  TABLE TABLE  3.  4.  5.  6. 7.  8. 9.  TABLE 10.  at Chandpur during  Catch of Hilsa i l i s h a from 1968 to 1982 of the Indus River, r a i n f a l l and mean a i r temperature of Hyderabad from 1962 to 1982  71  Regressions of Hilsa landings from 1967 to 1974 of the Padma River at Goalundo with r a i n f a l l for different lag periods  72  - :v -  TABLE 11.  Rainfall  TABLE 12.  Output of ice (* bundles) in Rajbari Ice Factory (after Nayudu, 1939)  TABLE 13.  TABLE 14. TABLE 15.  TABLE 16.  of Faridpur during the period 1930-40  75  (near Goalundo) 76  Regressions of Hi 1sa landings from 1968 to 1982 of the Indus River, with r a i n f a l l for different lag periods  81  Summary of landings of Hi 1sa, and of r a i n f a l l two years previously in the Ganges and in the Indus River  84  Regressions of Hi 1 sa landings from 1967 to 1974 of the Padma River of the Ganges at Goalundo with mean a i r temperature for different lag periods  86  Regressions of Hi 1 sa catch from 1968 to 1982 of the Indus River of Pakistan with mean a i r temperature for different lag periods  89  APPENDIX TABLE 1. APPENDIX TABLE 2.  Development of a r t i f i c i a l l y f e r t i l i z e d eggs Kulkarni 1950)  (after  Relationship between mean a i r temperature (°C) of Calcutta (near Hooghly area) with mean water temperature of Hooghly River of the Ganges  -  vt  105  106  LIST OF FIGURES FIGURE  1.  Map of the Ganges  4  FIGURE  2.  Map of lower Indus River  8  FIGURE  3.  Area of d i s t r i b u t i o n of Hilsa indicated by heavy dots. . .  11  FIGURE  4.  Diagram of Shangla j a l in operation (after 1959)  25  Jones  FIGURE  4a. Photograph of open mouth of Shangla j a l , at Chandpur. . . .  26  FIGURE  5.  Chandi jal  28  FIGURE  6.  Hi 1sa offloaded by standard basket at Chandpur landing centre  38  Relationship between riverine Hilsa landings with r a i l shipment record of Hi!sa in the Meghna River at Chandpur  44  Relationship of Hilsa landings in metric tonnes (MT) of the Padma River of the Ganges at Goalundo to r a i n f a l l of Faridpur (near Goalundo)  50  FIGURE  FIGURE  FIGURE FIGURE  7.  8.  8a. Relationship of freshwater Hilsa landings of the Meghna River at Chandpur to r a i n f a l l of Chandpur 9.  FIGURE 10.  FIGURE 11.  FIGURE 12. FIGURE 13.  FIGURE 14. FIGURE 15.  53  Relationship of Hi 1sa landings of the Padma River at Goalundo to mean water level of the Padma River at Goalundo  55  Relationship of Hi 1sa landings of the Padma River at Goalundo to minimum discharge of the Padma River at Goalundo  58  Relationship of Hi 1sa landings of the Padma River at Goalundo to maximum a i r temperature of Faridpur (near Goalundo)  61  Relationship of Hi 1sa landings of the Padma River at Goalundo with two-year lag in r a i n f a l l  73  Relationship of r a i n f a l l to maximum water level Padma River of the Ganges at Goalundo  78  in the  Relationship of Hilsa landings with two-year lag in r a i n f a l l in the Indus River  82  Relationship of Hi 1 sa landings of the Padma River at Goalundo with two-year lag in mean a i r temperature of Faridpur (near Goalundo)  87  -  V|j-  ACKNOWLEDGEMENTS It g i v e s me sincere  much p l e a s u r e  appreciation Lindsey,  and  to r e c o r d  profound  h e r e my  regard  research  C.C.  and  c o n s t r u c t i v e c r i t i c i s m in all p h a s e s of t h i s r e s e a r c h g r a t e f u l to  comments, and I Drs.  Dr.  have  N.J.  Dr.  N.R.  also  T.G.  and  my  Dr.  I am  f o r his c o n s t a n t  to  d e e p s e n s e of g r a t i t u d e ,  untiring help,  Northcote  for  his  supervisor,  scholarly  guidance  work.  invaluable  counsel  and  Liley for his c o n s t r u c t i v e c r i t i c i s m .  benefitted  Wilimovsky, J.D.  considerably  McPhail and  C.J.  from  discussions  with  Walters.  Much of the field work would not have been completed without the work,  enthusiasm  and  Md.  Sanaullah,  Mr.  Md.  N u r u l Islam  and  E r i c T a y l o r and puter  handling,  quent  queries  also  read  the  perseverance Bibhuti  of Md.  Das,  Abbas  Michael  the  first  of  Melvin,  Sattar,  Md.  Mr.  M.  Hossain,  Indra  Mohan,  Patwari. provided  patient a s s i s t a n c e with  their open-door policy regarding  n u a n c e s of draft  Dr.  Md.  Lapointe  p r o g r a m m i n g and  on  of  various  this  hard  thesis  statistical and  analyses.  provided  my  Eric  many  comfre-  Taylor  constructive  comments. D e e p e s t and brothers and  and  sisters for their blessings.  a p p r e c i a t i o n from my I  am  g r a t e f u l to  a w a r d i n g me was  most s i n c e r e g r a t i t u d e are also due I received  wife in completing  the  International  utmost  parents,  wife,  encouragement  this work.  Development  a pre-project fellowship d u r i n g  to my  Research  Centre  for  the t e n u r e of w h i c h t h i s work  c a r r i e d out. Last  but  not  least,  I would  like to t h a n k  siderable secretarial assistance.  - vi|| -  Linda  Duncan  for her  con-  I dedicate this thesis to my dearest people.  - IX : -  I 1. INTRODUCTION The  Hilsa shad  Hilsa ilisha  (Hamilton) is the most important  single  species of food fish caught in Bangladesh and is a major source of protein in  the people's diet.  The  Hilsa catch comprises about  22%  of the total  catch in Bangladesh, while no other single species contributes more than 5%.  Employing  also a major  50,000 to 100,000 fishing  source of employment.  boats, the fishery  The  for Hilsa is  importance of Hilsa as a food  source is such that the demand for Hilsa far exceeds its supply, and necessitate management of the harvest to prevent overexploitation. is as  yet almost  totally  Unfor-  tunately,  the fishery  mented.  Currently, the Hilsa fishery resource is threatened by the con-  struction of Farakka Barrage in India which Bangladesh,  and  by  irrigation,  flood  uncontrolled  may  diverts water  control  measures  and  undocu-  from and  entering industrial  effluents in Bangladesh. Basic life history knowledge of Hilsa is so rudimentary that measures to protect or expand  the catch cannot yet be formulated.  Successful stock  management requires a good understanding of the major factors survival and subsequent run size.  Although studies have been published on  several aspects of the biology of Hilsa ilisha (Day 1941, 1942,  affecting  1873,  Hora 1938,  1940,  Hora and Nair 1940, Jones 1957, Jones and Menon 1951,  Pillay  1952, 1954, 1955, 1957a, 1957b, 1958, Pillay and Rosa 1963, Quddus et a l . 1984a, 1984b, 1984c), little is known of the impact of environmental parameters such as rainfall on timing of runs, or on annual variations in this important commercial fishery. correlate  this  information  Nor has an attempt been made previously to  from  different  countries  where  (extending from the Persian Gulf to the Bay of Bengal).  Hilsa  occurs  2  T h e p r i m a r y goals of t h e p r e s e n t r e s e a r c h ( 1 ) to  establish  to  what  extent  records  of  were: rail  transhipments  r e f l e c t e d c h a n g e s of a b u n d a n c e of H i l s a in t h e r i v e r s ,  of  Hilsa  independent  of  varying fishing effort; (2)  to s t u d y Meghna  seasonal variations in Rivers  in  Bangladesh,  a b u n d a n c e of and  their  Hilsa in the Padma  relationship  to  and  rainfall  or  to s t u d y a n n u a l v a r i a t i o n s i n H i l s a in t h e Padma a n d M e g h n a R i v e r s  of  other environmental f a c t o r s , and (3)  B a n g l a d e s h a n d i n t h e I n d u s R i v e r of P a k i s t a n . An  attempt  model.  is m a d e ,  using  this  information  to  develop  a  run  prediction  3  2. STUDY AREAS 2.1  Ganges  River  The G a n g e s - B r a h m a p u t r a R i v e r system forms in the Bengal B a s i n a d e l t a of  25,000  square  s o u r c e of s u p p l y irrigation, ments.  miles e x t e n t .  in B a n g l a d e s h .  navigation  and fish  It  The  protein  is the life  river for  serves urban  line  a n d main  as a s o u r c e  and rural  of  settle-  T h e G a n g e s R i v e r b a s i n s u p p o r t s a c o n c e n t r a t i o n of 300 million  people. T h e G a n g e s , one of t h e major r i v e r s of t h e w o r l d , h a s a l e n g t h of 1570 miles down to t h e mouth of t h e M e g h n a R i v e r  (Rashid 1977).  It  r i s e s at an e l e v a t i o n of a b o u t 23,000 feet i n G a n g o t r i on t h e s o u t h e r n s l o p e of t h e H i m a l a y a n r a n g e . three highest mountain p e a k s : From its headwaters,  Along this  boundary  are located the  Mt. Everest, Kanchanjangha and Makalu.  the Ganges  flows  in a s o u t h - e a s t e r l y  direction  a n d , f u r t h e r d o w n s t r e a m , i n an e a s t e r l y d i r e c t i o n t h r o u g h I n d i a to t h e b o r d e r of B a n g l a d e s h ( F i g . 1 ) . A m o n g s t t h e major t r i b u t a r i e s w h i c h feed t h e G a n g e s , t h r e e v i z . t h e K a r n a l i ( G h a g h a r a ) , t h e G a n d a k a n d t h e K o s i , flow down f r o m N e p a l a n d t o g e t h e r c o n t r i b u t e a b o u t 41% to t h e a n n u a l flow a n d a b o u t 71% to the  dry  season  flow  Bhagirathi-Hooghly,  of on  the which  Ganges the  (Abbas,  Port  of  1982). Calcutta  The is  river  situated,  b r a n c h e s off f r o m t h e s o u t h b a n k of t h e G a n g e s at F a r a k k a a s h o r t d i s t a n c e above t h e p o i n t w h e r e t h e G a n g e s e n t e r s B a n g l a d e s h ( F i g . 1 ) .  It  i s at F a r a k k a t h a t a b a r r a g e w a s c o n s t r u c t e d a c r o s s t h e r i v e r b y t h e e n d of 1974 w h i c h  diverted  a l a r g e p o r t i o n of t h e G a n g e s w a t e r  into  4  FIGURE 1.  Map of the Ganges.  6  the Bhagirati-Hooghly  Channel.  After  reaching  the  Indo-Bangladesh  b o r d e r , t h e G a n g e s f o r m s t h e b o u n d a r y of t h e two c o u n t r i e s f o r a d i s tance  of  about  Bangladesh.  eight At  miles,  this  whereupon  point,  it  flows  it  diverges  for  completely  another  70  miles  joining the r i v e r B r a h m a p u t r a - J a m u n a (which flows southwest Assam)  at  Goalundo.  The  combined  course  of  the  into before  through  Ganges  and  B r a h m a p u t r a - J a m u n a , t a k i n g t h e name of P a d m a , is joined f r o m t h e east by another r i v e r ,  t h e M e g h n a off C h a n d p u r .  o l d B r a h m a p u t r a on i t s r i g h t  The Meghna receives the  b a n k at B h a i r a b B a z a r .  A little  t h e c o n f l u e n c e , t h e M e g h n a has a w i d t h of half a m i l e . c h a r g e at t h i s p o i n t ,  f r o m late May to m i d - O c t o b e r ,  cusecs with a recorded annual discharge  maximum of 431,500 c . f . s .  above  T h e mean d i s -  is about  250,000  i n 1960.  is e s t i m a t e d to be 92 m i l l i o n a c r e - f e e t .  Average Ten  miles  f r o m S h a i t n o l , w h e r e t h e c o m b i n e d G a n g e s a n d B r a h m a p u t r a - J a m u n a , as t h e Padma R i v e r , meets t h e M e g h n a , t h e c o n f l u e n c e is s e v e n miles w i d e in the  rainy  season.  From  this  point,  the  combined  course  of  the  t h r e e r i v e r s c o n t i n u e s as t h e L o w e r M e g h n a i n t o t h e B a y of B e n g a l . T h e e s t u a r y of t h e L o w e r M e g h n a is u s u a l l y t a k e n to s t r e t c h f r o m t h e R a b n a b a d I s l a n d s to t h e K u m i r a C o a s t , a d i s t a n c e of 95 m i l e s . water  is,  drawn  however,  from  the  s a l i n e f r o m half  middle  influence extends  together  to  be  the  Bhola  to  the  as f a r  north  as f a r u p s t r e a m as C h a n d p u r ,  i n f l u e n c e at G o a l u n d o . sidered  of  the year  Ilsa  of  north  The  as a l i n e  Shondip.  Tidal  but t h e r e i s no t i d a l  T h e e s t u a r y of t h e L o w e r M e g h n a may be c o n (or  Tetulia)  have a w i d t h of t w e n t y  and  Shahbazpur  miles at t h e s e a - f a c e .  Rivers, The  which  estuarine  d i s c h a r g e is not k n o w n , b u t at C h a n d p u r t h e mean d i s c h a r g e f r o m J u n e  7  t o O c t o b e r is a r o u n d 2 . 5 m i l l i o n c . f . s .  ( c u b i c feet p e r s e c o n d ) .  The  mean maximum i n t h i s p e r i o d of t h e y e a r is about 4 million c . f . s .  In  w i n t e r , t h e flow is about o n e - e i g h t h as m u c h , b u t t h e r i v e r e v e n t h e n i s s e v e r a l miles w i d e . not l e s s t h a n f i v e to  October,  its  In maximum f l o o d , t h e L o w e r Meghna's flow is  million c . f . s .  daily  load of  It  is also e s t i m a t e d t h a t f r o m May  s e d i m e n t s is  nearly  four  million t o n s .  T h e a n n u a l load of s e d i m e n t s c a r r i e d b y it is about 1,500 m i l l i o n t o n s a n d a n n u a l w a t e r d i s c h a r g e about 875 m i l l i o n a c r e - f e e t . 2.2  Indus  River  In P a k i s t a n , o n l y t h e R i v e r I n d u s s u p p o r t s a r u n of H i l s a .  About  5000-7000 f i s h e r m e n c a t c h about 8000 m e t r i c t o n n e s of H i l s a a n n u a l l y . The  I n d u s is t h e l o n g e s t H i m a l a y a n r i v e r ,  a b o u t 2000 miles i n l e n g t h .  T h e I n d u s a r i s e s i n T i b e t , f l o w s n o r t h w e s t f o r a b o u t 800 miles between r a n g e s of t h e H i m a l a y a n M o u n t a i n s , a n d t h e n a b r u p t l y t u r n s s o u t h w e s t , flowing  for  almost 1000 miles t h r o u g h  Pakistan before  emptying  into  t h e A r a b i a n Sea a b o u t 65 miles s o u t h e a s t of t h e major s e a p o r t c i t y Karachi.  A t S u k k u r ( a b o u t 475 miles u p s t r e a m f r o m t h e m o u t h , F i g .  of 2),  t h e volume of w a t e r f l o w i n g i n t o t h i s r i v e r v a r i e s f r o m a low of about 30,000 c . f . s .  during  peak  August.  flow  750 m i l e s . country  in In  where  the  winter The  to  river  about is  navigable  most of t h i s l o w e r a r e a , t h e irrigation  l a n d use of t h e r e g i o n .  410,000 c . f . s .  river  is n e c e s s a r y to s u p p o r t  in  only  during its  flows t h r o u g h farming, the  its  lower arid major  8  FIGURE  2. Map of lower Indus River.  9  10  3 . KNOWN F E A T U R E S OF BIOLOGY O F Hilsa ilisha O w i n g to i t s h i g h c o n s u m e r p r e f e r e n c e a n d h i g h t o n n a g e l a n d e d , t h e Hilsa  shad  western  (Hilsa  division  ilisha) of  ranks  the  as  a  Indo-Pacific  valuable  commercial  faunistic  fish  region.  in  Hilsa  the  ilisha  b e l o n g s to t h e s u b f a m i l y A l o s i n a e of t h e f a m i l y C l u p e i d a e a n d is  generally  t h o u g h t to be a n a d r o m o u s .  from the  Arabian  Geographically,  S e a to t h e B a y of B e n g a l  this  species ranges  ( F i g . 3 ) , but is concentrated  in the  w a t e r s of B a n g l a d e s h , I n d i a , P a k i s t a n a n d B u r m a ( P i l l a y a n d R o s a , 1 9 6 3 ) . The gation  fishery  for Hilsa ilisha and its biology  f o r o v e r one h u n d r e d  species  stems l a r g e l y  Although  years.  The existing  from observations  these observations  offer  h a v e been u n d e r knowledge  of c o m m e r c i a l f i s h i n g  only  investi-  about  operations.  a l i m i t e d d a t a set f o r d e d u c t i o n s ,  t h e y n e v e r t h e l e s s form a basis on which to b u i l d f u r t h e r r e s e a r c h . knowledge  of t h e l i f e h i s t o r y  of t h i s  this  fish  A clear  is an e s s e n t i a l p r e r e q u i s i t e  in  a n y p r o g r a m m e of i t s f i s h e r y r e s e a r c h a n d m a n a g e m e n t . 3.1  Migration Hilsa  ilisha  are  migrate into freshwater  reported  to  be  largely  anadromous;  from the sea for spawning;  the young  adults upon  h a t c h i n g rear in the r i v e r channels and estuaries before d e s c e n d i n g to the sea for f u r t h e r feeding and g r o w t h . for  potential exploitation:  during  T h u s , there are three phases  the breeding migration, the f r e s h -  water r e a r i n g s t a g e , and the marine phase (Raja 1984). Generally,  it  is  believed  that  there  are  three  ecotypes:  i) f l u v i a l a n a d r o m o u s s t o c k s w h i c h move b e t w e e n c o a s t a l w a t e r s a n d t h e l o w e r r e a c h e s of r i v e r s a n d b r e e d i n t h e a r e a a b o v e t h e l e v e l of t i d a l influence;  ii) f l u v i a l resident stocks that  live  and breed only  in the  n  FIGURE  3.  Area of d i s t r i b u t i o n of Hi 1sa indicated by heavy dots.  13  m i d d l e and u p p e r r e a c h e s of r i v e r s , a d d i t i o n to t h e s e t h r e e t y p e s , ment  of  a  reservoir  self-generating  in G u j r a t ,  a recent  stock  India ( R a j a ,  T h e descriptions by  and iii) p u r e l y marine s t o c k s .  in  the  confined  is t h e e s t a b l i s h waters  of  many w o r k e r s of t h e m i g r a t o r y  behaviour  on i t s o c c u r r e n c e  findings,  a r e t h o s e of P i l l a y et a l . (1962)  although  not  conclusive,  tagging  in the G a n g e s .  indicate that  of  in commercial  T h e o n l y s t u d i e s on t h e m i g r a t i o n of H i l s a , t h r o u g h  experiments,  Ukai  1984).  H i l s a i l i s h a a r e b a s e d almost e n t i r e l y catches.  development  In  Their  Hilsa marked in  the  l o w e r G a n g e s d e s c e n d e d to e s t u a r i n e a r e a s t h r o u g h t h e main P a d m a R i v e r that lies in B a n g l a d e s h . T h e movement of a d u l t H i l s a f r o m t h e s e a to f r e s h w a t e r i s c h a r a c terized  by  fish.  In  a rapid  increase  the Ganges  in  freshwater  catch  of  sexually  mature  Delta S y s t e m , this increase in landings  corres-  p o n d s to t h e commencement of t h e s o u t h - w e s t monsoon r a i n s (May) c o n s e q u e n t f l o o d i n g of a l l r i v e r s of B a n g l a d e s h a n d I n d i a . tions  in  the  intensity  of  the  monsoon  during  the  The  breeding  and  variaseason  a p p e a r to be r e l a t e d to the c o n s i d e r a b l e f l u c t u a t i o n s i n a b u n d a n c e the fish and catches in different a r e a s . breeding  A c c o r d i n g to D a y ( 1 8 7 3 ) , t h e  m i g r a t i o n in t h e I n d u s a n d t h e u p p e r  Irrawady  takes  w h e n r i v e r s a r e f l o o d e d b y m e l t i n g s n o w , not b y monsoon r a i n s . I n d u s R i v e r of P a k i s t a n , H i l s a b e g i n to e n t e r and  in  landings  some y e a r s occur  s t r e a m flow  during  does  into the I n d u s ,  remain i n t h e  not  June, appear  as r e p o r t e d  July to for  freshwater  river  as late  and  August.  be  the  other  of  as  stimulus  In t h e  January,  November. Although that  streams, the  d o e s o c c u r d u r i n g peak f l o w s (Islam and T a l b o t ,  in  place  increased  attracts  peak of t h e  1968).  Peak  Hilsa run  14  Water t e m p e r a t u r e has been g i v e n  l i t t l e a t t e n t i o n as an  mental stimulus for  H i l s a m i g r a t i o n , yet  a  many  critical  role  in  anadromous species.  aspects  of  t h i s f a c t o r is k n o w n to  clupeid  life  history,  Sujansinghani, February,  including  of c a t c h e s at C I F R I ,  s u g g e s t some a s s o c i a t i o n s w i t h t e m p e r a t u r e v a r i a t i o n ; migratory  movements  1951).  Jones  during  the  cold  (1957) o b s e r v e d  H i l s a show  season  very and  that from November  H i l s a move i n l a r g e s h o a l s at t h e m o u t h s of e s t u a r i e s  as t h e M e r g u i A r c h i p e l a g o on t h e B u r m a C o a s t ( K y a w 1 9 5 3 ) . in  India  (Jones  a l o n g t h e f o r e s h o r e a r e a s of t h e B e n g a l - O r i s s a C o a s t a n d as f a r  rise  play  T h e i n f l u e n c e of t e m p e r a t u r e on t h e movement of  H i l s a i l i s h a i s not k n o w n , b u t o b s e r v a t i o n  restricted  environ-  temperature  in  the  rivers  occurs  during  the  to and  south  The general  latter  part  of  w i n t e r w h e n H i l s a m i g r a t i o n also t a k e s p l a c e , s u g g e s t i n g t h a t t e m p e r a ture  is a c o n t r i b u t o r y  suggested  f a c t o r to i n i t i a t i o n of t h e  t h a t t h e u p s t r e a m m i g r a t i o n of  run.  J o n e s (1957)  Hilsa in the latter  part  of  w i n t e r i n t h e H o o g h l y R i v e r is s t i m u l a t e d b y i n c r e a s i n g w a t e r t e m p e r a ture. H o r a (1940) a n d H o r a a n d N a i r (1940) h a v e s u r m i s e d t h a t t h e r e i s a five-year  periodicity  i n t h e H i l s a f i s h e r i e s of t h e  Gangetic  Rivers.  In B a n g l a d e s h w a t e r s , D u n n (1982) o b s e r v e d t h e s u g g e s t i o n of a f i v e year  periodicity  monsoon  i n t h e H i l s a c a t c h w h i c h c o r r e s p o n d s to t h e i n d e x  severity.  U p s t r e a m m i g r a t i o n of rivers, i.e.,  of  H i l s a may  they ascend the entire  length  be e x t e n s i v e .  In  of t h e  Delta System;  a b o u t 500 km ( P i l l a y a n d R a s a 1 9 6 3 ) .  Gangetic  Bangladesh  In t h e I r r a w a d y R i v e r  of  B u r m a , H i l s a are k n o w n to a s c e n d i n t o u p p e r B u r m a to M a n d a l a y , a d i s t a n c e of about 724 km f r o m t h e s e a .  On t h e G a n g e s i n I n d i a , p r i o r to  15  t h e commission of t h e F a r a k k a B a r r a g e  in 1975, Hilsa were  captured  i n l a n d as f a r u p r i v e r as D e l h i , about 1287 km ( P i l l a y a n d R o s a 1 9 6 3 ) . In t h e I n d u s R i v e r of P a k i s t a n , t h e m i g r a t i o n e x t e n d s  to t h e  Ghulam  Mohammad B a r r a g e , a b o u t 161 km f r o m t h e s e a . It has o f t e n been o b s e r v e d t h a t d u r i n g y e a r s of g r e a t  abundance  of H i l s a t h e u s u a l l i m i t s of u p s t r e a m m i g r a t i o n may be e x t e n d e d .  Such  i n s t a n c e s have  Hilsa  been  recorded  in t h e B r a h m a p u t r a R i v e r  where  c a t c h e s w e r e made e v e n i n a r e a s above T e z p u r d u r i n g 1955 ( P i l l a y a n d G h o s h 1958) a n d i n t h e small t r i b u t a r i e s of t h e G a n g e s , t h r o u g h t h e f i s h a s c e n d e d i n t o L a k e M a h a s r a t a l d u r i n g 1954 ( B a n e r j i Day  (1873)  facilitate which fish  the  considered  migration  passes  constructed and  Devanesan  (1942)  obstructions  Prashad  and  have  the been  across  the  1918)  were  observed  that  to  provide  upper  constructed.  Coleroon found  and  not  migrating  Later investigators  f e a s i b l e to e r e c t  suitable fish  1955).  fish  reaches  of  passes  to  rivers  in  However, Mahanadi  suitable  fish  fishermen take large catches,  spawning escapement. not  essential  H i l s a to  artificial obstructions  (Southwell  is  of  it  which  greatly  Rivers  for  gather  the  Hilsa.  below  the  reducing  the  h a v e all c o n c l u d e d t h a t  passes  in  Indian  it  rivers  (Nair  fishery  above  1954). Ghosh(1976)  estimates that  the  production  of t h e  t h e F a r a k k a B a r r a g e d r o p p e d f r o m 1 7 6 . 1 k g / k m p r e - c o n s t r u c t i o n to l e s s than  1 kg/km  reported  the  post-construction.  Bilgrami  and  Munshi  (1982)  d e l e t e r i o u s e f f e c t of t h e F a r a k k a B a r r a g e on  the  also Hilsa  fishery. In activity  the  Ganges  River  system  in  Bangladesh,  the  is now i n t h e l o w e r r e a c h e s of t h e main r i v e r s  major and  fishing  estuarine  16  areas.  T h e r e i s l i t t l e f i s h i n g i n u p s t r e a m a r e a s of B a n g l a d e s h  such  as G o a l u n d o , P a k s e y a n d R a j s h a h i , o n c e c o n s i d e r e d to be c e n t r e s of t h e industry.  G a n a p a t i (1973) a s s o c i a t e s t h e r e d u c e d m i g r a t i o n s of  up Indian  rivers  Hilsa  w i t h t h e l a c k of h i g h d i s c h a r g e s to t h e s e a , c a u s e d  b y dams o r i r r i g a t i o n  diversions.  In P a k i s t a n , t h e G h u l a m Mohammed B a r r a g e was c o n s t r u c t e d in 1954, the  fish  ladders  provided  in  the  Barrage  were  ineffective  also  (Hossain and S u f i 1962). 3.2  Maturity and  reproduction  Conflicting  views  have  H i l s a at f i r s t  maturity.  first  at t h e e n d of  maturity  the second y e a r .  been  Day  expressed  (1873)  observed  the first  year,  the that  or  minimum s i z e H i l s a may  at the  attain  beginning  of  the Mahanadi and C h i l k a  T h e y h a v e r e c o r d e d t h a t males become m a t u r e w h e n 2 1 . 6 - 2 5 . 4 cm  in length and suggested  they  w e r e o v e r one y e a r  o l d , w h i l e females  became m a t u r e i n t h e s e c o n d y e a r w h e n 2 6 . 7 - 3 0 . 5 cm l o n g . Pillay  of  J o n e s a n d Menon (1951) r e a c h e d a s i m i l a r c o n c l u s i o n  b a s e d on t h e i r o b s e r v a t i o n s i n t h e H o o g h l y , Lakes.  on  (1958)  maturity;  found  still smaller sizes  in  the  Hooghly  River  However, at  first  some males m a t u r e at 16-17 cm a n d females at 1 9 - 2 0 cm in  t o t a l l e n g t h w h e n t h e y a r e b o t h about 1 1/2 y e a r s o l d . have e x p r e s s e d  Some w o r k e r s  t h e view t h a t males m a t u r e e a r l i e r t h a n f e m a l e s ,  but  c r i t i c a l e v i d e n c e is not a v a i l a b l e ( P i l l a y a n d R o s a 1 9 6 3 ) . F o r t h e G a n g e s at A l l a h a b a d / V a r a n a s i , M a t h u r (1964) r e p o r t e d t h a t 50%  of  maturity  the  females  were  mature  33 cm i n  at  35 c m ,  Allahabad and  while  the  31 cm at  smallest  Varanasi.  size He  at also  17  r e c o r d e d t h a t males m a t u r e at a l e n g t h of about 20 c m . s t r e t c h e s of t h e H o o g h l y ,  In t h e  upper  De (1980) o b s e r v e d t h a t females f i r s t  reach  m a t u r i t y at a s i z e of 3 4 . 1 c m .  R a j a (1984) r e p o r t e d t h a t female H i l s a  a t t a i n f i r s t m a t u r i t y at t h e s i z e of 32 c m .  The  smallest m a t u r e male  H i l s a o b s e r v e d i n t h e G o d a v a r i b y P i l l a y a n d Rao (1962) was 2 5 . 6 c m , a n d t h e smallest m a t u r e female 3 7 . 0 cm l o n g .  T h e y concluded that the  modal s i z e of 3 5 . 5 cm in t h e l e n g t h f r e q u e n c y g r o u p at f i r s t m a t u r i t y . aged 1  year.  +  In  studies represents  the  T h i s mode was s u g g e s t e d to r e p r e s e n t  fish  all o t h e r c a s e s , t h e age of t h e f i r s t m a t u r i t y  was  p l a c e d at 2 y e a r s . In (1940)  contrast suggested  maturity. were  to  at  Dunn least 4  +  the  that  foregoing, Hilsa  (1982) in  be  reported  age a n d  s p a w n i n g below t h i s a g e .  must  Hora  and old  almost a l l  he c o n c l u d e d  Hora  and  before  attaining  reproductive that  Nair  there  is  Hilsa little  T h i s age g r o u p c o r r e s p o n d s to a l e n g t h of  a b o u t 40 cm ( r e f e r to age a n d g r o w t h 3.3  5 years  that  thus  (1940)  section).  S p a w n i n g season The  spawning  season of  H i l s a i l i s h a has been  reported  f r o m a few months to y e a r - r o u n d , d e p e n d i n g on t h e r i v e r .  to  vary  Hora and  N a i r (1940) a n d H o r a (1940) s u g g e s t e d t h a t i n t h e H o o g h l y R i v e r , H i l s a p r o b a b l y b r e e d y e a r r o u n d w i t h a major p e a k i n J u l y - A u g u s t a n d a m i n o r peak i n M a y . the  breeding  On t h e o t h e r h a n d , J o n e s a n d Menon (1951) c o n t e n d e d t h a t in  the  Hooghly  is  very  restricted,  d u r i n g t h e w i n t e r m o n t h s of D e c e m b e r a n d J a n u a r y .  if  not  suspended  Their  contention  was b a s e d on t h e low d e n s i t y of p r e - a n d p o s t - l a r v a e of t h e s p e c i e s i n routine plankton hauls d u r i n g w i n t e r .  This indicated, however,  that  18  some  winter  breeding  temperatures  are  may  occur  higher.  larvae in the Hooghly  lower  Bhanot  down  (1973)  in  the  confirmed  estuary by  where  collection  of  R i v e r that Hilsa spawns throughout the year with  p e a k a c t i v i t y in F e b r u a r y - M a r c h , J u l y - A u g u s t ,  and  October-November.  Pillay  two  distinct  (1958)  seasons:  suggested  that  there  may  be  one w h i c h b e g i n s at t h e s t a r t of t h e s o u t h w e s t  spawning  monsoon a n d  c o n t i n u e s t h r o u g h to N o v e m b e r , a n d a s e c o n d peak o c c u r s f r o m J a n u a r y to  March.  Based  on  gonadosomatic  indices,  Quddus  et_ a l .  (1984a)  d e s c r i b e d two t y p e s of H i l s a f r o m B a n g l a d e s h w a t e r s ; t y p e " A " f r o m J u l y to O c t o b e r a n d t y p e " B " f r o m J a n u a r y to M a r c h . that  t h e two  morphology;  types  of  s h a d a r e also c h a r a c t e r i z e d  by  t y p e A is " d e e p - b o d i e d " a n d t y p e B is  breeds  T h e y claimed differences  "slender".  M o t w a n i et a l . (1957) r e p o r t e d t h a t t h e b r e e d i n g  of H i l s a i n  the  G a n g e s a p p e a r s to commence w i t h t h e o n s e t of t h e monsoon s e a s o n July,  with  Nangpal dent  peak  (1970)  slender  breeding  from September  found that winter  variety  to D e c e m b e r .  spawning  in the freshwater  in  Ghosh  is r e s t r i c t e d  s e c t i o n of t h e  in and  to t h e  resi-  Ganges,  while  N a i r (1958) o b s e r v e d t h a t o o g e n e s i s r e a c h e d i t s peak i n M a r c h a n d t h e ova  undergo  atresia and  indicate that there s e c t i o n of t h e  is no w i n t e r  Nair's  spawning  of  observations  appear  to  Hilsa in the  freshwater  Ganges.  A h m e d (1954) throughout  resorption.  observed  that  some g r a v i d  Hilsa have  been  t h e y e a r in B a n g l a d e s h w a t e r s , b u t t h e m a j o r i t y of  found indivi-  d u a l s w i t h well d e v e l o p e d g o n a d s a r e a v a i l a b l e d u r i n g monsoon m o n t h s . It a p p e a r s f r o m A h m e d ' s s t u d y  that Hilsa spawn throughout  b u t t h e peak season comes d u r i n g t h e r a i n y ova  maturation  studies,  Pillay  (1958)  season.  concluded  the  year,  On t h e b a s i s of  that  Hilsa  breeds  19  i n t e r m i t t e n t l y d u r i n g t h e b r e e d i n g season i n t h e H o o g h l y R i v e r .  The  o v a t h a t w e r e l i k e l y to be s p a w n e d d u r i n g t h e season h a d a s i z e r a n g e of  252 to  observed  882 m i c r o n s . among  the  Since  samples,  no  distinct  spawning  size  grouping  throughout  the  could year  be was  suggested. In s u m m a r y , o b s e r v a t i o n s w h i c h s u p p o r t two s p a w n i n g s , one d u r i n g monsoon a n d t h e o t h e r d u r i n g w i n t e r - s p r i n g , come f r o m t h e i n v e s t i g a t i o n s of M a t h u r (1964) w i t h r e s p e c t to t h e G a n g e s , a n d Q u a r e s h i (1968) a n d Q u d d u s et a l . (1984a) f r o m t h e Padma a n d M e g h n a R i v e r s .  3.4  Factors influencing spawning O n t h e b a s i s of o b s e r v a t i o n s on d e v e l o p m e n t s t a g e s c o l l e c t e d f r o m the  spawning  grounds,  Jones  and  Menon  (1951)  suggested  that  the  s p a w n i n g time of H i l s a is t o w a r d s t h e a f t e r n o o n a n d e v e n i n g . Very Hilsa.  l i t t l e is k n o w n  Southwell  about  the factors that  (1914) s u g g e s t e d  that  t r a n s i t i o n f r o m t h e sea to f r e s h w a t e r  induce spawning  the changes  involved  induce spawning.  Nair  in  in the  (1958)  s t u d i e d t h e v a r i a t i o n i n w a t e r t e m p e r a t u r e of t h e G a n g e s n e a r B a n a r a s and the gonadial activity throughout the y e a r , and suggested that v e r y h i g h t e m p e r a t u r e s have p e r h a p s an i n h i b i t o r y the ovaries.  e f f e c t on m a t u r a t i o n of  T h e f l o o d s d u r i n g t h e r a i n y s e a s o n , w h i c h make t h e w a t e r  t u r b i d a n d t h e c u r r e n t flow f a s t e r , w e r e c o n s i d e r e d b y N a i r to be most favourable for  spawning.  20  3.5  Spawning  grounds  S o u t h w e l l a n d P r a s h a d (1918) e x p r e s s e d t h e o p i n i o n t h a t t h e r e a r e no f i x e d s p a w n i n g g r o u n d s  for  Hilsa in the generally  accepted use  of  the t e r m , and that they probably breed d u r i n g the rains whenever c o n d i t i o n s s u c h as w e a t h e r ,  temperature  and other  undetermined  factors  are suitable. The  first  positive evidence  was d i s c o v e r e d  by  Hora  (1938)  of t h e when  l o c a t i o n of  spawning  he i d e n t i f i e d  grounds  the young  s p e c i e s f r o m t h e P u l t a Water Works t a n k s , i n t o w h i c h t h e y  of  would  the have  g a i n e d a c c e s s o n l y i n t h e f o r m of e g g s o r e a r l y l a r v a e , b e c a u s e of t h e v e r y n a r r o w s u c t i o n s p a c e i n t h e c e n t r i f u g a l p u m p s at t h e i n t a k e s . inferred  that  the  stretch  of  Hooghly  River  near  f o r m e d one of t h e s p a w n i n g g r o u n d s of H i l s a .  Pulta  Water  He  Works  T h i s was c o n f i r m e d  by  f u r t h e r o b s e r v a t i o n s made b y H o r a a n d N a i r (1940) a n d J o n e s a n d Menon (1951).  P i l l a y ( 1 9 5 8 ) , on t h e b a s i s of o v a s t u d i e s , i n f e r r e d  l o w e r limit of t h e s p a w n i n g g r o u n d s of H i l s a i n H o o g h l y B a z a r in C a l c u t t a .  that  R i v e r is  the Bagh  T h e r e i s e v i d e n c e to show t h a t t h e y b r e e d u p s t r e a m  u p to M e d g a c h i , a d i s t a n c e of about 251 km f r o m t h e s e a . C h i l k a L a k e s p a w n i n t h e l o w e r r e a c h e s of t h e D a y a R i v e r  T h e H i l s a of (Jones and  Sujansinghani 1951). Karamchandani freshwater migration  (1961)  concluded  r e g i o n s of t h e r i v e r , (about  161 km f r o m  obvervations  on  that  Hilsa  breeds  also  in  below t h e most u p s t r e a m limit of  the the  sea) size  in  a stretch  of  about  composition  of  catches,  the its  29 to  32 km.  From  observed  t h a t o n l y o l d e r H i l s a (males 3 1 . 5 cm to 4 8 . 5 cm a n d females  4 1 . 5 cm to 5 5 . 5 cm) m i g r a t e to t h e f r e s h w a t e r that the younger  Hilsa breed in the tidal zone.  zones for b r e e d i n g Southwell  (1914)  he  and has  21  also  suggested  such  a  possibility  in  the  rivers  of  eastern  India.  M o t w a n i , J h i n g r a n a n d K a r a m c h a n d a n i (1957) h a v e d e s c r i b e d t h e s p a w n i n g grounds  of H i l s a i n t h e  Ganges  as t h e s t r e t c h  P a t n a ( B i h a r ) and A l l a h a b a d ( U t t a r P r a d e s h ) . in the  stretch  of  L a l g o l a of t h e  Hilsa spawning in that a r e a .  Ganges  The  of t h e  river  between  T h e p r e s e n c e of l a r v a e  indicates the  probability  of  p r e s e n c e of s p e n t H i l s a i n t h e sea  o f f t h e S a u r a s h t r a C o a s t , w h e r e t h e r e a r e no l a r g e  rivers  H i l s a m i g h t a s c e n d , has i n d i c a t e d t h e p o s s i b i l i t y of t h e  up  which  stock  in  the  a r e a b r e e d i n g i n t h e sea ( P i l l a y 1 9 6 3 ) . Ahmed  (1952)  has r e c o r d e d  that Hilsa breed in the Indus  River  n e a r N a w a b s h a h a n d i n t h e s t r e t c h of t h e r i v e r immediately below Sukkur Barrage.  the  T h e spawning g r o u n d s have been r e s t r i c t e d by the c o n -  s t r u c t i o n of t h e G h u l a m Mohammed B a r r a g e i n 1954, below w h i c h  Hilsa  now s p a w n . In B a n g l a d e s h , Q u r e s h i (1968) o b s e r v e d H i l s a s p a w n i n g g r o u n d s in t h e Padma a n d M e g h n a R i v e r s a n d t h e i r 3.6  tributaries.  Eggs The  d i a m e t e r of t h e f u l l y - r i p e o v a r i a n e g g has been r e c o r d e d as  0 . 7 0 mm to 0 . 7 5 mm b y J o n e s a n d Menon ( 1 9 5 1 ) , 0 . 8 9 mm b y P i l l a y (1958) a n d 0 . 7 6 mm to 0.87 mm b y De ( 1 9 8 0 ) .  The e g g , when laid in water and  f e r t i l i z e d , s w e l l s to 2 . 1 mm to 2 . 3 mm i n d i a m e t e r a n d is d e m e r s a l i n still water;  but  as i t s d e n s i t y  easily buoyed up and d r i f t e d by  is  very  c l o s e to t h a t of  slight curents  coalesce  and  later  has to  numerous  form  a large  oil  globules  and  of  it  ( K u l k a r n i 1950).  e g g membrane is e l a s t i c a n d t h e v i t e l l i n e s p a c e i s w i d e . segmented  water,  varying  conspicuous  globule  The  The  yolk  sizes, (Jones  is  is  which and  22  Menon 1 9 5 1 ) .  K u l k a r n i (1950) a n d M o t w a n i , J h i n g r a n , a n d K a r a m c h a n d a n i  (1957) s t a t e d t h a t t h e H i l s a e g g  has a d o u b l e - l a y e r e d  membrane,  but  J o n e s a n d Menon (1951) o b s e r v e d t h a t t h e d o u b l e - l a y e r i n g t a k e s p l a c e s as a r e s u l t of p o s t - m o r t e m c h a n g e s .  T h e r e i s no i n f o r m a t i o n a v a i l a b l e  o n t h e p a r a s i t e s a n d p r e d a t o r s of H i l s a e g g s i n 3.7  Larval  nature.  history  Kulkarni  (1950)  has g i v e n  t h e f o l l o w i n g a c c o u n t of t h e  ment of a r t i f i c i a l l y f e r t i l i z e d e g g s  of H i l s a ( A p p e n d i x  develop-  Table 1).  t e m p e r a t u r e of t h e w a t e r i n w h i c h t h e e g g s w e r e h a t c h e d was 28°C a n d 2 8 . 5 ° C .  The  between  T h e h a t c h i n g time v a r i e d f r o m 18 h o u r s to 26 h o u r s ,  d e p e n d i n g on t h e t e m p e r a t u r e a n d o x y g e n a t i o n of t h e w a t e r .  Observa-  t i o n s b y J o n e s a n d Menon (1951) on d e v e l o p i n g e g g s , c o l l e c t e d f r o m t h e Hooghly R i v e r , showed a longer incubation period which might have been d u e to t h e low w a t e r t e m p e r a t u r e They  suggested  temperature.  considerable  (23°C)  retarding  in which  they  were  of g r o w t h w i t h d r o p  reared. in  water  M o t w a n i , J h i n g r a n and K a r a m c h a n d a n i (1957) r e c o r d e d t h e  i n c u b a t i o n time to be 24 to 28 h o u r s . The  newly  h a t c h e d l a r v a i s 3 . 1 mm a c c o r d i n g to K u l k a r n i  (1950)  a n d 2 . 3 mm a c c o r d i n g to J o n e s a n d Menon ( 1 9 5 1 ) .  Motwani, J h i n g r a n and  K a r a m c h a n d a n i (1957) f o u n d t h e l e n g t h of n e w l y  h a t c h e d l a r v a e to be  2 . 5 mm to 2 . 5 5 mm a n d K a r a m c h a n d a n i (1961) o b s e r v e d it v a r y i n g between 2 . 4 mm a n d 3 . 0 mm.  23  3.8  A g e and  growth  One of t h e major l i m i t a t i o n s i n t h e s t u d y  of H i l s a p o p u l a t i o n s  t h e l a c k of a s u i t a b l e method f o r age a n d g r o w t h d e t e r m i n a t i o n .  Aging  f r o m h a r d p a r t s , s u c h as s c a l e s a n d o t o l i t h s , h a s been a t t e m p t e d , t h e r e s u l t s h a v e not been e n c o u r a g i n g .  T h e most p r o m i s i n g  for  aging  are  Md.  Mokammel H o s s a i n ( p e r s .  are  the  otoliths,  S i n c e t h e s t o c k s of  which  reliable aging  Hilsa are exploited  and  growth  in  techniques  Hilsa.  structures  investigation  mostly  by  size  a n a l y s i s is of l i m i t e d u s e .  has led to many  H i l s a is t h o u g h t  7 y e a r s , a l t h o u g h age g r o u p s  but  by  comm.).  g e a r , aging by length frequency of  under  is  to  different  live  selective The  views  lack  of  a maximum of  age 5  to  2 to 4 a p p e a r to c o n t r i b u t e most to t h e  fishery. 3.9  Food Hilsa  ilisha  is  a  planktivore  exploiting  both  zooplankton  and As  phytoplankton.  In t h e y o u n g  s t a g e s , diatoms dominate t h e d i e t .  the  however,  composition  fish  grow,  the  crustacean items, especially copepods.  of  the  diet  shifts  towards  S p e n t f i s h a r e b e l i e v e d to  be  b e n t h i c f e e d e r s as c o n s i d e r a b l e q u a n t i t y of mud a n d s a n d a r e i n g e s t e d . T h e i n t e n s i t y of f e e d i n g is v e r y h i g h d u r i n g t h e p o s t - s p a w n i n g p e r i o d . Some a u t h o r s h a v e o b s e r v e d a d e c r e a s e o r c e s s a t i o n of f e e d i n g d u r i n g the spawning  run.  activity  24  4. S E A S O N A L V A R I A T I O N S IN HILSA IN THE PADMA A N D MEGHNA R I V E R S IN B A N G L A D E S H 4.1  D e s c r i p t i o n of "The  fishery  Hilsa  being  by  G a n g e s , and its f i s h e r y tional  fisher-castes  far  the  most  important  food-fish  in  one t h a t e n g a g e s t h e a t t e n t i o n of t h e  far  beyond  any  other,  it  is  the voca-  natural  that  extremely ingenious and effective methods have been evolved by a race noted for  its inventiveness  in this a r t "  (Hornell 1950).  The  choice  of t h e net d e p e n d s u p o n t h e d e p t h of w a t e r to be f i s h e d , v e l o c i t y  of  the c u r r e n t ,  of  time of t h e y e a r a n d a b o v e a l l t h e f i n a n c i a l c o n d i t i o n  t h e o w n e r of t h e net ( A h m e d 1 9 6 0 ) .  The following three types are very  common a n d  Meghna R i v e r :  generally  used  in the  (2)  C h a n d i , a n d (3)  (1)  S h a n g l a jal ( F i g . 4 a n d 4a)  (1)  Shangla jal,  Dora.  T h i s is a p u r s e - s h a p e d net w i t h h i n g e d mouth w h i c h c a n shut instantly when d e s i r e d .  be  It is also c a l l e d a c l a p n e t .  It c a n be u s e d f r o m t h e s u r f a c e to a d e p t h of s e v e r a l f a t h o m s , as t h e c l o s i n g r o p e may r u n to a l e n g t h of 15 f a t h o m s .  In  outline  t h e mouth is s e m i c i r c u l a r , t h e two f l e x i b l e bamboo l i p s o f t e n o v e r 8 m e t e r s i n l e n g t h , b e n t i n t o a deep g r a c e f u l c u r v e t h a t g i v e s an e a s y h i n g i n g motion w h e n t h e mouth has to be s h u t . a b o u t 3 to 4 m e t e r s d e e p .  The  n e t t i n g is of n y l o n t w i n e a n d t h e  mesh is f r o m 8 to 11 c m , k n o t to k n o t d i a g o n a l l y . k e p t open b y centre  of  direction  the of  a brick or lower the  lip.  current  The bag is  stone weight The  boat  with  the  The  mouth is  of 8 to 10 k g t i e d to is  allowed  mouth  of  to the  drift net  in  the the  facing  25  FIGURE  4.  Diagram of Shangla j a l in operation (after Jones 1959).  25a  26  FIGURE  4a.  Photograph of open mouth of Shangla j a l , at Chandpur.  26a  27  downstream t r a p p i n g any fish coming u p . cord,  dividing  at t h r e e  into three  p o i n t s on t h e  upper  disturbance caused by other  rope  emptied.  portion  held taut  the slight jerk or q u i v e r  haul  l i n e s at i t s lower of t h e  the  right  it t r a n s m i t s w h e n  hand.  The  left  is  then  a jerk hauled  net  of  the  up  and  w h e n t h e net is o p e r a t e d at bottom l e v e l it  entangled in submerged obstructions  a n d if e f f o r t s  nets are operated are  simultaneously  required  for  the  one at t h e  o t h e r s to o p e r a t e t h e n e t s a n d a s s i s t i n r o w i n g boats A  used  dinghi  for  operating  is a p l a n k  built  Shangla  it  When two  f r o m a boat a minimum of  purpose,  gets  to e x t r i c a t e  a r e of no a v a i l t h e r o p e is c u t a n d t h e net a b a n d o n e d .  dinghis.  hand;  a fish enters the  closed by  net  The  monsoon.  Occasionally  The  the  T h e net is o p e r a t e d r o u n d t h e y e a r , b u t peak o p e r a t i o n a l  season is d u r i n g  persons  attached  net to t r a n s m i t  in the fisherman's  s i g n a l ; t h e net i s i n s t a n t l y  in  end  feeler  t h e e n t r a n c e of a f i s h i n t o t h e n e t .  e n d of t h e l i n e is  is sufficient  branch  T h e r e is a f i n e  three  helm a n d  two  (Jones 1959). jal  are  round-bottomed  known  shallow  as boat  most common i n t h e G a n g e s , a b o u t 5 to 8 m e t e r s in l e n g t h a n d a b o u t 1 - 1 . 5 m e t e r s w i d e , w i t h l o n g p o i n t e d bow a n d s t e r n . strengthened bamboo  pieces  by in  ribs the  and c r o s s - b e a m s interspaces.  which serve in s t e e r i n g .  with  Long  front.  detachable  paddles  are  by  boat i s  half-split used  When s a i l i n g , a bamboo mast is  i n the f r o n t with t h i n split sail s u p p o r t e d y a r d stepped f a r in  The  a diagonal  also  carried bamboo  FIGURE 5.  Chandi  29  30  (2)  C h a n d i jal ( F i g .  5)  T h i s is a p o w e r f u l  drift  g i l l net  r i v e r s a r e i n f l o o d - May to The of  short  lengths,  which  generally  each  when  October.  C h a n d i jal i s made l i k e all l a r g e d r i f t  a b o u t to be s h o t .  deep.  and employed chiefly  are tied together  nets in a number  into a long  fleet  when  T h e s i z e of each p i e c e v a r i e s c o n s i d e r a b l y ,  piece  measures  12 m e t e r s  in  length  by  but  8 meters  T h e n e t s a r e of n y l o n t w i n e , and h a v e a mesh of f r o m 6 to  10 c m , k n o t to k n o t .  F l o a t s of bamboo a r e u s e d to b u o y t h e h e a d -  line  about  at  intervals  weighted  at  burnt-clay  of  similar  3-5  intervals,  meters, usually  while with  the thick  placed  hole, or  with  fragments  of  disc-shaped  brick.  c a n be a d j u s t e d to float v e r t i c a l l y at a n y d e s i r e d  75,  is  s i n k e r s each of about 10 to 15 cm in d i a m e t e r h a v i n g an  eccentrically  For  foot-rope  operational  are tied together  purposes  several  depending  net  depth.  p i e c e s of  on t h e l e n g t h  The  net,  from  required  25 to  and  the  r e s o u r c e s of t h e f i s h e r m e n .  To one e n d of t h e head r o p e a small  raft  and  of  bamboo i s  attached  the  net  is  r i v e r , t h e o t h e r e n d b e i n g t i e d to a b o a t . boat  drifts  down  in  the  current,  gilling  paid  out  across  T h e net as well as t h e any  ascending  Hilsa.  When f i s h i n g is d o n e at n i g h t , a l i g h t is k e p t b u r n i n g on t h e so t h a t t h e f i s h e r m e n i n t h e boat c a n get an i d e a of t h e of t h e o t h e r e x t r e m i t y of t h e n e t . is  sometimes  floating object.  substituted  by  a  pole  or  any  raft  position  For day-time f i s h i n g , the long  the  raft  conspicuous  T h o u g h t h e net is e m p l o y e d m a i n l y f o r  catching  H i l s a , o t h e r f i s h e s also sometimes get g i l l e d o r e n t a n g l e d i n i t .  31  The  boat u s e d f o r t h e o p e r a t i o n of t h i s net is k n o w n  Chandi nauka.  T h i s is a shallow p l a n k - b u i l t boat w i t h a  bottom,  and  longer  wider  than  the  dinghi.  It  is  provided  sail.  with  a hood  and  there  is  provision  T h e r e are  usually  5 to 8 p e r s o n s  for  12  The  to  boat  a mast  in a boat.  The  e m p l o y e d r o u n d t h e y e a r , b u t c h i e f l y u s e d f r o m May to  (3)  rounded  about  20 m e t e r s i n l e n g t h a n d about 2 . 5 - 3 . 5 m e t e r s i n w i d t h . is  as t h e  and  net  is  October.  D o r a jal This  net is s i m i l a r to C h a n d i j a l , b u t of smaller mesh (5 to  8 cm) a n d is m a i n l y e m p l o y e d f o r c a t c h i n g H i l s a . the  name of  Ilish  Bangladesh (Ahmed The  jal  in  the  districts  of  T h i s net goes b y  Khulna  and  Bogra  of  1962).  net may r u n  f r o m about 60 to o v e r 300 m e t e r s and  the  d e p t h f r o m about 5 to 8 m e t e r s a c c o r d i n g to t h e w i d t h a n d d e p t h of the  river.  The  net  is  employed  round  the  year,  but  mainly  o p e r a t e d a f t e r t h e Pooja ( O c t o b e r ) f o r a p e r i o d of about 6 m o n t h s until M a r c h - A p r i l .  The  Hilsa caught  i n t h e D o r a jal a r e  several  cm smaller t h a n t h o s e c a u g h t in t h e C h a n d i j a l . The  boat u s e d f o r t h e o p e r t a i o n of t h i s net is k n o w n as  Dora nauka.  It  i s t h e same t y p e of boat  as C h a n d i  nauka,  the but  smaller in s i z e . Generally  fishermen catch Hilsa every day.  r e s t , o n l y when p r e p a r i n g a n d t a k i n g t h e i r m e a l .  They take little T h e r e a r e a few  b r a v e f i s h e r m e n who p r e f e r n i g h t f i s h i n g to d a y f i s h i n g , a n d  who  32  take rest d u r i n g daytime.  D u r i n g t h e lean f i s h i n g s e a s o n some of  t h e m seek a l t e r n a t e e m p l o y m e n t . Few  fishermen  landing centres.  deliver  their  catches  directly  to  the  Most of t h e r i v e r f i s h e r m e n a p p e a r to u s e no i c e  a n d h a v e no means of m a i n t a i n i n g t h e q u a l i t y of t h e f i s h . they  fish  s e l l t h e i r c a t c h e s on t h e  river  to a f a r i a  Mostly  (collector).  The  c o l l e c t o r b u y s t h e f i s h f r o m t h e f i s h e r m e n , a n d t r a n s p o r t s them to the landing centres boats  to  the  most  are  where  wholesale  trans-shipped  packed with i c e . from freshwater  they  are off-loaded  market.  From  elsewhere  At C h a n d p u r ,  from the  truck  or  the collector  areas operate by  be d i s t i n g u i s h e d  by  there,  larger  collector  following  auction,  by  rail,  usually  boats b r i n g i n g  sail or o a r s , mechanized  from the  and can  fish  therefore  boats which  deliver  H i l s a of m a r i n e o r i g i n .  4.2  R e l a t i o n s of l a n d i n g s to 4.2.1  effort  Method of e s t i m a t i n g e f f o r t A s s u m i n g t h e amount of H i l s a t r a n s h i p p e d is a f a i r i n d i c a tion  of  later),  the  actual  amount  of  fish  the changes in freshwater  changes intensity.  in  availability Since there  of were  Hilsa no  caught  (as  is  discussed  c a t c h c o u l d be d u e e i t h e r or  to  data on  changes fishing  in  to  fishing  intensity,  c o n d u c t e d a r e g u l a r f i s h i n g boat c o u n t f o r two c o n s e c u t i v e  I  days  i n e v e r y f o r t n i g h t o v e r an 8 - m o n t h p e r i o d , i n o r d e r to e s t i m a t e t h e n u m b e r of boats d u r i n g t h e h i g h a n d low t i d e f i s h i n g o p e r a t i o n on a p a r t i c u l a r segment of t h e Meghma R i v e r [ f r o m C h a n d p u r  33  to N i l k a m a l f i s h i n g g r o u n d  (Fig. 1)].  T h i s 10-mile s t r e t c h of  t h e M e g h n a R i v e r p r o v i d e s a r e g u l a r s o u r c e of H i l s a s u p p l y t o the  Chandpur  counts)  landing centre.  and landings  Thus,  fishing  can be compared  from  intensity this  (boat  stretch  of  river. H i l s a f i s h i n g boat c o u n t s s t a r t e d i n J a n u a r y  1984 a n d c o n -  t i n u e d u n t i l August 1984 i n t h i s s e l e c t e d segment of t h e M e g h n a River.  O n t h e f i r s t week of e v e r y month I a n d a f i e l d a s s i s -  t a n t c o u n t e d t h e n u m b e r of boats e n g a g e d i n H i l s a f i s h i n g f r o m C h a n d p u r to Nilkamal b y a scheduled f e r r y .  T h e fleet consisted  of small b o a t s , medium boats a n d l a r g e b o a t s , a s d e s c r i b e d in the f o r e g o i n g  section.  While g o i n g  to N i l k a m a l b y t h e f e r r y  d u r i n g h i g h t i d e , I r e c o r d e d t h e n u m b e r of f i s h i n g boats a l o n g t h e n e a r s i d e of t h e r i v e r b y n a k e d e y e , a n d b o a t s a l o n g t h e other  s i d e was c o u n t e d  through  a binocular  b y an a s s i s t a n t .  T h e n e x t d a y , w h i l e r e t u r n i n g f r o m N i l k a m a l to C h a n d p u r b y t h e scheduled  ferry  during  low t i d e ,  the counts  were  repeated  (Table 1 ) . In  order  fishing  boats  to c o m b i n e into  a single  the effort index,  of  each  the three size  sizes  was a s s i g n e d  of a  w e i g h t a c c o r d i n g to t h e e s t i m a t e d a v e r a g e d a i l y c a t c h p e r b o a t . Small boats w e r e e s t i m a t e d to t a k e 1 k g / d a y personal observation boats  were  estimated  and discussions with to t a k e  on t h e b a s i s of  fishermen.  6.33 kg/day,  and large  Medium boats  1 7 . 6 k g / d a y , t h e l a t t e r t w o f i g u r e s b a s e d on r e c o r d s of m o n t h l y catch/boat over a ten-month period (Table 2 ) . intensity  of  fishing  effort  f o r each  time  T h u s , t h e total  was c a l c u l a t e d  by  TABLE 1.  Number of different types of Hi 1sa fishing gear/day that were in operation during different months of the year, the Meghna River between Chandpur and Nilkamal from January 1984 to August 1984. values reported are the mean and t h e i r standard e r r o r s .  The  Each monthly mean i s based on four  observations.  High Tide  MONTH Clap Net  Dora  Low Tide Chandi  Clap net  Dora  Mean o f High and Low Tide Counts Chandi  Clap Net  Dora  Chandi  January  22.0  347.0  56.0  15.0  211.0  22.5  18.5+2.2  279.0+43.4  39. 3+9.9  February  16.5  344.0  76.5  14.0  167.5  22.5  15.3+2.3  255.8+54.1  49.5+ 17.1  March  12.5  300.0  72.0  9.0  279.0  85.0  10.8+1.1  289.5+28.6  78.5+ 13.1  April  45.5  223.0  404.0  37.5  167.0  94.0  41.5+10.4  195.0+30.6  249.0+ 93.1  May  35.5  178.5  191.0  16.5  174.5  123.0  26.0+6. 5  176.5+17.5  157.0+ 20.2  June  60.a  124.0  330.5  52.0  102.5  178.5  56.0+8.0  113.3+23.0  254.5+ 44.7  July  299.5  62.5  297.5  97.0  50.0  123.0  198.3+58.8  56.3+3.8  210.3+ 51.9  August  101.0  31.5  186.0  50.0  29.0  127.0  75.5+15.9  30.2+3.5  156.5+ 24.6  35  TABLE 2.  Mean catch/day of Hilsa (kg) by two types of gear in different mouths in the r i v e r stretch from Chandpur to Nilkamal of  the  Meghna River (after Bangladesh Fisheries Resources Survey System, 1984).  Month  Chandi  Dora  May  1982  6.15  4.10  May  1982  10.03  6.12  September 1982  33.82  9.40  October  1982  25.90  6.33  January  1983  10.50  6.00  7.75  3.25  7.67  3.25  13.64  7.35  28.67  8.50  31.67  9.00  February April July  1983  1983 1983  October  1983  December 1983  Mean  17.58 kg/day  6.33 kg/day  36  a d d i n g t o g e t h e r t h e c o u n t s of each boat t y p e e a c h m u l t i p l i e d b y the weighting factor for that t y p e (Table 3 ) .  4.2.2  Method of e s t i m a t i n g l a n d i n g s T h e n u m b e r of b a s k e t s of r i v e r i n e H i l s a l a n d e d at C h a n d p u r l a n d i n g c e n t r e d u r i n g t h e l a n d i n g time ( f r o m 6 a . m . to 8 p . m . ) w e r e c o u n t e d b y two f i e l d a s s i s t a n t a n d b y me f o r each d a y fishing by  boat c o u n t s  (Fig.  6).  The  catch  is u s u a l l y  offloaded  s t a n d a r d s i z e b a s k e t s a n d t h e w e i g h t of f i s h p e r  known.  The  daily  total  weight  from collector's/fishermen's  of  riverine  boats which  had  Hilsa  of  basket  is  off-loaded  been o p e r a t i n g  in  t h e r i v e r was t h e r e f o r e e s t i m a t e d b y b a s k e t c o u n t s s u p p l e m e n t e d by  weight  slightly after  data  low  due  8 p.m.,  landing  to  but  available.  a  few  the  data obtained  trans-shipment  4.2.3  when  ratio  reaching  the  have  landing  is  slight.  this  way  were  also c h e c k e d  first  time to  in  been centre  Freshwater  Hilsa against  data.  attempt  between  fish  may  error  Marine versus freshwater An  Estimates  landings  was made f o r  riverine  or  the  freshwater  d e l i v e r e d to C h a n d p u r l a n d i n g c e n t r e . m a r i n e H i l s a was t h e same as f o r  versus  find  marine  out  the  catches  T h e method of e s t i m a t i n g  Hilsa originating  from  fresh-  w a t e r , e x c e p t t h a t m a r i n e H i l s a were t h o s e b r o u g h t u p s t r e a m to the landing centre by mechanized boats. 2319 m e t r i c  tonnes,  freshwater,  while  i.e.  about  1999 m e t r i c  54% of  tonnes;  It was o b s e r v e d the i.e.,  total  Hilsa,  46% were  that was  contri-  37  TABLE 3.  Monthly freshwater landings of Hilsa and f i s h i n g intensity  (cal-  culated as described i n text) f o r the River Meghna at Chandpur during the period of January to August 1984.  Monthly freshwater  landings are calculated from eight d a i l y observations. Regression s t a t i s t i c s shown below.  Freshwater Landings (metric tonnes)  Month  Fishing Intensity  January  57. 7+.1  2475.4  February  57.2+.3  2503.0 •  March  220.7+1.8  3223.4  April  203.9+1.4  5653.7  May  231.8+1.5  3904.6  June  506.8+2.2  5248.6  July  434.6+2.2  4251.7  August  606.1+1.9  3018.6  Y  = 59.5 + .06 * Fishing intensity  r  = .1286  P  2  = .61  38  FIGURE 6.  HiIsa offloaded  by standard basket at Chandpur landing centre .  3 9  40  buted by the marine Hilsa (Table 4 ) .  Only the riverine catches  at C h a n d p u r a r e c o n s i d e r e d i n t h e f o l l o w i n g c a l c u l a t i o n s . 4.2.4  Results and discussion The fishing only  regression intensity  12% of  was  calculated  (Table  the  3).  of  Fishing  variation  in  monthly  intensity  freshwater  landings  on  accounted  for  landings  at  Hilsa  C h a n d p u r , a n d t h e r e g r e s s i o n was not s i g n i f i c a n t . highest fishing intensity  (5654 i n A p r i l )  low l a n d i n g (204 t o n n e s ) ; August)  were  (3018).  Evidently,  by  the  produced  variations  in  by  highest only  variations effort,  produced a moderately landings  moderate  in  landings  among  T h e month of  the  (606 t o n n e s  fishing are  intensity  not  monthly  in  controlled samples  at  Chandpur. The  only  other  available  records  on  landings  and  effort  w e r e f r o m G o d a v a r i R i v e r on t h e east coast of I n d i a d u r i n g monsoon 1972). effort the  months  of  the  years  1963-1969  (Rajyalakshmi  the  et_ a l .  Regression calculations showed that here again f i s h i n g accounted  Godaveri  for  only  14.6% of  River,  and  the  the  variation  regression  was  not  in  yield  of  significant  (Table 5). One f u r t h e r shipment  records  available)  a  question (which  reliable  arises: are  to what  usually  indication  of  extent are  the only actual  trans-  historical  data  landings.  Since  b o t h s e t s of d a t a w e r e a v a i l a b l e f r o m C h a n d p u r f o r t h e m o n t h s of  January  calculated.  to  August  Monthly  1984  (Table 4 ) ,  their  t r a n s - s h i p m e n t s were  correlation  very  highly  was  corre-  41  TABLE 4.  Rail trans-shipment records, and observed r i v e r i n e and marine Hi 1sa landings i n metric tonnes f o r the Meghna River at Chandpur from January 1984 to August 1984. mean and t h e i r standard e r r o r s . and  The values reported are the Each monthly mean of freshwater  marine water Hilsa i s based on eight observations and  trans-shipment on 30/31 days of observation.  Marine Water Landing  Observed Total Landing (Riverine o marine water landings)  57.7+.1  124.7+2.2  182.4  232.2  57.2+.3  167.2+1.1  224.4  March  397.9  220.7+1.8  76.9+1.1  297.6  April  427.1  203.9+1.4  31.6+0.7  235.5  May  360.8  231.8+1.5  25.1+0. 5  256.9  June  918.4  506.8+2.2  372.8+4.3  879.6  July  1081.6  434.6+2.2  261.5+1.5  696.1  August  2337.3  606.1+1.9  939.7+7.3  1545.8  TOTAL  5863.8  2318.8  1999.5  4318.3  Month  Rail Trans-shipment  January  108.4  February  Ri veri ne Landing  42  TABLE 5.  Estimated y i e l d (y-j) in tonnes and effort in thousands of manhours (g-j) of Hi Isa i i i sha in Godavari River by d r i f t  gillnets  in the monsoon months of the years 1963-69 (after Rajyalakshmi et al.  1972).  Regression s t a t i s t i c s  Year  shown below.  9  i  1963  7.5  63.7  1964  43.9  306.2  1965  36.3  105.2  1966  15.0  165.3  1967  9.6  221.7  1968  14.3  226.7  1969  18.9  198.0  Y = 8.73 + .06 * Effort 2  .1465  r  =  P  =  .60  43  lated with observed freshwater lity  in the former accounted  the latter ( F i g . as  a  7).  reasonable  Chandpur.  H i l s a l a n d i n g s (p=.003)  f o r about 80% of t h e  variabi-  variation  T h e r e f o r e , c h a n g e s i n e i t h e r c a n be t a k e n indicator  of  changes  in  Hilsa  catch  at  It has been a s s u m e d t h a t t h e same c l o s e r e l a t i o n s h i p  w a s t r u e b e t w e e n t r a n s - s h i p m e n t s a n d l a n d i n g s at  Goalundo.  A s t h e f o r e g o i n g s e c t i o n has e s t a b l i s h e d that t r a n s m e n t s (or l a n d i n g s )  ship-  seem to v a r y p r i m a r i l y a c c o r d i n g to a b u n d -  a n c e of f i s h , not to e f f o r t , changes  in  I am now g o i n g to e x a m i n e  in s h i p m e n t s a n d t r y  to r e l a t e them to  monthly  environmental  factors. 4.3  R e l a t i o n s h i p of l a n d i n g s to e n v i r o n m e n t a l 4.3.1  factors  S o u r c e s of d a t a Records its  of  judicious  to  difficulties  in  complicated  the  the  and  way  of  Hilsa fisheries  include  the i n d u s t r y , practices.  s t a t i s t i c s of  exploitation  difficulties relating  catch  the  very  any  fishery  development. collection of  and  vital  There of  Bangladesh  diffuse  are  are  such  These  nature  l a c k of f i x e d l a n d i n g c e n t r e s , a n d d i v e r s e Further,  by  collection  of  Hilsa  the traditional nature  of  the  many  statistics  rivers.  scattered  for  landing industry  of  trade  data in  is that  neither fishermen nor government agencies keep detailed records of l a n d i n g s .  F o r t h e s e r e a s o n s i n d i r e c t m e t h o d s of e s t i m a t i o n  of l a n d i n g s must be e m p l o y e d ( i . e . , s h i p m e n t of H i l s a b y  such  railway).  as t r a n s - s h i p m e n t  records  44  FIGURE 7.  Relationship between r i v e r i n e Hilsa landings with r a i l record of Hi 1sa in the Meghna River at Chandpur.  shipment  2500  n  Y = - 1 9 2 . 2 +3.2*riverine hilsa landings  46  Of  all the t r a n s - s h i p m e n t  Bangladesh Railway analysis  of  advantage which  of  they  instance, have  a v a i l a b l e , t h o s e of  the  a r e most r e l i a b l e a n d t h e most u s e f u l  for  seasonal and this  have  daily  records  annual  source  of  been  kept  records  of  variation  records (Dunn Hilsa  been k e p t s i n c e 1967. T h i s  lies  in  landings.  in  the  1982, Melvin  trans-shipment  The  detail  with  1984). at  For  Goalundo  sometimes allows d e t e c t i o n of  o b v i o u s e r r o r s b y c o m p a r i n g d a y to d a y w e i g h t s . most s i g n i f i c a n t a d v a n t a g e is t h a t  records  The second and  a r e k e p t of  n u m b e r of p a c k a g e s , a n d t r a n s - s h i p m e n t c h a r g e s .  weight,  If an e r r o r  o c c u r s i n t h e w e i g h t , an a p p r o x i m a t i o n c a n be made f r o m e i t h e r of t h e o t h e r this  strategy  v a r i a b l e s a n d t h e e r r o r c a n be c o r r e c t e d . has led me to u n c o v e r  (1982) c a t c h i n d e x .  p r e s e n t e d as t h e w e i g h t . stable  Dunn's  A t G o a l u n d o o n t h e u p p e r r e a c h e s of t h e  Padma t h e n u m b e r of  relatively  in  Dunn's index documented l o n g - t e r m t r e n d s  in the Hilsa l a n d i n g s . river  several errors  Using  between  packages shipped  was  erroneously  T h i s e r r o r h a s made l a n d i n g s a p p e a r 1976-1981  whereas  landings  have  a c t u a l l y been i n c r e a s i n g . There records includes  are  however  as a m e a s u r e of packing  ice  some  problems  landings.  which  is  For  used  with  trans-shipment  instance, the  in  a c c o r d i n g t o s u p p l y a n d d i s t a n c e to m a r k e t .  variable  weight  quantities  A l s o , a small p o r -  t i o n of H i l s a l a n d e d w h i c h a r e c o n s u m e d b y t h e local people has not been t a k e n i n t o a c c o u n t ; h o w e v e r , c o n s u m p t i o n b y f i s h e r m e n i s small b e c a u s e of t h e h i g h c a s h v a l u e of H i l s a w h i c h may  be  47  almost  their  only  source  of  income.  Moreover,  the  use  c e r t a i n r a i l w a y s t a t i o n s f o r s h i p m e n t of H i l s a h a v e v a r i e d the  years  for  both  economic a n d  landing  centres  cost  rail t r a n s - s h i p m e n t ,  have  of  due  to  natural  siltation).  resulted in relatively  and  reasons  For  improved  greater  road  over  (closure  instance,  the  of  of  rising  construction,  t r a n s - s h i p m e n t of  Hilsa  by  t r u c k since 1975. From Bangladesh waters the only seasonal and i n t e r - a n n u a l records  of  riverine  trans-shipment  of  Hilsa  the  catch  fish  of  data  are  Goalundo  available  on  the  from  Padma  the  river.  S u b s e q u e n t to 1 9 7 4 , h o w e v e r , t h e t r a n s - s h i p m e n t d a t a f r o m t h i s s i t e a r e not  representative  of  riverine  Hilsa catch.  Firstly,  a f t e r 1974 t r a n s - s h i p m e n t s of H i l s a at G o a l u n d o h a v e  included  s i g n i f i c a n t b u t u n k n o w n p r o p o r t i o n s of b o t h r i v e r i n e a n d m a r i n e catches.  Secondly,  the  impact of  B a r r a g e i n 1975 on t h e s u b s e q u e n t  c o m p l e t i o n of  the  Farakka  Hilsa fishery  of t h e  lower  G a n g e s is q u i t e e v i d e n t ( A b b a s 1 9 8 2 , B i l g r a m i a n d M u n s h i 1 9 8 2 ) . Hilsa  landings  catches  of  declined  above  non-migratory  the  species  barrage did  in  not,  India while  although the  Hilsa  f i s h e r y i n I n d i a below t h e b a r r a g e has been s t e a d y a n d a c t u a l l y r e c o r d e d i n 1981 a b u m p e r c r o p t h r e e times t h e a v e r a g e c a t c h of the  earlier  Thirdly,  years  since  construction  (Anonymous  s u b s e q u e n t to 1974 t h e s e r e c o r d s  decreasing  i m p o r t a n c e of  railway  freight  t r a n s p o r t network improved ( D u n n 1982).  reflect the  as t h e  1984b). steadily  national  road  I have used Goalundo  t r a n s - s h i p m e n t d a t a o n l y f r o m 1967 to 1974 ( T a b l e 6) b e c a u s e of  TABLE 6.  Year/Month  Monthly trans-shipment  Jan.  Feb.  Mar.  of Hilsa through Goalundo Railway station  Apr.  May  June  July  Aug.  Sept.  (1967-74) i n metric tonnes.  Oct.  Nov.  Dec.  Total  1967  243.0  507.0  402.0  188.0  131.0  124.0  199.0  159.0  334.0  229.0  190.0  196.0  2875.0  1968  107.0  102.0  143.0  223.0  282.0  257.0  131.0  132.0  205.0  183.0  166.0  412.0  2323.0  1969  239.0  529.0  734.0  718.0  843.0  1524.0  1006.0  1128.0  1652.0  410.0  207.0  419.0  9409.0  1970  471.0  489.0  1250.0  206.0  893.0  1406.0  380.0  269.0  240.0  124.0  93.0  268.0  6089.0  1971  NR  NR  NR  NR  NR  NR  NR  1972  30.0  26.0  22.0  22.0  35.0  257.0  255.0  1973  206.0  237.0  240.0  294.0  365.0  975.0  1974  163.0  235.0  420.0  342.0  495.0  535.0  1  NR = no record  NR  NR  9.0  30.0  90.0  103.0  42.0  921.0  514.0  1269.0  6289.0  613.0  489.0  523.0  12014.0  52.0  31.0  72.0  45.0  42.0  3.0  2435.0  NR  NR  NR  NR  49  the above reasons.  A l l d a t a on t r a n s - s h i p m e n t s f r o m C h a n d p u r  have been excluded from y e a r - t o - y e a r c o m p a r i s o n s , because they i n c l u d e a v a r i a b l e b u t u n k n o w n p r o p o r t i o n of m a r i n e f i s h . It  has  also been  necessary  to  exclude  the Hilsa landings in Bangladesh d u r i n g to  December  effort.  1971) ,  b e c a u s e of  severe  While f i s h i n g was d r a s t i c a l l y  fishermen  in  the  Hooghly-Mattah  harvested  a bumper crop  s i m i l a r i n all y e a r s e x c e p t  calculations  the liberation disruptions  reduced  estuarine  ( D u t t a et a l .  p a t t e r n of l a n d i n g s i n t h e e s t u a r i n e  from  in  in  fishing  Bangladesh,  system  1973).  (March  of  The  India  seasonal  s y s t e m was more o r  M a r c h 1971 to F e b r u a r y  less  1972, when  u n u s u a l l y h i g h l a n d i n g s w e r e made in A u g u s t a n d S e p t e m b e r [ c o n t r i b u t i n g 31% of t h e a n n u a l l a n d i n g s i n 1971-72 as a g a i n s t  only  2-7% i n o t h e r y e a r s  this  (Mitra and Ghosh 1979)].  Clearly  in  i n s t a n c e , geographic s h i f t s in effort produced marked change in d i s t r i b u t i o n of t h e c a t c h . R a i n f a l l a n d maximum a i r t e m p e r a t u r e d a t a w e r e from the B a n g l a d e s h Meteorology  collected  Department, while water  level  a n d minimum d i s c h a r g e d a t a w e r e c o l l e c t e d f r o m t h e B a n g l a d e s h Water D e v e l o p m e n t B o a r d , D h a k a .  T h e s e d a t a a r e b e l i e v e d to be  reliable. 4.3.2  R e l a t i o n s h i p of l a n d i n g s to r a i n f a l l M o n t h l y H i l s a l a n d i n g s of t h e r i v e r P a d m a at G o a l u n d o f r o m 1967 t o 1974 a r e s h o w n i n F i g . 8 a , a l o n g w i t h m o n t h l y d a t a of  Faridpur  (near  Goalundo).  (Monthly  rainfall  rainfall data  of  50  FIGURE 8.  Relationship of Hilsa landings in metric tonnes (MT) of the Padma River of the Ganges at Goalundo to r a i n f a l l of Faridpur (near Goalundo).  52  1974 a r e not c o m p l e t e . ) most p r o d u c t i v e was i n  The  month of S e p t e m b e r 1973 was  (6289 m e t r i c t o n n e s ) ,  December  1974 (3  metric  while the  tonnes).  poorest  There  catch  were  major  d i f f e r e n c e s b e t w e e n y e a r s i n t h e p a t t e r n of l a n d i n g s , a n d i n t h e p a t t e r n of r a i n f a l l , b u t variations in the two.  no o b v i o u s  relationship  the  also  between  In t h r e e y e a r s , t h e l a n d i n g s s h o w e d two  d i s t i n c t p e a k s ( J u n e a n d S e p t e m b e r i n two y e a r s , J u n e a n d M a r c h i n o n e , a n d i n o t h e r y e a r s o n l y a s l i g h t peak i n May o r In  four  years,  r a i n f a l l s h o w e d two d i s t i n c t  p e a k s , and in  other years a single peak, with peaks o c c u r r i n g f r o m May to A u g u s t .  June).  in any  the  month  Peak l a n d i n g s could o c c u r either before or  a f t e r t h e month of peak r a i n f a l l . The only other  set of d a t a on H i l s a l a n d i n g s a n d  were those collected d u r i n g the present July  1984.  Monthly  Hilsa  landings  study  of  the  rainfall  from January Meghna  River  to at  C h a n d p u r f r o m J a n u a r y to J u l y 1984 a r e s h o w n i n F i g . 8 b , a l o n g with monthly regression, in  r a i n f a l l d a t a of C h a n d p u r . rainfall accounted  freshwater  positively  Hilsa landings,  correlated  for  about  and  the  (p < 0 . 0 3 ) ,  F r o m a simple l i n e a r 67% of two  but  the  the  were  variation  significantly  time  series  is  short. 4.3.3  R e l a t i o n s h i p of l a n d i n g s to mean w a t e r Monthly  level  H i l s a l a n d i n g s at G o a l u n d o  are  shown  in F i g . 9 ,  a l o n g w i t h m o n t h l y mean w a t e r l e v e l of t h e Padma at There  was  much  more  regularity  between  years  in  Goalundo. seasonal  53  FIGURE 8a.  Relationship of freshwater H i l s a landings of the Meghna River at Chandpur to r a i n f a l l  of Chandpur.  54  1400  8000-  1300 7000-  r-  V) O  • 1200  ' / / / /  6000 H  '  • 1100  1  I I \ I I  1000 • 900  5000-  z  Q Z <  |  • 800 -I ,<  4000700  <  £  < 3000-  r 600 \ \  500  X  2000-  400 300 1000 200 100 ~i— JAN  —i—  FEB  X  r  MAR  APR  i MAY  -O  HILSA  -X  RAINFALL  r JUN  LANDINGS  JUL  55  FIGURE 9.  Relationship of Hilsa landings of the Padma River at Goalundo to mean water level of the Padma River at Goalundo.  56  57  patterns level  of  water  was lowest  However,  level in  than  February  of  rainfall.  and  rose  Every  to  year,  a high  in  water  August.  as t h e r e w e r e major d i f f e r e n c e s b e t w e e n y e a r s in H i l s a  l a n d i n g s , as d e s c r i b e d a b o v e , t h e r e was no o b v i o u s  relationship  between variations in water level and in l a n d i n g s .  4.3.4  R e l a t i o n s h i p of l a n d i n g s to minimum d i s c h a r g e Monthly along  with  monthly  Goalundo. variation  H i l s a l a n d i n g s at G o a l u n d o minimum d i s c h a r g e  are shown of  Padma  river  at  S e a s o n a l p a t t e r n s of d i s c h a r g e s h o w e d somewhat more between  differences  years  than  did  water  levels,  in t h e r a t e s of r i s e a n d f a l l ,  o c c u r r e d in either A u g u s t or September. obvious  the  i n F i g . 10  relationship  between  variations  but  with  t h e peak  greater always  A g a i n , t h e r e was no in  discharge  and  in  landings. 4.3.5  R e l a t i o n s h i p of l a n d i n g s to maximum a i r  temperature  Water t e m p e r a t u r e d a t a of t h e Padma r i v e r at G o a l u n d o a r e not  available,  However, months  but  air  temperature  data  are  available.  w a t e r t e m p e r a t u r e s w e r e a v a i l a b l e f o r 13 c o n s e c u t i v e  for  the  Hooghly  River  of  the  t e m p e r a t u r e s at C a l c u t t a ( n e a r H o o g h l y ) .  Ganges,  and  A highly  also  air  significant  p o s i t i v e c o r r e l a t i o n (p < 0 . 0 1 ) was f o u n d between a i r a n d w a t e r temperature  (Appendix  Table  2).  A s s u m i n g "that a i r t e m p e r a t u r e of F a r i d p u r ( n e a r G o a l u n d o ) similarly  has  a  close  association  with  water  P a d m a r i v e r at G o a l u n d o , I h a v e p l o t t e d m o n t h l y  temperature  of  Hilsa landings  58  FIGURE 10.  Relationship of Hilsa landings of the Padma River at Goalundo to minimum discharge of the Padma River at Goalundo.  59  60  at G o a l u n d o i n F i g . 1 1 , a l o n g w i t h m o n t h l y maximum a i r t e m p e r a ture  of  Faridpur.  It  is o b s e r v e d  that  highest  temperatures  w e r e r e c o r d e d i n A p r i l o r M a y , a n d lowest t e m p e r a t u r e s d u r i n g December, J a n u a r y and F e b r u a r y . in  seasonal changes  of  V a r i a t i o n s f r o m y e a r to y e a r  temperature  are  slight,  and  bear  no  o b v i o u s r e l a t i o n s h i p to t h o s e of l a n d i n g s . 4.3.6  Discussion "Information from the environment received by the sensory s y s t e m of a f i s h c a n act i n two w a y s  to a f f e c t  behaviour.  stimulus  Firstly,  f a l l , water c u r r e n t ,  an e n v i r o n m e n t a l  its  migratory  such  as  rain-  t e m p e r a t u r e may a l t e r f i s h o r i e n t a t i o n  t h e r e b y act as a " d i r e c t o r " of m o v e m e n t .  and  Secondly, such stimu-  l u s may i n c r e a s e o r d e c r e a s e t h e i n t e n s i t y of m o v e m e n t , r e g a r d less  of  tion."  orientation,  environmental  been  several little  so  serve  as  a 'regulator'  of  migra-  reproductive  cycles  (Northcote 1984).  The has  and  of  closest  studied  work  relative  of  extensively  freshwater this  control  species has  whose  (de  in  been  teleost  Vlaming  India  (Sundararaj  directed  spawning  1972) ,  runs  to  Hilsa  have  including  1981),  but  ilisha.  been  The  studied  d e t a i l is t h e A m e r i c a n s h a d A l o s a s a p i d i s s i m a ( L e g g e t t  in  1977),  i n w h i c h t e m p e r a t u r e has b e e n shown to be an i m p o r t a n t e n v i r o n mental stimulus c o n t r o l l i n g r u n t i m i n g . In  tropical  subsequent  and  increased  subtropical stream  c l i m a t e s , monsoon  flow  appear  to  rains  trigger  and many  61  FIGURE 11.  Relationship of HiIsa landings of the Padma River at Goalundo to maximum a i r temperature of Faridpur (near Goalundo).  63  behavioural seasonal are,  responses  and/or  in  annual  to some e x t e n t ,  triggered  in  by  catch  of  suggest  that  riverine  Hilsa  seasonal and/or  Data supporting  this  long-term  hypothesis  seems  to  s e a s o n a l t i m i n g of P a d m a at landings  and  be  over  r a i n f a l l may  there  between t h e m .  no  close  Hilsa landings  Goalundo,  and  is  with  the  a n d of  7-year  show no  association rainfall  period  either  between  two  suggestion  of  in  While  there  context,  during  rising (Fig.  was  extensive  for  the  examined. peaks or causal  Both  one i n  a  relationship  between  January.  rainfall  and  on t h e M e g h n a R i v e r as m e a s u r e d i n t h e 7 m o n t h s ' d a t a i n one which  Much  the  time  rainfall  same t r e n d  same months i n  year  and  avail-  landings  appeared  1969.  were  at  were  Goalundo  S i n c e t h e much  more  d a t a b a s e f o r G o a l u n d o d e m o n s t r a t e s no s u c h c o r r e l a -  Chandpur  than  correlation  of  t i o n i n some y e a r s ,  The  a  only  most  monthly. 8)  river  A b o u t t h e o n l y commonality i n a l l y e a r s is t h a t  l a n d i n g s at C h a n d p u r  able,  the  the  r a i n f a l l a n d l a n d i n g s are b o t h low f r o m N o v e m b e r to  present  are,  largely circumstantial.  There  year,  Researchers  variation  environmental changes. however,  fish.  the correlation d u r i n g the short  is p r o b a b l y reason that  fortuitous. r a i n f a l l showed  (precipi-  snow-melt) Water  is  that  flow  throughout  level  and  in  the  discharge  the  fluctuations  B r a h m a p u t r a i s d e t e r m i n e d b y t h e summation of e v e n t s  watershed.  level  more e r r a t i c  Ganges-  plus  water  for  lower  tation  did  series  immense records  area were  of  the fairly  64  r e g u l a r f r o m y e a r to y e a r i n t h e i r s e a s o n a l p a t t e r n . which  displayed sharply  are therefore evidently The  other  different  Landings,  p a t t e r n s f r o m y e a r to  year,  not t i e d c l o s e l y to r i v e r f l o w .  environmental  variable  studied,  temperature,  a g a i n showed a f a i r l y c o n s i s t e n t s e a s o n a l p a t t e r n f r o m y e a r year.  Since  temperature  peak is  landings  responsible  did in  not, any  it  does  simple  not  way  seem for  to  that  annual  d i f f e r e n c e s in r u n t i m i n g . T h e c o n c l u s i o n must be t h a t s e a s o n a l v a r i a t i o n s in t i m i n g of  the landings  t a b l e to a n y  of  H i l s a do  of t h e  not  seem to  environmental  variables  water l e v e l , d i s c h a r g e s , air t e m p e r a t u r e ) . relatively always  low i n N o v e m b e r to J a n u a r y ,  experiences  temperature. show  an  low  directly  attribu-  studied  (rainfall,  Landings are always  and this winter  rainfall,  stream  season  flow  and  B u t in other m o n t h s , landings in the Meghna R i v e r  erratic  apparently  relatively  be  behaviour  both  within  and  between  years  i n d e p e n d e n t of t h e local c o n d i t i o n s s t u d i e d .  These  v a r i a t i o n s in l a n d i n g s h a v e been s h o w n not to be d u e to v a r i a tions in  in f i s h i n g e f f o r t .  the  estuarine  or  marine conditions  e n t r y into freshwater; at  Chandpur  considerably  may  Perhaps the  sources  of  variation  affecting the  timing  f l u c t u a t i o n s i n n u m b e r s of f i s h  principally  reflect  environmental  lie of  arriving  influences  r e m o v e d i n time a n d d i s t a n c e f r o m w h e r e t h e  fish  are landed. The suggests  presence that  in  there  some y e a r s may  be  two  of two (or  p e a k s of  more)  Hilsa  racially  runs  distinct  65  groups involved.  P r e s e n c e of a monsoon r u n ( J u n e to O c t o b e r )  and a winter  (November  India  run  ( M o t w a n i et a L  Rosa 1963).  In  to M a r c h )  1957, Nair  Bangladesh,  t h e r e a r e two t y p e s of H i l s a :  has been s u g g e s t e d  in  1958, Pillay 1958, Pillay  Quddus  et_ a l .  (1984a)  and  believed  t y p e " A " broad form r e p r e s e n t a -  t i v e of monsoon s p a w n i n g , a n d t y p e " B " s l e n d e r f o r m r e p r e s e n t a t i v e of w i n t e r s p a w n i n g . only  a single  wave  of  On t h e o t h e r h a n d , i n G o d a v a r i migration  has  been  observed  (June  O c t o b e r ) b y C h a c k o and G a n a p a t i (1949) (as is e v i d e n t c e r t a i n y e a r s at G o a l u n d o ) . r a c e of H i l s a r e a c h i n g first  distinguish  it may  them b e f o r e  i n t h e i r t i m i n g to p a r t i c u l a r e n v i r o n m e n t a l Previous observers ment  of  Hilsa  provide  of  factors  to  fluctuations  factors.  controlling  conflicting  one  be n e c e s s a r y  attributing  to  also in  If t h e r e a r e i n d e e d more t h a n  Meghna R i v e r ,  between  River  upstream  interpretations.  move-  Hora  and  N a i r (1940) s u g g e s t e d t h a t t h e u p s t r e a m movement of H i l s a was largely  dependent  s t a t e of  on two main f a c t o r s ;  sexual maturity.  The  fact  v i z . , monsoon and  that  mature  Hilsa  ascend  the r i v e r d u r i n g the winter s e a s o n , when water levels are suggests  however that  flood c o n d i t i o n s  i n d u c i n g t h e f i s h to move u p s t r e a m . observed  in  the  winter  that  a  are  not  necessary  In c o n t r a s t ,  secondary  Day  migration  the  of  low, for  (1873) Hilsa  o c c u r s i n t h e I n d u s a n d I r r a w a d y R i v e r s a n d i s i n d u c e d b y minor floods  caused  by  the  m e l t i n g of  snow  in t h e  upper  reaches.  H o w e v e r , K u l k a r n i (1951) o b s e r v e d t h a t t h e summer m i g r a t i o n of H i l s a in the  Narbada  River  cannot  be e x p l a i n e d  by  any  such  66  secondary increased  flooding. s t r e a m flow  Islam  and  does  not  Talbot appear  (1968) to  be  observed  that  a stimulus  that  a t t r a c t s H i l s a , a l t h o u g h t h e peak of t h e r u n does o c c u r  during  peak f l o w s . On the other  h a n d , Jones and S u j a n s i n g h a n i  c a t e d a d i r e c t c o r r e l a t i o n b e t w e e n flood w a t e r  (1951)  indi-  levels and  Hilsa  l a n d i n g s in C h i l k a lake and the Mahanadi R i v e r in O r i s s a . also  suggest  that  other  hydrological  salinity and higher temperature) t i o n of a d u l t H i l s a .  factors  They  (i.e.,  low  influence the upstream m i g r a -  R a m a k r i s h n a i a h ( 1 9 7 2 ) , h o w e v e r , f o u n d no  d e s c e r n i b l e t r e n d b e t w e e n w a t e r flow a n d f i s h e r y l a n d i n g s . contrast,  G a n a p a t i (1973) a s s o c i a t e d t h e r e d u c e d  H i l s a up S o u t h  Indian  rivers  m i g r a t i o n s of  w i t h t h e l a c k of h i g h  t o t h e sea c a u s e d b y dams or i r r i g a t i o n  In  discharges  diversions.  T h e general rise in temperature in the r i v e r s which o c c u r s d u r i n g t h e l a t t e r p a r t of t h e w i n t e r underway tion  of  terms, year  Hilsa migrations  the  is  run  (Jones  1957, Kyaw  is c o n s i s t e n t only  after  with  the  1953).  the present  start  of  In  may be t h e t r i g g e r mouth  from  very  data,  rise  in  F e b r u a r y t h a t l a n d i n g s may s t a r t to i n c r e a s e .  river  are  h a s b e e n s u g g e s t e d as a f a c t o r c o n t r i b u t i n g to i n i t i a -  this it  when  general  in that  each  temperature  Temperature rise  w h i c h i n d u c e s t h e f i r s t movement i n t o the  ocean,  but  neither  in  it  nor  the  the  other  e n v i r o n m e n t a l f a c t o r s e x a m i n e d c a n as y e t be i n v o k e d t o e x p l a i n the subsequent large monthly fluctuations in f i s h reaching upstream fishery.  the  67  5. A N N U A L V A R I A T I O N S IN Hilsa IN THE PADMA A N D MEGHNA RIVERS OF B A N G L A D E S H A N D IN T H E INDUS RIVER OF P A K I S T A N In  addition to seasonal variations in Hilsa, the total annual landings  may vary considerably from year to year.  The purpose of this part of the  study was to document levels of variation of landings betwen years and to try to uncover causes of such variation. Although available,  precise and comparable  it appears  that  Bangladesh  spatial and temporal data are not waters  contribute  metric tonnes (mt) of Hilsa (Melvin 1984).  This total may  about 50,000 mt realized by the mechanized  gill  sea  front (Raja 1984).  Burma about  Data  150,000  include up to  netters operating on the  In comparison, India contributes about 25,000 mt,  3,000-4,000  7,000-8000 mt.  about  mt  (Druzhinin  suitable  1970),  for analysis  were  and  Pakistan  available  only  about from  Bangladesh waters and from the Indus River. 5.1  Sources of data For periods  the river Padma at Goalundo the sources, methods and time of data collection  were outlined  in the foregoing chapter.  Landings of Hilsa from 1967 to 1974 of the Padma River at Goalundo, with rainfall and mean air temperature of Faridpur from 1962 to 1974, are  shown in Table 7.  Landings of Hilsa from 1937-1940 of the Meghna  River with rainfall from 1933-1940 are shown in Table 8. For  the Indus River I collected Hilsa catch data of 1968 to 1982  from the F A O Yearbook of Fishery Statistics - Catches and Landings. The rainfall and mean air temperature of Hyderabad the  rainfall  and  water  temperature  of Indus  which  were  represents  collected  from  68  TABLE 7.  Landings of Hilsa i l i s h a from 1967 to 1974 of the Padma River at Goalundo, with r a i n f a l l  and mean a i r temperature of Faridpur from  1962 to 1974.  Year  Landings (mt)  Rain (mm)  Mean A i r Temp.  (°C)  1961  -  1892  24.73  1962  -  1615  24.72  1963  -  1676  23.33  1964  -  2045  22.22  2007  25.28  1965 1966  -  1519  25.28  1967  2875  1246  25.00  1968  2323  1762  24.72  1969  9409  1526  25.00  1970  6089  2220  25.28  1971  -  1365  24.17  1972  921  1706  24.72  1973  12014  2918  25.28  1974  2435  2920  23.89  TABLE 8.  Annual landings of Hilsa and r a i n f a l l  at Chandpur during the  period 1933-1940.  Year 1933 1934 1935 1936  Landings (mt)  -  R a i n f a l l (mm) 2142 2073 1494 2224  1937  (456.78)  1736  1938  298.55  1907  1939  975.97  2204  1940  826.02  1791  70  Monthly Climatic Data for the Statistics.  World and  25  Years of Pakistan in  Landings of Hilsa of the Indus, rainfall and  temperature are shown in Table 9.  mean air  These data are believed to be  reliable. 5.2  Results 5.2.1  Relationship of landings to rainfall in the Padma River of the Ganges at Goalundo in Bangladesh I calculated a simple linear regression of the landings of Goalundo with rainfall over different lag periods of from 1 to 6 years (Table 10) for the years 1967-1974 using MISP (Hilborn 1980). negative  A two  year lag in rainfall is significant (p<0.05) with  slope, and  variability of rainfall accounted for  of the variation in landings at Goalundo (Fig. 12). other regression verging on significance was  57.6%  The  only  a positive regres-  sion for the 5-year lag (p=0.0812). An  interesting record which indirectly supports a negative  relationship between Hilsa catch and is the record of packing ice use. tioned into East and the two Bengals.  West there was  rainfall two  years  Before the Bengal was  earlier parti-  unrestricted trade between  Further, in view of the high demand for fish  in the cities of Calcutta and Howrah and their suburbs, most of the Hilsa catches were preserved in ice and Bengal.  The  dispatched to West  quantity of ice required to pack a unit weight of  fish varies from season to season. than in winter.  On  In summer more ice is used  an average it is observed  that a bundle of  TABLE 9.  Catch of Hilsa i l i s h a rainfall  from 1968 to 1982 of the Indus River,  and mean a i r temperature of Hyderabad from 1962 to  1982.  Year  Catch ( i n mt)  1967  -  1968  1962 1963 1964 1965 1966  Rainfall ( i n mm)  Mean A i r Temp. (°C)  394  27.46  65  28.13  387  27.11  -  -  79 .  28.38  348  27.23  2,500  22  27.43  1969  2,900  17  28.19  1970  12,700  271  27.92  1971  11,100  56  28.05  1972  10,828  27  27.65  1973  11,795  49  27.75  1974  9,098  22  27.75  1975  9,474  145  27.55  1976  9,545  335  27.50  1977  9,129  268  28.40  1978  4,813  416  27.55  1979  9,036  153  27.80  1980  4,427  119  28.20  1981  3,923  117  28.10  1982  6,032  54  27.65  72  TABLE 10.  Regressions of Hilsa landings from 1967 to 1974 of the Padma River at Goalundo, with r a i n f a l l  Lag Period (Year)  F  Total DF  for different lag periods.  Probability  2  r  Slope  Intercept  2.11  839.42  0  0.63  6  .5358  .1134  1  0.00  6  .9897  .0000  -  0.02  5201.40  2  6.77  6  .0474*  .5755  -  9.15  20612.13  3  0.32  6  .5947  .0616  2.73  498.53  4  0.88  6  .6080  .1507  5.94  15977.29  5  4.69  6  .0812  .4845  10.47  -12622.89  6  0.48  6  .5292  .1075  5.49  14562.13  -  73  FIGURE 12.  Relationship of Hilsa landings of the Padma River at Goalundo with two-year lag i n r a i n f a l l .  14000 -i  TABLE 11.  Rainfall  of Faridpur during the period 1930-40.  Year  R a i n f a l l (mm)  1930  1954  1931  2179  1932  -  1933  1987  1934  1813  1935  1415  1936  1977  1937  1691  1938  2148  1939  2225  1940  1507  TABLE 12.  Output of ice (* bundles) i n Rajbari  (near Goalundo) Ice  Factory (after Nayudu, 1939) .  Month/Year  1935  January  1,933  748  1,191  February  3,130  3,277  3,313  March  2,130  4,251  3,714  -  April  2,229  2,028  4,235  3,020  May  2,164  3,297  9,469  8,970  June  5,347  3,208  5,989  9,496  July  4,923  2,739  2,555  5,569  August  3,988  2,710  3,111  2,915  September  3,255  2,928  4,015  2,957  October  1,530  2,934  3,255  1,704  November  1,859  2,250  1,683  December  1,879  1,852  4,014  -  34,367  32,222  46,544  Total  1936  1937  1938  * The above figures are in bundles of i c e , each containing 1 1/2 mounds approximately (one mound = 82.28 l b s . )  77  1.5  mounds of ice is used to pack about 2.5  Even  without  converting  the output  weight, the figures should  mounds of HIisa.  of ice in terms of  give a rough index of the trend in  the Hilsa fishery in the Goalundo area of the Ganges. the rainfall was  Hilsa  very low, 1415  mm,  In  1935  (Table 11), while in  1937  (Table 12), the production  of ice bundles were the maximum  (46,544  1939),  bundles,  Nayudu  which  also  suggests  that  landings of Hilsa in the Padma river at Goalundo has a negative relationship with 2-year lag in rainfall.  5.2.2  Relationship of rainfall to maximum water level in the River of the Ganges at Goalundo in Bangladesh In order to find to what extent by  local  rainfall,  I calculated a  the  rainfall of Faridpur  (near  water level is controlled  simple  linear  Goalundo) with  level of the Padma River at Goalundo for 1967 regression  is  variability  in  significant rainfall  (p<.02)  accounted  Padma  with  regression of maximum water to 1974.  positive  for 71%  of the  slope;  The and  variation in  maximum water level ( F i g . 13). 5.2.3  Relationship of landings Chandpur in Bangladesh  to rainfall  in the  Meghna  River at  Trans-shipment data of Hilsa at Chandpur of the Meghna River for the period of 1937-1940 suggests that landings have a negative  relationship  In 1936 there was  with  2-year  lag  in  a heavy rainfall (2224 mm)  by a very low landings in 1938  rainfall  (Table 8).  which was followed  (298.55 mt) at Chandpur; in 1937  78  FIGURE 13.  Relationship of r a i n f a l l to maximum water level River of the Ganges at Goalundo.  in the Padma  80  t h e r e was a low r a i n f a l l (1736 mm) f o l l o w e d i n 1939 b y a b u m p e r H i l s a l a n d i n g s (975.97 m t ) .  5.2.4  Relationship Pakistan From linear  of  landings  Indus  river  regression  ent lag periods  of  to  of  rainfall  in  Pakistan  I  Hilsa landings  the  Indus  also  with  ( T a b l e 13) f o r t h e y e a r s  River  calculated  rainfall  simple  over  differ-  1968 t o 1982.  these analyses I again found that landings with 2 - y e a r rainfall  was  variability  significant  of  rainfall accounted  l a n d i n g s at I n d u s R i v e r s i g n i f i c a n t (p<0.05) 5.2.5  (p<0.05)  (Fig.  with  for  14).  negative  28.7% of  the  available for  1 9 7 2 , 1973 a n d 1 9 7 4 . different  localities,  in and  variation  in was  - a 4 - y e a r l a g , with negative slope.  q u e s t i o n comes to t h e m i n d w h e t h e r  data are  lag  slope  Hilsa landings  catch  fluctuations  are correlated in the Ganges and in the Indus R i v e r . able  From  One other r e g r e s s s i o n  C o r r e l a t i o n s between the Ganges and the Indus with a t w o - y e a r lag in rainfall A  of  only  the  years  Compar-  1 9 6 8 , 1 9 6 9 , 1970,  Catch and r a i n f a l l , given previously are  summarized  in  simplified  for  form  in  g e n e r a l a n n u a l r a i n f a l l f o l l o w e d t h e same t r e n d s i n  the  Table 14. In  two regions  (except  in 1969, when  rainfall 2-years earlier  b e e n low i n t h e G a n g e s a n d v e r y h i g h i n t h e I n d u s ) . on the other  h a n d , did  three  years  ( 1 9 6 9 , 1 9 7 2 , a n d 1974) a n d w e r e t h e same i n t h e  other  three  years.  1969 w h e n  trends  were  rainfall 2-years  opposite  Landings, in  In  not:  had  earlier  had  been  81  TABLE 13.  Regressions of Hilsa landings from 1968 to 1982 of the Indus R i v e r , with r a i n f a l l  Lag Period (Year)  F  Total DF  f o r different lag periods.  Probability  r  2  SI ope  0  0.20  14  .6606  .0156  1  0.65  14  .5625  .0480  -  2  5.23  14  .0377*  3  0.31  13  4  5.02  5 6  Intercept  3.32  7360.26  5.47  8683.66  .2869  -13.27  9878.62  .5923  .0253  -  3.56  8761.91  13  .0428*  .2950  -11.34  10151.16  1.43  13  .2535  .1066  -  0.24  13  .6333  .0220  7.53  8597.42  3.16  7083.90  82  FIGURE 14.  Relationship of HiIsa landings with two-year lag i n r a i n f a l l the Indus River.  in  14000 -i Y = 9878.6 - 13.3*RAIN 12000 H  r = 0.29 P = 0.038  C §  10000-  (/) O  8000  6000-  4000-  200050  100  150  200  250  300  2 YEAR LAG ANNUAL RAINFALL (mm)  350  400  450  TABLE 14.  Summary of landings of HiIsa, and of r a i n f a l l two years previously in the Ganges and in the Indus River.  River  Landings Ganges Indus Rainfall Ganges Indus  1968  very low very low  low low  1969  1970  1972  1973  1974  very high very low  high very high  very low very high  very high very high  very low very high  low very high  low very low  very high very high  very low very low  low very low  85  different  in the two regions, landins were also different in  the two regions. Evidently  annual  variations  of landings of Hilsa  in the  Ganges and in the Indus are not synchronous; they seem to be associated with environmental events which  may vary indepen-  dently in the two regions.  5.2.6  Relationship of landings to mean air temperature in the Padma River of the Ganges at Goalundo in Bangladesh I calculated a simple linear regression of the landing of Goalundo with mean air temperature (using data in Table 7) over different  lag periods from  1 to 6 years  (Table  15) for  the  years 1967 to 1974. Regression on mean air temperature 2-years earlier  is significant  (p=0.05)  with  negative  slope;  and  variability of mean air temperature accounted for 56.2% of the variation in landings at Goalundo (Fig. 15). A  multiple  temperature regression  regression  was calculated was  of  landings  with  with  a 2-year  lag period.  not significant  rainfall combined  (p=0.15),  with temperature  and  accounted  rainfall  and The  variability of  for less of the  variation (42%) than did rainfall alone. 5.2.7  Relationship of landings to mean air temperature in the Indus River of Pakistan I calculated a simple linear regression of the landings of Indus  River  with  mean  air temperature  over  different lag  periods from 1968 to 1982 (Table 16). There was no lag period  TABLE 15.  Regressions of Hilsa landings from 1967 to 1974 of the Padma River of the Ganges at Goalundo with mean a i r temprature f o r different lag periods.  Lag  Period  F  Probability  r  2  Slope  0  2.80  .1533  .3596  5239.67  1  0.05  .8197  .0105  -1105.73  2  6.42  *.0515  .5623  -7527.59  3  0.88  .6077  .1505  1443.43  4  1.26  .3117  .2024  1562.61  5  0.45  .5334  .0836  -1075.92  6  0.55  .5072  .1004  -1203.42  87  FIGURE 15.  Relationship of HiIsa landings of the Padma River at Goalundo with two-year lag in mean a i r temperature of Faridpur (near Goalundo).  HOOO-i  Y = 192750.7 12000 H  7527.6*TEMP  r = 0.56 P = 0.05  £  10000  8000 H  6000H  4000H  2000-  24  24.2  24.4  24.6  24.8  25  2 YEAR LAG IN TEMPERATURE ( C)  25.2  25.  89  TABLE 16.  Regressions of Hilsa catch from 1968 to 1982 of the Indus River of  Pakistan with mean a i r temperature for different lag  periods.  Lag  Period  F  Probability  r  2  Slope  0  0.05  0.81  0.00  -743.41  1  0.24  0.64  0.02  1381.35  2  0.12  0.73  0.00  911.55  3  2.36  0.15  0.16  -3641.89  4  0.95  0.65  0.07  2199.00  5  0.21  0.65  0.02  1053.96  6  0.06  0.80  0.01  -649.96  90  of  air temperature  which  gave a significant regression.  2-year lag period of air temperature,  The  which had given a signi-  ficant negative slope for the Goalundo data in the preceding section, was now  5.3  significant but with a positive slope for the  Indus River data.  Multiple regression of landings with  fall and temperature  also was non-significant.  rain-  Discussion Changes in environmental  conditions may  influence the spawning  success of the Hilsa fishery from year to year.  Dunn (1982) suggested  that there  was  a correlation  5-year lag, and that this  between  landings  supported  and  modified  present  in the data  data, as shown  between landings with  here  used.  After  no significant  5-year lag in rainfall,  Dunn (1982) is not supported and  he  with  the contention that Hilsa  recruit to the fishery when they are 5 years old. however,  rainfall  a  first  Some errors are calculation  correlation  was  of the found  and the hypothesis of  by my analysis.  Hora (1940), and Hora  Nair (1940), also postulated a five- year cycle in Hilsa landings,  but his evidence was rather circumstantial. Day  (1873) suggested  that Hilsa may  attain first maturity at the end  of the first year, or at the beginning of second hypothesis was supported  by Jones and Menon  year.  Day's (1873)  (1951) based  on their  observations in the Hooghly River, Mahamadi River, and Chilka Lake. Jones and Menon (1951) reported that males become mature when they are 21.6-25.4 cm in length and 1 second  +  in age.  Females become mature in the  year when they are 26.7-30.5 cm long (Jones and Menon 1951).  91  Also, Pillay at  (1958) observed  first maturity  still smaller sizes in the  males at 16-17  cm  and  females  Hooghly  at 19-20  cm  river  in total  length when Hilsa are both about 1 1/2 years old. De (1980) suggested that female Hilsa attained first maturity 34.1  cm  in the upper stretches of the  when they Hooghly  are at a size of  River.  Raja  (1984)  reported female Hilsa attains first maturity at the size of 32 cm.  As  can be seen from the above, there is disagreement among researchers as to  size at first maturity of Hilsa.  lack  of uniformity in the  standard  length),  rivers studied.  and  length  or  This may  be due  measurement  used  ecological  current research of M.  or  different  Hossain  that Hilsa first  a view supported  recruit by  the  (pers. comm.).  analysis I suggest that abundance of adult Hilsa has a moder-  strong negative correlation with  two  rainfall and  landings (both in the Padma River and  the fishery and  +  significant  years previously.  regulating this  be that Hilsa are 1  negative  rainfall  Mechanisms  may  fork  Although there is even less agreement on age at first  to the fishery well before 5 years of age,  ately  (total,  differences between  maturity, the weight of observations suggest  From my  in part to the  year old when they  the survival of the spawn and  association between the Indus River)  are first  On  rainfall may  consequently  the catch is comparatively  low.  larvae and  to  f r y are optimum when  there is a very low rainfall of that year. wash out eggs and  recruited  the other hand, heavy  In Bangladesh  waters,  after 2 years rainfall  has  been shown here to be positively correlated with water level (in Padma River at Goalundo, p=.05).  My  hypothesis is consistent with that of  Wickett (1958) and Vernon (1958) who  showed that the survival of spawn  92  and f r y of pink  and  chum  salmon  is much  less in years  of  severe  floods. In the Indus River there was  a significant negative regression of  Hilsa landings with rainfall not only 2-years earlier (Table 13). evident in the significant.  No  Ganges  A  such  trend  (Table 15),  earlier but also 4-years  regarding  the  4-year  was  where that regression was  possible explanation is that extreme  conditions in one year may  lag  non-  environmental  affect strength of a year-class so sharply  as to be reflected 4 years later even in the return of the offspring of that year dampened.  class.  Such  a  4  year  regularity  would  be  quickly  There is no convincing evidence of a sustained "cycle" in  any of the available data series on Hilsa landings. Although  the negative correlations between landings and  2-years earlier separated  are  statistically  (in each  of  two  widely  river systems), there is still a large residual variation in  landings unaccounted for by data and  significant  rainfall  rainfall.  the possible complexity  Considering the nature of the  of the Hilsa life history, this  resi-  dual variation is not surprising for several reasons. Firstly,  rainfall has been used  and while  the  Goalundo,  they  two are  were not  shown tightly  as an  to  be  coupled.  recorded, while river discharge may  index  of river discharge,  significantly Only  local  correlated  at  rainfall  was  also be affected by weather condi-  tions or snow melt farther upstream. Secondly,  environmental  likely also to affect  early  factors other than  survival.  river discharge are  Some evidence  of a  negative  correlation has been found between landings and temperature two years  93  e a r l i e r , b u t as t h i s o c c u r r e d o n l y in d a t a f o r t h e G a n g e s and the Indus,  i t s implications a r e c o n j e c t u r a l .  T h i r d l y , although t h e commmercial age,  and  most f i s h may  landings probably  p o s s i b l y of more t h a n  history patterns.  F o r t h e s e and  annual  be  harvest.  Bengal  H i l s a from  and  d u r i n g the  their  rainfall  freshwater  failure  clear relationship landings of  timing  events  and of  local entry  life  whether  some H i l s a  may  years.  in  in l a n d i n g s  e v e n t s which may  the two  two  a rough  means  possibility  has  years  necessarily  T h e y seem to be  vary independently in  separate  earlier  are a n a d r o m o u s  marine areas  first short  into  suggest  r a t h e r than  environmental fish  not  changes in  (Bay  of  H o w e v e r , t h e n e g a t i v e a s s o c i a t i o n beween  phases,  the  are  r i v e r s y s t e m s if t h e y  s e a - l i f e in two  between  of  this  in the I n d u s R i v e r s .  w h i c h a r e dominant i n d e t e r m i n i n g h a n d , the  somewhat d i f f e r e r n t  to o f f e r more t h a n  variations  and t h e A r a b i a n S e a ) .  landings  one  observation r e g a r d i n g annual  a s s o c i a t e d with e n v i r o n m e n t a l  spend  known  of more t h a n  Nevertheless, even  s y n c h r o n o u s in the G a n g e s and  presumably  race with  hatching,  now.  is t h a t a n n u a l  the regions.  one  expected  o t h e r p r i n c i p a l new  Hilsa catch  include a mixture  return in subsequent  not b e e n d e t e c t e d u n t i l The  years after  o t h e r r e a s o n s the d e p e n d e n c y between l a n d i n g s a n d  earlier rainfall cannot forecast  r e t u r n two  F u r t h e r , it is not  s u r v i v e s p a w n i n g and  to  not f o r  that  it is  oceanographic  year-class strength.  section term  of  this  seasonal  study  changes  conditions suggest river  in t h e e s t u a r i e s o r the o c e a n s .  mouths  may  that be  conditions,  On to  events  the  other  detect in the  any  riverine details  controlled  by  94  6. (1)  Monthly  variations  Bangladesh, India, place.  in fishing effort  and annual  were  CONCLUSIONS at C h a n d p u r  variations  not s i g n i f i c a n t l y  in  fishing  correlated  with  on R i v e r  effort  in  Meghna in Godavari  Hilsa landings  in  in  either  Variation in landings probably depend p r i n c i p a l l y on changes in  a b u n d a n c e of H i l s a r a t h e r t h a n o n c h a n g e s i n e f f o r t .  (2)  Seasonal changes i n recorded close and  positive  correlation  can therefore  rail shipments from C h a n d p u r  with  be u s e d  observed  landings  as an i n d i c a t o r  of  showed a  riverine  of l a n d i n g s  Hilsa,  in years  for  w h i c h no d i r e c t o b s e r v a t i o n s a r e a v a i l a b l e .  (3)  Historical  events  which  may a f f e c t  interpretation  of  rail  shipment  r e c o r d s i n c l u d e t h e i n f l u x of m a r i n e - c a u g h t H i l s a i n t o r i v e r i n e sites  with  road  transportation  centres,  the advent  of m e c h a n i z e d  of  construction  Bangladesh  to  Hilsa  vessels,  between  landing  of F a r a k k a B a r r a g e  Indian  waters,  and  the shift sites  which  the  disruption  from  and  diverted of  landing r a i l to  consumer  water  from  fishing  in  B a n g l a d e s h d u r i n g liberation in 1971.  (4)  Seasonal  timing  markedly  from  year  seasonal  timing  of  temperature.  and intensity to y e a r ,  of  Hilsa  and bore  r a i n f a l l , mean w a t e r  T h e only  runs  in  the Ganges  no e v i d e n t level,  seasonal r e g u l a r i t y  varied  association  minimum d i s c h a r g e  was t h a t  with or  in all years few  f i s h were taken i n winter months (November to J a n u a r y ) .  95  (5) Annual  variations  in  Hilsa  landings  showed  a  correlation with local rainfall 2 years previously.  significant This was  negative true both  in the Ganges River in Bangladesh and in the Indus River in Pakistan.  (6) The  mechanism regulating the negative association between landings and  rainfall 2 years earlier may and  larvae, and  be that heavy rainfall may  that Hilsa are 1  +  wash away eggs  years old when they  are  recruited  to the fishery.  (7) Annual landings sometimes vary in opposite directions in the Ganges and the Indus Rivers. on  In each region annual landings are dependent in part  rainfall 2-years earlier in that region.  means of rough rainfall data.  forecast of annual  This dependency offers a  harvest on  the  basis of  previous  96  LITERATURE CITED Abbas,  B.M.  Pvt.  Ltd.  Ahmed, M. Ahmed,  Waters D i s p u t e .  Publishing  House  157pp.  Hilsa  fishery  N.  1962.  Q.J.  Fishing  Agri.  Pak.  3:54-57.  of  East  Bengal.  of  East  Pakistan.  Gears  G o v t , of E a s t P a k i s t a n , 1960.  A  Agri.  Pak.  1967-1976.  preliminary  J.  Asiat.  Soc.  1968-1982.  Directorate  of  pp 1 - 3 5 . note  on  the  Hilsa fisheries  of  East  11:165-172.  Bangladesh  Railways  R a i l w a y O f f i c e s at C h a n d p u r Anon.  Vikas  20:7-14.  Pakistan. Anon.  Ganges  Hilsa fisheries in S i n d .  1954.  Fisheries. Ahmed,  The  New D e l h i .  1952.  N.  Sci. Ahmed,  1982.  Yearbook  Transhipment  and Goalundo,  of  Fishery  Data of H i l s a  ilisha.  Bangladesh.  Statistics  Catches  and  Landings.  FAO. Anon.  1961-1974.  R a i n f a l l and  B a n g l a d e s h Meteorology Anon.  1962-1982.  Commerce. Sponsored Anon.  National  Oceanographic  Discharge  and water  and  Years  of  U.S.  Atmospheric  Bangladesh.  D e p a r t m e n t of  Administration.  Organization.  l e v e l of  Bangladesh.  B o a r d , Hydrology Directorate,  Twenty-five  of  Dhaka, Bangladesh.  b y t h e World M e t e o r o l o g i c a l  1967-1974.  1972.  Department.  Temperature  Monthly Climatic Data for the World.  Water D e v e l o p m e n t Anon.  Maximum A i r  Pakistan  in  Bangladesh  Dhaka, Bangladesh. Statistics  1947-1972.  F e d e r a l B u r e a u of S t a t i s t i c s , S t a t i s t i c s D i v i s i o n , G o v t , of P a k i s t a n . Anon.  1984a.  stretch  Gearwise  from C h a n d p u r  monthly  catch/day  of  Hilsa  (kg)  to N i l k a m a l of t h e M e g h n a R i v e r .  Fisheries Resource Survey System, D h a k a , Bangladesh.  in  the  river  Bangladesh  97  Anon.  1984b.  fishery  Report  on  first  meeting  of the working  resources in the Upper Bay of Bengal.  Prepared for FAO/UNDP Bay of Bengal Banerji, S.R.  1955.  Gorakpur. Bhanot,  On  group  Dhaka,  on  Hilsa  Bangladesh.  Programme.  occurrence of Hilsa  ilisha  and  its fishery in  Sci. and Cult. 21:217-218.  K.K.  (Hamilton)  1973.  Observations  in  Hooghly  the  on  the  spawning  estuary.  J.  of  Inland  Hilsa Fish.  ilisha Soc.  India 5:50-54. Bilgrami, K.S. and J.S. Datta Munshi.  1982.  Limnological survey and  impact of human activities on the river Ganges Range).  Technical report.  UNESCO.  Man and the Biosphere programme project.  5.  Chacko, P.I. and S.V. Ganapati.  1949.  (Hamilton) in the Godavari River. Day, F.  1873.  1980.  Maturity, fecundity and spawning of post-monsoon run of  estuary system.  cycles:  V.L.  (Hamilton) in the upper  stretches of the  Hooghly  J . Inland Fish. Soc. India 12:54-63. 1972.  Environmental control  a brief review.  Devanesen, D.W.  J . Madras Univ. 18:16-22.  pp 22-23, 35-36.  hilsa, Hilsa ilisha  de Vlaming,  On the bionomics of Hilsa ilisha  Report on the freshwater fish and fisheries of India and  Burma, Calcutta, De, D.K.  (Barauni to Farakka  1942.  of teleost reproductive  J . Fish. Biol. 4:131-140.  Weirs  in south  India  and their  effect  on the  bionomics of the hilsa in the south Indian rivers - The Godavari, the Krishna and the Cauvery. Druzhinin, A.D.  1970.  Burmese fisheries.  C u r r . Sci. 11:398.  Report to the Govt, of Burma on some aspects of 2781/E.  FAO, Rome.  98  Dunn, I.G. 1982. The Hilsa fishery of Bangladesh, 1982: An investigation of its present prepared  status with  an evaluation of current data.  A report  for the Fisheries Advisory Service; Planning, Processing and  Appraisal Project.  F A O , Rome.  F I : DP/BGD/81/034  Field Document 2.  Dutta, P. , G.C. Laha, P.M. Mitra, D.K. De, A. Chaudhury, P.K. Pandit, A.R. Chaudhury,  R.N. De, B.K. Saha, H.S. Majumder, N.D. Sankar, N.C.  Mondal, G.P. Bhattacharya, A.K. Namasudra, 5.P. Ghosh and A.R. Paul. 1973.  Fishery  resources  of the Hooghly-Matlah  estuarine  system.  B u l l . Cent. Inl. Fish. Res. Inst. No. 19. 24p. Ganapati,  S.V.  India.  1973.  Ecological  of man-made  lakes of south  A r c h i v . f u r Hydrobiologie 71:363-380.  Ghosh, K.K.  1976. Inland fishery resources of India, their estimation and  utilisation.  CIFRI, Barrackpore, India.  Ghosh, A.N. and T.D. Nangpal. ilisha (Ham.). Hilborn,  problems  Ray.  1970.  On the winter breeding  of Hilsa  Proc. Indo-Pacif. Fish Coun. 13:132-142.  1980.  Microcomputer  interactive  statistics  and plotting  (MISP), University of British Columbia, Vancouver, B.C., 57 pp. Hora, S.L. 1938. A preliminary note on the spawning grounds and bionomics of the so-called Indian shad, Hilsa ilisha (Ham.) in the River Ganges. Rec. Indian Mus. 40:147-148. Hora, S.L.  1940.  Life-history and wanderings of Hilsa in Bengal waters.  J . Asiatic Soc. Beng. Sci. 6:93-112. Hora, S.L.  1942. Effects of dams on the migration of Hilsa.  Bangalore 11:470-471.  C u r r . Sci. ,  99  H o r a , S . L . and K . K . N a i r . fishery Rec.  of  Indian  F u r t h e r o b s e r v a t i o n s on t h e bionomics a n d  Shad,  Hilsa  ilisha  (Ham.)  in  Bengal  waters.  Indian Mus. 4 2 : 3 5 - 5 0 .  Hornell, J .  1950.  London. Hossain,  the  1940.  Fishing  In  Many Waters.  Cambridge  University  207 p p .  Z.  and  S.M.K.  Sufi.  1962.  Biological and  economic  effects  b a r r a g e s on H i l s a i l i s h a ( H a m . ) and i t s f i s h e r i e s i n t h e I n d u s . Pak.  dity  of  Soc.  97:350-355.  S.  Indus  1957.  Indian J.  shad,  Fish.  Jones, S.  River  On  Jones,  Agri.  J.  late w i n t e r  and  ilisha.  early in the  Trans.  spring  Amer.  Fish.  migration  Gangetic  of  delta.  the  Indian  F i s h i n g methods f o r t h e I n d i a n S h a d , H i l s a i l i s h a ( H a m . ) P a r t I.  J . Bombay Nat. H i s t . Soc.  Sujansingani.  1951.  Bombay N a t . H i s t . Soc.  M S . and P . M . G . Menon.  the  Indian  Sci.  31:101-125.  Shad,  Karamchandani, S . J .  River.  Hilsa  Hilsa ilisha (Hamilton),  S . and K . H .  shad,  Fluvial migration, spawning and f e c u n -  4:304-14.  1959.  Lake.  1968. Hilsa,  the  in the Indian r e g i o n . Jones,  of  13:346-359.  Islam, B . N . and G . B . T a l b o t .  Jones,  Press,  Hilsa  Hilsa  1961.  ilisha  1951. ilisha  The  Hilsa fishery  C u r r . Sci. 30:373-375.  in  of t h e  Chilka  50:264-280. Observations (Hamilton).  on t h e l i f e - h i s t o r y Proc.  On t h e l o c a t i o n of s p a w n i n g  (Hamilton)  56:250-275.  freshwater  regions  Indian  grounds of  the  of  Acad.  of  Indian  Narbada  100  Kulkarni,  C.V.  1950.  Indian s h a d ,  1953.  W.C.  Syst. Mathur,  Information  The  1964.  Hilsa  early  Narbada  life  River.  history Proc.  of  Nat.  Fishery  of  the  Mergui  District.  Communication.  ecology  Maturity  of f i s h m i g r a t i o n s .  Annu.  Rev.  Ecol.  and  fecundity  of  Hilsa ilisha.  Indian  J.  11:423-449.  CD.  1984. A  Investigation  report prepared  Project.  FAO,  M i t r a , P . M . and K . K . from  the  India  11:49-55.  Motwani,  M.P.,  V.G. of  the  S c i . and C u l t . Nair, K.K. Sci.  for  Rome. Ghosh.  1954.  the  the  1979.  Hilsa  Fisheries  fishery  of  Advisory  Bangladesh,  Service,  Phase  Seasonal patterns in the fish landings  estuarine  Jhingran, Indian  of  F l : D B / B G D / 8 1 / 0 3 4 F i e l d Document 5 .  Hooghly-Matlah  breeding  and  shad,  S.J.  system.  J.  Inland  Karamchandani.  Hilsa ilisha (Hamilton)  Fish.  1957. in  Soc.  On  the  freshwaters.  23:47-48. Dams  and  Hilsa  fisheries.  J.  Asiatic  Soc.  Beng.  Hilsa  ilisha  of  Bengal.  20:77-79.  Nair, P.V.  1958.  (Hamilton). Nayudu,  M.R.  Government Northcote, pp.  on  I.P.F.C.  1977.  P.K.  1983. II.  in the  and  8:285-308.  Fish Melvin,  eggs  15:169-176.  U n i o n of B u r m a . Leggett,  habits,  Hilsa ilisha (Ham.)  I n s t . S c i . India Kyaw B a .  Breeding  T.G.  317-355.  Seasonal  changes  in  the  gonads  of  Phillipp. J . S c i . 87:255-276. 1939.  Report  Press,  Calcutta.  1984. _In_ J . D .  on  a survey  Mechanisms McCleave,  of G.P.  of  the  fish  fisheries  migration  Arnold,  J.J.  in  rivers.  Dodson,  and  101  W . H . Neill ( e d . ) . New Pillay,  M e c h n i s m s of M i g r a t i o n i n F i s h e s .  York.  S.R.  1963.  MS.  i l i s h a (Hamilton) P i l l a y , S . R . and H .  Maturation  Rosa J r .  P i l l a y , S . R . and K . V . Hilsa ilisha  Coun.  tagging  of  hilsa,  Coun. Pillay,  1963.  the  Hilsa,  Hilsa  1882.  Rao.  (Ham.)  FAO  1962. of  S y n o p s i s of b i o l o g i c a l d a t a on H i l s a , Fish Biol Synopsis  25:1:1-6:8.  O b s e r v a t i o n on t h e b i o l o g y a n d f i s h e r y  river  Godavari.  R a o , and P . K . M a t h u r . hilsa,  Hilsa  ilisha  Proc.  1962.  Indo-Pacif.  Fish.  P r e l i m i n a r y report on the  (Ham.).  1952.  Proc.  Indo-Pacif.  Fish.  A p r e l i m i n a r y b i o m e t r i c s t u d y of c e r t a i n p o p u l a t i o n s  Hilsa  ilisha  (Ham.).  Proc.  Indo-Pacif.  Fish.  4:181-194.  T.V.R.  1954.  Morphological  Hilsa ilisha (Ham.)  tion.  J . Asiatic Soc. S c i . 20:69-74.  Pillay, T . V . R . (Hamilton). T.V.R.  1955.  The  biology  A Review. 1957a.  with  and  hilsa,  Pillay,  of  10:28-39.  Pillay, T . V . R . of  Spawning  10:37-61.  Pillay, S . R . K . V .  Coun.  and  of t h e S a u r a s h t r a C o a s t .  H i l s a ilisha (Hamilton)  of  Plenum P r e s s ,  special  serological reference  to  racial  of  the  investiga-  a n d f i s h e r i e s of t h e h i l s a , H i l s a i l i s h a  Proc. Indo-Pacif.  A morphometric study  H i l s a ilisha (Hamilton)  characters  of t h e R i v e r  Fish. Coun.  2:211-219.  of t h e p o p u l a t i o n of h i l s a ,  Hooghly  a n d of t h e C h i l k a L a k e .  Indian J . F i s h . 4:344-386. Pillay,  T.V.R.  (Hamilton) Fish.  1957b.  On  in the Hooghly  4:150-159.  the  abundance  of  and Padma R i v e r s  the  hilsa,  during  Hilsa  1955.  ilisha  Indian  J.  102  Pillay, T . V . R .  1958.  River Hooghly. Pillay,  T.V.R.  Assam.  B i o l o g y of t h e h i l s a , H i l s a i l i s h a ( H a m i l t o n ) Indian J . F i s h .  and A . N .  Ghosh.  1958.  A note on t h e h i l s a f i s h e r i e s  J . Bombay N a t . H i s t . Soc.  of two t y p e s  Soc. Fish. Quddus,  of  differences  Bangladesh waters.  Yukio  between  Nose.  two  M.R.  Res.  B u l l . Jap. Soc. F i s h .  Bull.  Jap.  of  Meristic  Hilsa  ilisha  and in  50:43-49. 1984c.  C o m p a r i s o n of age Bull.  50:51-57.  1968.  Hilsa  fishery  of  East  Pakistan.  Pak.  J.  Sci.  11:95-103.  Raja, Antony.  1984.  Consultancy Rajyalakshmi,  T.  Report  The  to  Hilsa Fishery  (Mimeograph)  et a l .  (Dowlaiswaram  1972.  Ramakrishnaiah, M.  MS.  Dummagudem  characteristics and t r e n d s , 1972.  1977.  Bangladesh.  the  Upper  On  Bay  t h e f i s h e r i e s of  grounds):  A  of  River  final  Bengal.  Godavari  appraisal  of  1963-69.  B i o l o g y of H i l s a i l i s h a ( H a m . )  Geography 579 p p .  of  p r e p a r e d f o r B a y of B e n g a l P r o g r a m m e .  w i t h an a c c o u n t on i t s r a c i a l s t a t u s . H.  waters.  of two t y p e s of H i l s a i l i s h a i n B a n g l a d e s h w a t e r s .  Soc. F i s h .  Qureshi,  Spawning and f e c u n -  1984b.  types  M . M . A . , Makoto S h i m i z u a n d Y u k i o N o s e .  Jap.  Rashid,  1984a.  50:177-182.  morphometric  and growth  of  55:174-177.  Hilsa ilisha in Bangladesh  M . M . A . , Makoto S h i m i z u a n d  Quddus,  the  5:201-257.  Q u d d u s , M . M . A . , Makoto S h i m i z u a n d Y u k i o N o s e . dity  of  Indian J . F i s h .  of B a n g l a d e s h .  University  from C h i l k a Lake 19:35-53. Press  Limited,  103  Southwell, T.  1914.  R e p o r t on t h e h i l s a h a t c h i n g o p e r a t i o n s c o n d u c t e d  M o n g h y r , B i h a r , d u r i n g A u g u s t , S e p t e m b e r , a n d O c t o b e r , 1912. Dep.  at  Bull.  F i s h . B e n g . B i h a r and O r i s s a 4 : 1 - 5 .  Southwell,  T.  and B .  Prashad.  B i h a r and O r i s s a . Sundararaj, review  B.I. of  Bull.  1981.  present  1918.  On  hilsa investigation  Dep. F i s h . B e n g .  Reproductive  knowledge  and  Bengal,  11:1-12.  physiology needs  in  for  of  future  teleost  fishes.  research.  A FAO  A q u a c u l t u r e Development and Coordination Programme A D C P / R E P / 8 1 / 1 6 . 82 p p . Vernon,  E.H.  1958.  A n e x a m i n a t i o n of f a c t o r s a f f e c t i n g t h e a b u n d a n c e  p i n k salmon i n t h e F r a s e r R i v e r . International  Pacific  Westminster, B . C . , Wickett,  W.P.  production  1958. of  Salmon  A progress  Fisheries  report prepared  Commission.  for  pp. 49.  of the  New  Canada.  Review pink  Canada 15:1103-1126.  of c e r t a i n e n v i r o n m e n t a l and  chum  salmon.  J.  factors Fish.  affecting Res.  the Bd.  104  APPENDIX  105  APPENDIX TABLE 1.  Development of a r t i f i c a l l y - f e r t i 1 i z e d eggs  (after  Kulkarni 1950).  Time i n Hours A f t e r Fertilization  Development Features  Within 1/2 hour  Blasto-disc is formed.  Within 4 1/2 hours  Segmentation of b l a s t o - d i s c , forming a cap of c e l l s covering half of the y o l k .  After 8 1/2 hours  Embryonic shield v i s i b l e .  After 12 hours  Embryo is d i s t i n c t with head and free t a i l . A few myotomes v i s i b l e but the optic v e r i c l e i s not discernible.  After 15 hours  Contrations of the embryo begin.  After 18 hours  Hatching takes place.  106  APPENDIX TABLE 2.  Relationship between mean a i r temperature (°C) of Calcutta (near Hooghly area) with mean water temperature of  Month/Year  Hooghly River of the Ganges.  A i r Temperature  Water Temperature  Sept. 1952  29.1  30.0  Oct.  1952  27.7  31.0  Nov.  1952  24.2  29.5  Dec.  1952  20.4  22.5  Jan.  1953  19.7  22.7  Feb.  1953  24.4  26.0  Mar.  1953  29.7  28.0  Apr.  1953  32.1  31.3  May  1953  31.9  33.0  June  1953  30.2  30.5  July  1953  29.4  31.5  Aug.  1953  29.3  30.5  Sept. 1953  29.1  31.2  

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