UBC Theses and Dissertations

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UBC Theses and Dissertations

Pt. 1. Criteria and techniques of scale reading. Pt. 2. Life history of the steelhead Salmo gairdneri… Maher, Frank P. 1954

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PART I CRITERIA AND TECHNIQUES OF SCALE READING  PART I I L i f e H i s t o r y o f the Steelhead Salmo g a i r d n e r i g a i r d n e r i Richardson as Interpreted from the Scales • by FRANK P. MAHER A THESIS SUBMITTED IN PARTIAL FULFILMENT OF ,THE REQUIREMENTS FOR THE DEGREE OF MASTER OF ARTS i n the Department of ZOOLOGY  We accept t h i s t h e s i s as conforming t o the standard r e q u i r e d from candidates f o r the • degree of MASTER OF ARTS  Members o f the Department o f ZOOLOGY THE UNIVERSITY OF BRITISH COLUMBIA September, 1954  L i f e H i s t o r y of the  Steelhead  as Interpreted from i t s scales  by Frank P. Maher  Abstract C r i t e r i a f o r i n t e r p r e t a t i o n of scales of steelhead  (Salmo  g a i r d n e r i g a i r d n e r i ) and f o r t h e i r use i n back c a l c u l a t i o n of e a r l y l i f e h i s t o r y were e s t a b l i s h e d .  With these c r i t e r i a , features of  the l i f e h i s t o r y of 784 steelhead from the anglers' catches of the C h i l l i w a c k R i v e r , B. C. were studied.  Age composition of adult  steelhead runs from 1948 to 1953 was uniform except f o r the suggestion of a s l i g h t l y dominant year c l a s s , represented 4 year o l d f i s h i n 1950, f i s h i n 1952.  5 year o l d f i s h i n 1951  as  and 6 year o l d  There was no suggestion that f i s h of any  parti-  c u l a r age, l i f e h i s t o r y , sex or length tend to r e t u r n as adults at any p a r t i c u l a r season of the year.  The age and s i z e of smolts  at migration i s v a r i a b l e , with the majority however i n the 2 and 3 year age groups and ranging i n s i z e from 15 t o 20  cms.  Smolt migration u s u a l l y occurs i n March, w i t h a small prop o r t i o n of l a t e migrants i n August. was reviewed.  Spawning frequency of adults  Females g e n e r a l l y spawn at an e a r l i e r age and more  frequently than males. I t i s concluded that the v a r i a b i l i t y i n the l i f e h i s t o r y of the steelhead acts as a safeguard i n i t s conservation.  ACKNOWLEDGEMENTS  The w r i t e r i s p a r t i c u l a r l y indebted to Dr. P. A. L a r k l n f o r h i s generous a s s i s t a n c e i n every phase of the work, f o r suggesting t h i s problem, f o r h i s help w i t h the s t a t i s t i c a l treatment of the data, and e s p e c i a l l y f o r h i s h e l p f u l c r i t i c i s m s and encouragement  throughout.  Dr. C. C. Llndsey gave much of h i s time to a c a r e f u l proofreading of the manuscript, and h i s c r i t i cisms and advice were deeply appreciated. Thanks are due also to Mr. S. B. Smith and Mr. D. P. Scott w i t h whom the' writer' discussed the work as i t progressed, and whose Interest and help was g r e a t l y stimulating. F i n a l l y thanks are due to the B r i t i s h Columbia Game Commission f o r permission to use the steelhead data i n t h i s t h e s i s , gathered while conducting an i n v e s t i g a t i o n i n t o the steelhead sport f i s h e r y .  TABLE OF CONTENTS Page ACKNOWLEDGEMENTS / PART I .  1  CRITERIA AND TECHNIQUES OF SCALE READING........ .........  1 1  INTRODUCTION...........  2  MATERIALS AND METHODS. .........'i... SECTION ( A ) . . . . . . . . . . . .  k  C r i t e r i a f o r Determination of A n n u l l . . . . . .  »  k  C r i t e r i a f o r D i f f e r e n t i a t i n g between S a l t and F r e s h Water Growth.  .......  11  Time of Annulus Formation..........  12  C r i t e r i a f o r Time of M i g r a t i o n . . . . .  12  C r i t e r i a f o r Spawning Marks  13 16  SECTION ( B ) . . . . . . . . . .....  l6  Method of Back C a l c u l a t i n g Lengths.... PART I I .  26  \  .'.  LIFE HISTORY OF THE STEELHEAD (Salmo g a i r d n e r i g a i r d n e r i  26  Richardson).  INTRODUCTION AGE COMPOSITION OF ADULT POPULATIONS.  ,  FORK LENGTH COMPOSITION OF ADULT POPULATION.  26 22  k-1  COMPARISON OF LENGTH, WEIGHT AND AGE, AND DATE OF CAPTURE OF MALE AND FEMALE STEELHEAD.  4-2  AGE AND SIZE AT MIGRATION  51  TIME OF SMOLT MIGRATION  58"  ii  Page RELATION BETWEEN GROWTH IN FRESH WATER AND SIZE AT CAPTURE AS ADULT. SPAWNING FREQUENCY.. . SIZE COMPOSITION OF SECOND SPAWNERS SUMMARY AND DISCUSSION. LITERATURE CITED.  ....  ...  60  .........  6k  , •••••  &5  .......... , 6&\ . 16 -  Iii  Page  Table. I .  Table I I .  Table I I I .  Table IV.  Table  V.  Table VI.  Table V I I ,  Table V I I I .  Comparison of a c t u a l fork length and fork length c a l c u l a t e d from scale s i z e of 27 Immature steelhead. . C h i l l i w a c k - r i v e r , 1953*•  19  Measurements .of the. .diameter .of the .scale, at smolt migration of three adult s t e e l head and the percentage d i f f e r e n c e of each scale diameter from t h a t of 'sample "station 13, which i s taken as a standard  25  Age composition of the 19^-8-4-9 sample of 124- f i s h from the C h i l l i w a c k r i v e r showing numbers of f i s h i n each age group and the percent of the t o t a l sample each group constitutes  30  Age composition of the 19^9-50 sample of 73 f i s h from the C h i l l i w a c k r i v e r showing numbers of f i s h i n each age group and the percent of the total.sample each group constitutes.  31  Age composition of the 1950-51 sample of 106 f i s h from the C h i l l i w a c k r i v e r showing numbers of f i s h i n each age group and the percent of t h e . t o t a l sample each group constitutes.  32  Age composition of the 1951-52 sample of 201 f i s h from the' C h i l l i w a c k r i v e r showing numbers of f i s h i n each age group and the percent of the t o t a l sample each group constitutes  33  Age composition of the 1952-53 sample of 266 f i s h from the C h i l l i w a c k r i v e r showing numbers of f i s h i n each age group and the percent of the t o t a l sample each group constitutes  3^  Age composition of 770 C h i l l i w a c k r i v e r steelhead samples f o r the p e r i o d 19^8 to 1953 showing numbers of f i s h i n each age group and the percent of the t o t a l sample each group c o n s t i t u t e s .  35  iv Page Table IX.  Table  X.  Table XI.  Table X I I .  Table X I I I . 5  Table XIV.  M u l t i p l e chi-square a n a l y s i s of age compos i t i o n of steelhead from the C h i l l i w a c k r i v e r f o r the f i v e years 19^8-53> c o n s i dering only the four major age groups, 2/2, 2/3, 3/2, and 3/3. Figures i n brackets are the observed numbers.of f i s h i n each age group...  36  Mean lengths and standard d e v i a t i o n s of • . . each age group of steelhead a d u l t s from the C h i l l i w a c k r i v e r f o r the f i v e year period 19^-53• • 37 •' Mean f o r k lengths of steelhead spending from 1 to k years- i n the sea.C h i l l i w a c k r i v e r catch, 1 9 ^ 8 - 5 3 . . . . . . '  •  Mean f o r k lengths f o r four major age groups of steelhead. C h i l l i w a c k r i v e r catch 19^2-53  33  39  Mean length and mean weight of male and female steelhead i n each age group i n the C h i l l i w a c k r i v e r catch from December to March of ( a f t e r L a r k i n , 1 9 5 0 ) . . . . . . . . 1|4 Mean length and weight of male and" female' " steelhead i n each age group i n the C h i l l i w a c k r i v e r catch from December to March of 19^9-50, ( a f t e r L a r k i n , 1950)  ^5  Table XV.  Mean l e n g t h and weight of male and female steelhead i n each age group i n the ' ' " C h i l l i w a c k r i v e r catch from December to March of 1950-51 ( a f t e r L a r k i n , 1950) 1+6  Table XVI.  Mean length and weight of male and female steelhead i n each age group i n the C h i l l i w a c k river- catch from December to March of 1951-52 ( a f t e r L a r k i n , 1950). . . . k-7  Table V l I .  Percentage of male and female steelhead f o r each of the months.from December to March i n the C h i l l i w a c k r i v e r catch i n the years 19*+2-52. ....'..'..v.'.".'... V.V.V.V  x  ~^  V  Page Table XVIII. Percentage of male and female steelhead i n four age groups of the C h i l l i w a c k r i v e r catch f o r the period 1 9 ^ g - R 2 . .  ^9  Table XIX.  Age and s i z e a t migration of steelhead smolts which returned as a d u l t s i n the years 19^8-53, to the C h i l l i w a c k r i v e r . . . . . . . 5*4-  Table XX-.  Events groups river, events  Table XXI.  Numbers of steelhead from various years of the adult run grouped for*year of migration as smolts. C h i l l i w a c k r i v e r ' catch 19^-53....  Table XXII.  i n the l i f e h i s t o r y of four age of steelhead from the C h i l l i w a c k and the year of occurrence. A l l assumed to-occur i n March ...v.. 55  57  Percent of run made-up of l a t e migrants from 19^-53>' C h i l l i w a c k * river-. >. -.;. •.«. %.;. -..> 59 s  Table XXI 1*1. Mean l e n g t h a t age 2, and a t migration, f o r l a t e migrants of the 2/2 and.2/3_age groups,'Chilliwack r i v e r l9^$-53»••••• Table XXIV,  Table XXV.  Table XXVI.  6l  Mean length a t smolt migration and a t capture f o r four age groups of.steelhead over the f i v e year.period 19^8-53, Chilliwack river. Numbers of "veteran" spawners i n age group i n which they occurred from 19^8-53» Chilliwack river  66  Mean length and weight of f i s h i n spawning run f o r second and t h i r d time, Chilliwack river, 19^-53.....  67  62  vi Page Figure  1.  .A.. Steelhead scale sample envelope. B. Steelhead record card  Figure  2.  Scales from a young steelhead taken i n the C h i l l i w a c k r i v e r , A p r i l 10, 1951. Arrows, point to f i r s t annulus •  7  Scales from a young steelhead i n i t s second year, l 6 . 2 cms. long, taken i n the C h i l l i w a c k r i v e r , October l 6 , 1951 .•..  2 9  Figure  3.  ' 6 6  Figure  4-.  Scales of young steelhead, 16.6 cms. long, .... taken i n the C h i l l i w a c k r i v e r , March 5, 1 9 5 2 . .  Figure  5«  Scale from adult female steelhead from C h i l l i w a c k r i v e r , captured A p r i l 11, 1952. Weight 9-g- pounds, f o r k -length 30^ inches,- .•:. . age 2/3 10  Figure  6.  Figure  Figure Figure  7.  2>. 9»  Figure 10.  Figure 11,  Scale from a d u l t female steelhead .from , t h e , , C h i l l i w a c k r i v e r captured January 13, 1953• .Weight ^\ pounds, f o r k l e n g t h 28 inches, 'age 2/3 ..*  15  Log-log p l o t of scale diameters i n mms. x 37.^ of young pre-smolt steelhead, against fork l e n g t h i n cms., ;  17  Graph used f o r converting scale diameters i n t o f i s h lengths, based on "Figure '1;:.  18  Diagram of a d u l t steelhead showing the area on the side of the f i s h ( s t i p p l e d ) from' which scales showed l e a s t . v a r i a t i o n i n ' b a c k * c a l c u l a t e d lengths 24Standard d e v i a t i o n s and f i v e percent confidence l i m i t s f o r the f o r k lengths of the four major age groups of steelhead from the C h i l l i w a c k r i v e r , 19:1-8-53 catch  4-0  Age and length at smolt migration f o r f i v e years (194-8-53). i n the Chillix^ack r i v e r . Numbers of f i s h r e f e r to a d u l t samples f o r each year from which the smolt h i s t o r y was derived  52  PART I  CRITERIA AND TECHNIQUES OF SCALE READING-  INTRODUCTION The l i t e r a t u r e concerning the determination of ages and rates of growth of fishes from the scales, o t o l i t h s , f i n rays, spines, and other bony body parts Is voluminous.  Since  Leeuwenhoek In l6S6 f i r s t surmised that the rings on a f i s h scale had something to do with the age of the f i s h , a formidable body of l i t e r a t u r e on the subject has come into being.  I t i s not  Intended here to construct a c r i t i c a l review of the l i t e r a t u r e on the subject; t h i s has been handled competently by many authors, foremost among whom are Thomson (1904-), Taylor (1916), Hutton (1921), Creaser (l9?6), Graham (1926, 1929), Van Oosten (1929), and Beckman (l9^3)»  However, since the present work  w i l l be concerned largely with results obtained by measuring growth rates of f i s h from scales, and determination of the age of the f i s h from this source, an attempt w i l l be made to indicate the c r i t e r i a used i n each part of the work. For convenience, the material i s divided into two parts.  Section A discusses the c r i t e r i a used f o r determining  year marks or annul! on scales, the d i f f e r e n t i a t i o n between salt and fresh water growth, the spawning mark, and the time of year of annulus formation.  Section B deals with c r i t e r i a used  to obtain growth rate data, by back-calculation of length from — scale measurements.  2  MATERIALS AND METHODS The 770 adult steelhead scale samples used i n this study were obtained largely through the e f f o r t s of interested anglers who submitted  them i n envelopes supplied for the purpose  by the B r i t i s h Columbia Game Department,,  (See f i g . 1 . ) Scales  were examined under a d i s s e c t i n g microscope, and three scales selected from each sample were placed face (the side ridged with circuli!;down, on a c e l l u l o i d s t r i p , which was then passed through a jeweller's s t e e l r o l l e r . scales with regenerated  Asymmetrical, scales and  central portions were rejected.  The r e s u l t i n g Impression was projected on to the back of a 5 x S, inch steelhead record card ( f i g . l ) by means of a Bausch and Lomb 6 v o l t , 25 watt, Triple-Purpose Micro-Projector. For greater accuracy, the fresh water part of the scale was examined at a magnification of 37.4- X, whereas the scale i n i t s entirety was examined at 1S"«0 X.  The diameters of the scale at  the fresh water annuli, at the c l r c u l i corresponding  to migra-  tion to sea, and at sea annuli were drawn on the back of the card.  Measurements of the diameters indicated on the cards  were made with combination c a l i p e r s graduated i n mms. A l l measurements made at the lower magnification were l a t e r corrected to 37«^ X for length calculation purposes. Small f i s h used to construct the scale-body  length  graph discussed l a t e r were c o l l e c t e d with a hand seine or f i s h i n g tackle.  A worm or a single egg on a size 1 0 hook was  found to be e f f e c t i v e f o r taking f i s h from 5 to 1 2 inches,, one occasion a small pool cut o f f from the main Chilliwack  On  r i v e r was poisoned with  "Fish-Tox".  These small f i s h were a l l preserved i n 5$ formalin* The  scales were removed from a point below the posterior i n s e r -  tion of the dorsal f i n and above the l a t e r a l l i n e , and examined as described above.  Scales were mounted on glass slides i n a  Canada balsam-dioxane medium, and examined at a magnification of k-0 X under a Spencer compound microscope.  Scale Images were  superimposed on standard steelhead record cards by means of a camera lucida; the diameters were marked with a p e n c i l and measured as before. n i f i c a t i o n of 37.k  These measurements were converted to a magX.  SECTION (A) C r i t e r i a for Determination of Annul! Hoffbauer (1898) working with carp of known ages published the f i r s t authoritative treatment of annulus formation in the scales of f i s h .  He established that the crowding  together  of c l r c u l i corresponded with winter growth, and that this crowding occurred only once each year, so that a r e l i a b l e Index of the age of the f i s h was obtained*  Since that time, the assump-  t i o n that only one crowding together of annul! occurs each year has.been frequently used as a method of determining the age of many species of f i s h .  Thomson (190*0 working with the Gadldae,  Masterman (1913) with Salmo salar,  Taylor (1916) with the  squeteague and p i g f i s h , Cutler (1918) with p l a i c e and flounder, and Marshall (1939) with the common shiner Notropla cornutus chrysocephalus, among many others, have used the "annulus" with success. While no general agreement appears to exist as to the cause of the annulus, or of the number of c l r c u l i l a i d down, i t i s generally agreed that since the scale and f i s h grow In some proportion to one another, the winter mark indicates a period when the growth of the f i s h has slowed down or ceased.  Creaser  (1926) states that i n many fresh water f i s h i n the north temperate zone, growth i s retarded or stopped e n t i r e l y i n the winter months.  C l r c u l i do not form a complete c i r c l e a l l at once, but  grow at the anterior and posterior ends f i r s t , and the sides last.  Creaser found that during the period of slow growth i n  winter many c l r c u l i f a i l e d to complete at the sides.  He took  as the annulus or year mark the place on the scale where the f i r s t complete circulus formed, with commencement of rapid growth i n the spring.  The t y p i c a l annulus then consisted of a complete  c i r c u l u s "cutting o f f " several Incomplete  circuli.  Examination -of the fresh water part of scales of adult steelhead, and of scales of young steelhead i n the r i v e r before migrating as smolts, confirmed that this situation apparently obtained f o r steelhead.  D i s t i n c t "cutting o f f " of c i r c u l i  seen at what was taken to be the annulus. of  was  To establish the type  annulus formed by young steelhead i n the Chilliwack r i v e r ,  samples of young f i s h were taken i n a l l months of the year. Small f i s h taken i n A p r i l , from 6 to 10 cms. i n length, exhibited as t h e i r f i r s t annulus a check such as described, at the margin of  the scale.  (See f i g .  2.)  This age class sampled i n the f a l l  showed summer growth at the edge of the scale.  After the end of  September l i t t l e growth occurred at the edge of the scale, since both the length composition of similar samples and the scale patterns of these f i s h were s i m i l a r i n October and the following March.  (See f i g s . 3 and  )  From the study of these scales i t was determined'that a r e l i a b l e c r i t e r i o n f o r the year mark or annulus i n fresh water was a crowding together of the c i r c u l i , together with the "cutting off"  of several c i r c u l i .  The number of years that the adult  steelhead spend i n fresh water,, and the age at smolt migration were determined i n t h i s manner.  6 B.C. GAME COMMISSION  STEELHEAD SCALE SAMPLE Locality  '.  Length  ;  sex  Remarks:  Date—  :  Weight  :  NOTB.—Ten or more scales should be taken just behind back (dorsal)fin,high up on side.  SM-15M796  A  STEELHEAD RECORD CARD DATE  STOMACH CONTENTS  LOCALITY  EMPTY  LENGTH (Sttl)  PLANKTON.  (Fork) WEICHT  SEX  AGE  F  BOTTOM ORGANISMS S  REMARKS  „ „ „ TERR. INSECTS  FISH  OTHER  B  F i g u r e 1.  A.  Steelhead  s c a l e sample envelope.  B.  Steelhead  record  card.  VOL CC  7  Figure 2.  Scales from a young steelhead taken i n the Chilliwack r i v e r , A p r i l 10, 195"U Arrows point to f i r s t annulus.  r~t9  Figure 3«  3  Scales from a young steelhead i n i t s second year, l6.2 cms. long, taken i n the Chilliwack r i v e r , October l6, 1951' A.  F i r s t annulus.  B.  Summer growth outside annulus.  9  Figure ^.  Scales of young steelhead, 16.6  cms.  long,  taken In the Chilliwack r i v e r , March 5> A.  195 -  F i r s t annulus.  B. Second annulus (on edge). Note s i m i l a r i t y of general pattern to f i s h taken previous October ( f i g . 3 ) .  2  10  Figure 5»  Scale from adult female steelhead from Chilliwack r i v e r , captured A p r i l 11, 1952. Weight 9i pounds, fork length 30-j Inches, age 2/3. Ocean annulus 1.  A.  Typical salt water annulus.  B.  Reabsorption of edge of scale i n spawning run.  C.  Demarkation between fresh and salt water growth.  D.  Ocean annulus 2.  11 Examination of the annuli formed i n the ocean showed that these occurred i n a d i f f e r e n t way than the fresh water checks.  I t was usually found that l i t t l e i f any "cutting o f f "  of c i r c u l i occurred i n the ocean check, but that a greater number of c i r c u l i tended to be Involved i n the formation of the annulus.  A t y p i c a l ocean annulus consisted of a crowding to-  gether of the c i r c u l i i n noticeable dark bands on the scale, ( f i g , 5)«  Fraser (1916) working with tagged spring salmon,  and Rich (1928) working with tagged chinobk salmon, showed that these marks on the scale represented true annuli.  Menzies (193*0  working with A t l a n t i c salmon of known ages also determined that these marks indicated true annuli. In a few instances there was no abrupt resumption of growth i n the spring as indicated by a sudden widening of the spaces between c i r c u l i , but rather there was a gradual narrowing and then widening of the spaces. phenomena on cod scales.  Graham (1926) reports similar  In these cases the center point of the  crowded c i r c u l i was taken as the annulus.  When an abrupt change  from slow to fast growth had taken place,  the outside edge of  the  slow growth was taken as the annulus.  C r i t e r i a f o r D i f f e r e n t i a t i n g between Salt and Fresh Water Growth Tagging work with both A t l a n t i c and P a c i f i c salmon has supplied ample evidence of the difference between fresh water and salt water growth on scales.  Smolts tagged or marked i n  12 fresh water with t y p i c a l fresh water growth evident on their scales have been recovered shortly afterwards i n the sea, with a noticeable increase i n size, and with the t y p i c a l widely spaced c i r c u l i of salt water growth on their scales.  Among many others  Menzles (1931) has shown this f o r the A t l a n t i c salmon. The steelhead scales examined exhibited a difference between salt and fresh water growth so evident as to need no mathematical expression of differences In c i r c u l i spaces f o r use as a c r i t e r i o n , (see f i g . 5)»  Time of Annulus Formation Scales of young f i s h caught i n March showed a check on the margin.  Scales examined In A p r i l and early May showed  beginnings of rapid growth at the edge of the scale.  Since  adult spawning takes place at t h i s time of year also, the month of March makes a convenient reference point from which to measure the age of the f i s h ,  Fraser (1917) found that the winter check  in the sea formed from January 6 to March 17.  For the purpose  of t h i s study March 31st was taken as the reference point f o r age determinations.  C r i t e r i a f o r Time of Migration Examination of the 770 scales from the Chilliwack r i v e r showed that f o r 73& f i s h the period of rapid sea growth commenced Immediately after formation of the winter annulus, or with l i t t l e additional growth.  Since the time of annulus  13 formation i s taken to be the end of March or beginning of A p r i l , i t would appear that the steelhead migrants move to sea shortly after t h i s time.  A sample of young steelhead taken on March 29,  1953 from the upper reaches of the Vedder r i v e r exhibited the s i l v e r y coating of guanin and the b l u i s h back t y p i c a l of smolts. From the scales alone i t would appear that i n the Chilliwack r i v e r most young steelhead migrate seaward i n A p r i l and May, Some scales exhibited additional growth after the annulus before migrating.  Nine smolts were recovered i n July 1951 from a trap  net i n the r i v e r .  It would appear .then that the peak of mlgra-  tion occurs i n A p r i l or early May but that some individuals may not move seaward u n t i l July.  C r i t e r i a f o r Spawning Marks When the adult f i s h enter fresh water active body growth apparently ceases, while the gonads develop r a p i d l y . Scales examined from f i s h newly i n from the sea, with as yet unripe gonads, show i n most cases a s l i g h t amount of unevenness at the edges of the scale.  As the f i s h moves closer to maturity  and the stay i n fresh water lengthens, the unevenness at the edge of the scale.becomes more and more pronounced.  Crlchton  (1935) showed that i n Salmo, salar t h i s unevenness was due to reabsorptlon of the scale i n a reversal of the scale formation process.  The hyalodentlne layer of .the scale especially i s  reduced by phagocytic c e l l action.  In some scales t h i s absorp-  t i o n i s s u f f i c i e n t to render them useless f o r age determination  11+  or measurement purposes.  However f o r most adult f i s h taken  by anglers the reabsorption i s only moderate.  (See f i g . 5«)  Those f i s h that survive the spawning act, the hazards of the sport fishery and other factors of mortality recover i n the sea and add c i r c u l i i n the usual manner to the edge of the scale, thus enclosing a "spawning scar".  These scars are  r e a d i l y distinguishable on the scale as shown i n f i g . 6„ mark i s apparently  The  obvious enough to be r e a d i l y recognizable  without establishing more formal c r i t e r i a f o r i t s detection. That these marks do indicate spawning has been shown by many workers including Menzies (1931) and B l a i r (1937) who tagged A t l a n t i c salmon a f t e r spawning and subsequently recovered the f i s h at l a t e r spawnings.  Figure 6 .  Scale from adult female steelhead from the Chilliwack r i v e r captured January 13, 1953• Weight 9^ pounds, fork length 26 inches, age 2/3. Arrows point to spawning scar from 1952 spawning run.  16  SECTION B Method of Back C a l c u l a t i n g Lengths I t has "been shown by many authors that a r e l a t i o n s h i p e x i s t s between scale measurements and lengths of f i s h .  In the  simplest case, the length of a f i s h at any d e s i r e d point of reference on the s c a l e , say annulus I , may be determined by simple a r i t h m e t i c proportion, i . e . , using the formula L]_  s  1  S  where L]_ length of the f i s h at annulus I , Sj^- the length of =  the scale at annulus I , L = the length of the f i s h at capture, and S = the length of the scale at capture.  This method was  used by Dannevig and H^st (1931), with the m o d i f i c a t i o n that an allowance was made f o r the l e n g t h of the f i s h when the scale was formed.  Others have described scale to body-length r e l a t i o n s on  a l o g - l o g basis x^ith c o r r e c t i o n f o r the length of the f i s h at the time the scale i s formed (Fry 19^3)• permit more accurate b a c k - c a l c u l a t i o n .  These methods probably  However, Mottley (19^-1)  pointed out that there was no need f o r elaborate b a c k - c a l c u l a t i o n of f i s h lengths, i f the only purpose of an i n v e s t i g a t i o n was to compare r a t e s of growth, since the scale measurements themselves were adequate f o r t h i s purpose without to f i s h lengths,  converting  Mottley demonstrated that f o r the rainbow  trout (Salmo g a i r d n e r i kamloops) scale measurements gave an unbiased estimate of f i s h lengths when they were r e l a t e d logarithmically. Mottley's observation i s p a r t i c u l a r l y p e r t i n e n t to studies of f i s h such as steelhead where reabsorption of the  17  3  Figure 7«  4 5 6 7 8910 15 20 25 FORK LENGTH (CM.)  Log-log plot of scale diameters i n mms. x 37.k of young pre-smolt steelhead, against fork length i n cms.  18  10 I 5 Figure 8.  1  6  I  L  I  I  7 8 9 10 FORK LENGTH  I  15 (CM)  L 20  Graph used for converting scale diameters into f i s h lengths, based on Figure 7.  Table I . Comparison of actual fork length and fork length calculated from scale size of Chilliwack r i v e r , 1953.  27 immature steelhead. Actual fork length cms.  Calculated fork length cms.  15.7  17A  15.8  17.6  V275  16.0  16,0  V276  16.7  15.9  ^277  15.9  16,3  ^278  15.5  16.4-  V273  16.3  V280  17-5  15.3  V2&1  18.1  19.1  7282  15*6  lKs  7283  10,7  11,5  7284-  10,7  12,2  7285  12.7  13.1  7286  12.9  12,5  Pish No* /273  No*  Actual fork length cms.  Calculated fork length cms.  Calculated length minus actual length ._.  1.7  V287  18.9  22.2  • 3.5  1.8  V288  12.4-  13.8  * 1.4-  0.0  V289  13.6  A.6  * 1.0  08  V290  13.9  13.1  - 0.8  o.k  V291  12.1  13.8  * 1.7  0.9  V292  1^.3  13.8  -  V293  10.1  10.4-  *• 0 . 3  V29k  10.5  11.6  *  V295  15.3  15.1  - 0.2  V296  15.8  14-.8  - 1.0  0.8  V297  16.1  12.0  - 4-.1  1.5  V298  16.3  17.8  * 1.1  0.H-  V299  15.2  * 0.9  A  Mean  14-. 86  * 0.28  Calculated ^length minus actual length  * •  o  *  . - 1.5 - 2o2  1.0. - 0.7  *  -a  Fish  1^.58  0.5  l.l  20 margin at spawning renders the scale measurements useless for any method of back-calculation using scale length at capture. Moreover, anglers' estimates of the lengths of the f i s h they catch are not r e l i a b l e and cannot be used with any confidence . as datum points.  Accordingly, an average regression l i n e f o r  the log-log relationship of scale diameter to fork length of f i s h was  constructed from samples of young f i s h ranging i n  size from 2.1  to 25 cms.  In each sample scales were taken  from a point midway between the l a t e r a l l i n e and the dorsum, under the posterior point of i n s e r t i o n of the dorsal f i n . This ' l i n e i s shown i n f i g . 7.  There i s obviously a change in curva-  ture of the l i n e which can a r b i t r a r i l y be described as a simple point of i n f l e x i o n (Martin 19^9). at a f i s h length of roughly 3.5  This i n f l e x i o n point occurs  cms.  Past this point the l i n e  appears to be r e c t i l i n e a r , and with a slope approaching  1,  i n d i c a t i n g that the scale and fork length were growing isometrically. Since a l l of the calculated lengths were going to be made well past the i n f l e x i o n point, i t was decided to a r b i t r a r i l y Ignore the points below a f i s h length of 5 cms. and obtain a l i n e of best f i t for the remaining of least squares.  This was done, and the r e s u l t i n g l i n e  found to have a slope of 1.01, 0.976.  88 points, using the method was  and a c o e f f i c i e n t of c o r r e l a t i o n  The l i n e i s shown i n f i g . 8".  Scale measurements, were  d i r e c t l y converted into f i s h lengths by using t h i s graph. Although the c o r r e l a t i o n c o e f f i c i e n t was 0.976 for t h i s graph i t was appreciated that the error involved i n  21 calculating lengths for any one f i s h might be considerable since v a r i a t i o n of scale diameters exceeds that of f i s h lengths (Mottley 194-2).  As a test of the method, a sample of 27 small  f i s h from the upper reaches of the Chilliwack r i v e r was taken by angling on March 2 9 , 1953* lS.l.cms. i n length.  These f i s h were from 10.7 cms. to  Scales were removed from the f i s h as i n the  preparation of the o r i g i n a l graph, and the t o t a l diameter of the scale measured.  The calculated length of each f i s h was then  compared to i t s actual length.  The r e s u l t s are tabulated i n  Table I. The greatest differences were found to be i n one case a f i s h calculated 4-.1 cms. too small, and one 3*3 cms. too large. These two were extreme cases* The difference between the means for the sample was 0.28  cms. and was not s t a t i s t i c a l l y s i g n i f i c a n t .  Since t h i s  work i s concerned with the means of large samples the lengths calculated from the large samples used should be v a l i d . A second source of error i n this study i s the p o s s i b i l i t y of great v a r i a t i o n i n scale size i n the samples from adult f i s h submitted by anglers.  Carlander  (1950) has pointed out the  need for taking the scales from the same place on each f i s h i f the results of back calculations are to be comparable.  Accord-  ingly, a b r i e f test was made to ascertain the' amount^ of scale size v a r i a t i o n from scales from d i f f e r e n t parts of the body of the steelhead trout, the method employed by Dannevig and H^st (l931)«  Three adult steelhead from the spawning run of the  Capilano r i v e r i n July 1952 were selected.  Scales were taken  22 in six series, each series being i n a l i n e perpendicular longitudinal body axis.  The  to the  six series were as follows:- from  immediately behind the g i l l cover, between t h i s point and  the  anterior Insertion of the dorsal f i n , from.the anterior insertion of the dorsal f i n , from the posterior i n s e r t i o n of the dorsal f i n , from between t h i s point and the mid point of the adipose f i n , and from the mid point of the adipose f i n . Along these l i n e s , single scales were taken from the dorsal surface, six rows above the l a t e r a l l i n e , six rows below the l a t e r a l line,, and where possible from the ventral surface.  F i g . 9 shows. 23  sampling stations and the simple system by which they were numbered.  Each scale was measured for diameter at migration.  measurement was  This  expressed as a percentage difference from the  measurement of the scale taken at station 13.  Station 13  was  taken as the reference point since t h i s i s the area from which anglers are requested to remove t h e i r scale samples. As shown i n Table I I , the percent v a r i a t i o n i n the scales i n the row was  six scales above and below the l a t e r a l l i n e  found to be small except from areas 5 and 6 which had  scales.  large  The area of smallest v a r i a t i o n i s shown stippled on  the diagram i n f i g . 9.  Since the instructions on the scale  sample envelopes stated "NOTE.- Ten or more scales should be taken just behind back (dorsal) f i n , high up on side." i t i s believed that most scales came from this general area of v a r i a t i o n in scale size.  small  In addition, further examination of  scales has shown that scales from t h i s area tend to be oval-  23 shaped and symmetrical, whereas scales from other parts of the body, especially those areas showing the greatest v a r i a t i o n i n scale size, tend to be asymmetrical, readily recognizable, and hence easy to discard as p o t e n t i a l sources of error.  214-  Flgure 9.  Diagram of adult steelhead showing the area on the side of the f i s h (stippled) from which scales showed least v a r i a t i o n i n back calculated lengths. (See t e x t ) .  Table I I , Measurements of the diameter of the scale at smolt migration of three adult steelhead and the percentage difference of each scale diameter from that of sample station 13, which i s taken as a standard. Adult characteristics Sample station 1 2  I  7 6 9 10 11 12  16 17 16 19 20 21 22 23  Female - 27 l / 6 " 2 f r e s h - 1 plus S.  Female - 27r" 2 fresh-1 plus S„  Male - 26£" 2 f r e s h - 1 plus S.  Scale % d i f f e r diameter ence from No,13  Scale 7° d i f f e r diameter ence from No,13  S c a l e % differdiameter ence from No. 13  24-„6 2.9 36.7 55.2 53,3 27.4  m  53o5 35-5 26.452.45Cl 7.2 2.6 52.9 50,1 4-0.0 6.3  I  9A  4-6. 44-6.2  -52.7 * 0.9 -16.2 -30.0 * 5»3 * 1.7 -^7,7 -24-, 6 * k.2 * 2.1 -32.2 45.6 00.0 * 3.2 -29.0 -16.3 *-o.9 - k'A -23 7 -27.0 - 5.7 - 7.6 -11.6 ?  24-. 2  k&'A 4-0.0  1+7.3  4-5.1 26.2 6.6 9.0 51.2  50.1 f97o 4-2.6 32,3 50.7 51.2 6.0 1.1 50.1 51.6  I  W.5  -51.7 - 1.0 - 3^ -20.2 - 5»6 -10.0 43-7 -26.9 - 2.2 * 0.2 -37.1 -31.3 00.0 - 2.2 -llU.6 -23.6 * 1.2 * 0.2 -26.1 -16.0 00.0  *  3A  -11.2  23.1 37.2 37.7 26.7 4-1.1 42.6 25,3 30.432.9 3^.1 29.9 27.0 39.4 3?' ,2 3*.• 9 37. .6 32-.9 31 ,0 36,,6 36,.3 V- ,1 32.7  -33,7 - 1.3 00.0 -26.5 * 9,0 *13.5 -32.9 rl9.4* 3.2 * .1.1 -20.7 -26.400.0 -11.9 -  7<k  * 0.3 «• 3-2 -17.6 - 2,9 * 1.6 * 9.0 -13.3  Average difference from No.13 sign Ignored 47.7 1.1 6.5 25.6 6.6 6.4 41.423.7 3 1 3Q 35 00 3 16 16 0 2 23 l6.0  2.4 6.7  12.1  ro VJI  26 PART II  LIFE HISTORY OF THE STEELHEAD (Salmo gairdneri gairdneri Richardson)  INTRODUCTION Using the techniques described i n the preceding portion of  the thesis, scales were examined and measured i n order to  obtain l i f e history information. The number of years spent i n fresh water, age at migration, length at migration, time spent in salt water, relationship between f r e s h water time and growth and salt water time and growth, frequency of spawning, and other points i n the l i f e history of the f i s h were ascertained. Certain calculations were not made because of errors involved i n handling data submitted by anglers. for  Many weights  example were given as even pounds on envelopes, and many  anglers admitted on questioning that the weights given were estimated, although t h i s was not stated on the envelope. comparison  of length-weight relations of male and female  would be almost valueless.  Thus, fish  Lengths•given were probably more  accurate, but only to the nearest Inch, since most measurements given were i n even inches. of  Information concerning sex  the f i s h may be r e l i e d upon because a l l fishermen i n t e r -  viewed by the writer were able to d i s t i n g u i s h sex of adult steelhead. A t o t a l of  scale samples were available from the  2  7  Chilliwack (Vedder) r i v e r f o r this study.  Of these, 14- were d i s -  carded because of incomplete information on the scale'envelope, or because of uncertain age determinations.  Because of the  variety of information sought i t was found necessary from time to time to discard specimens f o r lack of information for the study i n question.  For example, some envelopes lacked the sex  of the steelhead, and while these samples were used in age composition sutdles, they had of necessity to be omitted from the studies of sex differences. The term "age group" i s used throughout to denote the combination of fresh and s a l t water l i f e to which a f i s h belongs. The steelhead spends from one to four years i n a r i v e r before migrating to sea as a smolt, and from one to four years In the sea before returning to fresh water as a maturing adult. A l l combinations of fresh and salt water l i f e of these years have occurred in steelhead from various r i v e r s  i n the province.  The  Chilliwack r i v e r samples represent a l l combinations but one fresh/ four s a l t , four fresh/one s a l t , four fresh/two salt and four fresh/four s a l t .  In the tables throughout, the age groups are  referred to as 2/3,  4-/5 etc., the f i r s t number representing the  time spent i n fresh water i n years, and the l a t t e r number the time spent i n the ocean i n years. For the sake of convenience, the age of the steelhead i s expressed i n whole years.  Thus a f i s h caught i n December  which had spent 2 years i n the r i v e r as a young f i s h , 2 complete years i n the ocean, and part of another year i n the ocean and i n  28 the spawning migration, would be placed i n the 2/3 group, although i t s f i f t h year of l i f e would not be complete u n t i l March,  (As  pointed out previously, since winter checks on young f i s h form i n March or early A p r i l , and there i s reason to suppose that the ocean check forms about the same time, March i s taken as the reference point for age determination.)  AGE COMPOSITION OF ADULT POPULATIONS Tables III to VII show the age composition of adult steelhead samples from each of the winters 194-8-4-9 to 1952-53 respectively.  Table VIII shows t o t a l age composition f o r the  f i v e years combined. On the f i v e year average, the group which had spent 2 years i n fresh water before migrating to sea made up 6 2 , 1 $ of the sample, while the 3 years i n fresh water group were 35»5$ of the t o t a l .  The adults from each of these two major groups  were almost equally divided into those which spent two years i n the sea, and those which spent three years i n the sea. Thus the 2/2 group make up 31$ ot the run, the 2/3 group 3 0 . 6 $ , the 3/2 group 17o7$» and the 3/3 group 17«>3$»  These four groups  together form 9 6 . 6 $ of the sample. Age composition f o r each year i s remarkably similar to the average composition f o r the f i v e year period with regard to the four major age groups*  The smaller groups show a wider  29 v a r i a t i o n i n occurrence, A chi-square test was made of the age composition of the samples f o r the four main age groups ( 2 / 2 , 3/3)  over the f i v e year period, (Table XI).  2/3,  3/2,  and  A chi-square value  of 3 i « ^ was obtained, and at 12 degrees of freedom there was found to be a s i g n i f i c a n t difference i n the age composition from year to year at a p r o b a b i l i t y l e v e l of less than  .01.  There are two phenomena that could explain this departure from homogeniety: from year to year, (2)  ( l ) change i n l i f e history pattern  change i n r e l a t i v e size of year classes.  If the l a t t e r were the case then there should be some pattern to the deviations from expected values, while the former phenomenon might result i n some regular pattern of deviations.  This  type of analysis was explored and because of the smallness of deviation from expected f o r most cases no conclusions could be drawn.  The analysis suggested that the year class represented  by 2/2 i n 1950-51, by 2/3 and 3/2 i n 1951-52 and by 3/3 i n 195253 might have been s l i g h t l y larger than i t s contemporary year classes.  This suggestion i s not conclusive but can be e a s i l y  traced i n Table IX, and i f true could explain the s i g n i f i c a n t chi-square i n the analysis.  For the most part variations i n  age composition from year to year i n the Chilliwack r i v e r are not s t r i k i n g .  Table I I I .  sample of 124- f i s h from the Chilliwack  Age composition of the l$k&-k3  r i v e r showing numbers of f i s h i n each age group and the percent of the t o t a l sample each group constitutes. Years i n  Years in ocean plus migration back to r i v e r  Fresh Water  I  % of total  I II  1  0.8  III  y> of % of % of % of , II , t o t a l , i l l ,t o t a l , IV , total. V, t o t a l  1  0.8  Total  all fish  2  1.6  1  0.8  3  2.1+  38  30.7  38  30.7  77  62.1  19  15.3  2k  19.4-  ^3  3^.7  1  0.8  1  0.8  6k  51,7  IV Total  %  59  P7.6  _  12^  100  Table IV.  Age composition of the 194-9-50 sample of 73 f i s h from the Chilliwack r i v e r showing numbers of f i s h i n each age group and the percent of the t o t a l sample each group constitutes.  Years i n Fresh  II  of total  1  2  2.7  II  27  III  13  IV  1  Water  Total  %  Years i n ocean plus migration back to r i v e r I  0  % of total  0  III  y> of total  2  2.7  37.0  19  26.0  17.8  8  11.0.  /b  u  ^3  58.9  .  29  39.7  IV  % of total  V  \% of total  Total  fish  •  1  1  1.1+  1.*  all  5.5 1+6  63.O  22 .  30.I.  1  1.4-  73  100  Table V.  Age composition of the 1950-51 sample of 106 f i s h from the Chilliwack r i v e r showing numbers of f i s h i n each age group and the percent of the t o t a l sample each group constitutes.  Years i n  Years i n ocean plus migration back to r i v e r  Total  Fresh Water  I  % of total  II  %  Of  %  Of  V  %  Of  all  III  3-8  2  1.9  6  5.7  68  64.2  31  29.2  1  0.9  106  100  total  K  II  39  36.8  29  27.4  III  12  11.3  IS  17.0  1  0.9  50  47.2  IV 55  Of  total  I  Total  IV  %  %  51.9  1  1  total  0.9  Q.9  fish  total  Table VI.  Age composition of the 1951-52 sample of 201 f i s h from the Chilliwack r i v e r showing numbers of f i s h i n each age group and the percent of the t o t a l sample each group constitutes.  Years i n  Years i n ocean plus mlg^ration back to r i v e r  Fresh Water  I  % of total  II  % of total  % of total  III  58  28.9  55  27.4  IV  % of total  Total V  % of total  % .. a l l fish  I II III  -  113  56.2  1  0o5  58  28.9  28  13-9  1  0.5  88  43.8  1  0.5  116  57.7  83  41.3  1  0.5  201 .  100  IV  Total  Table VII., Age composition of the 1952-53 sample of 266 f i s h from the Chilliwack r i v e r showing numbers of f i s h i n each age group and the percent of the t o t a l sample each group constitutes.  Years i n  Years in ocean plus migration back to r i v e r  . Fresh I  % of total  I  I  0.4  II  1  0.4  Water  III  II  % of total  2  0.8  I  0.4  IV  . % of total  V  % of total  % all fish  2  0,8  174  65.4  77  28.9  95  35.7  34  12.8  55  20.7  89  33.4  1  0.4  1  0.4  152  57a  IV Total  III  % of total  Total  ill  41.7  1  1  0.4  0.4  266  100  Age composition of 770 Chilliwack river"steelhead samples f o r the period  Table VIII.  194-8 to 1953 showing numbers of f i s h i n each age group and the percent of the t o t a l sample each group constitutes.  Years i n  Total  Fresh •%  Of  %  Of  % of total  IV  Water  I  I  1  1.3  II  2  2,6  239  31*0  236  30.6  1  III  1  1.3  136  17.7  133  17.3  3  1  1.3  3^4-  49.9  IV Total  %  Year a in ocean p l u s migration back to r i v e r  total  -  14-  0.5  II  total  III  10.4-  6  3 . 37*5  % of total  V -  1+  fish 15  1.9  1.3  4-78"  62.1  3-9  273  35.-5  . 4-  0.5  3.9 49.1  % of total  • all  0.5  770  100  36  Table IX.  Multiple chi-square analysis of age composition of steelhead from the Chilliwack r i v e r f o r the f i v e years 1943-53, considering only the four major age groups, 2/2,  2/3,  3/2,  and 3 / 3 .  Figures i n brackets  are the observed numbers of f i s h i n each age group.  Age Group  2/2  3/2  2/3  Total  3/3  Year 19113-49  (32)  32.2  (32)  37.7  (19)  21.8  (24)  21,3.  1949-50  "(27)  21.5  (19)  21.3  (13)  12.2  ( 8)  12.0  67  1950-51  (39)  31.5  (29)  31.1  (12)  17.9  (18)  17.5  98  1951-52  (52)  63.9  (55)  63.1  (58)  36.4  (28)  35.6  199  1252-53  (77)  23.2  (95)  82.8  (34)  47.7  (55)  46.7  261  TOTAL . 239  236  136  133  119  744  37  Table X.  Mean lengths and standard deviations of each age group of steelhead adults from the Chilliwack r i v e r f o r the' five year period 1948-53.  Age Group  No. of f i s h  Mean fork length  1/1  1  19.0  -  1/2  8  27.9  2.3  1/3  6  31.9  3.4  2/1  2  18.7-  -  2/2  234  27-5  1.9  2/3  235. *  31.9  2.3  2/4  .1  38.0  3/1  1  18.0  -  3/2  134  27.6  2.3  3/3  126  32.2  2.6  3A  3  33.5  4/3  3  32.7  -  Group Means  754  29*7  3.2  Standards-  deviation  38  Table XI. Mean fork lengths of steelhead spending from 1 to 4 Chilliwack r i v e r catch, 1 9 4 8 - 5 3 .  years i n the sea.  Number of years i n sea  Year  1948-49 131949-50  1950-51  .  1  2  3  4  17.3  -  28.1  31.3  -  27.O  32.0  34.2  -  27.6  32.5  34.3  1951-52  18.0  27.1  31.6  32.0  1952-53  19.5  27.9  32.4  38.0  Mean  18.6  27.6  32.0  34.6  ,  39  Table XII.  Mean fork lengths f o r four major age groups of steelhead.  C h i l l i w a c k r i v e r catch 1948-53.  Years Ocean Years River  2 2  3 3  2  3  Mean Length  27.5  27.6  31.9  32,2  No. F i s h  234  134  235  126  Figure 10.  Standard d e v i a t i o n s and f i v e percent confidence l i m i t s f o r the f o r k lengths of the four major age groups of steelhead from the C h i l l i w a c k r i v e r , 1943-53 catch.  41 FORK LENGTH COMPOSITION OF ADULT POPULATION A l l available specimens with complete information on hand were used to calculate the size composition of the various age groups, as shown i n Table X.  A further treatment of length-  weight relationships by sex and age group i s given l a t e r . Each year of ocean l i f e adds substantially to the fork length of the steelhead i n each age group.  In the four largest  groups represented i t can be seen that the additional year of ocean l i f e has added 4,4 inches to the mean of the 2/3 group as compared to the 2/2 group, while the 3 / 3 group has added 4.6 inches over the mean of the 3/2 group. of  Table XI l i s t s the means  length f o r the groups spending 1, 2, 3 , and 4 years respect-  i v e l y i n the sea. These data emphasize the effect of an extra year of sea l i f e on the size steelhead a t t a i n . are  Arithmetically, the increments  less with each added year, I.e. 9*0 inches, 4.4 inches,  2.6 inches.  However, i f the lengths are cubed to give an i n d i -  cation of the proportionate change i n weight, the increments are respectively i n the r a t i o l4.6 to 11.7 to g.5.  This would sug-  gest that the annual increments of growth_get progressively smaller but not to the degree indicated by the fork lengths alone. Table .XII indicates that length of time spent i n fresh water apparently has l i t t l e Influence on length of the f i s h when they return to fresh water.  The 2/2 and 3/2 groups are much the same  in size, as are the 2/3 and 3 / 3 groups. the  As shown i n f i g . 10,  5 $ confidence l i m i t s imposed on these groups show that the  42 2 year sea groups are a d i f f e r e n t  11  s t a t i s t i c a l population" from  the 3 year sea groups, but that these l i m i t s overlap f o r the freshwater 2 and 3 year groups.  Although the l a t t e r difference  i s small i t shows the trend that the 3 year o l d smolts come back as s l i g h t l y larger individuals than the 2 year o l d smolts. These length relationships of smolts to.adults are discussed later.  COMPARISON OF LENGTH, WEIGHT AND AGE, AND DATE OF CAPTURE OF MALE AND FEMALE STEELHEAD The main movement of adult steelhead into the Chilliwack r i v e r occurs during the four months from December to March. The sample taken during these months f o r the four years from 1948-1949 to 1951-1952 was divided into i t s male and female components, and further sub&ivided into the various, age groups. The mean weight and length was then calculated f o r each group, and the mean age calculated f o r each month's catch.  The object  of t h i s phase of the study was to determine i f any changes occurred during the course of the run i n age composition, length and weight.  Larkin (1950) found that f o r one year's sample,  the 1946-194-9 sample presented here, the largest and oldest f i s h entered the r i v e r f i r s t , and that as the season progressed that the mean age and size declined (Table XIII).  Tables XIV, XV,  and XVI show that t h i s trend was not.found i n any of the three other years examined.  For example, i n 1949-1950 the smallest  43 f i s h o f the r u n o c c u r r e d i n December, w h i l e the l a r g e s t came i n January.  I t can be seen by c o n s u l t i n g the t a b l e s t h a t t h e r e i s  no p a r t i c u l a r p a t t e r n of age o r s i z e o f f i s h caught over the l e n g t h o f the season,  A c h i - s q u a r e t e s t f o r the f o u r major age  groups c o n f i r m e d t h a t t h e r e i s no s i g n i f i c a n t d i f f e r e n c e i n the age c o m p o s i t i o n o f the c a t c h by months when t h e d a t a f o r the f o u r y e a r s a r e lumped. The s e x u a l c o m p o s i t i o n o f the r u n s s t u d i e d a l s o f o l l o w e d no apparent p a t t e r n w i t h r e f e r e n c e t o time o f e n t r y i n t o the catch.  Table XVII shows the p e r c e n t c o m p o s i t i o n o f the r u n o f  males and f e m a l e s f o r the f o u r y e a r s 1942-52 d u r i n g the f o u r months under s t u d y .  While" the t o t a l sex r a t i o ? ) o f males t o  females i s a p p r o x i m a t e l y 2 t o 3 f o r the f o u r y e a r t o t a l ,  the  r a t i o changes from month t o month and from y e a r t o y e a r w i t h no apparent p a t t e r n . i n March, 1950, 1951.  The l o w e s t percentage of males, 27.3» o c c u r r e d  w h i l e the h i g h e s t was  66.6  percent i n February,  Of the s i x t e e n groups c o n s i d e r e d h e r e , i n o n l y 3 were the  males more numerous than the f e m a l e s , i n one t h e y were o f e q u a l numbers, w h i l e i n the r e s t the females predominated.  These v a r i -  a t i o n s would be a n t i c i p a t e d i n random sampling from a p a r e n t p o p u l a t i o n " w i t h a sex r a t i o o f 2 t o 3 and do not suggest  any  heterogeneity. The  sex c o m p o s i t i o n of the c a t c h by age groups i s shown  i n Table X V I I I .  Here a g a i n t h e r e was no apparent p a t t e r n except  t h a t of the approximate age groups,  (2/2,  2/3,  r a t i o of 2 to 3. 3/2  Only the f o u r major  and 3/3'), were c o n s i d e r e d s i n c e t h e  Table X I I I .  Mean l e n g t h and mean weight o f male and female s t e e l h e a d i n each age group i n the C h i l l i w a c k r i v e r c a t c h from December t o March o f 194-8-4-9 ( a f t e r L a r k i n , 1950) FEMALE  MALE Month December  TOTAL January  TOTAL February  TOTAL March TOTAL  Age Group • No.  2/2 2/3 3/2 ft  2/2  2/3  3/2 3/3  1/2 2/1 2/2 2/3 3/2 3/3 1/2 2/2 2/3  YEARLY TOTAL  2 2 I 1 b  Mean Length  29.5 33-7 30.0 3^.5  4 4 1 2 11  31.8 . 28.1 33-1 27.0 36.0 31.5  1  17.3  12 5 7 2  27  28.2 31.5 29.7 34.0 29.2  2 2 46  27.0 27.0 30.0  Mean Weight  ill*  8.3 17.5  No.  1 4 2 6 1  12.2 , 14 8.6 4 12 14.2 2 8.0 4 18.1 12.3 22 "1 2.1 1 8.0 13 12.1 9.4 8 6 14.5 9.i 389 1 1 1 10.0 10.0 ' ? 10.5 77  TOTAL  Mean Length  Mean Weight  No.  28.3 32.0 28.0 31.4 34.0 31.1 27.1 3O.3 27.4 33.0 29.9 31.0  3.5 12.1 7.8  1  30,5 27.6 26*8 29.4 28.8 28.0 27.0 30.0 28.3 29.5  11.8 1U5' 17.5 ' 7.8 10.7  13.6 10.4 1.0-3  '.  12.5 8.1 10.8 7.5 12.3 9.7 9.0 7.7 9.0 8.6 10.2  3 7 1 20 8 16  I  35 1 1 1 25 13 13 11 65 1 1  3  15 123  Mean Length  29.1 32.6 28.7 31.3 34.0 27.6 31.0 27.2 34.3 30.4 31.0 17.3 30,5 27.9 31.1 28.4 30.3 29.0 28.0 27.0 28.0 27.8 29.7  Mean Weight  8.9 12.9 7.9 12.6 17.5 11.7 8.2 11.5 7,7 15.1 11.0 10.3 2.1 12.5 8.0 11.3 8.5 12.7 9.6 9.0 7.7 9.7 ?•! 10.3  Mean Age  5.30  4.94  4.71 4.40 4.85  .  Table XIV. Mean length and weight of male and female steelhead i n each age group in the Chilliwack r i v e r catch from December to March of 1949-•50.  Month December  Total January  Total February  Age 3-roup  1/2 1/3 2/2 2/3 3/2 3/3  1 — 11 5 1 2 20  25.0  5.7  26.5 33.* 28.2  "7,1 15.4 8.2  28.9  9-9  2/2 2/3 3/2 3/3  1 1 1 — 3  29.5  36.0 30.4 — 32.0  14.5  2/2 2/3 3/2  l  -  26.0  6.3  l  25.0  ~6.5 6.4  Total March  Total  No.  MALE Mean Mean Length We ight  1/2 1/3 2/2 2/3 3/2 3/4  YEARLY TOTAL  2  28.5  7-5  10.3  10.8  - ,  25.5  1  33.8  17.3  — 2  — 31.3  -  3  32.1  28  29.3  _  '  11.0 — 13.1  10.1  No.  1 7 4 3 2 17  14.3  •  TOTAL  FEMALE Mean Length  30.2 26.4 32.1 25.7  Mean Weight  9,0 7,0 11.9 7.1 12.8 9.0  Mean No. Length  25.0 30,2  1 1 18  26.4  Mean Weight  5.7 9,0 7.1  ? 4 4 37  32.8 26.3  _  1  3 1 1 5  31.9 26.0 29.5 30.2  12.1  4  29.5 32,9  7,5 12.7  1 2 1 4  27.0 30.0 25.0 3^.5  1 — 3 3 — 1 8 34  31.0  25.6 28.7  -  26; 2 29.2 —-  9,0 10.0 11.1  3.3.4.,, 28.£  2  28.2  Mean Age  7.4 .1^5 _ , 9.5 ,  9.7  1 8  29.5  . 3Q..S,,.  10.0 11.0  5.00  7.5 10.3 6,5 8.6  2 2 2 6  26.5 30.0 25.0 27.2  6.9 10.3 6.5 7.9  4,67  15.3  1 1  31.0 33-8 26.2 29.2 31.3  ^ 5 29.£  15.3 17.3 7.4 10.3 11.0 10.2 10.8  4.64  29.1  9.7  -  7.4 10'. 3 -  34.3 28.9  10.8 9.9  28.9  9.5  3 3 2  1 11  62  L  4.63 •  Table XV.  Mean length and weight of male and female steelhead i n each .age group i n the Chilliwack r i v e r catch from December to March of 1950-51. FEMALE  MALE Month December Total January-  Total February Total March  Total  Age Group  No.  2/2 2/3 3/3  -  1/2 l/3 2/2 2/3 3/2 3/3  3 2 16 7 3 4 1 1  1 1  Mean Length  —  Mean Weight  -  26.8 36.1+ 3^,3  ?,3 16.8  5 7  3^ A  14.7  3 1  27.9 3o.O  8.6 16.0  4  30.0  10.5  .2/2 2/3 3/2  3 1 2'  3/3  29.5 31.0 30.g  6  — 30.2  10.5 15.0 9.3  48  3O.5  10.8 11.2  YEARLY TOTAL  11.2  —  —  Mean Length  Mean Weight  27.0 3P.0  7.0 10.3  28.5 25.8  3.9 7.3  —  10-  ?7  -  —  7,8 15.0 3.3  15.5  34.0  —  1  15.5  30 ..b  2/2 2/3 3/2  1  33.3 33.? 27.6 33,0 27.9  15.5 16.5  4/3  No.  2 1  14 — —  TOTAL  —  27.5 31.9 25,9 30.8  — —  37  29.5  1 1 2  31,5 26.5 28.0  2 1 1 1 5  46  -  -8.1  12.2 7.5 12.9  — —  10.4  Mean No. Length 1 1 i  3  4 2 26 21  8  11 1 1  27.0 30.0 33.3 30.1 27.2 33.0 27.8  32,8  26.3 32.3 3^.3  34.0  74  30.0  3  11.1 7.0 9.1  2 l 6  27.9 33,3 26.5 29.6  27,9 30.0 30.5 35.0 30.3  14.5 10.6 17.5 11.6  5 2 •z 1 11  28.9 30.5 30.7 35.0 30.0  29.5  10.4  94  30.0  Mean Weight  Mean Age  7,o  10.8 15.5 11.1 7.7 15.0 8.2 13.0  4.66  7.8 14.3 15,5 16.5 10.8 8,6 13.6 7.0 10.0 9.4  4.72  4.50  HI  1 tmt  14.8  9.7 17.5 10.8 10.8  4.64 4.69  wm  Table XVI. Mean length and weight of male and female steelhead In each age group i n the Chilliwack r i v e r catch from December to March of 1951-52. MALE Month December  Total January  Total February  Total March  Age Group 2/2 2/3 3/2 3/4 2/2 2/3 3/2 3/3 2/2 2/3 3/2 3/3 3/1 2/2 2/3 3/2  Total YEARLY TOTAL  FEMALE  No.  Mean Length  Mean Weight  7 3 l 3  27.1 32.9 28.8 33.5  7,7 12.8 8.9 13.3  l4  29.9  10.1  -  —  -  12 11 17 4 44  27.4 34.3 28.3 32.3 2?.?  8.1 13.8 8,3 12.2 10.0  2  26.0  6,3  4 1 1 8 4 2 1 1 8 74  27.8 33.5 18.0 26.9 27.6 33.0 28.0 31.0 29.4 29.5  9,2 13,5 3.5 8.3 6.8 12.3 8.5 14.5 9.3  —  —  9-7  No.  Mean Length  5 10  27,1 30.2 28.^  TOTAL  Mean':.. Weight  32.0 29.2  8.2 10.9 8.3 11.1 11.0 9.6  14 23 10 6 53 8 2 ,4 3  27,6 30.8 26.2 31.0 29.1  7.5 10.8 7.0 12.5 9.4  26.6 32,5 26.9 30.0  6.7 12,5 6.5 11.0  17 .  27.9  8.1 7.8 11.0 6.5 12.6' 8.8 9.2  ?  4 1 29  3 2 7 4 16 115  30.4  —  27,5 30.5 26.1 32.5 28.5 28.9  —  Mean No. Length 12 13 10 7 1 43 26 34 27 10  91 10 2 8 4 1 2^ 7 4 8 5 24 189  Mean Weight  Mean Age  27.1 30.8 28.5 21,7 32.0 29.4  7.9 11.3 8.4 12.0 11.0 9.8  4.93  27.5 31.9 27.5 31.5 29.5  7.8 11.8 7.8 12.4 9.7  4.84  6.$' 12.5 7.8 11.6 ' 3.5 8.2 27.6 7.2 31.8 • 11.6 26.4 6.7 32.2 13.0 28.8 9.0 29.1 [ — 9 . 4 26.5 32,5 27,4 30.9 18.0 27.6  4.72  4.92 4.85  Table XVII.  Percentage of male and female steelhead f o r each of the months from December to March i n the Chilliwack r i v e r catch i n the years 1948-52.  Year  1948-1949  December  M 30.0  F 70.0  M 54.1  F 45.9  M 33.3  F 66.7  M 32.6  F 67.4.  Combined Years M F 39-8 60.2  January  33.3  66.7  37.5  62.5  50.0  50.0  45.4  54.6  44.8  55.2  February  41.5  58.5  33.3  66.7  66.6  33.^  32.0  68.0  40.2  59.8  March  4o.o  60.0  27.3  72.7  54.5  45.5  33.3  66.7  37.3  62.7  37.4  62.6  45.2  54.8  51.1  48.9  39.2  60.8  41.9  58.1  Mean  1949-1950  1950- -1951  1951- -1952  Table XVIII.  Percentage of male and female steelhead In four age groups of the Chilliwack r i v e r catch f o r the period 1948-52,  Year Age Group  1948-1949  M  F  1949-1950  M  F  1950- -1951  M  F  1951-1952  M  Combined Years  F'  M  F  2/2  48.6  51.4  54.2  45.8  62.9  37.1  45.5  54.5  51.7  48.3  2/3  34.2  65.8  33.3  66.7  34.6  65.4  30.2  69.8  32.6  67.4  3/2  47.4  52.6  50.0  50.0  41.7  58.3  43.4  56.6  44.7  55.3  3/3  20.8  79.2  4o.o  60.0  38.5  61.5  34.6  65.4  30.9  69.I  Yearly Mean  38.1  61.9  45.6  54.4  47.7  52.3  39.0  61.0  41.3  58.7  50 small number of the other age groups when divided into male and female groups became too small to be of value.  No tendency was  discovered for any one age group to exhibit consistently a d i f ferent eex r a t i o from the others. Because of the lack of accurate weight data no attempt was made to show s t a t i s t i c a l comparisons for the weight of male and female steelhead.  Since length measurements submitted  by  anglers were considered to be accurate to the nearest inch, lengths i n the 1942U49 data were converted to the nearest inch, and an analysis of. variance made of male and female lengths. There was no s i g n i f i c a n t difference i n the mean fork length of male and female steelhead. In summary, the samples taken over a four year period indicated that there was no difference i n the age and length of steelhead taken i n the months from December to January; that an approximate sex r a t i o of male to female steelhead of 2 to 3 existed over the four year period and t h i s proportion held during the course of the run from December to March, and held roughly f o r each age group. male length and weight was  While i n nearly a l l cases the mean s l i g h t l y higher than that of the  females, no s t a t i s t i c a l differences could be demonstrated.  51  AGE AND SIZE AT MIGRATION The age and size at smolt migration were calculated as explained i n Part I. The results of these calculations using a l l available 770 specimens f o r the f i v e year period are given i n Table XIX. It should be noted that t h i s table compares features of smolts which returned as adults i n the years i n d i cated, and does not consider features of the smolt run i n any one year.  F i g . 11 has been prepared to f a c i l i t a t e  comparison  of the age and length at smolt migration over the f i v e year' period. Two and three year old migrants made up 97»5$ of the run i n the approximate  r a t i o of 2 to 1 respectively.  An analy-  s i s of chi-square was made to examine the age composition of the smolts over a f i v e year period.  Considering 1, 2 , 3 » and ;  4 year old f i s h for the f i v e year period there was a s i g n i f i cant difference i n the age composition from year to year, ( (P/.01).  I t was ascertained that t h i s difference arose from  wide fluctuations i n the small numbers of one year old f i s h from year to year.  Considering the 2 and 3 year smolts only,  for the f i v e year period, less v a r i a t i o n was found, with no s i g n i f i c a n t difference from year to year, (P = These results obtain to comparisons  .10-.20).  from samples of  the adult run f o r the years studied, and this might not give a £rue.picture of the year classes of smolts.  The data were  rearranged i n order to group the smolts into the years i n  52  AGE  3  AM  4  1952 - 1953  194 9-1950  1 , . J M ^ ^ *  FORK  to  LENGTH  (CM.)  F i g . 11. Age and l e n g t h a t smolt m i g r a t i o n f o r f i v e y e a r s (l9"4-g-53) i n the C h i l l i w a c k r i v e r . Numbers o f f i s h r e f e r t o a d u l t samples f o r each year from which the smolt h i s t o r y was d e r i v e d .  53 which they migrated to sea rather than the years i n which they returned as adults.  Since h a l f of the 2 year old smolts return  after 2 years in the sea, and half a f t e r 3 years, (see Table VHI) with the same applying to the 3 year smolts, i t was deemed permissible to make an analysis by chi-square of the rearranged data.  Because of the many age combinations  involved in s t e e l -  head runs, rearranging.of data as suggested above tends to be somewhat confusing.  Table XX shows when various events occurred  in the l i f e history of steelhead in various years and age Thus, r e f e r r i n g to Table XX, a f i s h of age group 2/2 1950,  came from an egg from the spawning run of 1946,  i t s f i r s t year of r i v e r l i f e i n 1947,  caught i n completed  migrated as a smolt i n  I94g, completed one year in the sea i n 1949, fresh water i n 1950.  groups.  For ease of comparison,  and returned to a l l events l i s t e d  are assumed to take place in March of each year.  The four most  common age groups, comprising 96.4 percent of the run, are considered. Table XXI gives the data rearranged as indicated i n Table XX.  For example the 2's from the 1948-49 adult run (2/2),  and the 2's from the 1949-50 run (2/3) are added together to make 57 smolts for the 1947  smolt migration.  The analysis of  chi-square of these groups showed that there was no s i g n i f i c a n t v a r i a t i o n i n age composition regarding 2 and 3 year old smolts for the years i n question. In view of the tests conducted above, i t may  be stated  that the age composition of the migrant run f o r a f i v e year  54 Table XIX.  Age and size at migration of steelhead smolts which returned as adults i n the years 194g-53» to the Chilliwack r i v e r .  Age at smolt migration  Year of adult capture  Age I No. % of of yearly fish total  Age I I I  Age II average No. % of fork of yearly length f i s h t o t a l cms.  average No. % of fork of yearly length f i s h t o t a l cms.  Total No. of fish  Age IV average No. % of fork of yearly length f i s h t o t a l cms.  average fork length cms.  Average fork length centimetres  1948-49  3  2.4  11.07  77  62.1  15.95  43  34.7  19.28  1  0.8  21.1  124  17.03  1949-50  4  5-5  10.0  46  63.O  15.74  22  30.1  20.81  1  1.4  24.8  73  17.08  1950-51  6  5.7  12.31  68  64.2  16.31  31  29.2  19.33  1  0.9  22.4  106  17.03  1951-52  0  0  0  113  56.2  17.04  88  43.8  19.80  0  0  201  18.25  1952-53  2  0.8  9.85  174  65.4  16.63  89  33.5  20.42  1  0.3  266  17.95  Total No. of f i s h Percent of total Average fork length centimetres  478  15  11.13  35.4 16.49  23.2  4  273 62.1  2.0  0  770 0.5  19.95  22.87  17.62  55 Table XX.  Events i n the l i f e history of four age groups of steelhead from the Chilliwack r i v e r , and the year of occurrence.  A l l events assumed to occur i n March.  Year of adult capture i n r i v e r 1950  19^9 Age groups L i f e history event Came from spawning run of Completed f i r s t year of r i v e r l i f e i n Completed second year of r i v e r l i f e i n Completed t h i r d year of r i v e r l i f e i n  2/2 3/2 2/3  3/3  2/2 3/2 2/3  3/3  2/2 3/2 2/3  4.5  kk  kk  43  46  45  45  44  4.7  46  46  45  45  44  47  46  46  45  kg  47* 46  46*  45  kg* 4.7  47*  46  46*  47*  48*  1952  1951  1953 i  3/3  2/2 3/2 2/3  3/3  2/2 3/2 2/3  3/3  46  45  4g  47  4.7  46  49  4.8  48  47  47  47  46  49  4.8  48  47  50  49  49  48  4 9 * 48  48*  47  50* 49  49*  47*  4.8*  4 9 * 48  50*  51* 50  50* 49  51*  49*  50*  Ocean l i f e year 1  48  48  47  47  49  49  48  48  50  50  49  49  51  51  50  50  52  52  51  51  Ocean l i f e year 2  49  49  43  48  50  50  49  49  51  51  50  50  52  52  51  51  53  53  52  52  49  49  50  50  51  51  52  52  53  53  Ocean l i f e year 3 * Migrated as smolt*  56 period i n the Chilliwack r i v e r has been remarkably constant. It should be noted that the numbers of f i s h i n Table XXI come from d i f f e r e n t  sample sizes, so that variation  i n actual  numbers of 2's and 3*s of any one year i s not tested.  The  r e l a t i v e composition only i s considered here. Lengths of migrants from year to year, grouped according to year of capture as adults, were compared by analysis of variance.  A s i g n i f i c a n t difference at the one per cent proba-  b i l l t y l e v e l was found between the lengths of the two and three year old migrants i n a l l years, (about 3 . 5 cms.). the 1951-52 and 1952-53 runs came from migrants larger (P <- 0 . 0 5 ) (about 1  Adults from  significantly  than those of the preceding three years,  cm.)• For the f i v e year average, one year old smolts migrate  at a mean length of 11,13 3 year olds at 19.95  cms.,  cms.,  2 year olds at 16.4-9  cms.,  and 4- year olds at 22.87 cms.  mean size at migration for the five years of a l l migrants 17.62  cms.  The was  (Table XXIV).  In summary, the age composition f o r the two major smolt groups i s constant within narrow l i m i t s from year to year, although the one year old smolts vary somewhat i n abundance.  The length composition i s also reasonably uniform  although smolts from the l a s t two years (194-9-50) are s l i g h t l y larger (about 1 cm.)  than smolts from the preceding years.  This may be due to t'he varying contribution of " f a l l migrants". (Compare Tables XXII and XXIV).  57  Table XXI.  Numbers of steelhead from various years of the adult run grouped f o r year of migration as smolts.  Chilliwack r i v e r catch 1948-53.  Age at migration  Year of migration as smolt  II  III  Total  1947  57  27  84  1948  56  31  87  1949  94  40  134  1950  153  113  266  Total  360  211  571  58 TIME OF SMOLT MIGRATION As i n d i c a t e d i n Part I , the winter check i s formed on , scales of young steelhead i n the Vedder r i v e r i n March and April.  '  /•  Examination of adult scales revealed that r a p i d sea  growth started immediately a f t e r the winter check was formed, or w i t h scarcely noticeable growth afterwards.  Since the  p e r i o d of r a p i d growth begins a f t e r the winter check i s comp l e t e d , i t f o l l o w s that migration to sea occurs s h o r t l y a f t e r the check was formed.  Even the stay of a month would add  noticeable growth to the s c a l e s .  The time of migration of  Vedder r i v e r smolts based on t h i s i n t e r p r e t a t i o n of scales must therefore occur i n A p r i l or e a r l y May. Of the 754 scales examined, kk were found to have a d d i t i o n a l growth past the winter check before migration took p l a c e . E x t r a growth i n these cases was remarkably uniform from f i s h to fish.  By comparing these scales with scales from young f i s h  taken i n September i t was judged that migration had taken place about August. The f i s h were examined as to d i s t r i b u t i o n i n the various age groups and year of migration.  Twenty s i x (59.1 percent) came  from the 2/2 age group, and Ik (31.8 percent) from the 2/3 age group.  These age groups ( i . e . two years i n f r e s h water)  normally make up about 60% of the run, while the combined p e r centages above are 90.9$.  There i s a higher percentage of these  groups represented than might be expected. Twenty one of these  7  59  Table XXII.  Percent of run made up of late migrants from 1942-53, Chilliwack r i v e r .  Year  No. of  No. of  fish in  late  sample  migrants  % of sample  19 kg J4.9  124  3  2.4  1949-50  65  0  0.0  1950-51  103  4  3.9  1951-52  192  20  10.1  1952-53  264  17  6.4  6o f i s h were males, and 23 females.  The percentage of the run  formed by these f i s h (Table XXII) was s i g n i f i c a n t l y d i f f e r e n t from year to year. The lengths of late migrants were examined, and the increment of growth from the winter check to actual migration determined.  These results are given i n Table XXIII.  Mean  length at age 2 was smaller than mean length of the migrants which went to sea i n the spring.  The mean fork length at  migration f o r 2 year old smolts i s 16.49 cms. while the late migrants have a mean length of 14.46  cms. at age 2.  The mean  of these f i s h at migration l a t e r i n the summer i s IS.53 cms., an increment of 4.07 cms. This i s less than the mean length of three year o l d spring migrants, 19.95 cms. RELATION BETWEEN GROWTH IN FRESH WATER AND SIZE AT CAPTURE AS ADULT The r e l a t i o n between fresh water growth and salt water growth was determined i n several ways.  The length at migration  was compared to ( l ) the length at capture f o r each of the four major age groups f o r each year, (2) the length at the f i r s t s a l t water annulus, and (3) the increment of growth from smolt migration to salt annulus I. Table XIV shows the mean length at smolt migration compared to the mean length at capture.  Only f i s h which were  spawning f o r the f i r s t time were used i n this part of the work, since spawning may retard growth of the f i s h , and t h i s would  61  Table XXIII.  Mean length at age 2, and at migration, f o r late migrants of the 2/2 and 2/3 age groups, Chilliwack r i v e r 1943-53.  Year  Number  Mean fork  Mean fork  Increment  of  length at  length at  i n fork  fleh  age 2  migration  length  cms.  cms.  cms.  1948-49  3  16.7  19.80  3.10  1950-51*  3  16.17  19.77  3.60  1951-52  19  14.11  18.24  4.13  1952-53  15  14.12  18.41  4.29  Total  40  14.46  18.53  4.07  * No late migrant specimens i n 1949-50.  62  Table XXIV.  Mean length at smolt migration and at capture for four age groups of steelhead over the f i v e year period 1948-53, Chilliwack r i v e r .  Age Group Year  3/3  2/2 Smolt  Adult  Smolt  3/3  Adult  Smolt  Adult  Smolt  Adult  of  length length length length length length length length  capture  (ins.) (ins.) (ins.) (ins.) (ins.) (ins.) (ins.) (ins.)  1948-  11,0.  6.48  27.9  6.04  31.0  7.47  28.2  7.68  31.7  1949- 50  6.37  26.5  6.00  31.9  8.46  27.8  7.72  32.3  1950- 51  6.91  27.8  6.03  32.3  7.42  27.4  7.80  32.6  1951- 52  7.06  27.0  6.35  31.7  7.97 .  27.2  7.42  31.5  1952- 53  6.67  27.8  6.45  32.3  28.0  8.11  32.6  I 7.92  63 tend to obscure the analysis. A regression of smolt length on adult length at was made for each of the age groups and years above. cant c o r r e l a t i o n between the two was  No  capture signifi-  found in any of the 20  analyses. Smolt length at migration and adult length at for the 1949-50 sample were converted  capture  to logarithms, and a  regression of smolt length on adult length was made.  The 1949-50  data were chosen because they represented an entire year's sample, were representative, and were small enough i n numbers to e a s i l y perform many s t a t i s t i c a l t e s t s .  Here again no good c o r r e l a t i o n  between smolt and adult length was s i g n i f i c a n t regression was  found. (Probability of  .30).  ^  Since extra v a r i a t i o n might occur due to  Inaccurate  measurement of adults, and varying scale sizes, a regression  was  made of diameter of scale at smolt migration, on the increment of growth from migration to ocean annulus I. verted to logarithms as before.  The data were con-  The Increment was obtained  by  measuring the diameter of the scale at ocean annulus I and subt r a c t i n g from i t the diameter at smolt migration.  The  n  t " value  obtained from the regression c o e f f i c i e n t was  such that l i t t l e  l i k e l i h o o d of a correlation seemed possible.  The p r o b a b i l i t y  l e v e l indicated a random d i s t r i b u t i o n of sea growth increments with smolt lengths.  It would appear that the length attained  by the smolt at migration has l i t t l e effect on subsequent growth i n the sea, i n the f i r s t  year of sea l i f e at l e a s t .  6*4It Is apparent however, that the smolt length for the 2/2 group Is higher i n each case than the smolt length of the 2/3 group.  An analysis of variance, considering the f i v e years  together, Indicated that 2/2 smolts and the 2/3 smolts were s i g n i f i c a n t l y d i f f e r e n t i n length at migration.  The 194-9-50,  and 1952-53 groups showed no s i g n i f i c a n t difference, at the 5$ probability  l e v e l , 194-8-4-9 was  5% l e v e l , 1950-51 at 1%, There was  s i g n i f i c a n t l y d i f f e r e n t at the  1951-52 at between 1% and 5 $ .  s i g n i f i c a n t difference between the 3/2  age  group smolt length, and the 3/3 age group smolt lengths. From the above i t would appear that the larger two year old smolts tend to return to the r i v e r as adults a f t e r  two  years i n the ocean, while the smaller two year old smolts tend to remain at sea for three years.  The size of the three year  old smolts apparently does not influence the time of return to the same extent. SPAWNING- FREQUENCY Of the 754 steelhead samples suitable for examination, 4-4- f i s h had spawned previously, 5.8 percent of the t o t a l .  Of  these, 2 f i s h had spavined twice before, making 4 . 6 percent of the run of previous second spawners.  Table XXV  shows the d i s -  t r i b u t i o n of the previous spawners by year and by age group. The highest returns of second spawners were from the age group which had spawned i n their second year of ocean l i f e and were captured as mature f i s h returning to fresh water again, t h i s  65 time i n t h e i r t h i r d year of ocean l i f e . 10.17  These f i s h made up  percent of the 2/3 age group, and 11.28" percent of the  3/3 age group. Indicated above.  Only two second spawners had spawned other than One had spent only a short time i n the ocean  before returning to the r i v e r .  The others had spent two f u l l  years i n the ocean before returning i n the t h i r d year of ocean life.  The f i s h which had spawned twice previously were of the  3/2 sp. 3 sp. 4 age group, having spawned a t ages 5 and 6. Of the 44 previous spawners, 5 were males and 39 were females.  One male occurred i n the 194g>-49 sample, one i n the  1949-50 sample, and three i n the 1950-51 sample.  The two  largest samples of second spawners, 11 and 13 f i s h from the1951-52 and 1952-53 runs respectively, were a l l females. SIZE COMPOSITION OF SECOND SPAWNERS The "veteran" spawners were compared with respect to mean weight and length to the age groups of "maiden" f i s h to which they were comparable. t h i s analysis.  Table XXVI l i s t s the r e s u l t s of  Fish which had spawned previously were, with  one exception, shorter and l i g h t e r than other f i s h i n the same run  and age group.  Table XXV.  Numbers of "veteran" spawners In age group i n which they occurred from 1948-53, Chilliwack r i v e r .  Year of Capture  Age Group 1948-49  1949-50  1950-51  Total  1951-52  -  -  -  2/2  -  2/3  7  1  3/3  2  1/3  3A Total number for year Total number of a l l f i s h i n sample Percent second spawners for year  1952-53  Percent total spawners  1  1  1  -  2.3  1  2.3  5  5  6  24  54.5  -  1  2  4  6  34.1  1  1  1  -  15 3  6.8  9  3  8  11  13  44  124  65  103  198  264  754  7.62  4.62  7.77  5.56  4.92  5.84  100  67  Table XXVI.  Mean length and weight of f i s h i n spawning run f o r second and t h i r d time, Chilliwack r i v e r ,  Veteran Fish Age  Number  Group  of fish  Mean Length ins.  Mean Weight pds.  1948-53.  Maiden Fish 4 year average Mean Mean Length Weight  1/3  1  30.7  11.3  32.1  13.8"  2/1  1  26.0  6.0  26.0  6.0  3A  3  33.5  12.4  33.5  12.4  3/3  14  30.7  n.3  32.1  13.1  2/3  25  30.7  10.6  31.7  12.0  68  SUMMARY AND DISCUSSION  The work i n Part I was i n i t i a t e d l a r g e l y because of differences i n Interpretation of the scales of steelhead made by experienced workers.  No completely objective method of age  determination of f i s h from t h e i r scales has as yet been described.  The wide range of scale patterns presented by one  species of f i s h from one l o c a l i t y , r e f l e c t i n g varying growth periods i n d i f f e r i n g environments, makes i t almost mandatory that a certain amount of subjective Interpretation be made based on a knowledge of these growth periods and  environments.  Before the work i n Part I had been started, steelhead scale samples f o r the f i r s t two years covered by the study had been read.  Following the completion of the work i n Part I these  scales were again read, r e s u l t i n g i n a considerable change i n the o r i g i n a l l y noted age composition. old  The number of three year  smolts was found to be greater than o r i g i n a l l y indicated,  t h i s discrepancy r e s u l t i n g from a misinterpretation of the f i r s t year of l i f e of the f i s h .  Yearling f i s h taken i n March  often showed a winter annulus enclosing as few as four or f i v e clrculi.  In the o r i g i n a l scale reading t h i s annulus had been  Interpreted as a summer check i n growth, r e s u l t i n g i n an incorrect age determination. The 1948-49 data presented here are  taken from the same scales on which Larkin (1950) based h i s  work.  In his paper the three year o l d smolts were described as  69 making up about 20.0$ o f t h e r u n , w h i l e a r e r e a d i n g i n c r e a s e d t h i s p e r c e n t a g e t o 35»5$» As a r e s u l t o f t h i s study i t i s c o n s i d e r e d t h a t t h e proper I n t e r p r e t a t i o n of scales f o r l i f e h i s t o r y Information s h o u l d be based on a knowledge o f t h e s c a l e p a t t e r n s o f f i s h o f many age groups o f f i s h sampled a t f r e q u e n t i n t e r v a l s the y e a r .  throughout  I t i s l i k e l y t h a t t h e same c a u t i o n s h o u l d be used i n  any attempt t o use t h e s c a l e diameter-body  l e n g t h growth c u r v e  p r e s e n t e d here f o r t h e d e t e r m i n a t i o n o f body l e n g t h s from s c a l e measurements f o r any body o f water o t h e r t h a n t h e C h i l l i w a c k r i v e r , o r any f i s h o t h e r t h a n s t e e l h e a d . I t w i l l be apparent from P a r t I I t h a t t h e l i f e of  history  t h e s t e e l h e a d i s so complex as t o d e f y Blmple u n q u a l i f i e d  statements as t o i t s major e v e n t s .  A brief recapitulation of  the l i f e h i s t o r y o f t h i s f i s h i s p r e s e n t e d here however t o c l a r i f y t h e d e t a i l e d d e s c r i p t i o n made above. In  the C h i l l i w a c k r i v e r adult steelhead begin to  a r r i v e from t h e ocean i n numbers i n mid-December.  The r u n  r e a c h e s a peak i n J a n u a r y , then s l o w l y d i m i n i s h e s i n s i z e the r u n may be s a i d t o be over i n March.  until  Most o f the f i s h a r e  from f o u r t o s i x y e a r s o f age, h a v i n g spent a l m o s t two o r almost t h r e e y e a r s i n s a l t water. are  S i x t y p e r c e n t o f these  fish  f e m a l e s , from 28 t o 32 i n c h e s i n l e n g t h . Spawning a c t i v i t y as n o t e d from o b s e r v a t i o n s on t h e  r i v e r o c c u r s from l a t e F e b r u a r y t o e a r l y A p r i l .  The young  70 steelhead are seen as f r y i n the shallow waters of the r i v e r during the late summer and early f a l l .  The following March as  one year old f i s h they are about 11 cms. i n length.  They grow  rapidly from A p r i l u n t i l September, then exhibit l i t t l e addit i o n a l growth u n t i l the following A p r i l .  By March they have  attained lengths of about l 6 cms. at the end of t h e i r second year.  I f they stay i n fresh water another summer they reach a  length of about 20 cms. at age I I I . The majority of steelhead smolts migrate to sea i n A p r i l or early May at the end of their second or t h i r d year. A few of the f i s h i n t h e i r t h i r d year migrate at l a t e r periods during the summer. Salt water growth i s rapid i n comparison to fresh water growth, the f i s h a t t a i n i n g lengths of approximately 19 inches, 28 Inches and 32 inches a f t e r one, two and three years of  s a l t water l i f e respectively.  Length of time spent i n fresh  water as young f i s h has l i t t l e influence on the size of the f i s h on return to fresh water, although a s l i g h t trend was noted f o r three year o l d smolts to come back s l i g h t l y larger than two year o l d smolts.  Smolt size has a bearing on the time of adult  migration, since the larger two year old smolts tend to return a f t e r two years of ocean l i f e , while the smaller two year smolts tend to return a f t e r three years. L i t t l e i s known of the l i f e history of steelhead i n salt water.  I t i s evident from the scales that the f i s h does  not experience retarded growth during the winter months to the  71 same extent that i t occurs i n fresh water.  The scale pattern  indicates that a slowing of growth occurs i n s a l t water a t the same time that i t occurs i n the r i v e r .  Probably because of the  greater abundance of food i n salt water, and the more stable environment,  the rate of growth i s not reduced to the same extent.  Over half of the scales exhibited a s l i g h t check i n growth at a time Judged to be late summer i n t h e i r f i r s t year of ocean l i f e . It has been suggested that t h i s might represent a b r i e f return to  the r i v e r estuaries, but there i s no evidence on hand to sub-  stantiate t h i s b e l i e f . After t h e i r period of ocean l i f e the f i s h return to the r i v e r s i n the spawning run.  Most have spent from two to  three years i n the ocean, and most are i n the run f o r the f i r s t time, only 6% being veteran spawners. For the f i v e year period studied, the age composition of  the adult run was s t r i k i n g l y similar from year to year.  Nearly a l l possible age combinations of fresh and s a l t water l i f e occurred.  The four age groups that make up 9 6 . 6 $ of the  run are the two and three year old smolts that return a f t e r two or  three years i n the ocean.  I t was intended o r i g i n a l l y to use  the data f o r only four years i n t h i s t h e s i s .  When the remarkable  s i m i l a r i t y of the percentage composition of the major age groups from year to year became evident, the 1952-53 sample was added to determine whether or not the same age group composition prev a i l e d here.  This substantially larger sample was found to be  of e s s e n t i a l l y the same age composition as the preceedlng four  72 years. A r e l a t i v e l y constant age composition from year to year would Indicate that the number of smolts leaving the r i v e r for the period that would affect the adult runs under study must also have been constant.  I f the r i v e r had produced an .  unusually large number of two year o l d smolts i n 1948, a larger 2/2 adult age group should have resulted i n 1950, 2/3 age group i n 1951«  and a larger  I t follows then that i f the age composi-  tion of the adult run remains constant, from year to year, that the number of smolts l a t e r making up those runs must also be constant.  An alternative explanation f o r the phenomenon i s that  the s a l t water environment  exerts an equalizing e f f e c t on the  numbers of smolts, reducing them a l l to the same r e l a t i v e l e v e l from year to year. water environment  I t i s d i f f i c u l t to believe that the s a l t  possesses a. l i m i t i n g factor of t h i s nature.  If the r i v e r produces the same number of smolts from year to year many new avenues of investigation are at once I n d i cated.  Records available suggest that angling pressure varies  considerably from year to year.  This would indicate that the  sport fishery f o r adults exerts l i t t l e Influence on the production of smolts.  The suggestion has been made that low water  l e v e l s i n the summer might be a l i m i t i n g factor for smolt production.  Almost the entire Chilliwack r i v e r v a l l e y has been  logged o f f , and t h i s might have the e f f e c t of allowing large freshets In the spring, with a f a i r l y constant low flow i n the ^summer.  Flow records for the period of the study are incomplete,  73 but those available point to a trend f o r f a i r l y uniform low l e v e l s i n the mid-summer and mid-winter months. of  The pursuit  t h i s investigation was considered to be beyond the scope of  t h i s work; and only a casual look into these further f i e l d s of research was made. It has been shown here that smolts which migrate l a t e r i n the summer than A p r i l or May were smaller than the early migrants. for  It i s i n t e r e s t i n g to speculate that a minimum size  any age group must be attained before migration w i l l take  place.  There i s however l i t t l e evidence to support t h i s view. In  the adult run 1.9$ of the f i s h went to sea as  yearling smolts, 62.1$ at age two, 3 5 . 5 $ at age three, and at age four.  0.5$  It i s probable that t h i s r e f l e c t s the actual pro-  portion of the four age groups of smolts that leave f o r the sea every year.  I t i s possible that large numbers of yearlings  leave, only to perish i n t h e i r f i r s t year of ocean l i f e .  This  i s a f i e l d of investigation which w i l l have to go beyond the examination of scales alone.  Trapping and counting the smolts  would appear to be the only feasible way of determining the actual age composition of the smolt run.  Analysis of the adult  catch alone suggests that the majority of yearling f i s h remain i n the r i v e r u n t i l reaching their second or t h i r d year. Most of the adult f i s h were entering the r i v e r i n the spawning run f o r the f i r s t time, only 6$ of the run being composed of veteran spawners.  With two exceptions these had  spawned i n t h e i r second year of ocean l i f e .  Of 1+4 veteran  74 spawners, 5 were males and 39 were females.  I t has been noted  elsewhere that the sex r a t i o of the run i s usually i n the order of 2 males to three females.  Following t h i s sex r a t i o , about  16 of the veteran spawners should have been males, whereas only 5 were found.  This phenomenon can be explained i n two ways.  The rigours of the spawning run f o r the males might be such that a higher mortality of males occurs.  Opposed to t h i s i s the pos-  s i b i l i t y that the rigours of the spawning run are l e s s d r a s t i c for the males, so that the scales do not suffer from reabsorption to the same extent as the female scales, making detection of the spawning scar d i f f i c u l t .  The scales of each of the f i v e  veteran males exhibited a pronounced spawning scar, while caref u l examination of the remaining male scales gave no i n d i c a t i o n of even minor scars.  L i t t l e information i s available as to the  physical condition of male and female steelhead i n the spawning run.  Again, a further f i e l d of investigation i s indicated. Veteran spawners tend to be s l i g h t l y smaller In length  and  weight than maiden f i s h i n the same age group.  This i s to  be expected since the spawning migration i n fresh water, with i t s attendant drain on the body resources would place these f i s h unfavourably i n a comparison of growth to f i s h which had spent the  same period e n t i r e l y i n the ocean. Although the spawning run i s divided almost evenly  between f i s h which have spent 2 or 3 years i n the ocean, 40 o;f the 44 veteran spawners -had spawned i n their second year  75 of ocean l i f e , while only 1 had spawned a f t e r three years of ocean l i f e .  There i s a strong i n d i c a t i o n here that f i s h which  have spent two years i n the ocean before returning to the r i v e r have a higher survival from spawning than f i s h which have spent three years i n the ocean.  Few dead steelhead are seen i n fresh  water after spawning has occurred, and spawned-out f i s h or "kelts" are often taken by anglers i n the lower reaches of the r i v e r s after spawning time.  It i s generally assumed that these  f i s h return to the ocean, but that few survive to spawn again. The present work has served l a r g e l y to point out the many p r o f i t a b l e l i n e s of investigation that might be carried on i n seeking more knowledge as to the l i f e h i s t o r y of the steelhead.  Runs of adult f i s h occur i n various r i v e r s at a l l  times of the year.  The same type of study could be made of a  variety of r i v e r s with some attempt made to relate the physical c h a r a c t e r i s t i c s of the r i v e r s with the l i f e h i s t o r y pattern of the runs each supports. The complexity of the l i f e history of the steelhead should serve the f i s h well to meet environmental reverses that would be dangerous to some f i s h populations.  Progeny from the  spawning run of any one year can migrate as smolts up to four years from the time of hatching, and can return a f t e r periods ranging from one to three years i n the ocean.  Straying of  f i s h from r i v e r to r i v e r has been known to occur also, so that a r i v e r oould present an environment unsuitable f o r steelhead i n most years without completely eliminating i t s run.  76 LITERATURE CITED Beckman, William C , 1943. Annulus Formation on the Scales of Certain Michigan Game Fishes. Pap. Mich. Acad. S c i . Arts and.Lett. (1942) 23: 231-312. B l a i r , A.A.,  1937. The V a l i d i t y of Age Determination of Landlocked Salmon. Science 36: 519-520.  from the Scales  Carlander, Kenneth D., 1950. Some Considerations i n the Use of Growth Data Derived from Scale Studies. Trans. Am. F i s h . Soc. 7 9 : 187-19 *-. 1  Creaser, C.W.,  1926. The Structure and Growth of the Scales of Fishes i n Relation to the Interpretation of t h e i r L i f e Histories, with Special Reference to the Sunfish Eupomotls glbbosus. Misc. Publ. Mus. Zool. Univ. Mich. No. 1.7; 1-80.  Crichton, I.Mv, 1935. Scale Absorption i n Salmon and Sea ^rout. Fisheries, Scotland, Salmon Fish. IV: Cutler, D.W.,  1918. A preliminary Account of the Production of Annual Rings i n the Scales of Plaice and Flounder. Journ. Mar. B i o l . Assn. N.S., 11 ( 1 9 1 6 - I 8 ) : 470-496.  Dannevlg, A l f and Per Hc^st, 1931. Sources of Error i n Computing L i - L 2 etc. from Scales Taken from Different Parts of the Fish. Jour. Du Cons, pour L'expl. de l a mer 6: 64-93, Fraser, C. McClean, 1916. Growth of the Spring Salmon. Trans. P a c i f i c Fish. Soc. 1915:  29-39.  Fraser, C. McClean, 1917. On the Scales of the Spring Salmon. Contribut. Can. B i o l . , Suppl. Sixth Ann. Rep. Dept. of Naval Service, Fish. Branch, 1915-16: 21-38.  77 Fry, F.E.J., 1 9 4 3 . A Method f o r the C a l c u l a t i o n o f the Growth o f F i s h e s from S c a l e Measurements. Univ. T o r . S t u d i e s . B i o l . Ser., Pub. Ont. F i s h . Res. Lab. No. 6 l : 5 - l S . Graham, M., 1 9 2 6 . Studies of Age-determinations i n F i s h . F i s h . Invest. I I : Graham, M., 1 9 2 9 . Studies o f Age Determination i n F i s h . P a r t I I . A Survey o f the L i t e r a t u r e . M i n i s t r y A g r i c . and F i s h . , 1922, F i s h . I n v e s t . ,  Ser. 2 , 1 1 ( 3 ) : 1 - 5 0 .  Hoffbauer,  C , 1898. Die Altersbestlmmung des Karpfen an S e i n e r Schuppe. A l l g . F i s c h . - Z t g . , 2 3 ( 9 ) : 341-343.'  Hutton, J.A., 1 9 2 1 . The L i t e r a t u r e o f F i s h S c a l e s . • Salmon and Trout Mag. 2 6 : L a r k i n , P.A., 1 9 5 0 . Report on the P r e l i m i n a r y Survey o f the S t e e l head o f the Lower F r a s e r R i v e r . Report o f B. C. Game Commission f o r 1 9 4 8 . M a r s h a l l , Nelson, 1939. Annulus Formation i n the S c a l e s o f the Common Shiner N o t r o p i s cornutus ohrysocephalus (Rafinesque). Copeia 1 9 3 9 ( 3 ) : 148-154. M a r t i n , W.R., 1 9 4 9 . The Mechanics of Environmental C o n t r o l o f Body Form i n F i s h e s . Univ. T o r . S t u d i e s B i o l . S e r i e s 58, Pub. Ont. F i s h . Res. Lab. No. 7 0 : 81 pp. Masterman, A.T., 1913. Report on I n v e s t i g a t i o n s Upon the Salmon w i t h S p e c i a l Reference t o Age Determination by Study of S c a l e s . Bd. A g r i c . and F i s h . I n v e s t . , S e r . l , l ( l - 3 ) : l - S O . Menzies, W.J.M., 1931. The Salmon - I t s L i f e H i s t o r y . W i l l i a m Blackwood & Sons L t d . , Edinburgh and London.  Mottley, C. McC, 1942. The Use of the Scales of Rainbow Trout (Salmo a l r d n e r l l ) to Make Direct Comparisons of rowth. Trans. Am. Fish. Soc. 71: 7 4 - 7 9 .  f  Rich, W.H.  and H.B. Holmes, 1928. Experiments i n Marking Young Chinook Salmon on the Columbia River, 1 9 l 6 to 1927. B u l l . U. S. Bur. Fish. 1928: 215-264.  Taylor, Harden F., 1916. The Structure and Growth of the Scales of the Squeteague and the P i g f i s h as Indicative of L i f e History. B u l l . U. S. Bur. Fish., 34(1914): 2 8 5 - 3 3 0 . Thomson, J . Stuart, 1904. The Periodic Growth of Scales i n Gadldae as an Index of Age. Jour. Mar. B i o l . Assn. United Kingdom, N. S., 7 ( 1 ) : 1-109. Van Oosten, John, 1929. L i f e History of the Lake Herring (Leuclchthys artedl Le Seur) of Lake Huron as Revealed by i t s Scales, with a Critique of the Scale Method. B u l l . U.S. Bur. Fish., 1928, 4 4 : 2 6 5 - 4 2 8 .  

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