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Variability in life-history characteristics of steelhead trout (Salmo gairdneri) along the Pacific coast… Withler, Ira Lewis 1961

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VARIABILITY IN LIFE-HISTORY CHARACTERISTICS OF STEELHEAD TROUT (Salmo gairdneri) ALONG THE PACIFIC COAST OF NORTH AMERICA by IRA LEWIS WITHLER B. A. University of B r i t i s h Columbia, 1954 A THESIS SUBMITTED IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE i n the Department of ZOOLOGY We accept t h i s thesis as conforming to the required standard THE UNIVERSITY OF BRITISH COLUMBIA October 1961 In presenting t h i s thesis i n p a r t i a l f u l f i l m e n t of the requirements for an advanced degree at the University of B r i t i s h Columbia, I agree that the Library s h a l l make i t f r e e l y available f o r reference and study. I further agree that permission for extensive copying of t h i s thesis f o r scholarly purposes may be granted by the Head of my Department or by his representatives. It i s understood that copying or publication of t h i s thesis for f i n a n c i a l gain s h a l l not be allowed without my written permission. Department of Zoology  The University of B r i t i s h Columbia, Vancouver 8, Canada. October 2„ 1961 ABSTRACT This study compares l i f e - h i s t o r y c h a r a c t e r i s t i c s of s t e e l -head populations within a r e s t r i c t e d area of the southwest coast of B r i t i s h Columbia, and within streams of the P a c i f i c coast from c e n t r a l C a l i f o r n i a to B r i t i s h Columbia. Variations ob-served within features of the l i f e - h i s t o r i e s of steelhead trout are related to physical features of stream environments and to the geographical location of study streams. Within B r i t i s h Columbia data r e l a t i n g to time of stream entry, sex r a t i o s , repeat spawning, mean lengths and duration of fresh and salt-water residence of winter and summer steelhead have been obtained from samples v o l u n t a r i l y submitted by anglers. Data r e l a t i n g to study streams have been obtained from map study, personal observation and through the courtesy of various governmental and municipal agencies. Several published studies from the coastal United States have permitted comparison of steelhead populations over a wide geographic range. Within a lim i t e d area steelhead enter and ascend spawning streams throughout a l l months. Fish which enter streams be-tween October 1 and A p r i l 30 are termed "winter steelhead*', while "summer steelhead" enter streams between May 1 and September 3 0 . Cheakamus River i s exceptional i n that i n i t i a l stream entry of winter steelhead i s delayed u n t i l A p r i l 1, with most f i s h entering during A p r i l and May. Late entry i s related to delayed freshet conditions within the stream. Almost twice as many female as male steelhead were angled. Comparison with trapping r e s u l t s suggests that sport f i s h e r i e s i i i s e l e c t for females of anadramous rainbow trout populations. Repeat spawning of winter steelhead was found to range from 5 . 0 percent for f i s h from the Seymour River to 3 1 . 3 percent for Cheakamus River. Repeat spawning among summer steelhead ranged from 4-4 percent (Seymour River) to 6 . 3 percent (Coquihalla River). Mean fork lengths of steelhead populations of winter and summer steelhead showed l i t t l e v a r i a t i o n (range 2 6 . 3 to 3 1 . 0 inches). Winter steelhead from the Cheakamus River were larger than f i s h from a l l other populations, and summer steelhead from the Coquihalla River had the least mean length. Mean fork lengths of winter and summer steelhead were not s i g n i f i c a n t l y d i f f e r e n t , despite the f i v e to eight month shorter term of salt-water residence of the l a t t e r . Variations of mean lengths of steelhead among d i f f e r e n t r i v e r systems i s a r e s u l t of d i f -ferences i n mean time of salt-water residence. Mean lengths increase with increased salt-water residence. Steelhead spent from one to four years i n fresh water and from one to four years i n s a l t water. Along the P a c i f i c coast from Central C a l i f o r n i a to south-ern B r i t i s h Columbia, timing of i n i t i a l stream entry showed l i t t l e v a r i a t i o n and the sex r a t i o was near one male to one female. Repeat spawning decreases from south to north. Mean fork lengths of steelhead populations are greater and f i s h spend more years i n fresh and more years i n s a l t water i n i v northern areas. Possib le fac tors causing va r ia t ions i n l i f e h i s t o r y c h a r a c t e r i s t i c s of steelhead along the P a c i f i c coast are d iscussed . V TABLE OF CONTENTS Page TITLE PAGE i ABSTRACT i i TABLE OF CONTENTS v LIST OF FIGURES v i i i LIST OF TABLES x ACKNOWLEDGEMENTS x i INTRODUCTION 1 MATERIALS AND METHODS 4 The Study Streams 4 B r i t i s h Columbia Streams 4 P a c i f i c Coast Streams 5 Sampling and Scale Reading 5 Some Limita t ions of Angler Sample Methods . . 8 STEELHEAD POPULATIONS OF THE SOUTH COAST OF BRITISH COLUMBIA 12 The Streams 12 Location 12 Water Flow (Volume) C h a r a c t e r i s t i c s . . . 12 Water Temperature C h a r a c t e r i s t i c s . . . . 13 P h y s i c a l C h a r a c t e r i s t i c s 18 Coquitlam River 20 v i Page Alouette River 21 Chehalis River 21 C h i l l i w a c k River 22 Coquihal la River 22 Capilano River 2 3 Seymour River 24 Cheakamus River 25 Steelhead Populations 2 6 Timing of Stream Entry of Adult Steelhead 26 Winter Steelhead 27 Summer Steelhead 29 Sex Ratios 32 Winter Steelhead 32 Summer Steelhead 33 Repeat Spawning 34 Winter Steelhead 34 Summer Steelhead 35 Lengths of Adult Steelhead 38 Winter Steelhead 38 Siommer Steelhead 40 L i f e - H i s t o r y Categories 42 Winter Steelhead 42 Summer Steelhead 45 STEELHEAD POPULATIONS OF THE PACIFIC COAST . . . 51 The Streams 51 v i i Page Waddell Creek, C a l i f o r n i a 51 Alsea River, Oregon 55 Streams of Coastal Oregon 56 Green River, Washington 56 Capilano River, B r i t i s h Columbia . . . . 57 Steelhead Populations 58 Timing of Runs 58 Sex Ratios and Repeat Spawning 59 Lengths and L i f e History Categories . . . . 62 DISCUSSION 67 LITERATURE CITES 80 v i i i LIST OF FIGURES Page Figure 1. Location of the B r i t i s h Columbia study streams 14 Figure 2 . Mean monthly water flow (volume) for a l l streams for which data are available . . . 15 Figure 3• Mean monthly water temperatures for a l l streams for which data are available . . . 16 Figure 4 . P r o f i l e s of the study streams. Broken l i n e s represent upper l i m i t of stream frequented by adult steelhead 17 Figure 5- Numbers of steelhead captured i n h a l f -monthly i n t e r v a l s for streams maintaining winter-run steelhead only (broken l i n e represents d i v i s i o n to early and late portions of winter run of steelhead). Ratios represent t o t a l numbers of male: female steelhead captured 2 8 Figure 6 . Numbers of steelhead captured i n h a l f -monthly i n t e r v a l s from streams maintaining summer and winter runs (broken l i n e repre-sents d i v i s i o n to early and late portions of winter run of steelhead). Ratios represent numbers of male:female steelhead captured during winter and summer runs. . . 30 Figure 7- L i f e - h i s t o r y categories of winter steelhead captured within each B r i t i s h Columbia study stream (except Cheakamus River), represented by month as a percent of t o t a l captures, for a l l years of record, 1949 to 1958 46 Figure 8 . L i f e - h i s t o r y categories of summer steelhead captured within B r i t i s h Columbia study streams, represented by month as a percent of t o t a l captures, for a l l years of record, 1949 to 1958 47 Figure 9- Location of the P a c i f i c coastal study streams 42 i x Page Figure 10. Mean monthly water temperatures for a complete year of record for some coastal study streams 54 Figure 11. Schematic representation of changes i n l i f e - h i s t o r y attributes of steelhead populations and mean stream temperatures along the P a c i f i c coast. Thick portions of the pointers suggest greatest f r e -quency or amount of an att r i b u t e , t h i n portion, the least 77 X LIST OF TABLES Page Table I Physical c h a r a c t e r i s t i c s of the B r i t i s h Columbia study streams 19 Table I I Numbers of repeat spawning winter s t e e l -head captured from B r i t i s h Columbia streams for a l l years of record, 1949 to 1958 36 Table I I I Numbers of repeat spawning summer s t e e l -head captured from B r i t i s h Columbia streams for a l l years of record, 1949 bo 1958 37 Table IV Mean fork lengths of summer and winter steelhead i n half-monthly i n t e r v a l s for a l l years of record, 1949 to 1958. Lengths i n inches 39 Table V L i f e - h i s t o r y categories of winter and summer steelhead captured from the B r i t i s h Columbia study streams for a l l years of record, 1949 to 1958 43 Table VI Physical c h a r a c t e r i s t i c s of P a c i f i c coastal study streams 53 Table VII Sex r a t i o s and frequency of repeat spawn-ing of steelhead captured from coastal study streams 60 Table VIII Mean lengths and age composition of adult steelhead captured within coastal study streams 65 x i ACKNOWLEDGEMENTS The author wishes to express his gratitude to Dr. P. A. Larkin for suggesting t h i s problem and the manner i n which i t should be pursued and for his review of the completed manu-s c r i p t . Thanks are also due to the many agencies which have provided water temperature and flow data for streams of B r i t -i s h Columbia and the United States; these are the B r i t i s h Columbia E l e c t r i c Company, Greater Vancouver Water D i s t r i c t , Department of Fisheries of Canada, International P a c i f i c Salmon Fisheries Commission, Fish and Game Branch of the B r i t i s h Columbia Department of Recreation and Conservation, and the Surface Water Branch of the United States Department of the I n t e r i o r . Scale samples were provided by the B r i t i s h Columbia Fish and Game Branch. F i n a l l y , s p e c i a l thanks to Dr. T. G. Northcote, Dr. C. C. Lindsey and Mr. S. B. Smith for t h e i r worthy comments and c r i t i c a l review of t h i s paper. INTRODUCTION The steelhead trout (Salmo g a i r d n e r i ) , d i s t r i b u t e d along the P a c i f i c Coast from C a l i f o r n i a to Alaska, i s a highly valued sport f i s h and contributes s u b s t a n t i a l l y to commercial f i s h e r i e s . In comparison to the extensive studies conducted on other commercially valuable salmonid species and equally or less important sport f i s h species, l i f e h i s t o r y and habits of steelhead have been studied r e l a t i v e l y l i t t l e . There are several reasons. F i r s t , pre-smolt steelhead are, as yet, morphologically indistinguishable from completely stream r e s i -dent rainbow trout. Second, adult f i s h are few i n number. Third, t h e i r spawning habits make d i r e c t observations under normal f i e l d conditions extremely d i f f i c u l t . Also, angling success for steelhead i s low. Despite the d i f f i c u l t i e s inherent i n b i o l o g i c a l studies r e l a t i n g to t h i s species, several have been undertaken i n P a c i f i c coastal states and i n B r i t i s h Columbia. Shapavalov and Taft (1954) conducted a comprehensive nine-year study of pre-smolt, smolt and adult steelhead at a counting fence on Waddell Creek, C a l i f o r n i a . Chapman (1958); studied the l i f e h i s t o r y of smolt and adult steelhead i n the Alsea River, Oregon. Also i n Oregon, B a l i (1958) considered differences amongst steelhead populations from d i f f e r e n t streams and related these differences to physical and geographical differences between the streams. 2 Pautzke and Meigs (1940) have reported upon a tagging and l i f e h i story study of the steelhead trout population of the Green River, Washington. Maher (1954) has established c r i t e r i a for the accurate i n t e r p r e t a t i o n of smolt and adult steelhead scales, and has presented data regarding the l i f e - h i s t o r y of steelhead i n the Chilliwack River, B r i t i s h Columbia. Also i n B r i t i s h Columbia, Neave (1949) has studied the game-fish popu-la t i o n s , including steelhead, of Cowichan River, Vancouver Island; and Milne (1948) has described the i n t e r n a l anatomy of the adult forms of t h i s species. Larkin (1948) has compared the commercial catch of steelhead of the Fraser River system with anglers* returns from the Chilliwack River. No published information presently i s available r e l a t i n g to steelhead trout populations of Alaska. The investigations c i t e d above have shown that the l i f e -h i s t o r y c h a r a c t e r i s t i c s of the steelhead are variable and B a l i (1958) has suggested that steelhead populations of Oregon streams may vary i n r e l a t i o n to t h e i r geographic d i s t r i b u t i o n . The objectives of the present study are twofold. F i r s t , an attempt has been made to determine the c h a r a c t e r i s t i c s of the steelhead trout popula tions of several streams i n south-western B r i t i s h Columbia, to determine what s i m i l a r i t i e s and .'differences e x i s t among d i f f e r e n t populations and to determine what relationships e x i s t between the c h a r a c t e r i s t i c s of the population and t h e i r d i f f e r e n t fresh-water environments. Second, data r e l a t i n g to steelhead populations from coastal 3 states and B r i t i s h Columbia have been compared to emphasize the v a r i a t i o n which e x i s t s between populations. Characteristics which d i f f e r between P a c i f i c coastal populations have been com-pared i n r e l a t i o n to the l a t i t u d i n a l location of the streams from which they have been obtained. 4 MATERIALS AND METHODS THE STUDY STREAMS B r i t i s h Columbia Streams The geographical location, length, gradient, size of drainage area and other gross physical features of each B r i t i s h Columbia stream studied have been obtained from detailed topo-graphical maps. Water temperature and flow data for each stream have been obtained from every source where extensive, accurate recordings were available. Water temperature and flow records for the Capilano and Cheakamus Rivers for a com-plete year were supplied by the Department of Fisheries of Canada, for the Seymour River by the Greater Vancouver Water D i s t r i c t and for the Chilliwack River by the International P a c i f i c Salmon Fisheries Commission and the Water Resources Branch of the Canada Department of Northern A f f a i r s and Natural Resources. Water temperatures only for the Chehalis and Coquihalla Rivers were made available by the International P a c i f i c Salmon Fisheries Commission and for the Alouette River by the B r i t i s h Columbia Fish and Game Branch. No water temperature or flow records were available for the Coquitlam River. The means of d a i l y recordings of water temperatures and flows have been ' recorded at monthly i n t e r v a l s . In some instances, pertinent information from personal 5 observation of physical features of the streams such as compo-s i t i o n of the stream bed, gradient of the stream and points of obstruction or d i f f i c u l t passage have been included. P a c i f i c Coast Streams Where steelhead populations have been compared over a wide geographic range, data r e l a t i n g to streams have been extracted from steelhead studies i n C a l i f o r n i a (Shapavalov and Taft, 1954), Oregon (Chapman, 1958) ( B a l i , 1958) and Washington (Pautzke and Meigs, 1940). Each study has included a b r i e f description of the physical features of the streams which con-t a i n the populations studied. Water flow and temperature data have been included i f they were available. SAMPLING AND SCALE READING Steelhead populations within southern B r i t i s h Columbia were selected for study where 100 or more scale samples were a v a i l -able from an i n d i v i d u a l stream. The populations of seven streams were selected on t h i s basis. Also, data for populations of the Chilliwack River tabulated by Maher (1954) are presented. The 1,374 adult steelhead scale samples used were obtained e n t i r e l y through a system of voluntary submission by anglers from 1949 u n t i l 1958. In t h i s sampling program, anglers were supplied with envelopes for return of scale samples taken from "j u s t behind the back T d o r s a l ' f i n , high up on the side". 6 L o c a l i t y and date of capture, length and weight of f i s h and remarks were recorded by the angler for each sample. A l l samples had been prepared for reading by personnel of the Fish and Game Branch p r i o r to commencement of t h i s study. Methods of selection, mounting and magnification of scales were i d e n t i c a l to those of Maher (1954). Using the c r i t e r i a for int e r p r e t a t i o n of markings of steelhead scales established by Maher (1954)., scales were read to determine features of the l i f e h i s t o r y . I f i t were impos-s i b l e to determine accurately the fresh-water history for an i n d i v i d u a l f i s h owing to regenerated central areas or poor mounting technique, only the salt-water growth portions of the scale were interpreted and recorded. Approximately 25 percent of a l l samples submitted were recorded only p a r t i a l l y on t h i s basis. A l l scale samples were re-read one month after the i n i t i a l reading. Agreement between readings was good. The following information was tabulated for each f i s h : l o c a l i t y of capture, sample number, half-month of capture, year of capture, summer or winter steelhead, length, weight, sex, years spent i n fresh water, years spent i n s a l t water, number and years of previous spawnings, year of hatching. Steelhead which were captured between November 1 and A p r i l 30 were classed as winter steelhead; f i s h captured from May 1 to October 30 were c a l l e d summer steelhead. Steelhead are known to spend 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 7 years i n the sea before returning to fresh water as a maturing adult (Maher, 1 9 5 4 ) . The term "age group" i s used to denote the combination of fresh and salt-water l i f e to which a f i s h belongs. In tables and i n the text, age groups are referred to as 2 / 3 , 4 / 1 , 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. L i f e - h i s t o r y categories of sum-mer steelhead have been recorded s i m i l a r l y , although i n each instance t h e i r ocean l i f e i s s i x or eight months shorter than designated by the number following the oblique stroke. Fortunately, the method of presentation of l i f e - h i s t o r y information and terminology r e l a t i n g to steelhead populations i s f a i r l y uniform. This has f a c i l i t a t e d a comparison of data extracted from various studies of steelhead populations from streams of P a c i f i c coastal states and B r i t i s h Columbia. The study of steelhead populations within Waddell Creek, C a l i f o r n i a , was undertaken between 1933 and 1 9 4 2 . Data from the Alsea River and other Oregon streams were coll e c t e d from 1951 through 1 9 5 6 . The study of steelhead populations of the Green River, Washington, extended from 1936 to 1 9 4 0 . In B r i t i s h Columbia, data for the Chilliwack River were co l l e c t e d from 1948 u n t i l 1953 and the present study u t i l i z e s samples obtained between 1948 and 1 9 5 7 . Unfortunately, there i s l i t t l e agreement i n the time periods during which these various studies were undertaken and therefore c l i m a t o l o g i c a l or physical conditions cannot be 8 assumed to be s t r i c t l y comparable. Probably studies have been undertaken during years when temperature conditions and pre-c i p i t a t i o n have d i f f e r e d from mean conditions. Also other factors such as oceanographic conditions, f i s h i n g pressure, watershed logging, water withdrawal and p o l l u t i o n , which may have an e f f e c t upon the nature of streams and t h e i r popula-tions, cannot be judged to be alike among streams, nor from one time period to another. Despite the foregoing, populations have been compared on the assumption that c h a r a c t e r i s t i c s of steelhead populations are f a i r l y uniform each year within each stream. Maher (1954) has found for steelhead of the Chilliwack River that "... 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 s i m i l a r from year to year." Because of the lack of information on summer steelhead from streams other than i n southern B r i t i s h Columbia, only winter steelhead are considered i n the section of t h i s work describing c h a r a c t e r i s t i c s of populations from a wide geographic range. SOME LIMITATIONS OF ANGLER SAMPLE METHODS Use of angler samples for b i o l o g i c a l studies of f i s h popu-la t i o n s has been c r i t i c i z e d because of several possible sources of bias. Some of these objections are discussed below. 9 1 . S e l e c t i o n of fas tes t growing f i s h Larkin et a l (1951) have shown that the fas tes t growing rainbow trout i n Paul Lake, B r i t i s h Columbia, were more r e a d i l y angled than were slower growing i n d i v i d u a l s . This phenomenon undoubtedly r e f l e c t s M s e l e c t i o n by the f i s h e r y of the larger and fas ter growing yearl ings* 1 . This s e l e c t i v i t y w i l l be l a r g e l y inoperat ive i n steelhead samples submitted by anglers because of the considerable s i z e which steelhead have at tained before enter ing the f i s h e r y . Most angled steelhead are too h i g h l y p r i z e d t rophies to be returned to the water to " t r y for a larger one". There i s , however, a tendency for anglers to report only larger f i s h . 2. Lure s e l e c t i v i t y The p o s s i b i l i t y e x i s t s that some types of commonly used steelhead l u r e s , because of t h e i r s i z e , are more a t t r a c t i v e to l a r g e r or smaller s teelhead. Lure s e l e c t i v i t y probably i s not s i g n i f i c a n t i n t h i s study as a l l f i s h captured are of a s i z e to e f f e c t i v e l y attack the larges t lure used. Further , Larkin (1949) found for rainbow t rout i n Paul and Kootenay Lakes that although d i f f e r e n t types of lures were more e f f e c t i v e i n d i f -ferent seasons, there was no measurable s e l e c t i o n for larger f i s h by any one type. Trout angled from Kootenay Lake were comparable i n s i z e to s teelhead. 3 . Escape of large f i s h The steelhead samples u t i l i z e d i n t h i s study were obtained 10 from f i s h captured i n r e l a t i v e l y small, swift-flowing streams. Capture of large, active f i s h from these surroundings required considerable adeptness by the angler. Under these conditions the larger the f i s h hooked, the greater are i t s chances of escape. I t i s probable, therefore, that a greater proportion of small and medium sized rather than large f i s h r e l a t i v e to t h e i r absolute numbers, i s captured. This bias may be most pronounced with summer steelhead which are less mature sexually than winter steelhead and are reputed to be the more agressive f i g h t e r s . Also, summer s t e e l -head are often angled with l i g h t e r tackle than are winter steelhead. 4• Selection of females A most serious consideration i n the use of anglers' samples i s the apparent s e l e c t i v i t y by steelhead sport f i s h e r i e s for females. Trapping records for adult steelhead entering streams at various stations indicate that males and females enter streams i n approximately equal numbers. Shapavalov and Taft (1954) at Waddell Creek, C a l i f o r n i a , report that "the sex r a t i o for the Steelhead runs as a whole was one male to 1.1 females 1 1. Pautzke and Meigs (1940) have tabulated 1,107 males and 1,115 females for two years of trapping records of adult steelhead i n Green River, Washington. Chapman (1958) records an "approximately 11 1:1 r a t i o i n f i r s t spawners*' for adult steelhead i n the Alsea River, Oregon. Larkin (1951), regarding c r e e l census records of rainbow trout from Paul Lake, B r i t i s h Columbia, has stated that "there i s a s i g n i f i c a n t preponderance of females i n the catch for a l l ages of f i s h except yearlings", yet there was no preponderance of females or males i n the spawning run. Data presented i n t h i s study (Figures 5 and 6) and Larkin's data from Paul Lake suggest very strongly that sport f i s h e r i e s select for females i n anadramous and lake resident populations of rainbow trout. This selection i s i n part related to appearance of angled steelhead. Male steelhead appear to deteriorate i n condition and appearance to a greater extent than do females as spawning approaches. During the l a t e r portion of the steelhead angling season there i s an increased tendency for anglers to release ali v e the male steelhead captured. 12 STEELHEAD POPULATIONS OF THE SOUTH COAST OF BRITISH COLUMBIA THE STREAMS Location The eight study streams are situated i n the extreme south-west coast of B r i t i s h Columbia (Figure l ) . They drain, either d i r e c t l y or v i a the Fraser River, to the P a c i f i c Ocean. Five of the r i v e r s drain to the Fraser River at distances varying from 23 to 100 miles upstream of i t s mouth; these are the Coquitlam, Alouette, Chehalis, Chilliwack and Coquihalla Rivers. The three remaining streams emptying d i r e c t l y to the P a c i f i c near to Vancouver are the Cheakamus, Capilano and Seymour Rivers. A l l these streams have r e l a t i v e l y short water courses with steep gradients (see Table 1, Figure 4)- However, reduced gradients and more meandering water courses are found i n the lower reaches of the three r i v e r s which flow through the Fraser River delta; these are the Coquitlam, Alouette and Chilliwack Rivers. Water Flow (Volume) Charact e r i s t i c s A complete year of water flow (volume) records for each of the study streams for which t h i s information i s available i s shown i n Figure 2. Flow data for the Chehalis River were obtained during 1956, for the Chilliwack, Cheakamus and Seymour Rivers from October 1955 to September 1956, and for the Capilano 1 3 River from October 1 9 5 4 to September 1 9 5 5 . With the exception of the Cheakamus River, flow character-i s t i c s are f a i r l y s i m i l a r for each stream. T y p i c a l l y , i n P a c i f i c coastal streams, water flows are extremely low during the mid-summer months owing to low p r e c i p i t a t i o n and again i n mid-winter months because of freezing conditions i n the upper watersheds. Peak water flows occur i n A p r i l , May and June when p r e c i p i t a t i o n i s high and ice and snow i n headwater areas i s melting. A lesser peak usually occurs i n October and November when p r e c i p i t a t i o n i s again high. The Cheakamus River i s exceptional i n that highest water flows occur from June to September, the normal period of lowest water flows for other coastal r i v e r s . This anomalous s i t u a t i o n r e s u l t s from mid-summer melting of g l a c i e r s situated near some t r i b u t a r y streams of the Cheakamus River. Within the study streams, the lowest mean monthly water flow of 78 cubic feet per second was recorded for the Seymour River during the month of August 1 9 5 6 ; the highest mean monthly flow of 18,200 cubic feet per second was recorded for the Cheakamus River for the month of July 1 9 5 6 (Figure 2). Water flow records are not available for a l l r i v e r s . Water Temperature Charact e r i s t i c s A complete year of water temperature records for each of the study streams for which t h i s information i s available i s shown i n Figure 3 . Temperature data for Chehalis, Chilliwack Figure 1. Location of the British Columbia study streams. 15 5000 4000-1 3000 2000-1000-0 5000-4000-3000-(A ul 2000-•3 5 1000 o _ j 0 C O Q U I T L A M R. N 0 W A T E R F L O W DATA AVAIL A B L E A L O U E T T E R. N 0 W A T E R F L O W DATA A V A I L A B L E 5000-cc 4000-LU I— 3000-^ 2000-I 000 0 5000-4000-3000-2000-1000-0 C H E H A L I S R. C H E A K / A M U S R. S E Y M O U R R. CHILLIWAC C A P I L A N O R COQUIHAL LA R . NO WATER FLOW DATA AVAILABLE - 1 1 r- - 1 1 1 r-J F M A M J J A S 0 N D J F M A M J J A S O N D M O N T H Figure 2 . Mean monthly water flow (volume) for a l l streams for which data are available. 16 (-3 5 -< 32 -oc 6 0-UJ 35 " 3 2 i 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 i i j F M A M J J A S O N D J F M A M J J A S O N D M O N T H Figure 3. Mean monthly water temperatures for a l l streams for which data are available. 17 5000 4 000-| 3 000-2000-1 000-0 • 5 000 4 000-3 000-2 000-I ooo-COQUITLAM R. ALOUETTE R u. 0 5000-bJ 4 000J CO - 3000^  2000 I 000 0 5000 4000 CHEHALIS R CHILLIWACK R 3000 2000 I 000 CHEAKAMUS R. CAPILANO R SEYMOUR R . COQUIHALLA R L E N G T H ( M I L E S ) Figure 4 . Profiles of the study streams. Broken lines represent upper limit of stream frequented by steelhead. 18 and Cheakamus Rivers were obtained during the period January to December 1958, for Capilano River during 1951j for Alouette River during September I960 to August 1961 and for Coquihalla River from January to August 1958, and September to December 1959- Data for the Seymour River represent mean temp-eratures from nine years of recording, 1951 to 1959-In a l l r i v e r s water temperatures are low (monthly means of 42°F or l e s s ) during the months of December, January and February. Mean temperatures begin to r i s e i n March with a gradual increase u n t i l mid-August when mean temperatures range between 50° and 62°F. Water temperatures decrease during the f a l l and early winter months u n t i l mid-winter when means between 33° and 42°F are experienced. The lowest mean monthly water temperature of 33.2°F was recorded for the Cheakamus River i n February 1957. The highest mean temperature of 56.6 F was recorded for the Seymour River during August (average from nine years of recording. Figure 3). Physical C h a r a c t e r i s t i c s The following section presents a b r i e f d escription of some physical features of each stream which indicate stream differences, Gradients for each stream are shown i n Figure 4 . Some physical features of each stream are presented i n Table I. The f i r s t f i v e streams, arranged i n order of increasing d i s t -ances from the mouth of the Fraser River, flow to the P a c i f i c Ocean via the Fraser River. The l a s t three r i v e r s described Table I. Physical Characteristics of the British Columbia Study Streams River Length (Miles) Drainage Area (Sq.Miles) Gradient **** Rise (ft)/Mile Water Flow (cfs) Mean Monthly Minimum Maximum Water Temp. ( F) Mean Monthly Minimum Maximum Lake Present in Drainage Elevation Area (Acres) Coquitlam 37 77 68 ** ** ** ** 350 feet 6000 Alouette 27 79 34 ** ** 36.6 Dec. 61.6 June 384 feet 3994 Chehalis 20 148 50 ** ** ** ** 750 feet 2500 Chilliwack 50 450 57 817 Feb. 5,350 June 34.0 Feb. 53.8 Aug. 2,052 feet 2957 Cheakamus 35 765 25 1,030 Feb. 18,200 July 33.3 Feb. 51.1 Aug. * * Capilano 22 68 66 *** 377 Mar. 2,370 Nov. 34.4 Jan. 52.0 Aug. * * Seymour 28 68 60 *** 78 Aug. 1,560 June 35.5 Jan. 58.0 Aug. 650 250 Coquihalla 40 360 65 *** ** ** 38.1 Jan. 56.2 Aug. 3,750 feet 400 Reservoir established since conclusion of study period No information available Temporary barrier in stream Gradient of stream to upper limit of steelhead ascent 20 discharge d i r e c t l y to the ocean. Coquitlam River The Coquitlam River flows from the Coast Range of mount-ains to enter the Fraser River 23 miles upstream from i t s mouth. One major t r i b u t a r y stream, Or (Gold) Creek, enters the r i v e r 11 miles upstream of the r i v e r mouth. A dam to regulate the water l e v e l s i n Coquitlam Lake for domestic and hydro-electric use, 12 miles upstream of the r i v e r mouth at the outlet of Coquitlam Lake, has been present since 1925- This dam has a considerable e f f e c t upon the regime of downstream water flows. Often, i n the summer months no water passes the dam and downstream water flow i s main-tained e n t i r e l y by Or Creek. This volume i s often i n the order of 10 to 20 cubic feet per second. Gravel removal and washing operations contribute s i l t to the lower eight miles of the r i v e r . The two factors outlined above, f l u c t u a t i n g water l e v e l s and i n d u s t r i a l operations, probably prompt a rapid movement of adult steelhead upstream to the more stable environment of Or Creek. Also, as upstream migrants cannot pass over the diversion dam constructed at the lake outlet, i t i s commonly believed that the majority of adult f i s h spawn and pre-smolt steelhead are reared within Or Creek. 21 Alouette River The Alouette River flows to the Fraser River 25 miles upstream from i t s mouth. A major t r i b u t a r y stream, the North Alouette River, enters the r i v e r s i x miles upstream of the r i v e r mouth. A dam at the outlet of Alouette Lake 13 miles upstream of the r i v e r mouth has controlled downstream water flows since 1925. Although flows past the dam are often eliminated, mini-mum flows of 20 to 30 cubic feet per second are maintained by contributions of small t r i b u t a r i e s . Steelhead ascend the r i v e r to the dam, an impassible b a r r i e r . Therefore, 13 miles of stream are available to adult and pre-smolt steelhead. The lower eight miles of r i v e r mean-der through the Fraser River delta and are suited to rearing of juvenile f i s h by reason of the r e l a t i v e l y stable nature of pool and r i f f l e areas. The upper f i v e miles of accessible r i v e r are t y p i c a l l y more precipitous and are composed of lengthy r i f f l e areas and few pools. The r i v e r bed here i s com-posed of coarser materials than are downstream areas. Chehalis River The Chehalis River flows to the Fraser River 53 miles up-stream of i t s mouth. One large t r i b u t a r y stream, S t a t l e r Creek, i s present seven miles upstream of the r i v e r mouth. The major steelhead spawning areas l i e within the lower 22 reaches of Stabler Creek and the p o r t i o n of Chehalis River above the j u n c t i o n of S t a t l e r Creek, but below Chehalis Lake. Much of the lower f i v e miles of the Chehalis River flows through steep-walled canyon areas containing deep p o o l s . Water v e l o c i t y i s slow. Upstream, and i n S t a t l e r Creek, stream bed gradient i s steep and water v e l o c i t y greater . The stream bed i s composed of large boulders and coarse rubble . C h i l l i w a c k River The C h i l l i w a c k River flows to the Fraser River 58 miles upstream from i t s mouth. Several t r i b u t a r y streams are present, but t h e i r p r e c i p i t o u s nature precludes t h e i r use as steelhead spawning areas. A sec t ion of C h i l l i w a c k River between 12 and 30 miles up-stream of the r i v e r mouth, used by steelhead for spawning, has a moderate gradient with few pool or s lack water areas. The bottom i s composed l a r g e l y of coarse gravel and boulders . The lower eight miles of the r i v e r are confined to a canal with a bed of mud and f i n e l y d i v i d e d m a t e r i a l s . In t h i s area stream gradient and water v e l o c i t i e s are g r e a t l y reduced. Coquihal la River The Coquihal la River flows to the Fraser River 100 miles upstream of i t s mouth. No major t r i b u t a r y streams are present . A w a t e r f a l l b a r r i e r , probably impassible for winter - run steelhead e x i s t s s i x miles upstream of the mouth of the r i v e r . Consequently, the spawning and rearing area for these f i s h i s r e s t r i c t e d to the lower s i x miles of stream. Near the mouth the r i v e r has a bed of coarse gravel and boulders and flows through shallow pool and r i f f l e areas. Nearer the obstruction the r i v e r flows through deeper pools contained within deep rock canyons; here the stream bed i s composed of bed-rock, coarse rubble and sand. Summer-run steelhead spawn and young f i s h are reared within 18 miles of r i v e r above the obstruction. Pools of moderate length and long r i f f l e areas characterize t h i s portion of the r i v e r . The r i v e r bed i s composed large l y of large boulders and coarse gravel. Capilano River The Capilano River flows to Burrard Inlet of the S t r a i t of Georgia near to the mouth of the Fraser River. No t r i b u -tary streams are present which are u t i l i z e d for steelhead spawning. A domestic water storage reservoir has been established approximately three miles upstream of the r i v e r mouth since 1954- P r i o r to reservoir construction, steelhead spawned i n an area between three and s i x miles upstream of the r i v e r mouth. This area had a stream bed composed of boulders i n t e r -spersed with coarse gravel, and because of i t s precipitous nature was the upper l i m i t of upstream migration. This area 24 has s i n c e been inundated t o a depth of almost 300 f e e t by establishment of the r e s e r v o i r . Steelhead are now t r u c k -t r a n s p o r t e d f a r t h e r upstream t o new spawning areas. S e v e r a l extensive pools are present downstream from the o r i g i n a l spawning areas. Seymour R i v e r The Seymour R i v e r flows t o Burrard I n l e t some two or three m i l e s t o the east of Capilano R i v e r . No t r i b u t a r y streams which serve as steelhead spawning areas are present. A domestic water supply storage dam i s present 11 mil e s upstream of the r i v e r mouth. Only the stream downstream of the dam i s a v a i l a b l e f o r steelhead. The r i v e r p r o f i l e and bottom composition i s s i m i l a r t o the Capilano R i v e r . A few l a r g e , deep pools are present. Elsewhere, the r i v e r bed i s composed of l a r g e boulders and coarse g r a v e l . Steelhead spawn i n the upper f i v e m i l e s of a c c e s s i b l e r i v e r . O c c a s i o n a l l y , during summer months, no water flows past the storage dam. Undoubtedly, t h i s i r r e g u l a r flow regime r e s u l t s i n some s t r a n d i n g of f i s h immediately below the dam, and a l s o i n near l e t h a l temperature c o n d i t i o n s f o r some d i s -tance downstream. 25 Cheakamus River The Cheakamus River flows to the Squamish River and thence to Howe Sound of the S t r a i t of Georgia, 30 miles north of Vancouver. One small t r i b u t a r y , Cheekye River, serves as a spawning ground for adult steelhead trout and as a rearing area for pre-smolt trout. Water flow data from the Cheakamus River vary consider-ably from those of the other study streams (Figure 2). The Cheakamus exhibits a reversal of the normal mid-summer low flow pattern of most coastal streams. The period of high water volume extends from May u n t i l September, with a maxi-mum mean flow i n July. Flows are moderate i n October and November and are lowest i n February. The mid-summer and autumn water volume anomalies are a consequence of elevation of the portion of the watershed which most greatly influences flow within spawning areas. The usual spring and early summer snow melt i s delayed at the elevation (2,000 - 3,000 feet) of the upper watershed area and consequently water volumes remain high during the summer months. During the autumn months much p r e c i p i t a t i o n i s bound i n the form of snow within t h i s area and consequently water flows are moderate during t h i s period. Water temperature data are presented i n Figure 3. The Cheakamus River i s unusual i n that the recorded mean d a i l y water temperature was lower from January 1 to February 15 (less than 34°F) than for a l l other study streams for the years of record. Summer temperatures increased u n t i l mid-26 August and despite the high water volumes mean monthly temp-eratures during July and August were s l i g h t l y greater than 50°F. Steelhead trout u t i l i z e the lower ten miles of the Cheakamus River for spawning. Numerous pool and slackwater areas are present within t h i s area. The r i v e r bed i s com-posed of boulders and coarse gravel. The gravel and boulders of the r i v e r bed are often displaced by the scouring action of occasional high water flows. A hydro-electric diversion dam has been constructed up-stream of the spawning area since conclusion of the study period. STEELHEAD POPULATIONS Timing of Stream Entry of Adult Steelhead Figures 5 and 6 indicate that there i s a marked v a r i a t i o n i n timing of adult steelhead entry into the streams studied. The timing of entry has provided a c l a s s i f i c a t i o n for d i f f e r -ent groups of steelhead. Depending upon the season during which adult steelhead enter streams, they are variously c a l l e d winter (or winter-run) or summer (or summer-run) steelhead. As yet, no taxonomic c r i t e r i a have been developed to d i f f e r e n t -iate these groups. Steelhead which enter and ascend streams between early November and late March are named "winter" steelhead. However, 27 i n a few i n s t a n c e s , winter f i s h have been reported captured as e a r l y as mid-October and o c c a s i o n a l l y winter steelhead which are l a t e to ascend streams are captured i n A p r i l . A l l winter-run f i s h have well-developed sexual products i n prep-a r a t i o n f o r spawning which takes place i n March and A p r i l . Winter steelhead were captured i n each of the study streams. Steelhead which enter and ascend streams dur i n g May, June, J u l y and August are named "summer** steelhead. Summer-run f i s h have only s l i g h t l y - d e v e l o p e d gonads at the time of t h e i r e n t r y to streams as spawning does not take place u n t i l e a r l y the f o l l o w i n g s p r i n g . Summer steelhead were captured i n three of the e i g h t streams s t u d i e d . These streams are not c l o s e l y r e l a t e d g e o g r a p h i c a l l y . Two of the r i v e r s supporting runs of summer steelhead (Capilano and Seymour R i v e r s ) d r a i n d i r e c t l y t o the ocean v i a Burrard I n l e t , w h i l e the C o q u i h a l l a R i v e r d r a i n s to the Fraser R i v e r 100 miles upstream of i t s mouth. Timing of Winter Runs Figure 5 shows the d u r a t i o n of the capture p e r i o d and number of f i s h taken f o r winter steelhead angled w i t h i n i n d i -v i d u a l study streams. Most win t e r - r u n f i s h entered streams duri n g January, February and March. The g r e a t e s t number of steelhead were captured during January, w i t h decreasing num-bers captured i n February and l e a s t numbers i n March. This 50 4CH 30H < LLI X _ ) UJ Ld 204 ^ I CH L L o 50-4 0 -tr CO ? 3 0 H 20-10-C O Q U I T L A M R C H E H A L I S R I : 2 NOV DEC JAN FEB ' MAR ' APR ' MAY ' JUNE A L O U E T T E R. era* ? 2 I 1-5 1 1 oo C H E A K A M U S R c f c f 2 2 I • 3 2 MALES FEMALES 1 J NOV DEC 1 JAN ' FEB 1 MAR 1 APR MAY JUNE Figure 5. Numbers of steelhead captured in half-monthly intervals from streams maintaining winter-run steelhead only (broken line represents division to early and late portions of winter run of steelhead). Ratios represent total numbers of male:female steelhead captured. 29 angling return information probably gives a f a i r l y accurate index of the proportion of steelhead entering streams i n v a r i -ous months. In the Capilano and Seymour Rivers, however, greater numbers of f i s h were captured during both February and March than during January. No steelhead were captured i n the Cheakamus River during January, February or March i n the three seasons of record available. In t h i s stream a l l f i s h were captured during A p r i l and May. Appreciable numbers of steelhead were captured from the Capilano, Alouette, Coquitlam and Chehalis Rivers during December. During the study period i n the above streams 1 6 . 5 , 21 .7 , 26.0 and 37.5 percent respectively of the t o t a l numbers of f i s h caught during the period December to March were cap-tured during December. Timing of Summer Runs The Capilano, Seymour and Coquihalla Rivers contained summer steelhead. Figure 6 shows the duration of the capture period and number of f i s h taken, within these streams. Timing of adult steelhead entry to the Capilano and Seymour Rivers i s s i m i l a r . Summer steelhead were f i r s t angled i n these r i v -ers during A p r i l and ind i v i d u a l s were captured u n t i l late July. During A p r i l , steelhead entering the Capilano River trapping f a c i l i t i e s are of two groups, distinguished by t h e i r degree of gonad development. Approximately one-half the f i s h 30 5 0-.4 0- C A P I L A N O R 3 0-2 0-I 0-Q 0 -< ^ 5 0 -I : I -7 n <f<f ? 8 I : I 7 I I • • I • 1 1 1 1 I NO LEGAL ANGLING _D_ U J LJJ •4 0- S E Y M O U R R 3 0-o2 0-I 1-7 cr o* S ? I 1-2 MALES FEMALES C o-cr UJ QD 2 - .1 J1 di - n n l H NO LEGAL ANGLING 5 0-4 0 -3 0-2 0 -o-C O Q U I H A L L A R I • 2- I ! I : 2 0 X L i R~ 8 . NOV DEC JAN F E B MAR A P R MAY JUNE JULY AUG SEPT OCT Figure 6. Numbers of steelhead captured in half-monthly intervals from streams maintaining summer and winter runs (broken line represents division to early and late portions of winter run of steelhead). Ratios represent numbers of male:female steelhead captured during winter and summer runs. 31 have well-developed gonads i n preparation for spawning which follows shortly; the remainder have only s l i g h t l y developed gonads for spawning the following spring. The former group are "winter** steelhead which are late to enter the r i v e r ; the l a t t e r are "summer** steelhead. Probably f i s h entering the Seymour River during A p r i l are i n sim i l a r stages of devel-opment . In the Capilano River approximately equal numbers of steelhead were captured during May and June, while i n the Sey-mour River 27 of the 34 f i s h reported during these months were taken i n June. In both r i v e r s samples during July were considerably fewer than during the previous two months. Summer steelhead of the Coquihalla River enter and ascend the stream l a t e r i n the summer than do steelhead of the Cap-ilano and Seymour Rivers. Steelhead f i r s t enter the r i v e r during late June. Their numbers increase u n t i l a peak i s reached i n mid-August; fewer f i s h are captured i n September and only a very few f i s h are reported during October and November. The three streams which maintain groups of both summer and winter steelhead support a fis h e r y throughout almost a l l months of the year. Winter steelhead f i r s t enter these streams during December and f i s h continue to enter and ascend streams u n t i l A p r i l and May. During these l a t t e r months early summer-run f i s h are captured i n small numbers. In the Coquihalla River a few summer steelhead are captured immedi-32 ately p r i o r to the a r r i v a l of the f i r s t winter-run f i s h . A somewhat sim i l a r s i t u a t i o n e x i s t s i n the Capilano and Seymour Rivers. However, no steelhead were reported captured i n the Capilano River and only a few from the Seymour River during August and September because of a fishery closure of much of the accessible r i v e r e f f e c t i v e between August 1 and September 30 of each year. The existence of populations of "winter 1' and "summer" runs throughout t h e i r range i s a unique feature of steelhead populations. This i s a phenomenon not r e a d i l y observed i n P a c i f i c salmon populations, although d i s t i n c t "spring" and " f a l l " runs of A t l a n t i c salmon i n eastern Canada have been reported by various authors (Belding and Kitson, 1934) (Huntsman, 1939). SEX RATIOS Winter Steelhead Figures 5 and 6 show the sex r a t i o of adult steelhead captured within the study streams i n two week i n t e r v a l s for the period of record. A s t r i k i n g feature of these data i s that females almost in v a r i a b l y outnumber males. In the Chehalis and Cheakamus Rivers females outnumbered males cap-tured i n each half-month i n t e r v a l of the capture period. Number of males exceeded females captured during only one period i n the Alouette and Coquihalla Rivers, and twice i n 33 the Coquitlam, Capilano and Seymour Rivers. The greatest difference i n r a t i o of males to females, 1:3-2, occurred i n the Cheakamus River (Figure 5). Near equal numbers were angled i n the Coquitlam River where the r a t i o was 1:1.3. In each instance females comprised between 56.5 and 76.1 percent of the t o t a l captures of winter steelhead. The captures of adult winter steelhead for each of the study streams were a r b i t r a r i l y divided into " e a r l y " and *»'lateM stream entrants by grouping captures from November 1 to January 30 as early entrants, and captures from February 1 to A p r i l 30 as late entrants (divided by 'dotted* l i n e i n Figures 5 and 6). In the Cheakamus River the month of A p r i l served as the early part of the season; the month of May served as the late portion. Percentages of males captured i n the early and late portions of the capture period were compared for each stream (Figures 5 and 6). Greater percentages of males were captured i n the early portion of the capture period i n the Alouette, Chehalis, Cheaka-mus and Seymour Rivers, and i n the late portion i n the Coquitlam, Capilano, and Coquihalla Rivers. No trend toward early or late entry of males or females was evident from t h i s analysis. Summer Steelhead Ratios of males to females captured i n summer f a l l within the range of the sex r a t i o s for captures of winter steelhead i n a l l study streams (Figure 6). 34 Although these data show that many more female than male steelhead of both winter and summer runs are captured by ang-l e r s , trapping studies on other P a c i f i c coastal streams strongly indicate that females are present i n equal, or near equal, numbers to males. REPEAT SPAWNING Winter Steelhead Of 618 winter steelhead examined, 54 or 8.7 percent were returning to spawn for the second time and 11 or 1.8 percent for the t h i r d time (Table I I ) . Second spawners were recorded from a l l the streams. Winter run steelhead returning to spawn for the t h i r d time were recorded from only four (Alouette, Coquitlam, Cheakamus, Coquihalla Rivers) of the seven study streams. No f i s h were recorded returning to spawn for a fourth time . The greatest percentage of repeat spawners was recorded from the Cheakamus River; 31.3 percent of a l l winter steelhead captured during 1954, 1955 and 1957, the years of available record, were returning to spawn for a second or t h i r d time. The lowest return of repeat spawners was recorded from the Sey-mour River; 5-0 percent of a l l steelhead captured during the eight winter seasons from 1949-50 to 1956-57 were returning to spawn for a second or t h i r d time. In a l l streams except the Alouette and Cheakamus Rivers repeat spawning ranged between 35 5 and 8 percent. Table II shows that female repeat spawners predominate amongst the captures. In each stream except the Seymour and Coquihalla Rivers, where only two repeat spawners were captured, more second spawning females than males were captured. At leas t two and as many as nine female repeat spawners were cap-tured for each male captured. Considering both second and t h i r d spawners, females represent 81 .5 percent of a l l repeat spawners captured. Summer Steelhead Of 302 summer steelhead examined 15 or 5 . 0 percent were returning to spawn for the second time and 1 or 0 . 3 percent for the t h i r d time (Table I I I ) . Second spawners were recorded from a l l of the study streams containing summer steelhead. One steelhead returning to spawn for a t h i r d time was captured i n the Coquihalla River; no t h i r d spawners were reported from the Capilano or Seymour Rivers. Repeat spawning was observed i n 4 to 7 percent of the captures from populations of summer steelhead. As was found for winter steelhead, numbers of female r e -peat spawners greatly exceeded males. Eighty-nine percent of the repeat spawners were females. No male repeat spawners were captured i n the Capilano or Seymour Rivers. Table I I . Numbers of repeat spawning winter steelhead captured from British Columbia streams for a l l years of record 1949 to 1958. Number Number % of Fish of Repeat Repeat River in Sample Spawners Spawners Alouette 132 19 14.4 Coquitlam 148 8 5.4 Chehalis 125 8 6.4 Chilliwack * 754 44 5.8 Cheakamus 64 20 31.3 Capilano 77 6 7.8 Seymour 41 2 5.0 Coquihalla 31 2 6.4 Second Spawners Third Spawners Male Female Male Female Nos. 7. Nos. 7. Nos. 7. Nos. % 3 2.3 12 9.1 2 1.5 2 1.5 1 0.7 4 2.7 0 0 3 2.0 1 2.6 7 8.1 0 0 0 0 1 1.6 16 25.0 1 1.6 2 3.1 2 2.6 4 5.2 0 0 0 0 1 2.5 1 2.5 0 0 0 0 0 0 1 3.2 0 0 1 3.2 * Data from Maher, 1954 Table III. Numbers of repeat spawning summer steelhead captured from B r i t i s h Columbia streams for a l l years of record 1949 to 1958. Number of Fish in Sample Number of Repeat Spawners <7 Second Spawners River /. Repeat Spawners Male Nos. 7o Female Nos. % Capilano 99 6 6.1 0 0 6 6.6 Seymour 45 2 4.4 0 0 2 4.4 Coquihalla 158 10 6.3 2 1.3 7 4.4 Third Spawners Male Female Ratio Nos. % Nos. % Male/Female C O 0 0 0 0 -0 0 0 0 -0 0 1 0.6 1:4 38 LENGTHS OF ADULT STEELHEAD The mean fork lengths of male and female summer and winter-run steelhead captured within the study streams are shown for bi-monthly i n t e r v a l s i n Table IV. Winter Steelhead The mean length was 28.4 inches for males and 2 8.2 inches for females. Within each stream males were of greater mean length than females except i n the Coquitlam and Chehalis Rivers (Table IV). In the Coquitlam River females were 0.6 inches longer than males, while i n the Chehalis River the d i f -ference i n mean lengths was only 0.1 inch. Comparing lengths of samples from a l l study streams from which winter-run f i s h were captured, both males and females from the Cheakamus River had the greatest mean length, 31.0 and 30.2 inches respectively. Males with the least mean fork length (26.6 inches) were cap-tured from the Coquitlam River, while females with the least mean length (26.9 inches) were captured from the Alouette River. Maher (1954), for the Chilliwack River suggests that " . . . . i n nearly a l l cases the mean male length and weight was s l i g h t l y higher than that of the female...." No large differences can be shown i n mean lengths of males or females during the period of capture of winter-run steelhead within each study stream. There appears, however, to be a trend toward capture of smaller f i s h of both sexes during the 39 Table IV. Mean fork lengths of summer and winter steelhead in half-monthly intervals for a l l years of record, 1949 to 1958. Lengths in inches. Time Period Alouette Coquitlam Chehalis Cheakamus Capilano 9 9 9. <** 9 $ Nov. 1-15 Nov. 15-30 29.50* Dec. 1-15 27.00 29.25* 25.00* 29.75* 28.75 29.75 30.05 Dec. 15-31 27.00 26.50 27.00* 26.75 30.00 28.00 Jan. 1-15 30.75 33.25 26.00 29.25 30.25 29.50 28.25* 25.50* Jan. 15-31 26.50 28.25 27.75 27.00 32.25* 29.75 28.00* 29.50 Feb. 1-15 30.00 25.25 26.75 26.00 28.00 29.50 28.00 28.25* Feb. 15-28 31.25* 29.50 26.50 26.75* 29.75 31.00 28.50 Mar. 1-15 35.00* 29.50* 27.00 28.00 33.00* 30.75 30.50 27.50 Mar. 15-31 25.50* 27.00 26.50 30.25* 31.50 25.00 Apr. 1-15 26.00* 28.50 27.75 29.25 28.75 28.50 Apr. 15-30 22.25 25.50 32.50 36.00 33.00* 28.50 Mean Length Winter 28.4 26.9 26.60 27.20 29.30 29.50 28.80 28.10 Steelhead Seymour Coquihalla 27.25* W I 32.00* 29.00* M T 31.25 28.75* 28.75* 27.75 1 E 30.00* 28.00* 29.75* 27.75* R 32.25* 29.00 25.75 27.50 28.00* 28.00* S 31.50* 32.25* 27.50* T 29.00* 29.00 30.25* 25.75* E 28.75 29.00 25.00* E 28.75* 30.50 29.00* L H E 29.30 28.90 28.70 27.00 A D May 1-15 May 15-31 June 1-15 June 15-30 July 1-15 July 15-31 Aug. 1-15 Aug. 15-31 Sept. 1-15 Sept. 15-30 Oct. 1-15 Oct. 15-31 * Fewer than five f i s h in sample. 32.25 30.75 29.25 29.50* 31.00 30.20 28.00 27.75 33.50 27.75 30.00 27.75 29.00 30.00 28.00 31.25 26.50 29.00* 28.50 28.75 29.25 26.75 30.75* 27.00* 29.50 27.25 29.00* 27.00 27.00* 28.75 28.00 27.00 27.25 25.75 26.00 26.75 25.75 26.75 23.50* 24.75 26.00* 30.25 27.25 26.25* 26.00* 29.20 28.00 30.30 27.50 27.30 26.30 s u M M E R S T E E L H E A D 40 very early and late portion of the periods of record. Summer Steelhead Mean length of males was 28.2 inches, and of females was 26.9 inches. Within each study stream males were of greater mean length than females. The greatest difference i n mean lengths was found i n the Seymour River where males were 3.1 inches longer than females. Comparing lengths of samples from a l l study streams from which summer-run f i s h were captured, males from the Seymour River had the greatest mean length (30.3 inches), while females from the Capilano River had the greatest mean length (28.0 inches). Males (27.3 inches) and females (26.3 inches) with the least mean length were captured from the Coquihalla River. Table IV indicates that considerable v a r i a b i l i t y e x i s t s i n mean length of summer steelhead captured i n each bi-monthly period. The mean length of male winter steelhead was 28.4 inches; male summer steelhead had a mean length of 28.2 inches. Female winter steelhead had an average length of 28.2 inches, while female summer steelhead had a mean length of 26.9 inches. No length data for adult summer steelhead from other sources are available owing to the infrequency of occurrance of sizeable populations of these i n d i v i d u a l s . In the streams studied summer steelhead ascend streams f i v e to eight months preceding the 41 normal one to four complete years of ocean residence experienced by winter steelhead. Smith (personal communication) has samp-led stomachs of summer steelhead from Coquihalla River; they were la r g e l y empty suggesting that l i t t l e , or very r e s t r i c t e d , feeding occurs i n fresh water. Presumably growth i n length ceases under these circumstances. Belding and Kitson (1934) found that a s i m i l a r condition prevails with early-run and l a t e -run A t l a n t i c salmon. Measurements of salmon entering the Mirimichi River showed p r a c t i c a l l y no difference i n length be-tween early and late-run f i s h , i n spite of the longer sojourn and longer feeding period of the l a t t e r i n s a l t water, i n d i -cating that the larger or more advanced salmon tended to enter the r i v e r e a r l i e r . 42 LIFE-HISTORY CATEGORIES Winter Steelhead Table V indicates the l i f e - h i s t o r y categories of winter steelhead from each of the study streams. Fourteen d i f f e r e n t l i f e - h i s t o r y categories are represented. The greatest number of d i f f e r e n t l i f e - h i s t o r y categories, ten, was represented by samples from the Alouette River; the lea s t number, f i v e , was obtained from the Capilano River. Steelhead which had spent two or three years i n fresh water ( i . e . , 2/, 3/) before migrating to the ocean and which had spent either two or three years i n s a l t water ( i . e . , /2, /3), represent 91-6 percent of the t o t a l sample from a l l streams. Yearling smolts ( l / ) were found only i n the Alouette River, where they represented only 8.4 percent of the samples. Steelhead which had migrated to the ocean as smolts at the age of two or three years were found from a l l streams and rep-resented 39-9 percent and 54-9 percent respectively of t o t a l samples from a l l study streams. Four year old migrants were also captured from a l l study streams, but represented only 3-4 percent of a l l samples. Greater numbers of smolts migrated to s a l t water at three than two years of age. Only i n samples from the Alouette River (and from the Chilliwack River from data of Maher (1954)) were two year old migrants more numerous than three year old mig-Table V. Life-history categories of winter and summer steelhead captured from the British Columbia study streams for a l l years of record, 1949 to 1958. * • B m o <-t i - i a) w to 3 ni o r - i o i - i ' U r-4 G & G H ca C M « U U r-t C O ' r l C d 3 JS CO 9 XS <U 1-1 (9 r - l i—( x-\ O ^—N -rH /"•> r-4 \ O ^"s i-l /—N 3 3 xi to ,-t i-l 3 a s 3 S ' H D D i m 3 w O O" <U 0) 1-4 Q . v - ' C C T V - ' r-i o j3 x i « t at o a) < u o «Jj U U O O O CO O O CO o n 0.1% Ix 3 8 1 1 _ ^ 2.37. 1.0% , 1.3% 0.7% 1 / 6 6 3^ 4.6% 0.8% 1/ 2 4^ 1.5% 2 , 1 2 1 2 3 A. 0.7% 0.2% 1.7% 5.1% 2.0% 2 y 42 34 9 10 239 18 11 6 5 4 23 2^ 32.1% 23.3% 8.2% 15.6% 31.0% 25.7% 18.9% 15.4% 5.7% 16.0% 15.3% 2/ 42 14 12 16 236 14 7 3 9 6 1 4 32.1% 9.6% 10.8% 25.0% 30.6% 20.0% 12.1% 7.7% 10.3% 24.0% 0.7% 2 / 2 3 1 4^ 1.5% 4.7% 0.1% 3/ 1 2 1 12 4 0.1% 3.4% 1.2% 8.0% 3/ 21 72 37 22 136 28 22 19 42 12 94 4 16.0% 49.3% 33.3% 34.4% 17.9% 40.0% 37.9% 48.8% 48.3% 48.0% 62.6% 3/ 11 20 38 10 133 9 13 7 27 3 7 3^ 8.3% 13.7% 34.2% 15.6% n.3% 12.9% 22.4% 17.9% 32.0% 12.0% 4.7% 3 / 1 4 1 2 3 1 1 0.8% 2.7% 0.9% 3.2% 0.4% 1.8% 1.2% 4/ 1 3 4 1.8% 2.0% 4/ 1 9 1 1 1 6 2^ 0.7% 8.1% 1.6% 0.1% 1.4% 4.0% 1 5 3 2 3 0.8% 4.5% 0.4% 5.1% 131 146 111 64 770 70 58 39 86 25 150 100% 100% 100% 100% 100% 100% 100% 100% 100% 100% 100% * Data from Maher, 1954 (w) Winter steelhead (s) Summer steelhead C O 44 rants. In the Alouette River 65-7 percent of a l l steelhead sampled had migrated at two years of age, 2 5 . 1 percent had migrated at three years. In other streams three year old mi-grants represented between 5 2 . 9 percent (Capilano River) and 6 8 . 4 percent (Chehalis River) of a l l samples. In each stream, excluding the Alouette River, two year old migrants represented between 1 9 . 0 percent (Chehalis River) and 4 5 . 7 percent (Capilano River) of a l l samples. A l l winter steelhead captured had remained i n s a l t water for a period of one to four years following migration from fresh water and p r i o r to returning to fresh water to spawn. Individuals which had spent one year i n s a l t water were uncom-mon ( 1 . 1 percent of the t o t a l sample). Steelhead which had spent four years i n s a l t water represented 2 . 6 percent of the t o t a l sample. Two and three year salt-water resident f i s h represented 9 6 . 3 percent of the t o t a l sample. Fish with three years of salt-water existence represented 37*2 percent of the t o t a l sample, while two year ocean resident f i s h comprised 59*1 percent of the t o t a l sample. The youngest winter steelhead captured were of the l / 2 age group; three of these were captured from the Alouette River. The oldest i n d i v i d u a l s captured were a t o t a l of eight steelhead from the Alouette, Chehalis and Coquihalla Rivers with a l i f e - h i s t o r y category of 4 / 3 , and a t o t a l of eight s t e e l -head from the Alouette, Coquitlam, Chehalis, Cheakamus and Sey-mour Rivers with l i f e - h i s t o r y categories of 3 / 4 . 45 Figure 7 shows for each study stream the percentages ( i n monthly i n t e r v a l s ) of winter steelhead represented by d i f f e r -ent major l i f e - h i s t o r y categories. No trend toward early or late season entry of p a r t i c u l a r age groups may be noted. How-ever, i f differences i n timing of stream entry by i n d i v i d u a l s of p a r t i c u l a r l i f e - h i s t o r y patterns do i n fact e x i s t from month to month, t h i s e f f e c t would tend to be masked by the grouping of captures from d i f f e r e n t years of record used to construct the composite figures i l l u s t r a t e d . Also, use of angling as a sampling technique would tend to obscure modality which may e x i s t by extending the capture period for a p a r t i c u -l a r group of steelhead over several months. Shapavalov and Taft (1954) found that representation of various age groups of winter-run steelhead within the run to Waddell Creek, C a l i f o r n i a , i s not the same throughout the sea-son. The / l f i s h of smaller size predominated i n the early part (November, December, January) of the run; the /2 f i s h appeared i n increasing numbers as the season progressed (February, March), and the larger / l f i s h increased i n abund-ance during the late portion of the run (March, A p r i l ) . Similar phenomena have not been reported by other investigators. Summer Steelhead Table V shows the number and percentage of summer s t e e l -head from each of the study streams with d i f f e r e n t l i f e - h i s t o r y 46 32 28 2 4 2 0 I 6 I 2 8 4 0 3 2 UJ ^ 2 8 ui cr 11 n o 2 0 o O , c COQUITLAM R. A L O U E T T E R. A .--^ \ \ CHEHALIS R. CAPILANO R. \ \ \ / \ \ \ / \ 8 4 0 3 2 28 24 2 0 I 6 I 2 8 4 0 JAN FEB MAR APR Vz 3 / Figure 7. Life-history categories of winter steelhead captured within each British Columbia study stream (except Cheakamus River), represented by month as a percent of total captures, for a l l years of record, 1949 to 1958. 47 3 2 30 28 26 24 22 2 0 I 8 16 14 12 10 8 6 4 2 0 C A P I L A N O \R. S E Y M O U R R. \ jl \ \ / ' • \ \ /'A \ // "A / / \\ / / \\ i / \ \ / 11 \ i \\ / \ / A \ x ' \ MAY JUNE JULY AUG SEPT OCT MAY JUNE JULY AUG SEPT OCT 2 / 2 3 / 2 Figure 8. Life-history categories.of summer steel-head captured within British Columbia study streams, represented by month as a percent of total captures, for a l l years of record, 1949 to 1958. MAY JUNE JULY AUG SEPT OCT 48 pat terns . Ten d i f f e r e n t age c lasses are represented. The great-est number of age c lasses , n i n e , was represented by samples from the Coquihal la River ; the leas t number, f o u r , were from the Seymour R i v e r . Summer steelhead which had spent two or three years i n f r e s h water ( i . e . , 2/, 3/) before migrating to the ocean and which had spent one to four years i n s a l t water ( i . e . , / l , / 2 , /3, /4) represented 95.6 percent of the t o t a l sample from a l l streams. Y e a r l i n g smolts were found i n the Capilano and Coqu-i h a l l a River ; they represented only 0.8 percent of a l l samples. Nine f o u r - y e a r - o l d smolts were recorded from the Coquihal la R i v e r ; they represented 6.0 percent of a l l samples from that stream. Two-year-old seaward migrants represented 19•7 percent of a l l samples, while 75.9 percent were t h r e e - y e a r - o l d migrants. Considerable v a r i a t i o n e x i s t s i n the percentages of each l i f e - h i s t o r y pattern represented from stream to stream (see Table V ) . However, i n a l l streams there are s i m i l a r r e l a t i o n -ships among most l i f e - h i s t o r y ca tegor ies . For example, i n each stream t h r e e - y e a r - o l d migrants outnumber two-year-old migrants. Adult steelhead representing the l i f e - h i s t o r y category 3/2 were captured i n greater numbers than were those of a 3/3 pat-t e r n ; and, except from the Coquihal la R i v e r , 2/3 adults out-numbers 2/2 a d u l t s . A l l summer steelhead captured had remained i n s a l t water from one to four years f o l l o w i n g migration from f r e s h water and 49 p r i o r to returning to fresh water to spawn. Only one i n d i v i d u a l had spent four years i n s a l t water; t h i s f i s h was of a 3/4 l i f e - h i s t o r y category and was from the Capilano River. S t e e l -head which had spent only one year i n s a l t water were captured from the Coquihalla and Capilano River; the 19 f i s h i n t h i s category represented 7«4 percent of the t o t a l sample. Eighteen of these f i s h were obtained from the Coquihalla River. Summer steelhead of the /2 and /3 category constituted the bulk of the samples from a l l streams. Three-year salt-water residents comprised 20.4 percent of the t o t a l sample from a l l streams. Fish which had spent two years i n s a l t water were i n the major-i t y ; they represented 71.8 percent of the t o t a l sample. The r a t i o of f i s h which had spent two years i n s a l t water to those which had spent three years i n t h i s environment i s not constant among streams containing summer steelhead. In the Capilano River the r a t i o of /3 to /2 f i s h captured i s 1:1.3, i n the Seymour River 1:1.8 and i n the Coquihalla River the r a t i o i s 1:15.5. Also, as noted previously, a much higher percentage of f i s h which had spent only one year i n s a l t water were cap-tured from the Coquihalla River than from other streams. Length at maturity i s related to the length of salt-water residence of steelhead. Maher (1954) has shown that winter steelhead from the Chilliwack River att a i n a length of approx-imately 19 inches after one year of salt-water l i f e , 2 8 inches after two years and 32 inches aft e r three years. The shorter term of salt-water residence experienced by summer steelhead of 50 the Coquihalla River i s r e f l e c t e d i n the smaller mean size at capture for these f i s h noted i n the discussion of adult lengths. At capture, summer steelhead from the Capilano and Seymour Riv-ers were of 1.8 and 1.9 inches greater mean length than were those from the Coquihalla River. The youngest summer steelhead captured were two i n d i v i d -uals from the Capilano and Coquihalla Rivers with a l/2 l i f e -h i story category and three f i s h from the Coquihalla River with a 2/1 category. The oldest i n d i v i d u a l captured was one f i s h from the Capilano River with a l i f e - h i s t o r y category of 3/4-The percentage of the t o t a l number of summer steelhead represented by d i f f e r e n t major l i f e - h i s t o r y patterns captured i n each study stream i n monthly i n t e r v a l s i s shown i n Figure 8. As was observed for winter steelhead, no trend toward early or late season entry of p a r t i c u l a r age groups i s noted. Grouping of samples and the use of angling as a sampling method would again tend to obscure any modality which may be present among captures. Also, except i n the Coquihalla River, the capture period i s of shorter duration than for winter steelhead, thus making trends which might e x i s t more d i f f i c u l t to observe. 51 STEELHEAD POPULATIONS OF THE PACIFIC COAST In the following section l i f e - h i s t o r y c h a r a c t e r i s t i c s of steelhead populations from a wide geographical range are considered. For t h i s purpose populations from several streams of the P a c i f i c Coast of North American from central C a l i f o r n i a to southern B r i t i s h Columbia are compared. THE STREAMS The geographical location of the streams considered i n t h i s section i s shown i n Figure 9- Physical features of each stream are given i n Table VI, and water temperatures for each stream, expressed as a mean of d a i l y recordings at monthly i n t e r v a l s , are shown i n Figure 10. Data for the Capilano River are included for comparison with more southerly streams. A b r i e f description of the char-a c t e r i s t i c s of each stream and i t s topography i s presented below. Waddell Creek, C a l i f o r n i a Waddell Creek flows to the P a c i f i c Ocean i n central C a l i f o r n i a . Approximately three miles upstream of i t s mouth the stream branches to a main west and east fork. The stream i s situated i n the humid coast belt which receives most of i t s annual p r e c i p i t a t i o n during December, January and February. P r e c i p i t a t i o n during the summer i s l i g h t . These con-52 Figure 9 . Location of the Pacific Coast study streams Table VI. Physical characteristics of the Pacific coastal study streams Water Temperature Lake Present Length Drain Area i n Latitude (Miles) (Sq. Miles) Minimum Maximum Drainage Waddell Creek, C a l i f . 37°6' N 12 26 36° F Jan. 68° F Sept. No South Coastal Streams, Oregon Coquille River, Oregon Alsea River, Oregon North Coastal Streams, Oregon 42 30»N 25-113 43°0' N 60 44"30'N 35 45 0» N 25-113 Green River, Washington 47°30'N 86 1,060 477 41°F Feb. * 40° F > 70° F > 70°F 73°F July o >70 F 55°F No No No No No Range Capilano River, B. C. 49 15'N 22 68 35° F Jan. 58°F Aug. No ** * No information available ** Reservoir established since conclusion of study period 54 Figure 10. Mean monthly water temperatures for a complete year of record for some coastal study streams. 55 d i t i o n s contribute to large variations i n the flow of the stream. T y p i c a l l y , d a i l y water flows range between 30 and 500 cfs from mid-December u n t i l mid-May, decrease to 5 cfs by the end of July and remain from 3 to 5 cfs u n t i l the heavy rains commence i n mid-December. The stream-bed i n the headwater portions of the stream i s composed of large boulders and bedrock; deep pools are numer-ous. The central regions of the stream are broader and con-t a i n fewer deep pools. The stream bed i s composed of coarse rubble and sand. Most coastal C a l i f o r n i a streams and some streams of the south coast of Oregon have a drowned mouth or M l a g o o n M which forms at the termination of the stream. The seaward sand-bar forming the lagoon at Waddell Creek opens and closes the stream mouth depending on stream flows, tides and wind and wave action. Normally the stream mouth i s closed from late July or August u n t i l the heavy rains of mid-December ap-preciably increase stream flows. Alsea River, Oregon The Alsea River flows to the P a c i f i c v i a a ten mile long estuary at Alsea Bay, Oregon. Four major t r i b u t a r i e s c o n t r i -bute most of the steelhead trout production i n the drainage. The stream beds of the upper t r i b u t a r y streams are composed largely of gravel and rubble areas; the main stream bed i s composed la r g e l y of bedrock. No closure of the r i v e r mouth occurs i n summer. 56 Water flow of the r i v e r i s c h a r a c t e r i s t i c of central P a c i f i c coastal streams. Runoff i s usually heavy during the period from October through A p r i l but decreases markedly i n the summer months. Streams of South Coastal, Central and North Coastal Oregon B a l i (1958) has compared the physical and b i o l o g i c a l feat-ures of 14 coastal streams of Oregon containing steelhead pop-ulations. He has noted that the physical c h a r a c t e r i s t i c s of the streams along the coast of Oregon are s i m i l a r . They are generally clear i n spring, summer and f a l l , but most often become muddy i n winter from heavy rains. The streams t y p i c a l l y have moderately rapid flows and steep channel gradients. Sim-i l a r i t i e s among l i f e - h i s t o r y c h a r a c t e r i s t i c s of some steelhead populations have allowed for grouping of these streams to four south coastal, one intermediate (Coquille River) and nine north coastal streams. Green River, Washington The Green River enters tidewater south of Seattle, Washing-ton. The upper 65 miles of the stream flow r a p i d l y through canyon and r i f f l e areas of coarse gravel and boulders. The lower portion of the r i v e r flows more slowly over a bottom of mud and sand. Three major t r i b u t a r y streams are present. No water flow or temperature data are available from the 57 Green River. However, water temperature data for the Chehalis River ( i n central coastal Washington) are presented i n Figure 10, assuming that the data are generally representative of temperatures experienced i n most larger streams i n central coastal Washington. Water temperatures are lower than those recorded for C a l i f o r n i a and Oregon. During the months of December and March mean monthly temperatures of s l i g h t l y less than 45°F were experienced. Water temperatures apparently r i s e i n the spring i n p a r a l l e l with those of Oregon and C a l i f -ornia, then decrease i n the f a l l months at a s l i g h t l y faster rate. Capilano River, B r i t i s h Columbia The physical features of the Capilano River were discussed previously (Page 23). Figure 10 shows that mean water temper-atures are approximately 10°F lower than those of more south-e r l y streams. This divergence i s greatest during the winter and early spring months. A complete year of water flow (volume) record for the Capilano River i s presented i n Figure 2. 58 STEELHEAD POPULATIONS Timing of Runs A comparison of data from the study streams shows that i n the central and southern parts of t h e i r geographic range, winter steelhead f i r s t enter and ascend streams to spawn during a r e l a -t i v e l y constant time period (October 15 to November 15). Num-bers of samples reported throughout the capture period suggest that i n south and north coastal streams near equal numbers of f i s h enter streams during December and January, the greatest number enter during February and thereafter numbers decrease. However, t h i s study and others (Shapavalov and Taft, 1954) ( B a l i , 1958) have shown that variations i n timing of stream entry and seasonal variations i n timing of the bulk of the migration do e x i s t . The existence of two peaks of stream entry at Waddell Creek, C a l i f o r n i a , has been shown to be a consequence of migration timing of steelhead o f / p a r t i c u l a r age classes. This phenomenon has not been documented elsewhere although ob-servations from the Green River, Washington (Pautzke and Meigs, 1940), suggest that a sim i l a r s i t u a t i o n obtains there. Unfort-unately, the anglers* samples u t i l i z e d i n t h i s present study and those used by B a l i i n Oregon would tend to mask such an e f f e c t . Spawning occurs i n a l l study streams during A p r i l and early May. Capture of spawned f i s h or * J k e l t s " commences shortly afterward. 59 Sex Ratios and Repeat Spawning Shapavalov and Taft (1954) have shown that when the sex r a t i o of a steelhead population as a whole i s determined, con-sideration should be given to the complexities created by the m u l t i p l i c i t y of l i f e - h i s t o r y categories, d i f f e r e n t i a l s u r v i v a l of sexes among repeat spawners, and variations of behaviour within c e r t a i n l i f e - h i s t o r y categories. Unfortunately, a pau-c i t y of data often makes such a thorough study of these related factors impossible i n the present study. Table VII summarizes the data available on sex r a t i o s and repeat spawning of some steelhead populations geographically separated by considerable distances along the P a c i f i c coast of the United States and B r i t i s h Columbia. I t i s apparent that the sex r a t i o s of the steelhead popu-l a t i o n s do not change from the southern portion of t h e i r range to the more northern ones. The trapping records of Shapavalov and Taft i n C a l i f o r n i a , Chapman (1957) i n Oregon and Pautzke and Meigs (1940) i n Washington show that a male:female sex r a t i o of near 1:1 i s found among adult steelhead populations of these geographically separate areas. The greater proportion of females (1 male : 1.3 females) i n the adult run to Waddell Creek i s large l y a r e s u l t of the influence of the disproport-ionate s u r v i v a l of female repeat spawners over males and the high incidence of repeat spawners i n the t o t a l run. A comparison of sex r a t i o s obtained from sampling by trap-Table VII. Sex ratios and frequency of repeat spawning of steelhead captured from Pacific coastal study streams Waddell Creek California South Coast Oregon Coquille River Oregon North Coast Oregon Alsea River Oregon Green River Washington Chilliwack River British Columbia South Coast British Columbia (t) Trapped (a) Angled Sex Ratio of 7. Total Run Repeat Male:Female Spawners (t) 1:1.13 17.2 (a) 1:1.8 53.3 (a) 1:1.4 38.3 (a) 1:1.6 27.9 1:0.9 11.1 (t) (1955-56) (Av. 1953-55) (t) 1:1 (a) 1:1.4 5.8 (a) 1:1.8 11.0 (Av. 1949-57) % % % Second Third Fourth Spawners Spawners Spawners 15.0 2.1 0.1 36.3 14.1 3.0 30.9 4.9 2.5 19.5 6.3 1.9 9.2 1.9 5.6 0.2 9.5 1.5 61 ping and angling may be obtained from Table VII. Angling appar-ently selects a greater proportion of female steelhead than i s representative of the population, and therefore i s unreliable as a method of determining the sex r a t i o s of the t o t a l population. This view i s supported by the findings of Larkin et a l (1951) for rainbow trout at Paul Lake, B r i t i s h Columbia. At Waddell Creek i t was found that males predominated i n the spawning run i n the early months (November, December), and that females were more numerous i n the l a t t e r portions of the run (January to March). B a l i (1958) has reported s i m i l a r f i n d -ings for streams of south and north coastal Oregon. This s i t u -ation has not been found to e x i s t i n other of the study streams. Within each study stream there i s a sharp decline i n num-bers from second spawners to t h i r d spawners and f i s h spawning for a fourth time represent a n e g l i g i b l e portion of the t o t a l run. Survival following spawning has been found to be higher among females than among males. At Waddell Creek, 1.6 female steelhead returned for each male repeat spawner. Chapman has found that repeat spawners i n the Alsea River were present i n the r a t i o of one male to 2.5 females. B a l i (1958), summarizing the r e s u l t s of a study of 14 Oregon coast streams has stated that "the females showed a greater s u r v i v a l after spawning than did the males " Pautzke and Meigs (1940) reported that a sample of 99 Puget Sound steelhead had f i v e repeat spawners present which had a sex r a t i o of one male to four 62 females. The 65 repeat spawners reported previously for B r i t i s h Columbia study streams (Table II) had a sex r a t i o of one male to 4-4 females. These data show conclusively that female steelhead survive the r i g o r s of spawning much more successfully than do males. This fact explains, i n part, the greater numbers of females captured by anglers. Within Oregon, B a l i (1958) has related the greater number of female steelhead captured i n south coastal than i n north coastal streams to the higher s u r v i v a l of spawn-ers i n southern streams. Table VII indicates that repeat spawning steelhead are fewer i n number i n north coastal populations. This trend sup-ports the finding of B a l i who has described a s i m i l a r phenomenon for coastal streams of Oregon. Also, the a b i l i t y of i n d i v i d u a l steelhead to return to spawn i n successive years appears to decrease i n more northern streams. No fourth spawning s t e e l -head were reported from the Alsea River, Oregon, Washington or B r i t i s h Columbia. Lengths and L i f e History Categories The length which an i n d i v i d u a l steelhead attains at matur-i t y i s dependent upon i t s growth i n the ocean environment and i s l a r g e l y independent of the size attained i n fresh water (Maher, 1954)- The amount of ocean growth i s large l y dependent upon the number of years spent i n that environment before matur-i t y , and may be modified by the f i s h e s ' previous spawning h i s t -63 ory and oceanic conditions. Chapman (1957) presented data which suggest that smolts of smaller sizes produce adults of the greatest ages at maturity. B a l i (1958) has shown that along the coast of Oregon s i m i l a r i t i e s e x i s t among l o c a l s t e e l -head populations which allow for t h e i r grouping as southern, central and northern populations. Among adults, northern f i s h had greater length and weight at maturity than southern f i s h , and f i s h from a central population (Coquille River) were i n t e r -mediate i n length and weight. This comparison i s expanded here to indicate the length differences of mature steelhead which e x i s t throughout a greater portion of t h e i r geographic range. Shapavalov and Taft (1954) have studied lengths and weights of a l l adult steelhead captured during a nine year trap-ping study at Waddell Creek. Analysis of these data has shown that growth varied with abundance, among d i f f e r e n t l i f e - h i s t o r y categories and between sexes. The mean length of a l l adult winter steelhead captured i n the upstream trap i n a l l years of study was 22.9 inches. In Oregon the mean length of a l l steelhead captured from the Alsea River by Chapman i n a tagging study extending from 1951 to 1956 was 25.5 inches. B a l i , analysing angler sample data from numerous watersheds of coastal Oregon found that the mean length of f i s h from the southern region was 26.1 inches, from the central region 26.3 inches and from the northern region 2 6.5 inches. In B r i t i s h Columbia, Maher (1954) analysing anglers' samples 64 from the Chilliwack River found the mean length of a l l adults captured to be 29-7 inches. The mean length of a l l f i s h sampled for the present study was 28.3 inches. I f the possible bias of anglers toward retaining and reporting upon larger f i s h may be disregarded, i t i s apparent that the mean size of steelhead entering streams to spawn increases i n more northerly areas. This e f f e c t i s apparent at least from central C a l i f o r n i a to southern B r i t i s h Columbia. The differences noted i n mean lengths of geographically separate steelhead populations can be explained, at least i n part, by a tendency for f i s h from more northern areas to spend a greater length of time i n the ocean before sexual maturity-i s attained. Table VIII i l l u s t r a t e s t h i s trend. Steelhead which have spent only one year i n s a l t water decline from 46.5 percent of the t o t a l adult population at Waddell Creek, C a l i f -ornia, to only 0.5 percent of the adult population i n the Chilliwack River, B r i t i s h Columbia. Numbers of /2 f i s h remain f a i r l y constant i n each area, while a progressively greater number of /3 f i s h are found i n more northern areas. Numbers of /4 f i s h are f a i r l y constant throughout t h e i r range. Data from scale samples of steelhead taken over a large portion of t h e i r geographic range indicate that f i s h comprising the smolt migration achieve t h i s condition at a variety of ages and that d i f f e r i n g percentages of f i s h of the same age groups are present i n smolt migrations. Ages at migration of smolts from d i f f e r e n t geographic locations are presented i n Table VIII. Table VIII. Mean lengths and age composition of adult steelhead captured within coastal study streams. Mean Length Freshwater Residence Saltwater Residence of Adults (inches) 1/ 2/ 3/ 4/ / l 12 /3 /4 Waddell Creek, C a l i f . 22.9 10.1% 72.3% 16.7% 0.9% 46.5% 47.0% 6.0% 0.5? Alsea River, Oregon 25.5 1.4 80.2 18.2 0.2 5.4 66.4 25.6 2.6 South Coastal Streams Oregon 26.1 0.7 43.0 53.3 3.0 85.2 14.1 0.7 -Central Coastal Stream, Oregon 26.3 - 54.4 44.4 1.2 50.6 44.4 5.0 -North Coastal Streams Oregon 26.5 6.9 71.7 21.4 - 25.0 64.7 10.3 -Green River, Wash. * 16.0 75.0 9.0 - 7.0 66.0 25.0 -Chilliwack River, B.C. 29.7 2.0 62.6 35.0 0.4 0.5 49.9 49.1 0.5 Southern British 28.3 1.8 39.9 54.9 3.4 1.1 59.1 37.2 2.6 Columbia Study Streams * Data not available 66 Steelhead smolts descend to the sea at ages from one to four years, with the bulk of the migrants at two or three years of age. Studies from various coastal streams from north-ern C a l i f o r n i a to southern B r i t i s h Columbia show that yearling migrants constitute between 0.0 and 16.0 percent of the v a r i -ous populations. In most instances two-year-old migrants are i n the majority, constituting between 39.9 and 80.2 percent of the various smolt populations. Three-year-old smolts are gen-e r a l l y present i n lesser numbers than two-year-old smolts, although exceptions occur. -'•hey comprise between 9.0 and 54 • 9 percent of the various populations. Four-year-old migrants are very few i n number; i n no instance do they comprise more than 3«4 percent of any population. 67 DISCUSSION L i f e - h i s t o r i e s of steelhead trout are complex and greatly varied. The f i r s t part of the present study has examined v a r i -ation i n l i f e - h i s t o r y c h a r a c t e r i s t i c s within and amongst popu-lat i o n s i n a r e s t r i c t e d area of B r i t i s h Columbia. The second part has considered the v a r i a t i o n between steelhead populations along the coast of North America and has suggested that diver-gence of some c h a r a c t e r i s t i c s i s p a r a l l e l to geographic separ-ation of the population studied. Maher (1954) has suggested that the variety of l i f e - h i s t o r y patterns exhibited by t h i s species may represent an adaptation which allows steelhead trout populations to survive through years of extremely adverse conditions. This v a r i a t i o n has probably allowed for the south-ward extension of sizeable steelhead populations beyond that experienced by most P a c i f i c salmon. I t i s also possible that f l e x i b i l i t y of steelhead population c h a r a c t e r i s t i c s allows for the existence of small populations within many stream systems uninhabited by some species of P a c i f i c salmon. WINTER AND SUMMER STEELHEAD Steelhead may be divided into two d i f f e r e n t groups by d i f -ferences i n behaviour p r i o r to spawning. Winter steelhead enter streams to spawn during the period October to A p r i l to spawn i n March and A p r i l . Summer steelhead- enter streams from May to September to spawn during March and A p r i l . They are 68 fur ther d i s t i n g u i s h e d i n that winter steelhead are found i n a larger number of coas ta l streams than are summer steelhead. L i f e - h i s t o r y c h a r a c t e r i s t i c s such as s e x - r a t i o s , frequency of repeat spawning, adult lengths and years of f resh and s a l t -water residence are s i m i l a r between the two populat ions . Smith (I960) has described d i f f e r e n c e s i n p h y s i c a l ap-pearance among spawning summer and winter steelhead from the Capilano R i v e r . Summer steelhead exhibi ted a t y p i c a l b r i g h t red "rainbow" c o l o r a t i o n on the g i l l covers and along the l a t e r a l l i n e , and males had well -developed hooked snouts. Both of these c h a r a c t e r i s t i c s were l a r g e l y absent among winter f i s h spawning at the same time. Of greatest i n t e r e s t i s the f i n d i n g by Smith (i960) that among a sample of 30 summer and winter steelhead, a l l summer f i s h examined exhibi ted g i l l raker t i p s which were f l a t t e n e d and b i f u r c a t e d . Winter f i s h d i d not ex-h i b i t t h i s c h a r a c t e r i s t i c . These f i n d i n g s suggest that d e f i n -i t i v e morphological d i f f e r e n c e s may e x i s t , at l eas t among adult forms, which w i l l d i s t i n g u i s h these populations more adequately. A l s o , a r i t i f i c a l l y spawned j u v e n i l e steelhead of "winter " and "summer" stock have been planted i n the Capilano R i v e r . To date re turning adults have been i n the same stages of sexual maturity as were t h e i r parents at capture. That i s , none of the summer steelheads T progeny returned as winter f i s h , and none of the winter steelheads* progeny returned as summer f i s h . The populations appear to be separated by s t rongly h e r i t a b l e c h a r a c t e r i s t i c s . 69 Adult sockeye salmon exhibit " r a c i a l " variations i n timing of entry to spawning streams. Gilhousen (i960) summarized i n -formation r e l a t i n g to the timing of ascent of races of sockeye salmon within the Fraser River system. He has concluded that "normal" or mean timing has arisen through evolution by selec-t i v e processes, the mean value representing the optimum point of s u r v i v a l conditions for a p a r t i c u l a r race. He has concluded that sockeye maturation i s a response to the pattern of chang-ing length of day, and i n d i v i d u a l populations which spawn at d i f f e r e n t times must d i f f e r g e n e t i c a l l y i n t h e i r response to changes i n day length. Belding and Kitson (1934) discussed possible causative conditions within streams which may operate to encourage dev-elopment of observed early and late run A t l a n t i c salmon.. F a l l runs of A t l a n t i c salmon (corresponding most c l o s e l y to winter-run steelhead) were observed to occur almost exclusively i n small r i v e r s with spawning grounds near to the stream mouth. Variations i n water flows and temperature resulted i n only temporary variations i n salmon migration patterns. Of greatest significance was the finding that early run f i s h had more highly developed gonads than did salmon which entered streams l a t e r . Also, early run and late run salmon showed p r a c t i c a l l y no d i f -ference i n mean fork length i n spite of the (assumed) longer feeding period of the l a t t e r i n s a l t water. I t was concluded that early r i v e r entry i s associated with precocity or acceler-ated development i n A t l a n t i c salmon. 70 Precocious gonadal development apparently i s not a prime cause of upstream migration of summer steelhead. Examination of f i s h sampled at the Cailano River trapping f a c i l i t i e s has shown gonads to be but s l i g h t l y developed. Also, i t i s d i f -f i c u l t to explain the early migrations of summer steelhead on a basis of se l e c t i o n for optimum stream conditions. During summer and early autumn months stream water l e v e l s are low and water temperatures are high, conditions which do not favour s u r v i v a l of salmonlds. Chapman (personal communication) has observed that within coastal streams of Oregon, summer steelhead are r e s t r i c t e d to streams which contain deep pools with slow moving water within which the f i s h may hold during periods of summer and autumn low water volumes. Within B r i t i s h Columbia, observation of the topography of streams containing populations of summer steelhead suggests that natural temporary ba r r i e r s (small w a t e r f a l l s , stretches of extremely turbulent water) which are navigable by f i s h only at summer water flows may be present within a l l streams which contain these populations. P a r t i a l b a r r i e r s are present within the Seymour and Coquihalla Rivers, and such a ba r r i e r was pres-ent i n the Capilano River p r i o r to establishment of a reservoir. Barriers of t h i s type may allow upstream passage of only the early, more vigorous stream entrants. This condition, would tend to perpetuate an i s o l a t e d population of separately repro-ducing, early migrating adult steelhead, the so-called summer steelhead. 71 TIMING OF STREAM ENTRY Populations of steelhead trout which inhabit t r i b u t a r i e s of the same r i v e r system ( i . e . , lower Fraser River) and those which inhabit coastal streams within a r e s t r i c t e d area ( i . e . , coastal Oregon) exhibit differences i n behaviour despite t h e i r proximity to each other. The timing of stream entry of popula-tions of winter and summer steelhead i s greatly divergent. Also, discreet populations of winter steelhead f i r s t entered the B r i t i s h Columbia study streams during d i f f e r e n t time i n t e r -v a l s . The dates of f i r s t capture extended from November 15 to January 1 except i n the Cheakamus River where the f i r s t capture of winter f i s h was reported after A p r i l 1. Instances of delayed entry to streams of winter steelhead s i m i l a r to that observed for the Cheakamus River have not been reported elsewhere. This late winter run coincides with the delayed freshet condition which e x i s t s within the stream (Figure 2). Correlation of the late run with the increased water volumes suggests that a freshet condition i s required to i n i t i a t e upstream movement of spawners. Briggs (1953, studying the winter steelhead population of the Mad River, C a l i f o r n i a , found that steelhead enter streams i n greatest numbers during periods of temporary high water flows (freshet conditions) accompanied by a b r i e f r i s e i n water temperature. Although timing of stream entry may vary within a r e s t r i c t -ed area, there i s no evidence of a progressive trend toward early or late stream entry between geographically separated 72 populations. Shapavalov and Taft (1954) have reported d i s t i n c t "peak11 numbers of steelhead entering Waddell Greek at i n t e r v a l s . Anglers have reported s i m i l a r occurances for other streams (Pautzke and Meigs, 1940), but t h i s phenomena i s d i f f i c u l t to detect i n c r e e l census studies where angling e f f o r t varies with favourable and unfavourable water and weather conditions. SEX RATIOS Almost twice as many female as male steelhead were cap-tured from study streams within southern B r i t i s h Columbia. A s i m i l a r s i t u a t i o n p r e v a i l s within anglers' samples from along the P a c i f i c coast. This sex r a t i o c o n f l i c t s with the near 1:1 r a t i o obtained from trapping studies (Shapavalov and Taft, 1954) (Chapman, 1957). Apparently, sport f i s h e r i e s select for females i n anadramous populations of rainbow trout. Two factors are known to emphasize t h i s observed s e l e c t i v -i t y . F i r s t , frequency of repeat spawning i s greater for female steelhead than for males. The s l i g h t l y greater numbers of females present i n populations because of t h e i r greater s u r v i v a l following spawning r e s u l t s i n capture of greater numbers of t h i s sex by anglers. Within southern B r i t i s h Columbia repeat spawning was most frequent among steelhead from Cheakamus River; here also the r a t i o of females to males captured was greatest. Second, males deteriorate i n appearance to a greater extent than females as spawning approaches, therefore, greater 73 numbers of males than females are released a l i v e during the l a t e r portion of the spawning run. Shapavalov and Taft (1954) and B a l i (1958) have reported entry to streams of a greater proportion of males than females during the early (October 1 to January 1) portion of the spawning run of winter steelhead. This condition was not discovered for streams of southern B r i t i s h Columbia, nor from data presented by Maher (1954). REPEAT SPAWNING Repeat spawning has been found to range from 5 to 31.3 percent among winter-run steelhead populations and between 4.4 and 6.3 percent among summer-run steelhead populations i n lower coastal B r i t i s h Columbia. The high incidence of repeat spawning observed for f i s h from the Cheakamus River (31.3 percent) may be a consequence of a contracted term of fresh-water residence p r i o r to spawn-ing, as few f i s h enter the stream to spawn u n t i l A p r i l 1. Such a thesis assumes that a fresh-water existence for adult anadromous trout i s more rigorous than i s a salt-water e x i s t -ence . This assumption i s supported by the observation that within streams of southern B r i t i s h Columbia the incidence of repeat spawning i s s l i g h t l y greater for winter steelhead than summer steelhead. The l a t t e r spend the greatest length of time i n fresh water p r i o r to spawning. 74 Along the P a c i f i c coast females more commonly survive to spawn a second or t h i r d time than do males, and t h i s tendency increases from southern to northern areas. Idler and Clemens (1959) measured loss of f a t , protein and energy ( i n c a l o r i e s per kilogram of weight) of sockeye salmon during t h e i r spawning migration from the sea to lakes i n the upper Fraser River system. Females from both the Chilko and Stuart runs u t i l i z e d a higher percentage of fat s , proteins and energy reserves than did t h e i r male counterparts. This finding agrees with Belding (1934) who determined that the percentage of body weight l o s t by spawning female A t l a n t i c salmon i n the Mirimichi River, New Brunswick, was greater than that l o s t by males. I t may be assumed that female steelhead trout lose a greater percentage of body weight during the spawning migration, as do members of some other salmonid populations. Probably the lower s u r v i v a l of males i s related to causes other than condition factors. These other causes are not known precisely, but they may be associated with early stream entry (as at Waddell Creek and within coastal streams of Oregon), a tendency to remain on the spawning grounds for extended periods of time or f i g h t i n g i n defence of spawning t e r r i t o r y . 75 FORK LENGTHS Mean fork lengths of populations of winter and summer steelhead within a lim i t e d geographic range were found to vary-only s l i g h t l y . However, winter steelhead from the Cheakamus River were larger than f i s h of a l l other populations. This greater mean length i s a c o r o l l a r y of the high incidence of repeat spawning (and therefore the greater number of years of salt-water residence) of the ind i v i d u a l s sampled. The summer steelhead of the Coquihalla River had the lowest mean length, a consequence of a shorter mean time of salt-water residence than exhibited by other summer steelhead populations. Mean fork lengths of steelhead populations from streams along the P a c i f i c coast increase from central C a l i f o r n i a to southern B r i t i s h Columbia. This may be a consequence of the tendency for steelhead to spend more years i n salt-water i n more northern than southern areas. Marr ( 1 9 4 3 ) observed that older pink, chum and coho salmon from various P a c i f i c coast watersheds are more abundant i n northern areas of t h e i r range of d i s t r i b u t i o n . LIFE-HISTORY CATEGORIES This study, and others, show that the number of years which steelhead from the same or c l o s e l y associated watersheds spend i n fresh and s a l t water i s not constant. Juvenile s t e e l -head spend from one to four years i n fresh water pr i o r to migra-76 t i o n , and one to four years i s spent i n s a l t water pr i o r to return for spawning. The youngest mature steelhead captured was three years of age; the oldest was seven. The r a t i o s of years spent i n fresh and s a l t water by s t e e l -head i s not constant along the P a c i f i c coast. In a l l streams except those of south coastal B r i t i s h Columbia two-year-old smolts predominate. Numbers of three-year-old smolts increase i n northern areas. Some instances (Shapavalov and Taft, 1954, B a l i , 1958) of large numbers of three-year-old smolts have been observed to r e s u l t from delay of smolt e x i t by "trapping 1 1 through closing of bars at stream mouths i n C a l i f o r n i a and southern Oregon. Fish with longer salt-water residence are progressively more abundant i n northern areas. CONTROL OF POPULATION CHARACTERISTICS Figure 11 i l l u s t r a t e s the manner i n which l i f e - h i s t o r y c h a r a c t e r i s t i c s of steelhead populations vary along the P a c i f i c coast. Change, i n mean monthly water temperature i s included as a possible environmental factor governing population charac-t e r i s t i c s . The greater mean adult lengths observed among northern steelhead populations i s a r e s u l t of the longer oceanic growing period of these f i s h . Lengths of adult steelhead are la r g e l y independent of lengths obtained i n fresh water. The decrease i n frequency of repeat spawning noted for north coastal populations i s probably related to the greater number NORTHERN MEAN MONTHLY YEARS OF RESIDENCE WATER SEX RATIO REPEAT SPAWN. ADULT LENGTH FRESH-WATER SALT-WATER TEMPERATURE S T E E L H E A D POPULAT IONS SOUTHERN S T E E L H E A D POPULATIONS Figure 11. Schematic representation of changes in life-history attributes of steelhead populations, and mean stream temperatures, along the Pacific coast; thick portions of the pointers suggest greatest frequency or amount of an attribute, thin portion, the least. 78 of years which f i s h of these populations spend i n both fresh and s a l t water. The p o s s i b i l i t y of s u r v i v a l to subsequent spawning migrations decreases as the age of steelhead increases. The divergence of c h a r a c t e r i s t i c s may be related to gen-e t i c or environmental influences, or both. Marr ( 1943) showed that some species of P a c i f i c salmon diverge progressively i n some l i f e - h i s t o r y c h a r a c t e r i s t i c s throughout t h e i r range. Svardson ( 1954) demonstrated that smolt age of A t l a n t i c salmon within the B a l t i c Sea increased from south to north. Elson ( 1957) has suggested for A t l a n t i c salmon that the age at which smolts migrate to sea i s governed by t h e i r rate of growth i n fresh water. Chapman ( 1957) has related the age of steelhead smolts to the number of years which they spent i n s a l t water; the youngest (and presumably most rapid-growing) smolts spend the shortest periods i n s a l t water. Ricker ( 1959) states that the v a r i a t i o n which P a c i f i c salmon and steelhead trout exhibit has both a genetic and environmental basis, and "scores of g e n e t i c a l l y d i f f e r e n t stocks of a species can e x i s t i n one and the same r i v e r system, ha l f a dozen or more even within a single lake". This view i s supported by Vernon (1957) who has determined that several d i f f e r e n t races of kokanee e x i s t within Kootenay Lake, B r i t i s h Columbia, but he has suggested that growth, age at maturity, and morphological differences are g e n e t i c a l l y controlled. Whitesel (personal communication) has postulated that environ-mental control of l i f e - h i s t o r y pattern may operate i n steelhead producing streams which possess headwater lakes. He believes that the moderation of downstream temperatures and water v o l -umes provides a most suitable environment within which s t e e l -head may grow, p r i o r to downstream migration. The differences i n mean temperatures of streams contain-ing salmonid populations has been suggested by Aim (1959) as a major factor i n regulating growth and maturity of A t l a n t i c salmon. Differences i n stream temperatures along the coast of North America have been demonstrated i n t h i s study (Figure 10). However, other environmental factors which vary geograph c a l l y may act to regulate growth and migration ages. I t i s u n l i k e l y that changes i n frequency of repeat spawn-ing among populations i s related to variations i n mean temp-eratures . Other factors governing changes i n steelhead population c h a r a c t e r i s t i c s along the coast of North America might be the influence of l a t i t u d i n a l changes i n day lengths upon feeding habits or p i t u i t a r y stimulation. C h a r a c t e r i s t i c differences may arise from the action of a combination of several environ-mental variables related to climatology and the fresh and s a l t water environment of the f i s h . 80 LITERATURE CITED Aim, G., 1959- Connection between maturity, size and age i n fis h e s . I n s t i t u t e of Freshwater Research, Drottning-holm, Report No. 4 0 : 5 - 1 4 5 . B a l i , J. M., 1 9 5 8 . Scale analyses of steelhead trout, Salmo  gairdneri gairdneri Richardson, from various coastal watersheds of Oregon. M.Sc. thesis, Oregon State College. Belding, D. L., 1 9 3 4 . The cause of the high mortality i n the At l a n t i c salmon after spawning. Trans. Amer. Fish. S o c , 64 : 2 1 9 - 2 2 4 . Belding, D. L. and J. A. Kitson, 1 9 3 4 . Spring-run and f a l l -run A t l a n t i c salmon. Trans. Amer. Fish. S o c , 64 : 2 2 5 - 2 3 0 . Briggs, J. C , 1 9 5 3 . The behavior and reproduction of salmonid fishes i n a small coastal stream. C a l i f o r n i a Dept. Fish and Gam, Fish B u l l . , No. 9 4 . Chapman, D. W., 1957- Studies on age, growth, and migration of steelhead trout, Salmo gairdneri gairdneri, i n the Alsea River, Oregon. Masters th e s i s , Oregon State College. Elson, P. F., 1957 . The importance of size i n the change from parr to smolt i n A t l a n t i c salmon. The Canadian Fish C u l t u r i s t , No. 21 : 1 -6 . Huntsman, A. G., 1939- Salmon for angling i n the Margaree River. B u l l . Fish. Res. Bd. Canada, No. 57-I d l e r , D. R. and W. A. Clemens, 1 9 5 9 . The energy expendi-tures of Fraser River sockeye salmon during the spawning migration to Chilko and Stuart lakes. International P a c i f i c Salmon Fisheries Commission, Prog. Rep. Larkin, P. A., 1949- Report on r e l a t i v e e f f i c i e n c e s of v a r i -ous types of f i s h i n g gear with s p e c i a l reference to Kamloops trout. Report of P r o v i n c i a l Game Convention. Larkin, P. A., 1 9 5 0 . Report on the preliminary survey of the steelhead of the lower Fraser River. Reprinted from Report of the P r o v i n c i a l Game Commission, 1 9 4 8 . 81 Larkin, P. A., G. C. Anderson, W. A. Clemens, and D. C. G. Mackay, 1950. The production of Kamloops trout (Salmo g a i r d n e r i i kamloops, Jordan) i n Paul Lake, B r i t i s h Columbia. University of B r i t i s h Columbia and B r i t i s h Columbia Game Department. Gilhousen, P., i960. Migratory behaviour of adult Fraser River sockeye. International P a c i f i c Salmon Fisheries Commission, Progress Report. Maher, F. P., 1954- L i f e h i s t o r y of the steelhead as i n t e r -preted from the scales. M.A. thesis, University of B r i t i s h Columbia. Marr, J. C , 1943- Age, length, and weight studies of three species of Columbia River salmon (Oncorhynchus keta, Q. gorbuscha, and 0_j_ kisutch) . Stanford Ichthy. B u l l . , Vol. 2, No. 6 : 157-197-Milne, D. J., 1948. The growth, morphology and rel a t i o n s h i p of the species of P a c i f i c salmon and the steelhead trout. Doctoral thesis, McGill University. Neave, F., 1949- Game f i s h populations of the Cowichan River. B u l l F i s h . Res. Bd. Canada, No. 84. Pautzke, C. F. and R. C. Meigs, 1940. Studies on the l i f e h i s t o r y of the Puget Sound steelhead trout (Salmo  g a i r d n e r i i ) . Trans..Amer. Fish. S o c , 70 : 209-220. Ricker, W. E., 1959. Evidence for environmental and genetic influence on certain characters which d i s t i n g u i s h stocks of the P a c i f i c salmons and steelhead trout. Fish. Res. Bd. Canada (mimeo.). Shapavalov, Leo, and A. C. Taft, 1954. The l i f e h i s t o r i e s of the steelhead rainbow trout (Salmo gairdneri g a i r -dneri) and s i l v e r salmon (Oncorhynchus kisutchj with s p e c i a l reference to "Waddell Creek, C a l i f o r n i a , and recommendations regarding t h e i r management. C a l i f . Dept. F i s h and Game, Fish . B u l l . No. 98. Smith, S. B., i960. A note on two stocks of steelhead trout (Salmo^gairdneri) i n Capilano River, B r i t i s h Columbia. J. Fish. Res. Bd. Canada, 17 (5) : 739-742. Svardson, G., 1954. Salmon stock fluctuations i n the B a l t i c Sea. Inst i t u t e of Freshwater Research, Drottningholm, Report No. 36, : 226-262. Vernon, E. H., 1957- Morphometric comparison of three races of kokanee (Oncorhynchus nerka) within a large B r i t i s h Columbia lake. J. Fish. Res. Bd. Canada, 14 (4) •* 573-598. MEAN MONTHLY T E M P E R A T U R E ( ° F ) 2 J\ ^  — J J z\ o O —I CO - i — r -g o 

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