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The age, growth and mortality of the lemon sole (Parophrys vetulus Girard) on the British Columbia fishing… Ketchen, Keith Stuart 1947

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THE AGE, GROWTH AND MORTALITY OF THE, •LEMON SOLE (Paropnrys vetulua Girard) ON THE (BRITISH COLUMBIA. FISHING GROUNDS BY Keith S. Ketchen A Thesis submitted i n Partial Fulfilment of (The Requirements for the Degree of MASTER OF ARTS in the Department of ZOOLOGY THE UNIVERSITY OF BRITISH COLUMBIA Ap r i l , 1947. ABSTRACT Part of the general investigation "being conducted by the Fisheries Research Board of Canada into the condition of the P a c i f i c coast otter trawl f i s h e r y deals with the length and age analysis of the species of f i s h caught. The age of one of these species, the lemon sole, Parophrys vetulus GIrard has been determined through a study of the o t o l i t h s or ear-stones. In general the older f i s h e r i e s and those closest to large Canadian and American markets produce the youngest and the smallest f i s h . Soles of four and f i v e years of age pre-dominate i n the catches from the S t r a i t of Georgia and from the west coast of Vancouver Island, The comparatively recent f i s h e r i e s of Queen Charlotte Sound and Hecate S t r a i t show a predominance of six and seven year old f i s h . The male lemon sole reaches an age of ten years and a length of 400mm., while the female reaches twelve or thirteen years of age and grows to a length of over 500mm. The female sole, between four and eight years of age grows approximately 11 mm. more per year than the male. The f i s h i n the S t r a i t of Georgia and i n northern Hecate S t r a i t have a s l i g h t l y greater growth rate than those on the west coast of Vancouver Island and i n Queen Charlotte Sound. Marked differences i n t o t a l annual mortality rates have been shown. In the S t r a i t of Georgia and on the west coast of Vancouver Island the rate i s between (>0% and 70f. . In Queen Charlotte Sound the rate i s 52%, and i n northern Hecate S t r a i t i t i s between 30% and 40f». The r e l a t i v e recency of the northern Hecate S t r a i t f i s h e r y has raised the suggestion that the t o t a l mortality rates of 30?« i n female f i s h and 39% i n male f i s h approach the natural mortality rate. Dominance of the 1939 year class has been observed i n the s study of f i s h taken during ,1944, 1945 and 1946 i n northern Hecate S t r a i t . In the l a s t year another strong year class, that of 1942, made i t s appearance. The r e l a t i v e lack of success i n the brood years of 1940 and 1941 was the factor responsible for the absence of small f i s h i n the catches during the f i s h i n g seasons of 1944 and 1945. TABLE OF CONTENTS . .Page INTRODUCTION 1 MATERIALS AND METHODS . 7 LIFE HISTORY 13 THE ANALYSIS OF THE COMMERCIAL CATCHES OF LEMON SOLES 18 S t r a i t of Georgia 18 West coast of Vancouver Island.... 23 Q,ueen Charlotte Sound 26 Hecate S t r a i t . . . . . . . . . . . . . . . . . . . . . . 27 GROWTH RATES ........................................ 34 MORTALITY RATES 39 DISCUSSION 44 Growth 44 Mo r t a l i t y . 47 The relationships of mortality and fluctuations i n strengths of .year .classes to .age ~ ' composition. •• 52 SUMMARY AND CONCLUSIONS 56 ACKNOWLEDGMENTS 60 REFERENCES 61 APPENDIX 63 - 1 -I . INTRODUCTION On the P a c i f i c coast of Canada during the past s i x or seven years there has "been witnessed an extensive development of the trawl f i s h e r y . This expansion has arisen mainly as a r e s u l t of the need fo r f i s h products, both here and abroad, to a l l e v i a t e the shortages i n meat supplies brought about by war-time conditions. The F i s h e r i e s Research Board of Canada, fore-seeing the p o s s i b i l i t y of over-exploitation of t h i s new i n -dustry and of i t s possible c o n f l i c t with other marine f i s h i n g methods, i n 1943 began an investigation designed to accumulate information which could be employed i n a sound program of con-servation and management. One of the f i r s t objectives i n studying the condition of the trawl f i s h e r y has been to determine the nature and abun-dance of the species of f i s h captured, and to determine the factors which l i m i t t h i s abundance. The Problem One of the p r i n c i p a l species of f l a t f i s h landed by ottarr trawlers i s the lemon sole (Parophrys vetulus Girard), a f i s h of considerable market importance because of i t s abundance and the high q u a l i t y of i t s f l e s h . As part of the general invest-ig a t i o n being conducted on t h i s species, primary consideration i s given i n t h i s work to the study of the size and age compos-i t i o n of catches landed at important B r i t i s h Columbia ports during 1945 and 1946. Analysis of t h i s sort i s an e s s e n t i a l requirement i n revealing the condition of the fishery i n that i t shows in what way production i s influenced 1. by the general age d i s t r i b u t i o n i n the various populations, 2. by the growth rate, 3. by the mortality rate, and 4. by fluctuations i n the strength of year classes brought about by varying successes of brood years. These aspects w i l l be considered i n detail, along with important related subjects on size and age at maturity, reproductive ca-pacities, and the growth and habits of young, post-larval f i s h . Afie Determination, The age of the lemon sole has been determined through ex-amination of the otolith, a small hard, calcareous body situated i n the saccular portion of the ear. The method has long been employed by European investigators of the North and Baltic Sea fisheries. Such men as Graham (1928) and Van Oosten (1941) however have emphasised that too often the r e l i a b i l i t y of age determination i n one species of f i s h i s used as j u s t i f i c a t i o n of the r e l i a b i l i t y i n another, a practice which could undoubtedly lead to substantial error i n results. With this i n mind the study of the lemon sole otolith has been approached with con-siderable caution. In a preliminary investigation of this sub-ject by the writer (1945 a) measurements of the otolith showed a f a i r l y constant ratio to the length of the f i s h . Further studies of the alternating l i g h t and dark rings appearing on the otolith have been found to form reasonably consistent pat-terns related to annual temperature changes. On the basis of these correlations, the otolith of the lemon sole i s believed to give a f a i r l y accurate picture of age, especially for the lower and middle age groups. - 3 -H i s t o r y Qt Afte p e ^ r g i n a ^ g n , Graham (1928) i n h i s review of the l i t e r a t u r e s t a t e s t h a t R e i b i s c h i n v e s t i g a t i n g the North Sea p l a i c e i n 1899 was one o f the f i r s t to suggest t h a t the d i f f e r e n t i a l s t r u c t u r e o f the o t o l i t h I s r e l a t e d to temperature. However Cunningham (1905) was the f i r s t to show that the opaque or white r i n g represents the summer growth and tha t the transparent or dark r i n g r e p r e -sents t h a t o f the w i n t e r . Wallace (1905) a l s o i n v e s t i g a t i n g the p l a i c e f i s h e r y gave s t a t i s t i c a l evidence supporting the f i n d i n g s o f Cunningham. I n 1916 Storrow extended age determina-t i o n by t h i s means to other species o f f l a t f i s h . Since t h a t time the method has spread to the study of other types of ground f i s h , the hake by H i c k l i n g (1933)» and cod and haddock by many-workers seeking c o r r e l a t i o n s w i t h s c a l e readings. On the P a c i f i c coast of North America most noteworthy advances i n t h i s f i e l d have been made by the I n t e r n a t i o n a l F i s h e r i e s Commission w i t h r e s p e c t to the study of the age o f the h a l i b u t . Apparently the o n l y published work on f l a t f i s h other than h a l i b u t from t h i s coast has been by Smith (1936) i n which he gi v e s a general s u r -vey of the ages of s e v e r a l species taken i n Puget Sound waters. HlSfrffY off *fre ?ra.wl Pigftgyy The t r a w l f i s h e r y f o r f l a t f i s h and l i n g c o d on the P a c i f i c coast o f Canada began about 1912 and was con f i n e d mainly to E n g l i s h Bay and the waters adjacent to P o i n t A t k i n s o n and P o i n t Grey, regions a l l w i t h i n s i g h t o f Vancouver. According to the old e r fishermen the f i s h were very p l e n t i f u l i n those days, but because o f a very l i m i t e d market the occupation was pursued by only one or two boats. However, during the f i r s t World War an i n c r e a s e d demand saw the f i s h i n g grounds extended around P o i n t Grey and south along the Sand Heads of the F r a s e r R i v e r e s t u -a r y . I n the same p e r i o d three o l d country-type steam t r a w l e r s began operating out o f P r i n c e Rupert i n n o r t h e r n Hecate S t r a i t . By 1921 however these boats had been converted to other employ-ment as a r e s u l t of a c o l l a p s e of the market to i t s pre-war l e v e l . On the southern p a r t o f the coast f i s h i n g was continued by a few boats from Vancouver, and by 1923 the grounds had been extended from the F r a s e r estuary to the waters among the a d j a -cent i s l a n d s i n the lower p o r t i o n o f the S t r a i t o f Georgia. The Baynes Sound t r a w l i n g grounds, along the e a s t c o a s t of Vancouver I s l a n d and about f o r t y m i l e s n o r t h o f the G u l f I s l a n d s were not discovered u n t i l 1930 and d i d not r e c e i v e much a t t e n t i o n u n t i l 1938 or 1939. I n 1937, w i t h the improvement of boat designs and engines, one or two boats began operating i n the summer season o f f the southern p a r t o f the west coast of Vancouver I s l a n d near P o r t San Juan. By 1939 the number of boats had increased to e l e v e n and the grounds were extended northward to B a r k l e y Sound. With the d i s c o v e r y of the h i g h v i t a m i n A content i n dog-f i s h l i v e r o i l , l a r g e American boats which had p r e v i o u s l y been centered on the S w i f t s u r e Banks o f f Cape F l a t t e r y moved n o r t h -ward l n 1940 to the La Perouse Bank o f f the west coast of Van-couver I s l a n d . By 1942 these boats f a r outnumbered the s m a l l e r Canadian boats, and w i t h i n a few years had made t h e i r appearance on the Queen C h a r l o t t e Sound and Hecate S t r a i t grounds. The Goose I s l a n d grounds i n Queen C h a r l o t t e Sound were opened up i n the e a r l y years of the second World War, but Fig. 1 Parophrys vetulus Girard b e c a u s e o f the l o n g d i s t a n c e f r o m p o r t and the s e v e r e weather c o n d i t i o n s p r e v a i l i n g y e a r - r o u n d i n t h e s e w a t e r s , o n l y l a r g e t r a w l e r s have b e e n a b l e t o f i s h w i t h any degree o f s u c c e s s . The grounds o f n o r t h e r n H e c a t e S t r a i t , f o l l o w i n g the w i t h -d r a w a l o f the steam t r a w l e r s i n 1921 have b e e n f i s h e d o n l y s l i g h t l y . U n t i l 1944 o n l y t h r e e o r f o u r b o a t s were engaged i n the i n d u s t r y * S i n c e t h a t t ime the number o f C a n a d i a n b o a t s i n t h i s r e g i o n has i n c r e a s e d t o a b o u t s i x t e e n . P e s c r i p t l o R and, PJstrjbu .UQn o f 1foe Lemon, S o l e The l e m o n s o l e ( F i g . 1) i s a member o f the f l o u n d e r f a m i l y , the P l e u r o n e c t i d a e . The name " s o l e " i s a c t u a l l y a n e r r o n e o u s o n e , f o r t h e r e a r e no t r u e s o l e s ( S o l e i d a e ) o n t h e P a c i f i c c o a s t o f N o r t h A m e r i c a . The name " l e m o n s o l e " i s a p p a r e n t l y a c a r r y - o v e r f r o m the l e m o n s o l e o f the c o a s t o f n o r t h - w e s t e r n E u r o p e , ffliffrofftppius k ^ t t . I n the s t a t e o f W a s h i n g t o n t o the s o u t h , P a r o o h r y s v e t u l u s i s g e n e r a l l y c a l l e d the E n g l i s h s o l e , and i n C a l i f o r n i a , the P o i n t s o l e b e c a u s e o f i t s c h a r a c t e r -i s t i c a l l y p o i n t e d h e a d . The s p e c i e s was f i r s t d e s c r i b e d b y G i r a r d i n 1854, a n d , a c c o r d i n g t o Clemens and W i l b y (1946) was f i r s t r e c o r d e d i n B r i t i s h C o l u m b i a w a t e r s i n 1862. Norman (1934) s t a t e s t h a t the s p e c i e s i s the o n l y member o f the genus P a r o p h r y s and t h a t i t i s d i s t r i b u t e d a l o n g the P a c i f i c c o a s t o f N o r t h A m e r i c a f r o m S a n t a B a r b a r a , C a l i f o r n i a t o S i t k a , A l a s k a . I n B r i t i s h C o l u m b i a w a t e r s t h e l e m o n s o l e o c c u r s i n c o n s i d e r a b l e abundance l n the S t r a i t o f G e o r g i a , l n Queen C h a r l o t t e Sound and i n n o r t h e r n H e c a t e S t r a i t . On the w e s t c o a s t o f V a n c o u v e r I s l a n d t h i s f i s h r e a c h e s s i g n i f i c a n t - 6 -p r o p o r t i o n i n catches only i n the r e g i o n o f P o r t San Juan. Progressing northward along the coast from t h a t p o i n t there i s a decreasing frequency of occurrence. H , MATEfilMS AND METHODS The m a t e r i a l f o r t h i s work has been c o l l e c t e d almost en-t i r e l y from t r a w l landings a t the two important B r i t i s h Columbia ^centres, Vancouver and P r i n c e Rupert. The year round landings a t the l a t t e r p o r t are from the f i s h i n g grounds of northern Hecate S t r a i t ( F i g . 2 ) , p r i n c i p a l l y Butterworth Rocks and nearby r e g i o n s . The f i s h landed a t Vancouver, during the l a t e s p r i n g and summer months, are i n greater p a r t from the west coast o f Vancouver I s l a n d and the Goose I s l a n d grounds i n Queen C h a r l o t t e Sound. I n the f a l l and w i n ter however, the samples are obtained almost e x c l u s i v e l y from the S t r a i t of Georgia. This seasonal f l u c t u a t i o n i n the l o c u s o f f i s h i n g e f f o r t i s the r e s u l t of 1. severe winter weather c o n d i t i o n s on the west coast which f o r c e the boats t o seek the compara-t i v e l y s h e l t e r e d waters o f the S t r a i t of Georgia, and 2. an a t t r a c t i v e f i s h e r y produced by the c o n c e n t r a t i o n o f f i s h on spawning grounds and m i g r a t i o n routes i n the S t r a i t during the winter months. Primary a t t e n t i o n w i l l be g i v e n to samples c o l l e c t e d dur-in g the years 1945 and 194-6. A r e l a t i v e l y s m a l l number taken during 1944 w i l l be r e f e r r e d to p e r i o d i c a l l y , but because of the small s i z e s o f the samples comparisons w i t h the succeeding years are somewhat d i f f i c u l t . The data on l e n g t h and age were acquired from the lemon sole i n the f i s h f i l l e t i n g sheds. Sex determination which - F i g . 2 A map showing the general lemon sole f i s h i n g . grounds of the coast. (1) S t r a i t of Georgia/ (2) West coast of Vancouver Island, (3) The Goose Island grounds, (4) northern Hecate S t r a i t . - 8 -o r d i n a r i l y r e q u i r e s i n c i s i o n o f the body w a l l was g r e a t l y f a c i l i t a t e d through sampling i n t h i s manner. Two methods of o t o l i t h c o l l e c t i o n have been employed. The f i r s t method, p r a c t i c e d during 1944 and 1945 i n v o l v e d the ex-t r a c t i o n of both o t o l i t h s and the recording, and f i l i n g of each p a i r i n a s h e l l v i a l under separate paper d i v i d e r s . This prac-t i c e was found to be too slow to meet the requirements f o r ade-quate sampling and was subsequently d i s c a r d e d i n favor of a more e f f i c i e n t technique, whereby only one o t o l i t h , the l e f t hand one, was removed. For t h i s method an " o t o l i t h board" was set up c o n t a i n i n g v i a l s f o r each centimetre l e n g t h group and f o r each sex. At the completion of the sampling a l l o t o l i t h s from f i s h of the same l e n g t h and sex are counted, recorded under a s i n g l e s e r i a l number and st o r e d i n a v i a l along w i t h other such samples, separated by paper d i v i d e r s . A f i f t y percent s o l u t i o n of g l y c e r i n e which helps to c l e a r the o t o l i t h s , i s added to each v i a l . The speed w i t h which t h i s method of sampling can be c a r r i e d out enables the handling of l a r g e samples i n a very s h o r t p e r i o d (approximately 200 f i s h per hour). The o t o l i t h samples f o r 1945 and 1946 which have been ex-amined f o r t h i s work amount to a l i t t l e over 18,000. C o l l e c t i o n s during 1945 were composed of 1842: samples from the S t r a i t o f Georgia, 760 from the west coast of Vancouver I s l a n d , 265 from Queen C h a r l o t t e Sound and 2530 from Hecate S t r a i t . For the f i s h i n g season, of 1946 examination was made o f 12,670 samples, of which 3500 were from the S t r a i t of Georgia, 2065 from the west coast, 860 from the Goose I s l a n d s area and 6250 were from Hecate S t r a i t . - 9 -lire itefitiiLflfi of tire Otoliths A common c r i t i c i s m of o t o l i t h reading i s t h a t much depends upon the i n t e r p r e t a t i o n by the i n v e s t i g a t o r of what c o n s t i t u t e s a w i n t e r check and what does not. Unless the methods and c r i -t e r i a f o r these determinations are d e f i n i t e l y s t a t e d the work i s of l i t t l e value to other i n v e s t i g a t o r s i n the same f i e l d . Age determination of the lemon sole has been r e s t r i c t e d to the l e f t hand ( b l i n d s i d e ) o t o l i t h , and r e s t r i c t e d s t i l l f u r t h e r to the p o s t e r i o r h a l f of the c l e a r surface (Fig,. 3 ) . The e f f e c t of accessory checks i n the reading o f the o t o l i t h i s minimal i n t h i s r e g i o n . The o t o l i t h i s f i r s t placed a g a i n s t a b l a c k background i n a small d i s h and examined under water w i t h a b i n o c u l a r micro-scope (mag.. - 9 diam.) using.a b r i g h t i l l u m i n a t i o n d i r e c t e d from above. Where a transparent r i n g shows up w i t h equal i n -t e n s i t y along s e v e r a l angles on the p o s t e r i o r h a l f of the o t o l i t h i t i s considered to be a w i n t e r check. With reference to o l d e r f i s h i n p a r t i c u l a r the r e s u l t s may or may not be e n t i r e l y r e l i a -b l e because of the d i f f i c u l t y i n d i s t i n g u i s h i n g the r i n g s near the margin of the o t o l i t h . However, a determined e f f o r t has i been made throughout the a n a l y s i s to keep the readinp c o n s i s t e n t . <* The determinations have been made independent of data on l e n g t h and sex. Data on time of capture have of n e c e s s i t y been employed because of the h i g h degree of v a r i a b i l i t y as to the p e r i o d during which the new growth begins i n the s p r i n g . I n order to keep a consistency of a p p r a i s a l of t h i s s p r i n g growth a numerical system was f o l l o w e d , whereby the amount of opaque growth outside the F i g . 3 An o t o l i t h of a lemon sole i n i t s s i x t h year of growth. Note the f i v e transparent (dark) winter checks. 10 -preceding transparent r i n g was estimated i n terms of the opaque growth during t h a t preceding year. That i s to say, an o t o l i t h w i t h no apparent transparent (dark) r i n g on the margin, but w i t h opaque (white) growth equal to about 8/10 of the growth of the previous year would be designated, i f j u s t completing i t s f i f t h year, as age 4 . 8 . Whereas other might be 5.0 or 5 . 2 , de-pending on the amount of white growth present on the margin. The decimal f r a c t i o n then would i n d i c a t e whether the new growth had begun or not. That i s , 4 .8 would mean that the dark ( w i n t e r ) check was not present, 5*0 would mean tha t the w i n t e r check was on the margin, and 5*2 would i n d i c a t e t h a t the s p r i n g growth had begun. Checking back through l a r g e s e r i e s of such determinations i t i s p o s s i b l e to g a i n some i d e a o f the approximate time when spri n g growth begins. The method i s admittedly an approximation and subject to e r r o r , but i t i s more accurate than any estimate by c a s u a l o b s e r v a t i o n . As o t o l i t h s may show the white growth beginning as e a r l y as January and as l a t e as June, e r r o r s i n year c l a s s determination would be considerable without some such e v a l u a t i o n . The u n c e r t a i n t y o f age determination has been mentioned w i t h r e s p e c t to higher age group f i s h . This i s p a r t i c u l a r l y so i n the case o f male f i s h . Beyond f i v e or s i x years o f age much of the annual d e p o s i t i o n o f calcareous m a t e r i a l on the o t o l i t h goes to i n c r e a s i n g the thickness of the o t o l i t h . This t h e r e f o r e gives the r i n g s a cramped appearance beyond four or f i v e years of age which makes age determination d i f f i c u l t . The increase i n s i z e of the female o t o l i t h i s more i n l e n g t h and width than i n depth, hence i t u s u a l l y appears l a r g e r and f l a t t e r than the 11 otolith of the male f i s h . The uncertainty of age determination i s not confined en-ti r e l y to f i s h i n the higher age groups. Frequently samples of fis h are obtained where a l l otoliths of both sexes are very opaque and contain many accessory checks. Outstanding i n this respect are samples from the vicinity, of the Fraser River estu-ary. Whether this phenomenon i s related to low salinity, type of food or some other factor, has yet to be determined. Sampling Pifflgwltipg One of the major analytical problems i n the investigation of the fishery has been the question of to what degree sampling must be carried before i t can be considered representative of any particular population. During the latter part of 1945 arid throughout 1946 a criterion was ar b i t r a r i l y established whereby sampling was considered sufficient when thirty individuals were present i n the best represented centimetre length group. Such a sample i s no doubt representative of a catch, but i s i t rep-resentative of the population? Many factors such as tides, depth, light, temperature and food supply either dependent on or independent of one another are at a l l times undoubtedly i n -fluencing the distribution of f i s h . A trawl net may capture a representative sample for one particular depth or series of depths for one particular time-interval, but to assume complete representation of the population would no doubt lead to erroneous conclusions. Another important factor which Influences the distribution of the sizes of f i s h i n a catch i s that of selec-tion. Not only does the trawl net select the larger members of the population, but the fisherman further c a l l s out a l l f i s h < - 12 -below commercial size. Neither of these selective agents i s a l l together constant. These points have been mentioned i n the hope that some appreciation may be gained of the limitations of the data. In an attempt to remedy these d i f f i c u l t i e s large numbers of samples have been aggregated, and u n t i l such times when specially equipped research boats can be employed, only broad general-izations can be expected. , 13 -I I I . LIFE HISTORY As an understanding of the r e s u l t s of the present i n v e s -t i g a t i o n depends to some extent upon a knowledge of the general l i f e h i s t o r y of the lemon so l e a b r i e f account of t h i s i s given at t h i s p o i n t , i n f o r m a t i o n on the l i f e h i s t o r y i s r e s t r i c t e d i n greater p a r t t o the S t r a i t of Georgia, and i s s t i l l incomplete f o r some of the e a r l y phases. Spawning takes place from Jan-uary to March i n w e l l d e f i n e d l o c a l i t i e s , u s u a l l y i n waters of 30 t o 40 fathoms i n depth where the ocean f l o o r i s somewhat muddy. The eggs are p e l a g i c , and h a t c h i n g takes p l a c e i n approx-imately 100 t o 130 hours a f t e r f e r t i l i z a t i o n , depending on the temperature of the water. The l a r v a e are d i s t r i b u t e d over a wide area by the a c t i o n of t i d e s and wind blown w a t e r s i A c e r t a i n p r o p o r t i o n of these are swept i n t o sandy inshore r e g i o n s of the coast. Whether they reach these l o c a l i t i e s i n a passive or a c t i v e s t a t e , before or a f t e r metamorphosis takes place has not as yet been determined. Metamorphosis, t h a t l s t h e as-suming of the s i d e swimming behavior, i s b e l i e v e d t o take p l a c e when the l a r v a reaches about one (Centimetre i n l e n g t h . Beach x s e i n i n g o p e rations have shown t h a t the young f i s h remain i n the i n t e r - t i d a l zone d u r i n g the summer months, growfing t o a l e n g t h of 10 cm. by August. With i n c r e a s e i n s i z e and the ad-vance of autumn, there i s a p r o g r e s s i v e m i g r a t i o n i n t o deeper and deeper water. This movement away from the i n t e r - t i d a l zone i s apparently complete by at l e a s t the beginning of November. D e t a i l s on the l i f e h i s t o r y of the lemon s o l e between the beach - 14 p e r i o d o f i t s e x i s t e n c e and when i t f i r s t appears i n the com-m e r c i a l catch are l a c k i n g . The s i z e at which the f i s h becomes f u l l y a v a i l a b l e t o the standard f o u r - i n c h mesh of the t r a w l i s about 27 or 28 cm., but no q u a n t i t a t i v e data can be obtained u n t i l experimental nets of v a r i o u s s i z e s of mesh are employed. M a t u r i t y Again the i n f o r m a t i o n on t h i s s u b ject i s r e s t r i c t e d t o the f i s h of the S t r a i t of Georgia and i s not n e c e s s a r i l y a p p l i c a b l e t o other regions of the coast. From the examination of 1425 t r a w l caught f i s h taken during or near the spawning season i t was found that approximately 50% of a l l female f i s h were mature at a l e n g t h of 295 mm. The a r r i v a l at sexual m a t u r i t y i s shown g r a p h i c a l l y i n f i g u r e 4. F i s h of 260 mm. i n l e n g t h were 100% Immature, w h i l e those at 360 mm. were 100% mature. S i m i l a r i n f o r m a t i o n w i t h regard to male f i s h i s l a c k i n g , f o r the reason t h a t no r e l i a b l e c r i t e r i o n of m a t u r i t y was a v a i l a b l e which oould be employed r a p i d l y enough t o cover a l a r g e number of f i s h . I t would appear, however, that males mature at a s m a l l e r s i z e than do females. F i f t y percent may p o s s i b l y be mature at a l e n g t h of 270 mm. The r e l a t i o n s h i p of age t o s i z e at m a t u r i t y i s not d e a l t w i t h i n great d e t a i l . However,data on age d i s t r i b u t i o n of f i s h taken i n the S t r a i t of Georgia d u r i n g the spawning season show t h a t approximately 85 t o 100% o f the two-year-old females are immature, 40 t o 50% o f the t h r e e - y e a r - o l d s , and 10% of the f o u r - y e a r - o l d s . Beyond t h a t age a l l f i s h oan be considered mature. Spawning i s presumed t o take place each year a f t e r m a t u r i t y i s reached, and i s apparently continued u n t i l death. 4" I IOO R Of ixi 50-2 5 300 350 L E N G T H - M M • 400 A graph showing the r e l a t i o n s h i p of sexual maturity to the size of female f i s h . - 15 -Fecundity E s s e n t i a l t o a l l f i s h e r y i n v e s t i g a t i o n s i s an es t i m a t i o n of the re p r o d u c t i v e c a p a c i t i e s of the species concerned. Q u a n t i t a t i v e data w i t h respect to t h i s subject have been ob-t a i n e d from the female lemon s o l e . The r i p e o v a r i e s of 32 f i s h were c o l l e c t e d j u s t p r i o r t o the time of spawning, and were preserved i n a f o r m a l i n s o l u t i o n f o r approximately s i x weeks. For the sake of consistency i n the measurements, the eggs w e r e - f i r s t f r e e d of the membrane m a t e r i a l and then tho-roughly d r i e d . The r e l a t i o n s h i p of the weight of eggs produced t o the lengt h of the f i s h i s shown g r a p h i c a l l y i n f i g u r e 5. Although time has not permitted a d e t a i l e d a n a l y s i s of the r a t e of i n -crease, a general t r e n d i s apparent. As the mature lemon sole egg measures only one m i l l i m e t e r i n diameter, and approximately 0.5 mm. when d r i e d , i t can perhaps be appreciated t h a t great d i f f i c u l t y experienced i n o b t a i n i n g accurate determinations of the a c t u a l numbers of eggs produced. However from a number of small counted and weighed samples i t was found that f i s h of 290 mm. produce approximately 240,000 eggs, and at the other extreme of the a v a i l a b l e data, a f i s h of 430 mm. produces approximately 2,100,000 eggs. The r e l a t i o n s h i p of f i s h l e n g t h t o weight of eggs produced i s better-understoodyby c o n s i d e r i n g that between 280 and 320 mm. the weight of eggs i s t r i p l e d , between 280 and 360mm., i t i s m u l t i p l i e d by f i v e , between 280 mm. and 400mm., by e i g h t and between 280 and 440mm. by fourteen. S i m i l a r r e -s u l t s are shown by R a i t t (1936) i n h i s study of the haddock i n 50 -300 550 400 H50 FISH LENfrTH - MM, F i g . 5 A graph showing the rel a t i o n s h i p of the size of female f i s h to the weight and number of eggs produced. -16 -the North Sea. The P o s t - L a r v a l Growth of the Lemon Sole As mentioned i n the s e c t i o n of l i f e h i s t o r y , q u a n t i t a t i v e growth data f o r the e a r l y p a r t of the l i f e of the lemon sole are a v a i l a b l e only f o r the pe r i o d of t h e i r s tay i n i n t e r - t i d a l waters. Samples of these f i s h were taken at monthly "O-Tide" i n t e r v a l s w i t h a small meshed seine (£"•) i n Departure Bay, Vancouver I s l a n d . The s i z e s of f i s h captured have been grouped t o the nearest h a l f centimetre and are presented g r a p h i c a l l y i n f i g u r e 6. The average s i z e of f i s h caught i n May was 40.4 mm., and i n June 63.7. T h i s represents an i n c r e a s e of 23.3 mm. However f i s h caught i n J u l y showed an in c r e a s e of only 15.3 mm. T h i s was found by experimentation t o be the r e s u l t of the employment i n J u l y of two nets of the same mesh but of d i f f e r e n t depth, one 1 fathom and the other 2 fathoms. The same nets were used again i n August, but the r e s u l t s were kept separate. The l a r g e net c a p t u r e d . f i s h averaging 107 mm., w h i l e the average f o r the small net was 86 mm. The r e s u l t s i n f i g u r e 6 are f o r May, June and August from the l a r g e seine. The J u l y sample was produced by both n e t s . Comparing the catches of t h e l a r g e net,then,the average i n c r e a s e i n s i z e was approx-imately 43.3 mm. which would represent a monthly i n c r e a s e of 21.1 mm. This compares with the 23.2 mm increase shown f o r May and June. These r e s u l t s are demonstrative of a very r a p i d growth during the f i r s t summer. The average i n c r e a s e i n s i z e between May and June amounts t o 55%, and between June and August about 32%. The r e l a t i o n s h i p of t h i s r a t e of growth t o t h a t of the adult f i s h w i l l be discussed i n a l a t e r s e c t i o n . LENGTH - r*\*. : • — - J F i g . 6 Graphs showing the size frequency d i s t r i b u t i o n s of young lemon soles captured i n beach seines at month l y intervals;during the summer of 1946, at Depart-ure Bay, B.C. - 17 -The d i f f e r e n t i a l s e l e c t i v i t y of the two seine nets i m p l i e s a m i g r a t i o n i n t o deeper water as the f i s h i n c r e a s e i n s i z e . By November of the same year t h i s m i g r a t i o n had proceeded to such a point t h a t even w i t h the l a r g e net weighted to f i s h at a depth of f o u r or f i v e fathoms below the low t i d e mark only two f i s h were captured. The great range of s i z e s present i n each h a u l as shown by the graphs i s i n a l l p r o b a b i l i t y the r e s u l t of the pro-longed spawning season. Furthermore the s i z e d i s t r i b u t i o n and numbers of f i s h taken i n beach seine samples w i l l depend upon the success o f the spawning, the height of the t i d e and on the depth of net employed. C a r e f u l l y c o n t r o l l e d s e i n i n g operations performed over a p e r i o d of years i n a number of l o c a l i t i e s , oould no doubt be employed i n p r e d i c t i n g the streng t h of a brood year, two or three years before i t s e n t r y i n t o the f i s h e r y . F i g . 7 A map showing some of the more important lemon sole trawling grounds (shaded areas) o f f the Fraser River estuary and i n the Gulf Islands. - 18 -i IV. THE ANALYSIS OF THE COMMERCIAL CATCHES OF LEMON SOLES A. THE STRAIT OF GEORGIA. 1. The F i s h e r y of the Fra s e r R i v e r Estuary and V i c i n i t y . Hauls of marketable f i s h are made o f f P o i n t Grey and south-wards to the F r a s e r R i v e r l i g h t s h i p ( F i g . 7) i n shallow water (5-20 fathoms) i n the summer months and i n deeper waters (30-45 fathoms) i n the w i n t e r months. South of the l i g h t s h i p f i s h i n g i s conducted i n waters of depths down to 75 fathoms, Small f i s h i n g areas. E n g l i s h Bay to the east of P o i n t Grey, and a winter spawning ground near P o i n t Atkinson are now c l o s e d to a l l but one s m a l l boat. Samples from the whole r e g i o n cover a p e r i o d extending from the s p r i n g of 1945 to the f a l l of 1946. (a) Length Frequency D i s t r i b u t i o n s . F i g u r e 8 shows d i s t r i b u t i o n graphs of f i s h sampled during f o u r periods i n . 194-5 and 1946. A f i f t h sample from P o i n t Atkinson has been kept separate from the main w i n t e r sample because i t represents spawning f i s h . I n g e n e r a l , the lemon s o l e s captured from the F r a s e r R i v e r r e g i o n are s m a l l . Male f i s h average from 290 t o 310 mm. i n l e n g t h , w h i l e female f i s h w i t h the exception of those from the P o i n t Atkinson grounds, average be-tween 310 and 340 mm. The f i s h from the spawning ground averaged about 36O mm. The sharp drop i n the frequency curves below 290 or 300 mm. i s due to net s e l e c t i o n and t o the c u l l i n g of unmarketable f i s h . No male f i s h l a r g e r than 36O mm. were encountered: the upper I FRRSCR RIVER H H P V I C I N I T N M q t E — — -F E M A L E . 3 0 0 3 5 0 LENGTH - * r * V 3 0 0 3 S 0 L E N G T H - K \ K \ . V 0 1 M T A T K I N S O N M O L E 3 0 0 350 F i g . 8 Graphs showing the length frequency d i s t r i b u t i o n s of lemon soles captured i n the v i c i n i t y of the> Fraser River during 1945 and 1946. F R R S E R R I V E R » N » V I C I N I T Y 1 9 4 5 HO a S to & 10 • III- 1 i w n i l i i t i 1110 m i n w iqm wt I I I I wo W M 1 1 3 ? POINT ftTKlNSOW ISHH W l l l tJ W l I I * 1131 113* V E B R C U M 1 W I H 3 I W H M I W O M M 11V) N f f i t C L A S S T > e c - p ' R i i -I W 111} M l A l l 1110 N31 1118 NEAR CLASS n u i w m i m« i w ii3? >(E<W CLASS FEMALE. . N i l R1J i*iii H i ' ' i i ? ' ^ " i 1113 1 1 1 1 1111 IH10 1131 M 3 ? F i g . 9 Graphs showing the year c l a s s d i s t r i b u t i o n s of lemon soles captured i n the v i c i n i t y of the Fraser River during 1945 and 1946. - 19 -s i z e l i m i t of females however was much g r e a t e r , v a r y i n g from 450 to 510 mm. (b) Sex R a t i o . For the two periods i n the summer and f a l l of 1 9 4 5 male f i s h comprised 30 and 37 % of the t o t a l number sampled. The winter sample contained 18% males. At P o i n t A t k i n s o n however where spawning was t a k i n g place 44% of the f i s h taken were males. Considering the shape of the frequency curve f o r these f i s h i t i s probable t h a t t h i s percentage was much higher i n the a c t u a l unselected p o p u l a t i o n . I n the summer sample f o r 1946 only 15% of the f i s h taken were males. (c) Age D i s t r i b u t i o n . The d i s t r i b u t i o n s of the year c l a s s e s are presented g r a p h i c a l l y i n f i g u r e 9« During the summer and f a l l of 1945 the 1941 year c l a s s predominated i n both sexes. Gn the P o i n t Atkinson ground male f i s h of the 1941 and 1942 year c l a s s e s ap-peared most f r e q u e n t l y . However the female s o l e s were best r e -presented by the 1941 and 1940 year c l a s s e s . The main winter sample and the succeeding summer sample contained f i s h i n which the dominating male year c l a s s was 1941 and f o r females the 1942 c l a s s . The o l d e s t male f i s h encountered were members of the 1938 year c l a s s — a n d the o l d e s t females were of the 1936 year c l a s s . 2. The F i s h e r y of the G u l f I s l a n d Grounds. The waters of the Gulf I s l a n d s ( F i g . 7) together w i t h those of Bayne Sound 40 miles to the north are the f o c a l p o i n t s of an i n t e n s i v e f i s h e r y during the winter months of the year. S t a r t i n g GULF I S L A N D S F i g . 10 Graphs showing the length frequency d i s t r i b u t i o n s of lemon soles captured i n the v i c i n i t y of the Gulf Islands during 1945 and 1946. QULF ISLRMDS J h , . Mi nit m« NJI w un i«t Y E A R C L A 5 S L iLL I 1 H I'm W f i PWO iw nw put,.-DEC 3 0 ns> m; iqqi i<w iw mt W J i iu • | H FEMALE. . IH . nn ni» mi nio nn w» mi iiiv, N e o n C L A S S •I mo, l i b - J I I . : nit nn is«o i n ii» I S J I C L A S S I<WJ I I I I mi mg un mn F i g . 11 Graphs showing the year class d i s t r i b u t i o n s of lemon soles captured i n the v i c i n i t y of the Gulf Islands during 1945 and 1946. - 20 -i as early as September the winter spawning migration of the lemon sole i s heralded by sizeable catches i n the regions of Porlier Pass and Active Pass. During January, February and March most of the f i s h are caught on what i s known as the Boat Harbour ground, an area at the northern end of Stuart Channel. The samples taken, were for the greater part representative of these migrating and spawning f i s h . (a) Length Frequency Distributions. The samples from the Gulf Islands (Fig. 10) coyer a period from the f a l l of 1945 to the f a l l of 1946, In general the f i s h are larger than those encountered off the Fraser River estuary. The f a l l of 1945 sample representing f i s h i n the process of migrating contained male f i s h averaging 320 mm. and females averaging 370 mm. The spawning ground sample from Boat Harbour i n the early part of 1946 contained small males avera-ging 310 mm. However the average length of female f i s h was 36O mm. During the summer of 1946 the average lengths of males and females were 330 and 36O mm. respectively. The largest male f i s h reached a length of 390 mm,, and the upper l i m i t for females appeared to be about 500 mm. (b) Sex Ratio. During the f a l l of 1945 and during the summer of 1946 male f i s h comprised 21% and 27% respectively of the total numbers of f i s h sampled. However, as can be seen from the graph representing the spawning season only a very small percentage (17%) of the f i s h taken on the Boat Harbour grounds were male f i s h . Assuming that the sexes are present i n equal numbers at - 21 -( the time of spawning, the occurrence of such a r a t i o might a r i s e from two c a u s e s — 1. d i f f e r e n t i a l movement of the sexes on the spawning ground, 2. the presence of a l a r g e p r o p o r t i o n of males below commercial s i z e and below net s e l e c t i o n s i z e * Considering the shape of the male d i s t r i b u t i o n curve and i t s r e l a t i o n s h i p t o a maximium c u l l s i z e of 290 mm. the l a t t e r e x p l a n a t i o n would seem the more reasonable. (c) Age D i s t r i b u t i o n . As shown i n f i g u r e l l ^ t h e 194-5 f a l l sample of male f i s h the 1941 year c l a s s appears most f r e q u e n t l y and the females are best represented by both the 1940 and 1941 year c l a s s e s . The spawning ground sample taken during January and February of 1946 shows the 1941 year c l a s s predominating i n both sexes. S i m i l a r r e s u l t s are shown f o r the f i s h taken during the summer of the same year. 3. The F i s h e r y of Baynes Sound. The Baynes Sound f i s h i n g grounds are s i t u a t e d between Denman I s l a n d and Vancouver I s l a n d , approximately 40 miles n o r t h -west of the Gulf I s l a n d s ( F i g . 12). As i n the southern waters the most i n t e n s i v e f i s h i n g i s c a r r i e d on during the w i n t e r months. During the e a r l y months of the year the important dragging area f o r s o l e s l i e s outside of Baynes Sound i n the waters j u s t south of Cape Lazo. I t i s i n t h i s r e g i o n t h a t the major spawning has been found to take p l a c e . JE1&. 12 A map showing the general trawling grounds (shaded areas) i n Baynes Sound and to the south of Cape Lazo. B R Y M E S S O U N D F i g . 13 Graphs showing length frequency d i s t r i b u t i o n s of lemon soles captured i n the v i c i n i t y of Baynes Sound during 1945 and 1946. B f l V N E S S O U N D SEPT.- Dee. i<m iw iw mo iw w i iw F 6 I M A U E 1111 I W I W W O I W l i l t 1931 l i s t Me«<* C L A 5 S T O M . - F E B -t<m mi H H I w o is3S n3j u n n % X£AA CLASS F E M A L E . MM3 1112 1111 1110 IW I13J u n V60R CLASS FEB. (CAPE LMO) MAL£ F E M f t L E 1115 l i l t I W mo f)3S I T O I W VEAR. CLASS 111} IW 1111 l<Ho 1131 11S8 1131 I13t VeiR CLASS F i g . 14 Graphs showing the year c l a s s d i s t r i b u t i o n of lemon soles captured during the f a l l of 1945 and during the spawning season i n 1946. v - 22 -•I Samples presented are f o r the f a l l of 19-45 and f o r the e a r l y months of 1946, Because of the s c a r c i t y o f f i s h during the other periods of the year s a t i s f a c t o r y samples were not obtained. (a) Length Frequency D i s t r i b u t i o n s . The d i s t r i b u t i o n s of the s i z e s of f i s h captured are shown i n f i g u r e 13. The male f i s h captured were s m a l l , averag-i n g from 310 to 320 mm. i n the v a r i o u s samples. Female f i s h i n the f a l l sample averaged 350 mm. and between 370 and 38O mm. i n the spawning season. The marked decrease i n frequency below lengths of 280 and •r*\-. 290 mm. i s due to c u l l i n g and net s e l e c t i o n . Male f i s h up t o lengths of 390 or 400 mm. were encountered. Females i n the other hand reached lengths up to 490 mm. (b) Sex R a t i o . During the f a l l p e r i o d 24% of the f i s h landed were males. The f i r s t samples from Bayne Sound, taken during the spawning season^contained only 14% male f i s h . The p r e c i s e l o c a l i t y from which these f i s h were captured i s not c e r t a i n . However a l a t e r sample taken i n the waters o u t s i d e Baynes Sound j u s t south of Cape Lazo contained f i s h of which 56% were males. The shape of the frequency curve would i n d i c a t e t h a t the a c t u a l percentage of male f i s h present on the grounds at t h a t time was much h i g h e r , but t h a t many had been c u l l e d out of the c a t c h or s e l e c t e d out by the net. (c) Age D i s t r i b u t i o n . The graphs i n f i g u r e 14 show the male f i s h best r e p -- 2 3 -resented by the 1941 year c l a s s . The same year c l a s s pre-dominated w i t h r e s p e c t to female f i s h i n the f u l l p e r i o d . How-ever, the graph of f i s h taken during the e a r l y p a r t of the spawning season shows three year c l a s s e s o c c u r r i n g w i t h about equal frequency, the 1942, 1941 and 1940 c l a s s e s . Female f i s h from the Cape Lazo sample were best represented by the 1940 year c l a s s . The o l d e s t male f i s h present were from the 1937 yea r c l a s s and the o l d e s t females were from the 1935 year c l a s s . Reviewing the age d i s t r i b u t i o n of f i s h caught i n the S t r a i t of Georgia, i t can be seen t h a t during the periods of the 1945 and 1946 f i s h i n g seasons d e s c r i b e d , the 1941 year c l a s s , g e n e r a l l y speaking,predominated i n the catches. B. THE WEST COAST OF VANCOUVER ISLAND F i s h i n g on the west coast of Vancouver I s l a n d i s r e s t r i c t e d i n g r eater p a r t to the summer months of the year. The grounds extend from P o r t San Juan northward t o Kyuguot Sound (see map, F i g . 1 5 ) . The lemon s o l e does not occur i n great abundance i n the waters of t h i s p a r t of the coast and as a r e s u l t c o n s i d e r -able d i f f i c u l t y has been experienced i n the c o l l e c t i o n of ade-quate samples, and much of the data have been combined. For the purposes of t h i s work two regions are recognized, the waters be-tween P o r t San Juan and Tofino on the lower c o a s t , and between Esteban P o i n t and Kyuquot Sound along the upper coast. F i g . 15 A map showing lemon sole trawling grounds (shaded areas) situated o f f the west coast of Vancouver Island. - 24 -1. Port San Juan to Toflno. Lemon soles are taken most frequently from a narrow strip of trawling ground off Port San Juan between 30 and 40 fathoms in depth; and along the inner part of the La Perouse Bank be-, tween Long Beach and Tofino. The samples represent two periods during the summers of 1945 and 1946, (a) Length Frequency Distributions. The graphs for the length distributions are shown i n figure 16. During the two periods i n 1945, April to July and August to November the average lengths of male lemon soles were 330 mm. and 320 mm. respectively. The average lengths of female fi s h were 380 mm. and 370 mm. For the same general periods i n 1946 the average length of male f i s h i n the early summer was 320 mm. and of female f i s h , 350 mm. In the later part of the season males averaged 330 mm. and females 370 mm. No male f i s h larger than 390 mm..were recorded during 1945 and 1946, and the upper limi t for female f i s h appears to be i n the v i c i n i t y of 500 mm. (b) Sex Ratio. The samples from the west coast of Vancouver Island are characteristic i n that very few male fish: appear, i n the catches. In 1945, during the early part of the summer only 8% of the f i s h caught were males* and i n the later part of the summer and f a l l , only 13%* In 1946 for the same periods the percentages of males was 4% and 5%» The analysis of 1944 catch data by the writer (1945 b) showed only 8% male f i s h . This was at f i r s t thought to be the result of the culling of small fish* SflKI J U f l M r o T C F I N O ESTcBRN TO KVUQuor F i g . 16 Graphs showing the length frequency d i s t r i b u t i o n s of lemon soles captured i n two regions o f f the west coast of Vancouver Island during the summers of 1945 and 1946. SfiN lUfiM TO TOFlNQ N45 " M A L E ISI l W l IHHO iMi t 1118 30 H P E M B L E l :Lilli« |<lHi W i l «**HI WHO ISM I W W l W W45 Rufc<- Nov-K3o- | , 1 A L £ JO" — F E M A L E . I •••• - J l l u . W J i<Ht W l 1*140 fli8 J W I^Hl WHI I W W ? i w w VC^R. C L A S S W I W I f O l<WI I W N N VE3R ClRSl 1913 W l )SVI| iSHO 113") 1*)3* veil! c :.«•>•; M R N - T U L Y MBit W ! l * ( l H1I I W TO<| m j 1131 |<(J(, RL>^.- SEPT. ' yo • B F E M A L E w m i w N n iqni W o i w isi» F i g . 17 Graphs showing the year class d i s t r i b u t i o n s of f i s h captured during the summers of 1945 and 1946 between San Juan.and Tof ino, on the west coast of Vancouver Island. - 25 -However f i e l d observations by Mr* J. Manzer have shown that there is no appreciable increase i n the percentage of males i n unculled catches* Male lemon soles are apparently not present i n any numbers on the commonly trawled grounds of the west coast. (c) Age Distribution. Samples taken during the two 1945 periods show the females to be best represented by the 1940 year class (Fig. 17). Male f i s h were too few to warrant consideration i n this respect. The 1942 year class predominates in both sexes i n the 1946 samples, with the exception that i n the f i r s t part of the year the females are strongly represented by the 1943 year class i n addition to the 1942 year class. Between 1945 and 1946 then, there has been a striking change i n year class dominance. This matter w i l l be dealt with i n detail i n a later section. Suffice i t to say that this change could result from either an increase in mortality rate brought about by an intensive fishery, or from the influx of a new year class. 2. Esteban Point to Kvu^uot Sound. Fishing i n this region i s confined to l o c a l i t i e s off Esteban Point, Nootka Sound, Esperanzo Inlet and Kyu^uot Sound. Most of the species of f i s h captured (lingcod, rockfish, rock sole, etc.) are inhabitants of rough and broken ground, a fact which probably accounts for the relative infrequency of appearance of lemon soles in the catches. Because of the limited sampling oppor-tunities and material the data have been combined and cover the period from May to August in 1945 and i n 1946. ESTEBRN TO K X U Q U O T - FEMALES -n u m i mi wo i w mt PHI n»t> lea*, CLASS I 1 U 1112 IfHI 1110 1131 113? N e a t CLASS F i g . 18 Graphs shewing the year class d i s -t r i b u t i o n of f i s h captured during the summers of 1945 and 1946 between Esteban Point and Kyuquot Sound on the west coast of Vancouver Island. - 26 -(a) Length Frequency Distribution, The distribution graphs are shown i n figure 16. Male f i s h were too few for consideration. Females, however, averaged approximately 38O mm, i n the 1945 samples while i n 1946 the average length was slig h t l y over 36O mm. The upper size li m i t i n both years appears to have been around 450 or 460 mm, (b) Sex Ratio, The percentage of male f i s h i n the samples for this region was-even lower than i n the region to the south. In 1945 only 3 % of the f i s h examined were males, and i n 1946 out of a total of 3 7 0 f i s h only 6 or 1,6% were male, (c) Age Distribution. As in the lower region of the coast, the predominating year class i n 1945 was the 1940 class (Fig. 18), In 1946 the dominance had changed to the 1942 year class. C. THE GOOSE ISLAND GROUNDS. To the north of Vancouver Island, lying i n the middle of Queen Charlotte Sound are the Goose Island grounds. This region is one of the important halibut grounds of the coast, and the operation of the trawlers i n the area has been objected to by the halibut fishermen on the basis of alleged serious interfer-ence with set-lining. L i t t l e information i s available on the exact regions in which dragging i s carried out, but the general area i s indicated i n the maps (Fig. 2). Large trawlers operate on these grounds during May and June. Data have been collected during 1945 and 1946 for these periods. I G O O S E I5LRND 3o r 300 350 HOO 150 500 B R I M K S I S L A N D L E N G T H - M M . F i g . 19 Graphs showing the length frequency d i s t r i b u t i o n s of f i s h taken during the summers of 1945 and 1946 on the Goose Island grounds i n Queen Charlotte Sound, and i n the summer of 1946 o f f Banks Island i n Hecate S t r a i t . GOOSE ISLAND I VEHR . C L A S S ^ I E A K C L A S S I B R N K S I S L R N D m i MHI n m nvo IWI m k NII m i m i m o i u t I i F i g . EC-Graphs showing the ygar c l a s s d i s t r i b u t i o n of f i s h captured on the Goose Island grounds i n 1945 and 1946, and on the Banks Island ground i n Hecate S t r a i t i n 1946. - 87 -(a.) Length Frequency D i s t r i b u t i o n * The graphs of 1945 and 1946 samples are shown i n f i g u r e 19* Male f i s h i n 1945 averaged 320 mm. i n l e n g t h and 330 mm. i n 1946. Female f i s h on the other hand averaged 360 mm. i n l e n g t h i n 1945 and 390 mm. i n 1946. No male f i s h l a r g e r than 38O mm. were encountered. The upper s i z e l i m i t of female s o l e s at the time of sampling i n 1945 was 450 mm. However i n 1946 f i s h as l a r g e as 510 mm. were encountered. (b) Sex R a t i o . I n 1945 samples 12% of the f i s h examined were males, and i n 1946, 16.5% were males. (c) Age D i s t r i b u t i o n . Male s o l e s i n 1945 were not i n , s u f f i c i e n t numbers to warrant c o n s i d e r a t i o n . Female soles were represented most f r e -quently by members of the 1940 and 1939 year c l a s s e s ( F i g . 20). Because of the smallness of the samples i n t h a t year much s i g -n i f i c a n c e cannot be attached to t h i s r e s u l t * However i n 1946, w i t h much more adequate sampling, these year c l a s s e s again pre-dominated* Male f i s h showed the same s i t u a t i o n , dominance of the 1940 and 1939 year c l a s s e s . Although d e t a i l e d c o n s i d e r a -t i o n of t h i s occurrence w i l l be made l a t e r , i t may be s a i d t h a t there i s an i n d i c a t i o n here of t r u l y dominant year c l a s s e s . That i s , year c l a s s e s which anethe r e s u l t of s u c c e s s f u l brood years remain outstanding over a number of y e a r s . t D. THE FISHERY OF HECATE STRAIT The greater p a r t of the f i s h i n g i n Hecate S t r a i t i s c a r r i e d F i g . 21 A map showing the approximate lo c a t i o n of the lemon sole grounds i n northern Hecate S t r a i t - Banks I s -land, Butterworth Rocks, T r i p l e Island, Two Peaks, and Rose S p i t . 28 on in the northern part between Prince Rupert on the mainland and Rose Spit on the Queen Charlotte Islands (see map, Fig. 21). Four dragging grounds are generally recognized by the fisher-men, Butterworth Rocks, Two Peaks, Triple Island and Rose Spit. Their exact limits have not as yet been determined. Future tagging experiments:may possibly show that they are inter- con-nected. Another lemon sole fishing area l i e s approximately 40 miles south-east of Butterworth Rocks i n the v i c i n i t y of Banks Island. Samples to be considered cover the spring and summer months of 1945 and 1946. 1. The Banks Island Ground. Satisfactory samples from this region were obtained- during the summer of 1946 only. Apparently most of the fishing takes place between the buoy at the north end of the island and Bonilla Rock to the south-west, i n waters between the depths of 15 and 45 fathoms. (a) Length Frequency Distribution. Fig. 19. The average length of male f i s h was 310 mm, while the average for females was 330 mm. The sharp decline i n numbers below 300 mm, may be a t t r i -buted to net selection and culling. The largest, male sole en-countered was 410 mm, i n length and the\largest female was 510 mm. Small f i s h predominated i n the sample examined, Male fish comprised 41% of a total of 617 f i s h ex-- 29 -amined from t h i s region. (c) Age D i s t r i b u t i o n . The 1942 year class highly predominates i n both sexes (Fig . 20). Thirty-nine percent of the female f i s h and 28% of the males were found to be from t h i s c l a s s . 2. The Butterworth Rock Grounds. Most of the lemon soles landed at Prince Rupert through-out the year are from t h i s ground. Fishing takes place for the most part to the south and west of Butterworth Rocks i n waters between 30 and 60 fathoms i n depth, Samples were collected from t h i s region during the spring of 1945 and the spring and summer of 1946. (a) Length Frequency D i s t r i b u t i o n s . The r e s u l t s of sampling during 1945 and 1946 are shown graphically i n figure 22, In A p r i l 1945 the average sizes of male and female soles were 350 and 38O mm*respectively. In 1946 during the same period the averages were 340 and 370 mm. The l a r g e s t male f i s h encountered was 420 mm. i n length, and the largest female was 500 mm. The summer samples taken during 1946, May to June, and August show considerable differences i n the d i s t r i b u t i o n . In May and June the average length of male f i s h caught was 340 mm. and the average length of females was 38O mm. In August,how-ever, male soles averaged 360 mm. and females 420 mm. Such d i f -ferences: may be .attributed mainly to differences i n depth and l o c a l i t i e s f ished. F i g . 22 Graphs showing the length frequency d i s t r i b u t i o n of lemon soles taken on the Butterworth Rock grounds during the spring Of 1945 and 1946," and during the summer months of 1946. BU T T E D W O R T H B O C K S Wi\ tVii I9V0 WJ9 M l ? Ktj7 l<Wv |?3S" |qu;H |<M3 |<1H2 MHI \<\HO I931 ( H i ? I W 1135" FEMALE i l l * IIHI n s i m o <q§«i i«m 11% iqasr HMI i<m ism m o i w H j * i w . ms* n w M O N - J U N E - • • H i ! - . l l i l l l . . J944 K m l < m I W 1151 I W 1911 iSXfc H 3 r I<(MM I l H i l<f««0 M l ^ W i ? I W ISJ% I l l y i S i H VEfit CLASS >jEn^ Ci.n:i Bu«,uvr m i H I ) i H t IIXI n v o N i l I W i i t i m i . i w m » m i HII H i o m i n i r n n n i . n i l ' I D I h « F i g , 23 Graphs showing the year class d i s t r i b u t i o n of-f i s h caught during the spring of 1945 and 1946, and during the summer months of 1946,on the Butterworth Rock grounds. - 30 -The upper size limit for male f i s h i s between 420 and 430 mm. Female f i s h of lengths up to 500 or 510 mm. were en-countered i n a l l samples. (b) Sex Ratio. In April of 1945, 48% of the lemon soles captured were male f i s h . During the same period i n the following year, 45% were males. In May and June the number amounted to 43% and in August to 25%. (c) Age Distribution. The year class distributions are given in, figure 23. The samples of female soles taken during April 1945 show the 1939 year class best represented. The distribution for male fish , shows three years predominating, the 1940, 1939 and 1938 year classes. In April 1946 the predominating class i n male fi s h was the 1939 year class, and i n females the 1942 year class. May and June samples i n 1946 showed the 1939 year class domin-ant in both sexes. In addition to this class,however,in the distribution for female fish,the 1942 year class also shows up prominently. In the August sample the 1939 year class predom-inates i n both sexes, and the 1942 year class i s represented by only 7*4% of the female f i s h . The alternating (and sometimes concurrent) predominance of the 1939 and 1942 year classes w i l l be discussed i n a later section. 3. The Triple Island Grounds. This fishing area l i e s approximately six miles north of Butterworth Rocks. L i t t l e i s known as to i t s extent aside from TRIPLE. ISLftND i I F i g . 24 Graphs showing the length frequency d i s t r i b u t i o n s of f i s h captured during 1945 and 1946 on the T r i p l e Island, Two Peaks and Rose Spit grounds i n north-ern Hecate S t r a i t . I : I - i Si x • TRIPLE ISLAND MALE l l U t 1113 1111 111 I 1110 m i N 3 J I W 113b N E A R C L A S S IS45 ISM6 F E f l S V J E -1113 1112 1111 1110 1131 H3» 1131 " 3 1 . ! 1 W H E A R C L A S S m i i n s m i m i m o i i 3 i H3« u n I I J L l i l y n i l N E A R C L A S S g 2 0 -T W O PEAKS 1111 1110 I1J1 I1J8 1131 1131, I13S NEAR C L A S S IS45 * jo F E M A L E iw mi m« HOT im un ins mi N E A R CLASi n i l i i 4 j m n i l m o mi n3» nn l i s t N E A R . C L A > 4 FEMALE IS11 I S 1 J 111 ! 1111 M O 1131 M S 1131 1131, 1135 \ E « L C L A S S JFig. 25 Graphs showing the year c l a s s distributions:-of f i s h captured on the T r i p l e Island and Two Peak grounds during 1945 and 1946. - 31 -from the fact that f i s h sampled in the summer of 1946 were from shallow water near the Triple Island Light. Samples taken rep-resent two periods, September 1945 and July 1946. (a) Length Frequency Distribution, The graphs of the data taken i n this region are shown in figure 24. The average length of female f i s h i n both years was approximately 38O mm. Male soles i n 1946 averaged 340 mm., while the average i n 1945 was 320 mm. (b) Sex Ratio. Male f i s h i n the 1945 catch, amounted to only 11% of the total number present. In 1946, approximately 39% were male f i s h . (c) Age Distribution, The graph for the age distribution of f i s h caught i n 1945 (Fig, 25), shows the 1939 year class dominant with respect to female f i s h . Male lemon soles were too few to warrant con-sideration. In 1946 two year classes, the 1939 and 1942 classes were dominant i n both sexes. This situation i s similar to that shown by samples from Butterworth Rocks during the same period, 4. The Two Peaks Fishing Ground, This fishing ground l i e s approximately 10 or 15 miles north and west of Butterworth Rocks (Fig. 21), between depths of 40 and 50 fathoms. Samples were collected during two periods:June, 1945, and i n January 1946. (a) Length Frequency Distribution. The f i s h taken i n June of 1945 (Fig. 24) were con-32 -siderably larger than those taken i n the following January. The average length of male f i s h was 38O mm, and females aver-aged 430 mm. In January the average lengths of male and female 0 soles were 310 and 340 mm., respectively. Culling and net selection show their effect i n the shape of the frequency curve for January. However the June sample shows no culling effect. Apparently there were no small f i s h present on the ground at the time fishing took place. In January there were no large f i s h present, (b) Sex Ratio, In the June sample 22% of the f i s h captured were males, while i n January 41% were male, (c) Age Distribution. The age distributions are shown i n figure 2% Male fis h i n June of 1945 were best represented by the 1937 year class. The 1938 year class.predominated i n the distribution of female f i s h . The samples taken during January of 1946 show the same situation that has already been observed i n the study of Butterworth and Triple Island f i s h , that of bimodality In the distribution curves. The 1939 and 1942 year classes dominated i n both sexes, 5, The Rose Spit Fishing Ground. Lemon soles sampled from this region are apparently caught i n relatively shallow water (10-12 fathoms) about eight miles east of Rose Spit just off the edge of the Dogfish Bank (Fig,21) . Sampling was carried out during June of 1945 and 1946, ROSE SPIT - l l l l l - i : l - J i l l . -Mil W l I9«f0 1919 I1» lUT (931- 19JS |QW m i H W M M MW H H USfc MJ5 1111 <*tii IS46 I l l l l l l . - l l l l l l a . -i w mi m i m i m i m\ i t s n n n » n v m i »«» ni« m i "*> « w '•""> ' i * i " * " ' I v e c e CL«5S N E W < X « S F i g . 26 Graphs showing the year c l a s s d i s t r i b u t i o n s -of lemon soles captured on the Rose Spit grounds during the summers of 1945 and 1946. - 33 (a) Length Frequency Distribution, In Fig. 24, the graph for f i s h caught during 1946 shows an increase i n the proportion of small-fish as compared with 1945* The average lengths of male and female f i s h i n 1945 were 370 mm. and 41G mm, respectively. In 1946 the aver-ages were 340 mm. and 390 mm, (b) Sex Ratio. Male f i s h i n the 1945 catches amounted to 19% of the total number sampled. In 1946 this percentage was slightly higher, approximately-26%, (c) Age Distribution, In 1945, the 1939 year class appeared to dominate i n both sexes (Fig. 26). With respect to the male fish,however, the 1937 year class was also well represented. It w i l l be remembered that this was the dominating year class i n the age distribution of male f i s h from the Two Peak grounds during the same period. In the 1946 graph for female f i s h , two year classes predominate, the 1939 and 1942 classes. Dominance i s not as distinct i n the samples of male f i s h , but there i s some indica-tion of similarity to the females* - 3 4 -is V. RATES OF GROWTH The r a t e of growth of the lemon s o l e i n the d i f f e r e n t l o -c a l i t i e s of the coast has been determined on the b a s i s of the average lengths of f i s h encountered i n the v a r i o u s year c l a s s e s . Suoh determinations can be made a c c u r a t e l y o n l y where sampling has been p a r t i o u l a r l y intense and where i t has been c a r r i e d out i n a f a i r l y short p e r i o d of time. Dependence upon samples from the commercial catoh creates s e v e r a l d i f f i c u l t i e s i n the e s t i m a t i o n of growth r a t e . I n the f i r s t p l a c e , data on the growth d u r i n g e a r l y l i f e are l a c k i n g e n t i r e l y . Furthermore the average s i z e s of f i s h i n the lower age groups whioh f i r s t enter the f i s h e r y are a c t u a l l y .greater than the t r u e averages, as the net and the fishermen s e l e c t out the l a r g e r members of these age groups. Henoe, as shown by R i o k e r (1940) the d i f f e r e n c e s between age groups which are a f f e c t e d by s e l e c t i o n and those which are not w i l l be l e s s than i n the n a t u r a l s t a t e . With respeot t o f i s h i n the o l d e r age groups the p o s s i -b i l i t y of sampling e r r o r i n c r e a s e s as the number of f i s h i n each suooeeding age group decreases. A l s o t o be oonsidered i s the p o s s i b i l i t y of age s e l e c t i o n by the net. That i s t o say, are o l d e r f i s h more l i k e l y t o get caught than young ones? I n an e f f o r t t o discount the p o s s i b l e e f f e c t s of the above men-ti o n e d f a c t o r s , the a c t u a l determinations of growth r a t e have been confined to a p e r i o d between four and ei g h t years of age . Two graph!o methods of p r e s e n t i n g growth r a t e have been 500 F R A S E R R IVER 500 H00 • •soo. v vi vn vm BRYNES SOUND• V V I VII VIII 500 l I 100 w o t t 1 too <Moo 300 Ql /LF I S L A N D S v VI VII Aft. -HEARS 5 A N T U R N T O TOFINO v vi vu vm E S T E B R N T O K Y U Q U O T SNP-'v v vi vn vui IX x RCit - \«RAS F i g . 27 Graphs showing the growth of the lemon sole i n the S t r a i t of Georgia and on the west coast of Vancouver Island. ( M A L E . J F E I ^ A U L SCiOr GOOSE I S L R N P T R I P L E I S L H N D MI iv v vi «H vm ix < 500 i I HOO 300 III IV V VI VII VIII IX X XI B U T T E R W O R T H R O C K S 50  I 1 0 0 -30 III IV V VI VII v m R<1£ - NGCWS ROSE SPIT III IV V VI VII VIII F i g . 28 Graphs showing the growth of the lemon sole on the Goose Island ground and i n three regions i n northern Hecate S t r a i t . (^MAU=_ .PEr^A^e. -35-employed. The f i r s t of these deals with absolute growth, a straight p l o t t i n g of age against length. Graphs of t h i s type, .shown l n figures 27 and 28, give a picture of the general trend i n growth and serve well f o r rough comparisons. Most s t r i k i n g are the consistent differences i n the rates of growth between the sexes. In general the female soles show an increase of approximately 11 mm. more per year than do the males. In table I are determinations of growth rate i n the various regions, shown as averages i n millimetres per year from the fourth to the eighth year. From these r e s u l t s i t i s apparent that the growth rate i s greater i n the s t r a i t of Georgia and i n northern Hecate s t r a i t than on the west coast of Vancouver i s l a n d , Queen Charlotte sound and i n the middle of Hecate s t r a i t . This i s most readi l y seen with respect to female f i s h . These values represent a general growth rate and do not take into consi-deration the fact that growth i s steadily decreasing during the f i v e year period. In an attempt to represent t h i s changing growth rate a second method of determination has been employed. The growth rates during three time-intervals, four to six years, f i v e to seven years, and six to eight years, have been obtained by using the generalized formula for the groxtfth curve S = P e & t , where t, i s the time i n t e r v a l , P the i n i t i a l s i z e , S the size at the end of time t, and G the growth rate. The value so obtained i s a natural logarithmic expression, referr e d to by Ricker (19^5) as an "instantaneous growth rate," that i s , -36-TABLE I The average growth rate between the fourth and eighth year. Growth Rate (mm. per year) Male Female Fraser River 10 23 Gulf Islands 9 22 Baynes Sound 13 23 San Juan to Tofino 11 19 Esteban to Kyuquot - 19 Goose Islands 10 19 Banks Island 11 18 Butterworth Rbcks 13 20 T r i p l e Island 12 23 Two Peaks Ik 20 Rose Spit 13 21 W - V I V - V I I V I - V I M T W O " Y E R R T I M E - I N T E R V A L S I F i g . 29 Graphs showing the change i n the i n -stantaneous growth rate "intfemale f i s h between four and eight years of age. -37-the growth rate at any one Instant during a f i s h i n g season. The re s u l t s obtained f o r female f i s h are shown i n figure 2 9 . Similar treatment of the data for male f i s h proved unsatis-" factory probably because of the inadequacy of sampling. However, the rates as determined are given i n the appendix. The growth rate between the fourth and s i x t h year appears to be greatest i n female f i s h from the Butterworth rocks region. Baynes sound and the Fraser r i v e r samples show a s l i g h t l y lower growth rate for the same period. The rates are about equal i n the Gulf islands, on the lower west coast of Vancouver island, and on the Two Peak grounds. The lowest growth rates between four and six years of age are shown by samples from the upper west coast of Vancouver is l a n d , and from the Goose is l a n d grounds. In general the greatest decrease i n growth rate i s shown by the samples from the northern part of the coast. This i s evident from the slopes of the l i n e s between the f i r s t two time-intervals. Between the second and t h i r d time-intervals trends are Indefi n i t e , probably because of sampling d e f i c i e n c i e s . The general r e s u l t s from the various l o c a l i t i e s show that differences i n the growth rate of the lemon sole, a f t e r i t reaches commercial size, are not s t r i k i n g . More pronounced differences may occur during the period p r i o r to when the f i s h enters the f i s h e r y , but because of the l i m i t a t i o n s i n sampling methods, nothing can be said i n t h i s respect -38-at present. The employment of small meshed nets In the future, i n a l l p r o b a b i l i t y w i l l reveal l o c a l differences which are not detectable i n the samples from the commercial oatch. - 39 -V I . MORTALITY RATES One of the important f a c t o r s which a f f e c t the abundanoe of f i s h i s that of m o r t a l i t y . This may be of two k i n d s — 1. Death due t o n a t u r a l causes and 2. Death due to f i s h i n g . Together they represent the t o t a l annual m o r t a l i t y . The determination of t o t a l annual m o r t a l i t y i s made e i t h e r through tagging experiments or by the examination of the age composition of the stock. The l a t t e r method has been employed f o r t h i s work. According t o Baranor (1918), i n a s t a b l e p o p u l a t i o n , where the number of r e c r u i t s added each year i s constant /the per-centage r e d u c t i o n of a year c l a s s from any given season t o the f o l l o w i n g season should represent the t o t a l m o r t a l i t y r a t e . However as has been i n d i o a t e d already i n the s e c t i o n on age a n a l y s i s recruitment does not occur w i t h such r e g u l a r i t y . I n a f i s h e r y t h a t i s only r e l a t i v e l y s t a b l e other methods must be sought which are l e s s subject to e r r o r . The percentage de-crease from year t o year may be obtained by p l o t t i n g the l o -garithms of the numbers of f i s h i n a l l age groups and d e t e r -mining the slope of the l i n e . T h i s v a l u e , when converted t o a n a t u r a l l o g a r i t h m i c expression becomes what R i c k e r (1944) c a l l the "instantaneous m o r t a l i t y r a t e , " a f i g u r e whioh i s p r o p o r t i o n a l to the number of f i s h k i l l e d d u r i n g any one short i n t e r v a l i n the f i s h i n g season. The instantaneous m o r t a l i t y r a t e " i " may then be converted to the t o t a l seasonal mortal i t y - 40 -r a t e "a" by a p p l y i n g the formula a s l-e""* d e r i v e d by R i e k e r (1944). In the u t i l i z a t i o n of t h i s method f o r the c a l c u l a t i o n of m o r t a l i t y r a t e s i n populations of lemon s o l e s , o n l y those age groups were used which were b e l i e v e d t o be e n t i r e l y f r e e from such f a c t o r s as net s e l e c t i o n and incomplete r e c r u i t m e n t . Furthermore the a n a l y s i s has not been a p p l i e d where sampling has been inadequate. I n f i g u r e s 30 and 31 are the graphs of the numbers of f i s h i n the v a r i o u s age groups, p l o t t e d l o g a -r i t h m ! cal l y and f i t t e d by l e a s t squares. The instantaneous m o r t a l i t y r a t e values together w i t h t h e i r corresponding t o t a l annual m o r t a l i t y r a t e values are shown i n t a b l e I I . 1. S t r a i t of -Georgia Female lemon s o l e s from the F r a s e r R i v e r area show a s t r a i g h t l i n e r e l a t i o n s h i p , from which the m o r t a l i t y was c a l -c ulated t o be 63%. Somewhat l e s s c o n c l u s i v e l y , the r e s u l t f o r male f i s h was approximately 65% between s i x and seven years of age. The smallness of t h e samples or p o s s i b l y f l u c t u a t i o n s i n recruitment may have been r e s p o n s i b l e f o r the i r r e g u l a r i t y of the r e l a t i o n s h i p . The Gulf I s l a n d s show a somewhat s i m i l a r s i t u a t i o n ^ With a t o t a l annual m o r t a l i t y r a t e of 56% f o r female f i s h and 69% f o r males. Once again the d i s p e r s i o n o f the p o i n t s on the graph f o r male f i s h makes the accuracy of the r e s u l t somewhat d o u b t f u l . I n Bayne Sound the m o r t a l i t y r a t e was found t o be 52% f o r males, and 59% f o r female s o l e s . m the whole S t r a i t of Georgia then, the t o t a l annual m o r t a l i t y r a t e appears t o be between 50 and 70%-averaging F i g . 30 Graphs showing the regression l i n e s of age group frequencies i n the S t r a i t of Georgia and on the west coast- of Van-couver Island. The regression coeff-i c i e n t s (converted to nat. log.) are given as instantaneous m o r t a l i t y rates i n Table I I , page 41. F i g . 31 Graphs showing the regression l i n e s of age group frequencies on the Goose Island grounds and i n Northern Hecate S t r a i t . The regression c o e f f i c i e n t s (converted to nat. log.) are given as instantaneous mortality rates i n table I I , page 41. - 41 -TABLE I I ~ The t o t a l m o r t a l i t y r a t e s i n the v a r i o u s regions of the coast, J TOTAL TOTAL INSTANTANEOUS ANNUAL MORTALITY RATE MORTAL ITT RATE Fr a s e r R i v e r Male 1,06 Female • 99 Male • 65 Female • 63 Gul f I s l a n d s 1.18 • 83 .69 • 56 Baynes Sound .74 •89 • 52 • 59 West Coast • 55 1,11 • 41 .67 Goose I s l a n d s .81 — .73 .56 • 52 Butterworth Rocks ,48 • 34 .38 • 29 T r i p l e I s l a n d .48 • 32 .38 .27 Rose S p i t .51 .42 .40 • 34 - 42 -approximately 60%. 2. West Coast of Vancouver•Island For t h e purposes of t h i s study the samples from the two regions of the coast have been combined. The graph f o r female f i s h shows a s t r i k i n g change i n m o r t a l i t y r a t e a f t e r seven years of age. Two r e g r e s s i o n l i n e s have been p l o t t e d t o demon-s t r a t e the d i f f e r e n c e s . During the e a r l y p e r i o d the percent-age m o r t a l i t y r a t e was found to be 35% and i n the l a t t e r p e r i o d , 67%. Assuming t h a t net s e l e c t i o n and c u l l i n g are not respon-s i b l e f o r t h i s i n f l e c t i o n of the curve between the ages of fo u r and s i x years, i t would appear t o be the r e s u l t of decreased recruitment. T h i s oould be brought about by n a t u r a l c o n d i t i o n s or by an I n t e n s i v e f i s h e r y which removed a l a r g e p r o p o r t i o n of adult f i s h s e v e r a l years p r e v i o u s l y . The value of 67% m o r t a l i t y i s perhaps c l o s e r t o the a c t u a l r a t e . The graph f o r male f i s h has been based on the lower age groups. The r a t e determined from t h i s i s perhaps, f o r the same reason as s t a t e d above, lower than the a c t u a l c o n d i t i o n e x i s t i n g i n the p o p u l a t i o n . 3. Goose I s l a n d Grounds The t o t a l annual m o r t a l i t y r a t e s c a l c u l a t e d f o r t h i s area show a 56% m o r t a l i t y f o r male s o l e s and 52% f o r females. The slope of the female r e g r e s s i o n l i n e has been determined f o r age groups VTI t o H n e g l e c t i n g the o l d e r ages because of a n o t i c e -able downward i n f l e c t i o n i n the lower part of the l i n e . 4. Morth Hecate S t r a i t C h a r a c t e r i s t i c of the three graphs presented f o r t h i s area i s the manner i n which the r a t e of d e c l i n e i n numbers of i n -d i v i d u a l s i n the o l d e r age groups i n c r e a s e s sharply a f t e r nine - 43 -years of age i n the male and a f t e r ten years i n the female* The p o s s i b i l i t i e s as to the cause of t h i s i n f l e c t i o n are given d e t a i l e d c o s i d e r a t i o n under the t o p i c of D i f f e r e n t i a l M o r t a l i t i e s Rates i n the D i s c u s s i o n s e c t i o n . The annual m o r t a l i t y r a t e s have been determined from the s e c t i o n s of the graphs e x h i b i t i n g a s t r a i g h t l i n e r e l a t i o n s h i p , between seven and nine years i n the case of the males and be-tween seven and t e n years i n females. Butterworth Rock sen p i e s show a 38% m o r t a l i t y r a t e i n male f i s h and 29% i n females. The r e s u l t s from T r i p l e I s l a n d are q u i t e s i m i l a r , 38% f o r males and 27% f o r females. The m o r t a l i t y r a t e s f o r male and female s o l e s from the Rose S p i t r e g i o n are 40% and 34% r e s p e c t i v e l y . The t o t a l annual m o r t a l i t i e s as c a l c u l a t e d f o r the v a r i o u s r egions of the coast show marked d i f f e r e n c e s , the s i g n i f i c a n c e of which w i l l be d e a l t w i t h i n the d i s c u s s i o n . - 44 -VII. DISCUSSION 1. Growth Rate. The growth of animals follows a pattern whioh is frequently referred to as the lo g i s t i c curve. During the early stages the curve i s concave upward, beginning, almost horizontally and rising very steeply. Along this steep part of the curve an inflection occurs wherein the concavity changes from upward to downward and the slope of the line steadily decreases towards the horizontal. With regard to the lemon sole, sampling methods together with the nature of the l i f e history have permitted the analysis of only certain sections of this growth curve. However, the results obtained from beach seizing and from examination of commercial sized f i s h supply sufficient information to show the general trend. In the graph in figure 32 the heavy lines re-present the known growth rate and the dotted lines that which has s t i l l e d to be determined. Plotted on this same graph i s the arithmetic growth rate. From this i t can be seen that the great-est rate of increase (min. per year) takes place in the f i r s t year, when there i s an estimated growth of 120 to 140 min. Upon entry into the fishery the growth rate has dropped to approxi-mately 30 min- per year and continues to decrease as age increases. What are some of the environmental factors which influence growth rate? Temperature for one, has a profound effect on the ftevelopment of f i s h during their early stages especially prior to the absorption of the yolk sac. According to Eudd (1940) 'Fig. 32 A graph showing a t o t a l growth curve f o r the lemon sole as drawn from Departure Bay and Gulf Island data. The broken l i n e part of the curve represents that part of the growth which i s yet to he determined. - 45 -hatching of the lemon sole egg takes place about 90 hours after f e r t i l i z a t i o n at a temperature of 13° C. However Mr. F. Taylor has found that at temperatures of 5° c" hatching does not take place before 130 hours. Both food and temperature play an important role during the post-larval period. The eulittoral zone of the sea, and in particular the inter-tidal area, presents a great diversity of conditions which influence the growth rate. Through the i n -fluence of the Fraser River the surface temperatures of the strait of Georgia during the summer months are much higher than in the other regions of the coast. As these waters would show a correspondingly higher productivity i t i s reasonable to believe that the growth rate of the lemon sole during the summer months would be higher i n the strait of Georgia than i n the other regions. Migration into'8*&eeper waters brings the f i s h into zones of more constant conditions. Hence variations in growth rates between areas would not be as great as in the inshore regions. This may serve to^ explain why no striking differences in growth have been shown between wide-spread areas of the coast. Another factor which should be considered,however, is-that of competition for food. In European waters i t has been found that the growth rate in a heavily populated region i s lower than in a sparsely populated one. Such conditions have not a been observed in the study of the lemon sale. In Hecate Strait where fishing operations have begun only recently and where supposedly there siae an abundance of f i s h the growth rate i s apparently as high as in regions which have been fished - 46 -for a good many years. This perhaps would indicate that there is an abundant food supply, and that competition or over-crowding i s not a determining factor. To this point no mention has been made of the differences in growth rate between the sexes. The analyses of unculled samples of small f i s h by the writer (1945 a) have shown l i t t l e or no difference i n rate of growth between the sexes to the end of the second year. Beyond that point however the growth rate of the male becomes much slower than that of the female. This change of the growth rate may be correlated with tie advent of sexual maturity, and has been attributed by various authors primarily to the differential requirements for the generation of sex products. Hickling (1933) in his studies of the hake, and Wallace (1904) investigating the North Sea plaice have suggested that as the male f i s h matures at a smaller size than does the female, i t must detail a certain amount of energy to the production of spermatozoa which might otherwise have been employed in increasing body size. Thus there results an i n i t i a l difference in growth rate between the sexes. In each succeeding year the male devotes more and more energy to re-production at a considerably greater rate than does the female, with the result that the difference i n growth rate steadily increases. Another explanation might be that male f i s h are more vigorous or more aggressive than females. The conversion i n the male of a considerably greater amount of metabolic energy into activity rather than into growth would result in a lower growth rate. - 47 -Somewhat less l i k e l y i s the p o s s i b i l i t y that the differences i n growth rates are due not to inherent factors but to some factor i n the environment. The low percentage of male f i s h i n the catches during the summer months suggests differences i n migratory habits between the sexes. Such differences i n the grounds inhabited might r e s u l t i n differences i n type or quantity of food consumed, which would produce differences i n the growth rates. 2. M o r t a l i t y . I f , i n a population of lemon soles where female f i s h pro-duce an average of 1,000,000 eggs each per year, only two f e r t i l i z e d eggs from each f i s h survive to develop into mature f i s h , the population w i l l show no decrease. In a region * supporting a f i s h e r y the occurrence of even such an i n f i n i t e l y small s u r v i v a l as t h i s would be considered optimal. What then are the factors which contribute to the tremendous mortality? In the f i r s t place, f e r t i l i z a t i o n w i l l to a c e r t a i n extent be incomplete. A c e r t a i n number of individuals w i l l die during the incubation period or shortly after hatching. However the greatest mortality i s generally assumed to take place during the short period when the yolk sac becomes absorbed anfi the l a r v a turns to food material i n the environ-ment. I f t h i s required food (presumably phytoplankton) i s not present, then a vast mortality ensues. Another important f a c t o r , as described by Sette (1943) i n his work on the A t l a n t i c Mackerel, Walford (1938) on the haddock, and HIckling (1933) on the hake, i s that of the - 46 -direction of ocean currents. Unusual wind conditions at the time of spawning haver been found to cause the eggs and larvae to d r i f t into regions unfavourable to their development and thereby produce a heavy mortality. These two factors, food supply and direction of d r i f t either together or separately i may be considered of prime importance in determining the success or failure of a brood year. Beyond the larval stages the percentage mortality steadily decreases. The predation factor undoubtedly takes on increas-ing importance. Another physical condition, however, which has been observed to have considerable effect on the survival of young soles during the early period of their stay in the inter-tidal zone is that of stranding. Because of the nature of the regions inhabited (sandy beaches of gradual slope), the receding tide leaves large numbers of the very small f i s h stranded on the sandbars or trapped i n tide-pools which soon heat up to a lethal temperature. This effect w i l l , of course, be most pronounced at the very low tide periods of each month, and w i l l influence the survival of only the smaller f i s h . As the f i s h grow larger they inhabit deeper and deeper waters and therefore become less and less susceptible to stranding. Beyond the inshore period the young lemon soles become subject to predation by such species of f i s h as dogfish, lingcod and other f l a t f i s h ( b r i l l and halibut), and to some extent by hair seals and sea lions. To a certain indeterminate extent injury i n escaping from trawl nets may account for some mortality. Death due to fishing does not, however, become a prominent factor u n t i l the third or fourth year. - 49 -The r e s u l t s of the mortality study i n f i s h of commercial siz e have shown considerable differences among^st the various regions of the coast. Assuming that the natural death rate i s f a i r l y s i milar i n a l l areas these differences can be considered r e f l e c t i o n s of the i n t e n s i t y of f i s h i n g which the respective grounds have experienced. In a v i r g i n f i s h e r y the mortality rate as determined from the age composition of the stock w i l l represent the natural mortality rate. In a f i s h e r y such as that of northern Hecate S t r a i t , which has been i n progress f o r only a few y e a r s — t h e mortality rate, determined from the older age groups w i l l be a rough approximation of the natural mor-t a l i t y . The r e s u l t s have shown an average mortality rate of 38% for male f i s h and 30$ for females. These values may be possibly higher than the actual natural mortality. Thompson and Herrington (1930) by means of tagging experiments have estimated the natural mortality of the P a c i f i c halibut to be approximately 36%. H. Thompson, (1929) has shown"a 32% natural mortality i n haddock, calculated from studies of v i r g i n f i s h i n g grounds i n European waters. D i f f e r e n t i a l Mortality Rates. The analysis of the Hecate S t r a i t samples has uncovered differences i n t o t a l mortality rates which give r i s e to con-siderable speculation. In the l a t e r years of l i f e , a f t e r nine years of age i n the male and after ten or eleven years i n the femal?/ there i s a sharp downward i n f l e c t i o n of the regression l i n e . Assuming that sampling has been adequate, there are two p o s s i b i l i t i e s as to the cause of t h i s apparent change i n mortality rate. - 50 -i (1) . I f older f i s h are more e a s i l y caught than young ones there would be a preponderance of the former i n the catches when the f i s h e r y i s f i r s t begun. After a period of time the proportion of these more catchable f i s h to the others would be so reduced that the regression l i n e would be i n f l e c t e d downwards i n a manner similar to that shown i n the Hecate S t r a i t mortality graphs. I t i s however, doubtful that such a s i t u a t i o n could arise i n the short period i n which the f i s h e r y i n t h i s region has been operating. Furthermore, the change i n the slope of the graphs i s too abrupt. I f a f i s h becomes more easy to catch with increasing age the graph would show a more gradual i n f l e c t i o n . (2) . I f older f i s h are not more e a s i l y caught than young ones the change of slope could be attributed to an increase i n the natural mortality rate. I f t h i s suggestion Is true, what i s the explanation of i t s occurrence? It w i l l be noticed that the i n f l e c t i o n i n the slope of the l i n e occurs i n both sexes, but not at the same ages. Mention has been made i n previous sections that males following the onset of sexual maturity grow at a greatly reduced rate i n comparison to the females, and i t has been suggested that the differences might be due to differences i n reproductive requirements. Furthermore, length data have shown that female f i s h grow to a much larger size than do male f i s h . Few females are encountered over 500 min. and few males are found larger than 400 m:tai. I t would appear then that nearing these sizes, some factor enters the picture w hich greatly increases, the mortality rate. The inference i s , that towards the upper size ranges of both sexes and possibly - 51 -at the point of i n f l e c t i o n i n the mortality curve a l e t h a l r a t i o i s reached, between body weight and t e s t i s or ovary weight. Considering now the occurrence of d i f f e r e n t i a l mortality rates between the sexes, i t may be seen that p r i o r to the sudden change i n rate i n the older age groups, the males generally speaking have a higher mortality rate than the f e -males. This has been found to be the case f o r several species of f i s h i n the North Sea. Wallace (1925) and Atkinson (1907) (quoted by Wallace) i n t h e i r studies of the p l a i c e could f i n d no evidence of unequal incidence i n the two sexes of e x t r i n s i c factors tending to the longer s u r v i v a l of one sex. Studies of the p l a i c e i n the Barents Sea, a v i r g i n f i s h i n g ground showed a higher mortality rate i n male f i s h than i n females. The lesser v i a b i l i t y of the male f i s h would then be the only explanation. * The dominance of female lemon soles i n the catches during periods of the year other than the spawning season could be regarded as a factor which would produce differences i n the mortality rates. I f male f i s h are not present on the tr a v e l i n g grounds i n t h e i r true proportions i t i s reasonable to believe that the t o t a l seasonal mortality • rate would be lower i n that sex than i n the other. This, however, i s not the case, as samples from most of the regions show a higher mortality rate i n the male. Increased death, then,from natural causes appears to be the reason f o r differences i n mortality, and the most l i k e l y cause of this i s the d i f f e r e n -t i a l e f f e c t produced by the processes involved i n sexual reproduction. - 52 -I (^). The R e l a t i o n s h i p ^ of Mortality and Fluctuations i n Strenfths of Year Clastes to Age Composition. In areas which have experienced a f a i r l y intensive f i s h e r y over a long period of time, the proportion of old f i s h to young f i s h i s much lower than i n areas where f i s h i n g has been r e l a t i v e l y l i g h t . In the S t r a i t of Georgia where the t o t a l annual mortality rate has been estimated from 1946 samples to be 60%, between 70 and 80% of the f i s h entering the commercial catch are less than s i x years of age. On the west coast of Vancouver Island 80 to 85% of the f i s h captured were w i t h i n th i s range, and the mortality rate for the population as a whole amounted to approximately 67%. On the Goose Island grounds i n the same year the t o t a l mortality rate was found to be about 54%, and 28% of the f i s h caught were less than s i x years of age. In northern Hecate S t r a i t the average mortality rate was 34%, and f i s h of less than s i x years comprised 38% of the t o t a l catch. The proportions of younger f i s h i n the catches from the various areas do show a general trend re l a t e d to the h i s t o r y of the f i s h e r y , but there are indications of another factor which i s also influencing the r e l a t i v e proportions of the age groups, namely,fluctuations i n the strengths of year classes. On the west coast of Vancouver Island i n 1945, 65% of the f i s h captured were les s than s i x years of age,approximately 15% more than i n 1946. This difference may be correlated with the marked change i n dominating year class which took place i n this area between 1945 and 1946. In 1945, the 1940 year class pre-dominated i n the catches, but i n the following year the 1942 - 53 -year (class was best represented. This s h i f t i n g of dominance may have been due either to the i n t e n s i t y of the f i s h e r y or to the advent of a new year c l a s s . On the Goose Island grounds i n 194-5, 53% of the f i s h taken were under s i x years of age. However, i n the following year, as mentioned above, the proportion of these f i s h went down to 28%. Age group analysis has shown that i n both years the 1939 and 1940 year classes predominated. On the North Hecate S t r a i t grounds i n the summer of 1945 less than 20% of the t o t a l number of f i s h taken were under s i x years of age. In 1946, however, the number of f i s h i n t h i s range had increased to 3&%» This increase may be explained by the f a c t that i n 1945 the 1939 year class predominated, and i n the following year the 1939 and 1942 year classes predominated. The question now arises as to how a l l these fluctuations have arisen and to what degree they are related. In the f i r s t place, samples of f i s h collected from Hecate S t r a i t and Queen Charlotte Sound have displayed an i n t e r e s t i n g c h a r a c t e r i s t i c i n that the frequency graphs for length and age show no s t r i k i n g skewness which can be attributed to net se l e c t i o n and c u l l i n g . That i s to say, the decrease i n numbers of f i s h to the l e f t of the mode i s apparently independent of these selec t i v e factors. This might at f i r s t suggest that the smaller f i s h are not available to the f i s h e r y . However, examination of data which cover a period of years shows that the absence of smaller f i s h i s actual. In a preliminary study by the writer (1945 a) of the age composition of Hecate S t r a i t f i s h during 1944, i t was found that female f i s h of f i v e years of age (1939 year c l a s s ) occurred most f r e q u e n t l y . Both the 1939 and 194-0 year c l a s s e s -could be considered unaffected by s e l e c t i o n . Yet the 1940 year c l a s s was p o o r l y represented. This 1944 graph i s shown i n f i g u r e 33» 3 1 1 ( 3 compared w i t h Butterworth Rock samples taken during the summers of 1945 and 1946. I n the 1945 samples the 1939 year c l a s s again predominated. The r e l a t i v e infrequency of the members of the 1940 and 1941 year c l a s s e s could not be a t t r i b u t e d to the net s e l e c t i o n or c u l l i n g f a c t o r . I n 1946 two year c l a s s e s were s t r o n g l y represented, the 1939 and 1942 year c l a s s e s . The obvious c o n c l u s i o n i s then t h a t the years 1940 and 1941 i n the v i c i n i t y of Butterworth Rocks were poor brood years and thus accounted during 1944 and 1945 f o r the r e l a t i v e p a u c i t y of younger f i s h i n the catches. In 1946 w i t h the advent of the strong 1942 year c l a s s the p r o p o r t i o n of smaller f i s h i n c r e a s e d . How f a r - r e a c h i n g and how constant was t h i s e f f e c t ? Samples from other regions of Hecate S t r a i t i n 1945 w i t h the exception of those from the Two Peak grounds, showed the 1939 year c l a s s dominating i n the age d i s t r i b u t i o n of female f i s h . I n 1946 a l l samples showed e i t h e r the 1939 year c l a s s or the 1942 year c l a s s , or both, dominating. F i s h from Banks I s l a n d were predominantly 1942 year c l a s s , w h i l e those from Two Peaks, T r i p l e I s l a n d and Rose S p i t were w e l l represented by both the 1939 and 1942 year c l a s s e s . The f l u c t u a t i o n s i n dominance of these two year c l a s s e s w i t h i n short periods have been shown i n the Butterworth Rock samples. This i n a l l p r o b a b i l i t y i s the r e s u l t I YEflft CLHSS DOMINRNCE. fcUTTERwOBTH ROCKS - F E M B l . E S -I'm I ' m \<w i^to m in? wn isss* NEAR CLASS F i g . 33 Graphs showing the dominance of the 1939 year c l a s s i n female lemon soles from Butter-worth Rocks during 1944, 1945 and 1946. In the l a t t e r year there i s an appearance of another strong year class, that of 1942. - 55 -of d i f f e r e n c e s i n the depths at which f i s h i n g was c a r r i e d out. The o v e r - a l l p i c t u r e , however, f o r the summer months from t h i s area (Figure 33) shows the dominance of both year c l a s s e s . Throughout Hecate S t r a i t then i t i s apparent that 1940 and 1941 were not as s u c c e s s f u l spawning years as those immediately preceding and f o l l o w i n g . On the Goose I s l a n d grounds there i s an i n d i c a t i o n of dominance by the 1939 and 1940 year c l a s s e s i n both 1945 and 1946. The decrease i n the r e l a t i v e proportions of small f i s h between these two years can be a t t r i b u t e d to the poor represen-t a t i o n of the 1941 and 1942 year c l a s s e s . Although f u r t h e r sampling i s necessary before a d e f i n i t e statement can be made, there i s an i n d i c a t i o n that 1941 and 1942 were poor brood years i n t h i s r e g i o n . Sampling from the west coast of Vancouver I s l a n d during 1945 and 1946 has shown a change i n dominance from the 1940 to the 1942 year c l a s s . I t i s d i f f i c u l t to say at present whether t h i s i s due t o the i n t e n s i t y of the f i s h e r y or t o the advent of a new year c l a s s . 56 VIII. SUMMARY AND CONCLUSIONS The analysis of the length and age composition of catches of lemon soles landed at the p r i n c i p a l B r i t i s h Columbia ports during 194-5 and 1946 has revealed interesting, features which are i n d i c a t i v e of some of the conditions p r e v a i l i n g i n the f i s h e r y . In general the older f i s h e r i e s and those closest to large Canadian and American market centers show the lowest age d i s -t r i b u t i o n i n the populations. In the S t r a i t of Georgia where the f i s h e r y has been i n progress f o r a^.good many years, soles of four or f i v e years of age predominate i n the catches. On the west coast of Vancouver Island where a very intensive fi s h e r y has been c a r r i e d on f o r no more than s i x years the age d i s t r i b u t i o n i s s i m i l a r to that i n the Gulf of Georgia. The comparatively recent f i s h e r i e s of Queen Charlotte Sould and "2" Hecate S t r a i t , however, show a predominance of large f i s h averaging s i x or seven years of age. S t r i k i n g differences i n the t o t a l annual mortality rates are also evident. Considering female f i s h only, the mortality rate i s approximately 60% i n the Gulf of Georgia, 67% on the west coast of Vancouver Island, 52% i n Queen Charlotte Sound and 30% i n Northern Hecate S t r a i t . . In general the mortality rate of male f i s h i s somewhat higher than that of females, being 62% i n the Gulf of Georgia, 50% i n Queen Charlotte Sound, and 39% i n Hecate S t r a i t . Results from the west coast are inconclusive because of inadequate sampling. The r e l a t i v e recency of the Northern Hecate S t r a i t f i s h e r y has raised the suggestion that the t o t a l annual mortality rates 30% i n the female and 39% i n the male, calculated as they are from the older age groups, present a rough estimation of the natural mortality r a t e . ' In the Hecate S t r a i t samples where the older age groups are well represented i t has been found that there i s a sharp increase i n the mortality rate beyond nine years of«ge i n the male, and beyond ten or eleven years i n the female. This i n c r increase has been attributed to an increase i n the death rate due to natural causes, but there i s the p o s s i b i l i t y that i t i s the r e s u l t of a greater c a t c h a b i l i t y of older f i s h . In a l l areas of the coast the female lemon sole has been found to grow at a considerably greater rate than the male. Between four and eight years of age the growth i n the female averages 11 mm. per year more than i n the male. Comparisons of the growth rates i n various areas show s l i g h t differences. With respect to female f i s h the average rate between four and eight years of age i s highest i n the S t r a i t of Georgia, being approximately 23 mm. per year. In Northern Hecate S t r a i t the rate during the same period i s 21 mm per year. The lowest rate of growth, 19 mm. per year takes place on the west coast, i n Queen Charlotte Sound and i n the middle of Hecate S t r a i t . In the male f i s h the growth rate appears to be greatest i n Northern Hecate S t r a i t , but d i f -ferences i n the various regions are not as d i s t i n c t as i n the case of the females. - 58 -A study of the changes i n rates of growth i n female f i s h shows a tendency toward a sharper drop i n the rate between f i v e and s i x years of age i n northern Hecate S t r a i t than i n the other regions. Through beach seizing operations some information has been obtained on the growth of the lemon sole during i t s f i r s t year of l i f e . The growth rate i n Departu«?«Bay during the summer of 194-6 was approximately 23 mm. per month. By l a t e August the average length was about 107 nun. Information c o l l e c t e d on the maturity of the female lemon sole i n the S t r a i t of Georgia has shown that 50% of the f i s h are mature at a length of 295 mm. Studies of the fecundity of female'fish from the S t r a i t of Georgia show that production of eggs r i s e s r a p i d l y from 280,000 i n f i s h of 290 mm. i n length, to 2,100,000 i n f i s h of 430 mm. This information on maturity and fecundity, i f correct for a l l regions of the coast would indicate that the reproduc-t i v e p o t e n t i a l of Hecate S t r a i t and Queen Charlotte Sound populations i s very much greater than i n the populations i n the Southern part of the coast. That i s to say, i n the l a t t e r region where the average size of female f i s h i s 355 mm. the average production of eggs per f i s h i s 650,000, while i n the northern region where the average size i s 390 mm. the average production i s possibly as high as 1,100,000 eggs. The fact that lemon sole populations are subject to fluctuations i n the strength of year classes has been shown i n the study of the Hecate S t r a i t f i s h e r y . The 1939 year class has predominated i n the catches during 1944, 1945 and 1946. In the l a t t e r year another strong year c l a s s , that of 1942, made i t s appearance. The r e l a t i v e lack of success i n the brood years of 1940 and 1941 was the factor responsible for the absence of small f i s h i n the catches during 1944 and 1945* - 60 -IX. ACKNOWLEDGMENTS . The author wishes to express h i s sincere appreciation and thanks to Dr. R. E. Foerster, d i r e c t o r of the P a c i f i c B i o l o g i c a l Station, and to Dr. J . L. Hart, i n charge of the otter trawl investigation, f o r granting the use of f a c i l i t i e s and materials necessary f o r t h i s work. The author i s indebted to Dr. W. A. Clemens and Dr. W. S. Hoar of the Department of Zoology f o r t h e i r h e l p f u l suggestions and c r i t i c i s m s . G r a t e f u l appreciation i s extended to fellow f i e l d workers, W. E. Barraclough, J*. I. Manzer and F. H. C. Taylor for t h e i r cooperation i n the c o l l e c t i o n of commercial catch data, f o r t h e i r assistance i n the beach seining operations, and f o r information and advice supplied with regard to aspects of the trawl investigation unfamiliar to the author. - 61 -X. REFERENCES Baranov, F. I. 1918. On the question of the b i o l o g i c a l basis of f i s h e r i e s . U.S.S.R. B u l l . Dept. F i s h , and S c i e n t i f i c - I n d u s t r i a l Invest. 1/1/ 1918. Budd/ P. L. 1940. The development of the eggs and early. larvae of s i x C a l i f o r n i a f i s h e s . Calif.„ Div. F i s h and game. F i s h B u l l . 56, 1940. Clemens, W. A. and G. V. Wilby. 1946.' Fishes of the P a c i f i c coast of Canada, F i s h . Res. Bd. Can. B u l l . 68, 1946. Graham, M. 1929. Studies.of age determination i n : f i s h / Part I I . A survey;of the l i t e r a t u r e . Min. A g r i c . &,Fish. ; Fishery Investigations. Series U , 11/ 3^ 1928. H i c k l i n g / C. F.; 1933. The natural h i s t o r y of the hake. Part IV. „ Age determination and rate of growth.; Min. Agric. & Fish."1 Fishery Investigations. Series II,' 13? 2,' 1933.' Jordan,' D. S. and B. W. F^ermann. 1898. Fishes of North and Middle America.' Washington^ Govt. Print Off. Ketchen/ K.' S. 1945a.1 Age determination and rate of growth of the lemon sole i n B r i t i s h Columbia;waters. Essay manuscript,- Deptj? of Zoo!.' Univ. B r i t . f C o l . ^ 1945. 1945b. Preliminary report on age and growth of lemon soles from B r i t i s h Columbia f i s h i n g grounds.. F i s h . Res. Bd. Can. Prog.' Rep. Pac./ 63/ 1945. Norman, J . R. 1934. A systematic monograph of the f l a t f i s h e s (Heterosomata). B r i t . Mus. Nat. H i s t . , 1, 1934. R a i t t / D. S. 1936. Stock replenishment and f i s h i n g i n t e n s i t y i n the haddock of.the North Sea. Jour.; Cons.,' Cons.1' Perm. Internat. Explor. mer. 11, 1936. Ricker, W. E. 1942, The rate of growth of blue g i l l sunfish i n lakes of northern Indiana. Invest, of Indiana Lakes and Streams, _2/ 1942. - 62 -1944. Further notes on f i s h i n g m o r tality and e f f o r t . Copeia, 1944/ 1. 1945. A method of estimating minimum size l i m i t s f o r obtaining maximum y i e l d . Copeia,' 1945, 2. Sette, 0. E. 1943. Biology of the A t l a n t i c mackerel of North America. Part I. E a r l y l i f e h i s t o r y . U. S. Dept. Int. F i s h and w i l d l i f e service. F i s h B u l l . 38, 1943. Smith, R. T. 1936. Report on the Puget.Sound otter.trawl. i n v e s t i g a t i o n s . Wash. State Dept. F i s h . B i o l . Rep.,! 36B,1 1936. Thompson/H. 1929. Haddock biology_(North Sea). Rapp. et. Proces-verb.Cons,' Perm. Internat. Explor. Mer, 54,1 1929. Thompson, W. F. and W. C. Herrington. 1930. L i f e h i s t o r y of th e , P a c i f i c h a l i b u t . (1) Marking experiments. Rep. of Internat. F i s h . Comm., 1930 Van Oosten, J . 1941. The age and growth of freshwater f i s h e s . A Symposium of.Hydrobiology. Univ. Wise. Press,' Madison,5 Wise. Walford,' L. A. 1938. The e f f e c t of currents on the d i s t r i b -u t ion and sur v i v a l of eggs and larvae of the. haddock on Georges Bank. U.S. Dept. of Int. F i s h and w i l d l i f e service. F i s h . B u l l . 29, 1938. Wallace, W. 1904. Report on the' age and growth rate of the pl a i c e i n the southern North Sea as deter-mined by the inv e s t i g a t i o n of o t o l i t h s . Jour. Mar. B i o l . Assoc. Internat,'.Invest. Second Rept. Southern Area,' 1904-5. 1925. M o r t a l i t y i n p l a i c e . Nature, 115. no. 2888 1925. - 63 -XI. APPENDIX Table 1 Length Frequency D i s t r i b u t i o n of Young Lemon Soles Caught i n Departure Bay, between may and August 1946. Length (mm.) May June July Aug. 20 1 -25 4 30 11. 1 35 21 5 40 11 4 45 11 14 1 50 15 5 .55 5 14 5 60 1 13 9 65 1 17 16 70 10 13 1 75 9 11 1 80 15 14 4 85 7 9 3 90 4 4 12 95 7 9 100 7 10 105 1 8 9 110 1 3 10 115 12 120 1 "8 125 5 130 4 135 • 3 140 145 3 Table 2 Length Frequency Di s t r i b u t i o n s of F i s h Captured i n the V i c i n i t y of the Fraser River during 1945 and 1946. (See f i g . 8) 1945 1945 1945-46 1946 * 1946 Length May-July .-Oct. Dec. -Apr. Jan. -Mar. May-Aug. (mm.) M F M F M F M F M F 240 1 3 250 6 6 4 4 260 27 12 32 22 270 53 33 89 62 7 15 1 280 81 76 127 89 10 42 19 1 3 2 290 54 91 144 124 15 '54 47 9 12 7 300 65 126 76 125 29 61 45 19 9 45 310 44 121 49 151 20 68 49 20 12 36 320 23 95 20 117 18 53 25 23 13 30 330 14 91 13 88 12 49 15 17 8 44 340 4 63 4 56 2 44 7 23 4 44 350 1 50 1 43 3 45 5 27 2 44 360 1 45 3 25 33 3 24 31 370 20 20 20 25 21 380 14 15 13 19 18 390 14 10 13 21 14 400 8 5 13 16 8 410 13 7 3 8 5 420 2 3 1 8 1 430 2 5 7 4 440 1 1 2 2 1 450 1 2 3 1 460 2 1 470 1 480 1 490 500 1 510 1 * Point Atkinson. Table 3 Length Frequency D i s t r i b u t i o n s of F i s h Captured i n the Gulf Islands and i n Baynes Sound During 1945 and 1946. (See F i g . 10 and 13) q r u l f Islands E laynes Sound 1945 1946 1946 1945 1946 * 1946 Length Sep. -Dec. Jan.--Feb. Jun. -Sep. Aug .-Dec. Jan. -Feb. Fjsb. (mm.) M" F M F M F M F M F M F 260 1 1 2 4 1 270 1 3 1 22 14 1 280 11 4 7 2 29 36 2 13 290 12 4 3 7 64 39 2 5 24 1 300 25 13 19 16 2 2 77 95 11 ' 11 30 2 310 41 37 19 12 14 4 93 129 15 26 11 5 320 36 36 11 19 23 13 90 165 12 24 15 4 330 37 56 7 33 35 13 53 166 14 31 14 5 340 17 60 4 33 14 17 32 145 5 31 7 2 350 8 59 32 10 34 ' 21 138 3 49 4 3 360 8 72 43 3 35 8 142 1 39 2 7' 370 7 84 1 39 4 29 6 113 2 35 1 4 380 3 81 26 2 29 103 25 10 390 2 59 21 17 1 67 29 11 400 53 20 24 55 21 1 13 410 47 7 19 50 24 11 420 32 11 22 28 14 7 430 19 3 11 18 16 4 440 23 4 8 7 9 6 450 14 3 7 16 15 2 460 22 2 2 9 5 1 470 4 3 5 1 480 5 2 3 2 490 1 4 1 500 1 ^ Cape Lazo. Table 4 Length Frequency D i s t r i b u t i o n s of F i s h Captured i n the Waters o f f the West Coast of Vancouver Island during 1945 and 1946. (Fig.* 16) Port San Juan to Tofino Esteban 1 io Kyuquot 1945 1945 1946 1946 1945 1946 Length Ap: p.-July Aug. -Nov. May- Jul y Aug.-Sep. May-Aug. May-Aug. (mm.) M F M F M F M F M F" M F 250 1 1 260 1 3 ' 1 1 1 270 1 1 2 1 1 280 4 8 8 1 7 1 290 8 7 15 5 18 2 6 1 2 300 6 17 16 29 7 54 5 14 3 8 310 3 19 6 35 4 117 2 23 3 9 15 320 11 15 16 55 7 126 7 31 2 12 1 19 330 10 39 28 42 4 124 5 52 1 20 2 25 340 5 29 9 44 5 101 6 65 1 20 1 39 350 8 52 11 70 4 82 2 55 2 31 46 360 5 53 6 62 1 • 86 3 57 1 27 2 46 370 1 53 5 65 1 81 1 59 38 61 380 60 2 77 2 57 54 42 35 390 57 66 1 47 50 39 23 400 57 65 27 27 41 23 410 36 61 28 33 30 8 420 32 30 28 24 30 14 430 25 26 13 20 10 7 440 17 15 8 11 8 450 10 6 8 4 2 460 6 4 3 6 470 2 3 6 480 1 1 1 490 1 3 500 1 Table 5 Length Frequency D i s t r i b u t i o n s of f i s h Captured i n Queen Charlotte Sound and Hecate S t r a i t During 1945 and 1946. (Fig.'s 19 and 22) Length (mm.) Goose Island 1945 May-June M F 1946 May-June M F-Banks I s . M 1946 Butterworth Rocks 1945 A p r i l DM F 1946 A p r i l M F 1946 May-June M F 1946 August M F 250 260 270 280 290 300 310 320 330 340 350 360 370 380 390 400 410 420 430 440 450 460 470 480 490 500 510 3 2 8 7 3 4 1 1 4 13 22 16 .13 24 19 25 19 21 15 11 4 3 2 4 4 3 7 12 25 22 25 20 13 8 1 1 1 4 6 18 27 33 56 68 60 59 61 84 66 67 37 20 19 8 5 4 1 2 2 3 7 14 26 29 53 37 26 18 15 10 7 1 4 1 1 7 8 10 25 42 41 48 35 43 24 22 15 9 10 5 6 1 1 4 2 1 1 2 1 1 3 11 11 1 1 4 5 6 16 10 13 7 34 11 19 15 22 9 22 25 21 20 13 17 12 31 8 12 2 16 8 10 4 10 1 1 4 3 8 10 26 30 31 31 45 35 41 25 34 27 34 29 30 27 32 25 16 35 11 21 11 31 4 24 1 12 10 7 13 11 5 1 3 5 7 29 38 6 1 3 1 4 8 15 11 20 15 23 17 35 24 18 19 46 34 34 38 23 34 27 35 13 38 12 30 "30 30 14 16 15 9 8 3 4 1 o 1 1 1 2 1 4 8 11 18 10 18 11 21 10 14 16 6 15 5 28 2 1 1 9 Table 6 'Length Frequency D i s t r i b u t i o n s of F i s h captured i n Hecate S t r a i t During the years 1945 and 1946. Length (mm.) T r i p l e Island Two Peaks Rose Spit 1945 1946 1945 1946 1945 1946 M F M F M F M F M F M F 250 2 2 1 4 • 260 1 2 8 2 3 1 270 4 5 7 3 3 4 280 7 6 6 5 8 9 . 290 2 1 7 6 17 9 9 18 300 3 4 12 11 24 20 2 31 27 310 3 5 15 10 1 22 13 3 39 36 320 3 9 23 18 2 17 24 2 55 77 330 5 8 37 28 3 17 23 8 4 52 69 340 2 16 35 25 5 15 24 8 3 46 71 350 12 41 47 11 1 11 24 15 13 47 76 360 2 14 50 37 11 7 5 18 16 14 43 52 370 2 16 32 38 17 13 2 17 20 19 43 67 380 14 20 29 27 9 4 22 12 34 22 87 390 16 16 23 18 19 10 11 47 17 78 400 19 7 30 :;8 38 1 8 7 51 13' 94 410 18 2 22 5 35 1 3 4 59 4 89 420 16 27 2 43 2 2 51 2 88 430 8 30 40 45 2 73 440 7 19 24 33 68 450 3 23 45 34 61 460 3 25 34 15 35 470 1 10 21 11 26 480 9 15 14 16 490 5 5 4 9 500 4 4 3 7 510 1 520 p 530 1 540 1 Table 7 Percentage Age Composition of Fi s h Caught i n the V i c i n i t y of. the Fraser River During 1945 and 1946. (Fig. 9) May-Oct. 1945 MALE No. 1 FEMALE No. i 1944 194? 1942 1941 1940 1939 1938 1937 I936 1^35 1 34 52 27 5 .8 28.5 43.7 22.6 4.1 3 58 162 87 26 7 .9 16.9 47.2 25.3 7.6 2.0 Dec.-Apr. :1945-46 MALE No. 1 FEMALE No. i 1 15 39 54 24 6 . .7 10.8 28.1 38.8 17.3 4.3 1 122 201 106 36 19 7 3 2 .2 24.5 40.4 21.3 7.2 3.8 1.4 .6 .4 Jan.-Mar. 1946 MALE NO. % FEMALE No. 7. 2 13 68 67 42 17 3 .9 6.1 32.7 31.1 19..8 8.0 1.4 13 61 89 80 24 8 3 1 4.7 21.9 31.9 28.7 8.6 2.9 1.1 .4 May-Aug. 1946 MALE No. i FEMALE No. i 1 4 19 26 9 "3 1 1.6 6 .3 30.2 41.3 14.3 4.8 1.6 33 145 114 37 11 3 1 9.6 42.2 33.1 10.8 3.2 .9 .3 Table 8 Percentage Age Composition of Fish Captured i n the V i c i n i t y of the Gulf^Islands During 1945 and 1946. (Fig. 11) Aug.-Dec. 1945 MALE No. % FEMALE No. ' i 1944 194? 1942 1941 1940 1939 1938 1937 1936 1935 6 17 13 9 7 2 2 10.6 30.6 23.2 16.1 12.5 3.6 3.6 1 9 57 64 36 20 9 7 .5 4.4 28.1 31.5 17.7 9.9 4.4 3.4 Jan.-Feb. 1946 MALE „ No. i FEMALE No. 1 6 22 25 It) 12 1 7.9 28.9 32.9 13.2 15.8 1.3 20 93 136 50 25 8 3 3 1 5.9 27.4 40.1 14.7 7.4 2.4 .9 .9 .3 Jun.-Sep. 1946 MALE No. i FEMALE No. % 13 26 50 25 1 1 1 2.8 24.3 46.7 23.4 .9 .9 .9 14 74 115 56 18 7 7 1 4.8 25.3 39.3 19.2 6.2 2.4 2.4 .3 Table 9 Percentage Age Composition of Fish Captured i n the V i c i n i t y of Baynes Sound During 1945 and 1946. (Fig. 14) Year Class 1936 Aug.-Dec. 1944 1943 1942 • 1941 1940 1939 1938 1937 1935 1945 MALE •4l No. 2 86 72 22 17 1 1 % •8 16.9 33.5 29.8 9.1 7.0 • 4 .4 FEMALE . . . No. 13 163 22$ 116 44 33 8 7 3 % 2,0 25.4 39.7 18.1 6.9 5.1 1.2 1.1 .5 Jan.-Feb. 1946 MALE No. 1 13 22 18 4 6.5 3 1 1.6 21.0 35.5 29.0 4.8 1.6 FEMALE — No. 8 130 126 112 22 8 5 1 * 1.9 31.6 30.6 27.2 5.3 1.9 1.2 .2 February 1946 MALE 46 (Cape No. 4 32 23 10 4 3 Lazo) 3.3 26.2 37.7 18.9 8.2 3.3 2.5 FEMALE No. 2 16 26 35 12 6 3 1 2.0 13.8 25.7 34.7 11.9 5.9 3.0 1.0 Table 10 Percentage Age Composition of Fish Captured Off the West Coast of Vancouver Island, Between Port San Juan and Tofino,. During the Summers of 1945 and 1946. (See f i g . 17) Apr.-July 1945 MALE No. % FEMALE No. i Year Class I944 1943 1942 1941 1940 1939 1938 1937 1936 1935 2 11 5 5 2 8.0 44.0 20.0 20.0 8.0 3 45 86 101 51 22 6 2 1 .9 14.2 27.1 31.9 16.1 6.9 1.9 .6 .3 Aug.-Nov. 1945 MALE No. % FEMALE No. 1 4 14 5 6 - 1 13.3 46.7 16.7 20.0 3.3 3 27 28 42 17 15 6 1 2.2 19.4 20.1 30.2 12.2 10.8 4.3 .7 May-July 1946 MALE No. f. FEMALE No. i 1 5 15 11 6 2 2.5 12.5 37.5 27.5 15.0 5.0 1 360 309 161 92 46 20 2 4 1 .1 36.1 31.0 16.2 9.2 4.6 2.0 .2 .4 .1 Aug.-Sep. 1946 MALE No. % FEMALE No. f. 7 10 4 6 3 6 19.4 27.8 11.1 16.7 8.3 16.7 8 150 189 109 91 31 17 6 1 1.3 24.9 31.4 18.1 15.1 5.1 2.8 1.0 .2 o Table 11 Percentage Age Composition of Fish Caught between Esteban Point end Kyuquot Sound on the West Coast of Vancouver Island, and i n Queen Charlotte Sound During 1945 and 1946. ( F i g . 18 and 20) o Year Class • - -ESTEBAN Summer 1944 1945 1942 1941 1940 1939 1938 1937 1936 1935 1934' 1945 MALE to No. - - 2 1 - - -KYUQUOT '* FEMALE 0 No. 1 .6 7 42 67 38 19 8 1 i 3.8 23.0 36.6 20.8 10.4 4.4 .6 Summer 1946 ' MALE No. 1 - 1 3 1 h FEMALE No. 64 158 80 34 17 2 -0 % 18.0 44.5 22.5 9.6 4.8 .6 Summer 1945 MALE GOOSE No. 3 8 4 6 1 1 % 13.0 34.8 17.4 26.1 4.3 4.3 ISLAND FEMALE No. 9 36 49 43 23 9 2 1 i 5.2 20.9 28.5 25.0 13.4 5.2 1.2 .6 Summer 1946 MALE No. 1 2 11 28 35 36 18 '• 7 5 % .7 1.4 7.8 19.9 24.8 25.5 12.8 5.0 2.1 FEMALE No. •1 13 61. 123 178 186 81. 39 21 8 2 i .1 1.8 • 8.6 17.3 25.0 26.I 11.4 5.5 2.9 1.1 .3 3 , Table 12 Percentage Age Composition of Fish Caught i n the V i c i n i t y of Banks Island and T r i p l e Island i n Northern Hecate S t r a i t During 1945 and 1946. (See F i g . 20 and 25) Year Class 1936 . . . . Summer 1944 1943 1942 1941 1940 1939 1938 1937 1935 1934 1946 MALE BANKS NO. 25 72 51 41 44 13 7 1 ISLAND % 9.8 28.3 20.1 16.1 17.3 5.1 2.8 .4 FEMALE No. 1 56 142 70 36 31 11 8 8 2 % .3 15.3 38.9 19.2 9.9 8.5 3.0 2.2 2.2 .5 Sept. 1945 MALE No. 1 7 7 6 1 1 TRIPLE % ISLAND FEMALE 26 8 No. 1 26 25 35 53 15 1 . i .5 13.7 13.2 -18.4 27.9 13.7 7.9 4.2 .5 July 1946 MALE 56 61 No. 3 23 61 52 37 12 5 i 1.0 7.5 19.7 16.8 18.1 19.7 11.9 3.9 1.6 FEMALE 38-7 38 114 68 66 73 55 28 2 > 1.4 7.6 22.8 13.6 13.2 14.6 11.0 7.6 5.6 2.0 .8 Table 13 Percentage Age Composition of Fish Caught i n the V i c i n i t y of Butterworth Rocks In Northern Hecate S t r a i t During 1945 and 1946. (Fig. 23) Year Class A p r i l MALE 1944 1943 1942 1941 1940 1939 1938 1937 1936 1935 1934 1933 1945 No. 1 9 13 53 46 48 25 14 1 i .5 4.3 6.2 25.2 21.9 22.9 11.9 6.7 .5 FEMALE No. 1 11 33 38 59 40 18 15 11 % .4 4.9 14.6 16.8 26.1 17.7 7.9 6.6 4.9 A p r i l 1946 MALE No. 5 25 53 73 79 56 30 8- 2 1.5 7.6 16.0 22.1 23.9 16.9 9.1 2.4 .6 FEMALE ••-No. 6 26 111 83 54 59 46 15 22 2 t 1.4 6.1 26.2.19.6 12.7 13.9 10.8 3.5 3.2 ,8 May-June MALE - - • No. 4 16 27 47 66 84 46 36 12 1 1 % 1.2 4.7 7.9 13.8 19.5 24.7 13.5 10.6 3.5 .3 .3 FEMALE No. 7 19 80 55 50 100 61 45 26 12 2 1.5 4.2 17.5 12.0 10.9 21.9 13.3 9.8 5.7 2.7 .4 August MALE -No. 2 5 13 17 21, 29 15 9 4 % 1.7 4.3 11.3 14.8 18.3 25.2 13.0 7.8 3.5 FEMALE No. 2 12 26 43 54 63 51 46 33 11 7 1 %' .6 3.4 7.4 12.3 15.5 18.1 14.6 13.2 9.5 3.2 2.0 .3 Table 14 Percentage Age Composition of Fish Caught i n the V i c i n i t y of Two Peaks and Rose Spit i n Northern Hecate S t r a i t During 1945 and 1946. (Fig. 25 and 26) Year Class ... . June L944 1943 1942 1941 1940 1939 1938 1937 1936 1935 1934 1933 1945 MALE No 9 4 12 20 23 30 15 4 TWO % 3.7 11.1 18.5 21.3 27.8 13.9 3.7 PEAKS FEMALE 63 No 1 1 11 22 71 78 63 39 11 t .3 3.1 6.1 19.8 21.7 17.5 17.5 10.9 3.1 Jan. 1946 MALE Cl No . 6 4 30 10 38 53 21 9 2 1 % 3.4 2.3 17.2 5.7 21.8 30.5 12.1 5,2 1.1 .6 FEMALE No 3 11 52 38 28 45 26 15 9 5 •1 t 1.3 4.7 22.3 16.3 12.0 19.3 • 11.2 6.4 3.9 2.1 .4 June 1945 MALE 6 No 1 14 27 18 25 - 11 4 - 2 SPIT % -FEMALE .9 5.6 13.0 25.0 16.7 23.1 10.2 3.7 — 1.9 No » 4 13 40 120 89 82 58 34 13 2 i .9 2.9 8.8 26.4 19.6 18.1 12.7 7.5 2.9 .4 June 1946 MALE * No • 6 46 76 66 84 77 50 28 7 1 1 % 1.4 10.4 17.2 14.9 19.0 17.4 11.3 6.3 1.6 .2 .2 FEMALE • - . -•• No .4 127 238 163 164 202 158 93 59 31- 8 % .3 10.2 19.1 13.1 13.2 16.2 12.7 7.6 4.7 2.5 .6 Table 15 Instantaneous Growth Rates During Three Time-Intervals as Calculated from the 1946 Data. (See F i g . 29) Time-Intervals (Years) L o c a l i t y 1Y-VI M F V-M -VII F VI-VIII M F Fraser River .039 .073 .044 .062 .006 .052 Gulf Islands .030 ;069 .026 .061 .036 .045 Baynes Sound .035 .080 .036 .066 .026 .036 San Juan to Tofino .043 .071 .031 .052 .037 .032 Esteban to Kyuquot - .058 - .051 mm .032 Goose Island .029 -.057 .019 .040 .029 .035 Banks Island .033 .044 .022 .048 .035 .056 Rose Spit .049 .066 .030 .045 .026 .043 Butterworth Rocks .037 .086 .034 .061 .040 .036 T r i p l e Island .050 .066 .033 .048 .035 .051 Two Peaks .060 .070 .023 .053 .024 .030 Table 16 Percentage Age Composition of Female F i s h Captured i n the V i c i n i t y of Butterworth Rocks During 1944, 1945 and 1946. (See F i g . 53) 1944 1944 1943 1942 1941 1940 1939 1938 1937 1936 1935 1934 1933 FEMALE No. i 5 9 11 40 28 21 12 7 3.7 6.7 8.2 30.0 21.0 15.7 9.0 5.2 1945 1 11 33 38 59 40 18 15 11 .4 4.9 14.6 16.8 26.1 17.7 7.9 6.6 4.9 FEMALE No. i 1946 15 57 217 171 158 222 158 106 81 25 9 1 1.2 4.7 17.8 14.0 12.9 18.2 12.9 8.6 6.6 2.0 .7 .08 FEMALE No. % 

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