[}{I&WJ~& c ~00&®©© r- Susitna Joint Venture Document Number I' /8:1b Please Return To ('~~ DOCUMENT CONTROL
FI I::.. Studies r of J:l Alaska
pI' , Red l'~ Salmon r;
~: EDITED BY f Ted S. Y. Koo .. ~~ SEATTLE • UNIVERSITY OF WASHINGTON PRESS • 1962 t
~~ • r I ,, THE LIBRARY . CHICAGO TEACHERS COLLEGE l I NORTH CAMPUS ~I • r f"
l· ~~ I h ll
I..;~ Studies of r Red Salmon
!• :i .. Smolts I .,.. , from the
..' .i Wood River Lakes, Alaska
BY ROBERT l. BURGNER
ll
·:
Contribution No. 110, College of Fisheries, University of Wash ington, Seattle, Washington. This is a revised version of the first .. of two installments of the author's. thesis accepted in 1958 by . the University of Washington in partial fulfillment of the require ments for the degree of Ph.D. ,I '! •I I,.
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r;:L r CONTENTS
Abstract 251 introduction 251 The Seaward Migration 253 Age Groups in the Seaward Migration 253 Determining the Migration Index 254 II 256 [ .1 Size and Age of Migrants Procedure for Processing Samples 256 i•' •• l Correction for Shrinkage of Fish in Formalin l' Preservative 257 Evidence Regarding Selectivity of the Fyke Nets 258 :t f.,.. Diurnal Changes in Size of Smolts Migrating 260 Samples Taken for Length Frequency and Age Composition Studies 262 Method of Age Determination 264 Relationship between Parent Escapement and Seaward .,. Migration 265 .I I Influence of Climate on Timing of Seaward Migration 268 Sun1mer Growth of Yearlings Prior to Seaward Migration 271 Growth as Indicated by Scales 271 Relationship between Scale-Growth Increments and Seasonal Climate 274
249 250 Contents
Seasonal Changes in Length Frequency of Smolts 276 Pattern of Seasonal Changes 276 Effect of Lake-Ice Breakup and Distance from Outlet h on Pattern of Seasonal Migration 278 [I Origin of Size Groups in the 1955 Seaward Migration 279 Causes of Difference between Lakes in Size of Smolts £;; Produced 283 [ J 6. Studies of Red Salmon Climate 283 Level of Basic Nutrients 284 Competition for Food 284 Relation of Growth Rate to Survival 288 Fresh-Water Survival 288 Red salmon Bay, Alaska, were Marine Survival 290 and survival and to ascer Indexes of seasonal and Effect of Smolt Size on Adult Population Size 291 seaward were obtained by Summary 292 Sampling systems to developed, including a m Acknowledgment 294 m~asured alive and r were found. Literature Cited 294 The relationship betw smolts produced was Figures 1-27 inclusive following page 298 through 1955. Sources of sought. Amount of growth the growing season and of breakup of lake ice and and of returning adults varied with lake of origin.
in ~rrowthi::> attained during in spawning population"'"'"""~ w~s shown to influence grounds.
THE STUDIES desc search Institute causes of fluctuations in Alaska. This report or seaward migrants, of of Bristol Bay. Sockeye or red salmon • " • • ~ I -.., 4" .. ~ • ' :~ -:__ • -. : ~~ I' ". ,. .'"' ~ ·- .' ~ • "•\ ' ~,. .: •. \ • _, ,4 ~ • ~ • • " • ~ .,. •
• ' • • I I ...... - ~
[ Contents
276 276
278 279
283 6. Studies of Red Salmon Smolts from the Wood River Lakes, Alaska 283 Robert L. Burgner 284 284 ABSTRACT 288 288 Red salmon (On.cm·hynchus n.erka) smolts of the Wood River lakes, Bristol Bay, Alaska, were studied to determine fluctuations in abundance, growth, 290 and survival and to ascertain causes of the fluctuations. Indexes of seasonal and annual variation in numbers of smolts migrating ,1 '-· e I' sf··.·. ~! 291 seaward were obtained by fishing fyke nets ~t the outlet of the lake system. I .... 292 Sampling systems to determine changes in age and growth of smolts were developed, including a method whereby the majority of fish sampled were 294 measured alive and released. Diurnal changes in size of smolts migrating were found. 294 The relationship between numbers of parent spawners and numbers of following page 298 smolts produced was found to be highly variable for the year classes 1949 through 1955. Sources of variability in growth and survival were therefore t;; sought. Amount of growth attained by yearling srnolts during the early part of the growing season and timing of seasonal migrations were related to timing of breakup of la...lte ice and te:r,nperatures following breakup. Scales of smolts !! and of returning adults were utilized to show that size at seaward migration [ · varied with lake of origin. Differences between years and between lake areas . ... in growth attained during first year of life were associated with differences in srawning population density. Size of yearlings at time of seaward migration r:: ., was shown to influence marine survival and age at return to the spawning t grounds.
INTRODUCTION
THE STUDIES described in this paper are a part of the ::t•'isheries Re search Institute program directed toward furthering knowledge of the causes of fluctuations in abundance of red salmon runs in Bristol Bay, Alask.a. This report concerns primarily studies of red salmon smolts, or seaward migrants, of the Wood River system in the Nushagak district q •t of Bristol Bay. t Sockeye or red salmon (Oncorhynchus nerka Walbaum) spend approxi-
251 l1 252 Alaska Red Salmon Smolts from Wood River
mately half their life in fresh water, enter the marine environment at an advanced stage and do not come in contact with the coastal fishery until their return migration. Such distinctive environments allow the con venient division of fluctuation in abundance into those which occur in Length fresh water, at sea, and as a direct result of the fishery. Name (Miles) The anadromous life history of this species permits detailed study of spawning and early life. For studies to be effective in evaluating mor Aleknagik 20 talities at these stages, adequate systems of observation are needed to Nerka 25* cover the fresh -water history year after year in such a manner as to Beverley 22 17 be quantitative and comparative. Determination of t..he mortalities causing Kulik fluctuations in abundance is essential to proper management and sus *Longest arm only. tained utilization of the very valuable red salmon resources of Pacific Sources: Mertie (1938) coast rivers. (1957). Maximum scund Seaward migrants are of key significance, for they have reached the in Nushagak district. threshold of the marine phase of their life history. Number of seaward creeks , spring ponds,. rivers migrants related to number of parent spawners provides a direct measure areas. All four spawnmg area of production of young. This relationship provides a measure of vari beach-are of importance in ·-' ability in survival rate resulting from interplay of natural causes and tance varies considerably +',.., ...... ,..,.,,L establishes the existence of possible cyclic patterns in fresh-water sur The following terms will be •· ~- vival. Evaluation of seaward :mlgrants with respect to their later return red salmon in fresh water: as adults in catch and escapement provides a measure of marine sur Fry-stage from time of vival. With the latter information as a basis, forecast of adult returns - season in the lakes; from seaward migrations of known relative magnitude follows logically. fish In this report the procedures used in determining abundance, size, Yearling-fish in second year age, and migration timing of Wood River smolts are described. Evi Age II fish-fish in third ye dence is presented to relate differences between years in migration Finger ling-general term timing, growth and survival, to factors of climate, population density, or third year of fr e and locale of embryonic and juvenile growth. young salmon after The main lakes of the Wood River chain are piedmont lakes of glacial Smolt-seaward migrant in , origin occupying essentially bedrock basins, and lie in a general east west axis bordered on the west by the Wood River Range (Fig. 1). They are joined by short rivers, with the 18-mHe-long Wood River connecting ' __·_, .. ,fl the lowest lake with Nushagak Bay. Wood River drains a basin of ap pro~5.mately 1,415 square miles in which the principal lakes cover 174 square miles (U.S. Army Corps of Engineers, 1957). The annual seaward The Wood River lakes are deep, temperate, and typically oligotrophic, three age groups of young with bottom water temperatures varying near that of maximum density. adult spawning of the previous They are ice ...· covered for approximately 6 months of the year, but show in their third year of life, age distinct thermal stratification h'ith formation of a true thermocline in for young red salmon has oe~~m::" ~I summer. Average annual precipitation recorded at Dillingham, Nushagak sonallength-frequency Bay, over a period of 35 years was 25.86 inches (U.S. Army Corps of Fry migrations from the Engineers, 1957). Elevation, dimensions, and depths of the primary smolt indexing procedu:re used lakes are recorded in Table 1 as seen on the following page. the magnitude of the seaward The Wood River lakes constitute the main spawning area for red salmon adults with no fresh -water
'.. I t'I [ Alaska Hed Salmon Smolts from Wood River Lakes 253 .·i ent«=;r the marine environment at . c1·.·1tact with the coastal fishery TABLE 1. PHYSICAL DATA ON PRINCIPAL LAKES ~· . I . OF THE WOOD RIVER SYSTEM ;c t1 ~ envll"orunents allow the con- _:ldance into those which occur in Maximum Area Surface Length 1rei;·~1t of the fishery. Name Recorded {Square Elevation (Miles) -~ s !~;cies ~ermits detad.~ed study Depth (Feet) Milas) (Feet) .o effective in evaluating mor Aleknagik 20 360 34 34 tms.. of observation are needed to Nerka 25* 538 78 70 terl :ear in such a manner as to Beverley 22 617 38 100 1 ;ina.\ :m of the mortalities causing Kulik 17 525 24 140 ;o proper management and sus- . ! ed~-aimon resources of Pacific *Longest arm only . So"ilrces: Vertie (193R); U.S. Army Corps of Engiueers (1957). Maximum soundings furnished by author. for they have reached the tUl~e, in Nushagak district. Spawning is distributed over the lakes in tributary tife history. Number of seaward creeks, spring ponds, rivers between the lak~s, and al~ng lake beach tme[i· ·: provides a direct measure areas. All four spawning area types-creek, sprmg pond, r1ver, and lake ip l .. ovides a measure of vari- beach-are of importance in the Wood River lakes; their relative impor ;.nterplay of natural causes and tance varies considerably from year to year. ·lie ~~.tterns in fresh-water sur The following terms will be used in discussion of the stages of young :th t:!spect to their later return red salmon in fresh water: de ~a measure of marine sur Fry-stage from time of emergence in spring through first gJtowing .asis, forecast of adult returns - season in the lakes; synonymous with underyearling, and age 0 .ve rlagnitude follows logically. fish !det._:: rmining abundance, size, Yearling-fish in second year of life; synonymous with age I fish r smolts are described. Evi- Age II fish-fish in third year of life s ~f:~.w een years in migration Fingerling-general term applied to young salmon during the second L pf •' ··mate, population density, l '!'ltll;;':, or third year of fresh -water life prior to seaward rrdgration; young salmon after fry stage r : are piedmont lakes of glacial Smolt-seaward migrant in second or third year of life ns {·:md lie in a general east Ri(':;:r Range (Fig. 1). They are THE SEAWARD MIGRATION j-long Wood River connecting · .i R~r;··.:o. rer drains a basin of ap Age Groups in the Seaward Migration :h }••rincipallakes cover 174 1 ~e !J-, 1957). The annual seaward migration in the Wood River lakes is comprised of and typically oligotrophic, three age groups of young reds. These age groups are: (1) fry from the .J Jat of maximum density. adult spawning of the previous year, (2) yearling smolts, and (3) smolts .t of the year, but show in their third year of life, age II. The validity of these age designations '( . :ion of a true thermocline in for young red salmon has been established by a combined study of sea de~. ~ Dillingham, Nushagak 1 sonal length-frequency progression and scale structure (Koo, 1962). ·nc :l!S (U.S. Army Corps of Fry migrations from the Wood River lakes were not sampled by the ~~d depths of the primary smolt indexing procedure used at the system outlet. However, wh...ttte~er the following pa.ge. the magnitude of the seaward migration of fry, the numbers of returnmg :av.l.. '.· .. mg area for red salmon adults with no fresh-water annulus on their scales have been inconse- f lJ .. .• • • • 01 ' ... ~'. I 254 Alaska Red Salmon Smolts from Wood River Lake
quential in the Nushagak District. The highest percentage :return of this Most of the smolt migration . rr group was found in adult returns from the 1949 spawning (1950 fry), and shovm by Koo in studies of the amounted to 6.3 per cent of the return run. gra.tion at Wood River. During Yearling smolts have constituted the major portion of the seaward fyll~e nets in 1951, over 95 per l migration in every year. During the season of migration they are readily evening period from 2100-0200 distinguished from fry by their size and scale pattern. There is no over during this evening period ~or lap in size between fry in the lakes and migrating yearlings during June data collected by Koo, is Large fluctuations in smolt r~.I and July (see length-frequency curves prepared by writer in Koo, 1962). '· Smolts migrating after two years in fresh water form a smaller pro (Table 9, p. 267), but no direct portion of the total migration than do year lings. was made. Evidence as to from consistency of results: E.K.t Determining the Migration Index (1) The seasonal trend of ' magnitude with fluctuations in Responsibility for studies of the seaward migration of red salmon at and catches in relationship to Wood River was divided between Dr. Koo and the writer. Dr. Koo's ~ork outlet have all shown a pattern t:! was primarily concerned with the enumeration of young salmon in the (2) The proportion of the seaward migration and with the calculation of an index t;o show the rel consistent from year to year. ative abundance between one year and the other. His work included in the evening fyke-netting period l~ this report covered the years 1951 to 1958; the year 1952 was used as 0200. Catches for the 2100-23 the base year in the computation of indexes. The method used to ob averaged close to the same tain an annual index to magnitude of the Wood River seaward migration 0200 period in each of these {!· ·, will be described briefly, since the data are utilized in discussion of 1955 ' . fresh -water survival and of size and age changes in the migration. 1956 Although fyke nets have long been used to obtain samples of seaward 1957 r·; migrants (Babcock, 1905; Chamberlain, 1907), the Fisheries Research 1958 :! ' Institute was first to apply the gear as a means of indexing annual mag 1959 nitude of smolt migrations in large rivers. This gear, installed at the outlet of the Wood River lake system in 1951, has been used in the major (3) Magnitude of adult return river systems in Bristol Bay and in the Chi~£1ik River. At Wood River a dance at time of seaward r~,·· winged fyke net (Fig. 2) was fished annually during the seaward migra explainable largely on the bas tion period of approximately two months. The net was set daily for a tality. fixed period during the evening migration in the same location on the (4) In 1952 a second fyke net '·'t r·· gravel shoal at Mosquito Point (Fig. 3 ). · The method of fishing was kept days during the season in a ·~ as constant as possible from yea.r to year. Total catch for each season net. The total calculated catches furnished the annual index to abundance of seaward migrants. were in very close agreement The fyke net used for indexing was set on the river bottom in approx in the offshore net. This was in · r:.~ . .... imately 4 feet of water. The net intercepted a cross section of the river be tended as carefully or fished approximately 8 feet wide and 4 feet deep. According to calculations stances as a single net. based on river measurements taken by Koo on June 15, 1955, the net Comparison of fishing results intercepted about 1/75 of L'le river width and 1/145 of the cross-sectional presented in Table 2 (p. 256). t·L area across the outlet in line with the net site. Maximum current ve of time the nets were fished • • n 'tu-4 f • at• locities occur across the shoal where the fyke net was set. Average t_:wns 1.11 Il".....gnl.. • ...eo ... m1,;.a:r __ JQ!!t current velocities taken at the fyke-net location on the date stated above high catch in the other, and low .!~t r exceeded 3 feet per second. relation between the unadjusted tl!.t ·~~
~:,\'. Alaska Red Salmon Smolts from Wood River Lakes 255 'hig~~st percentage return of th. Most of the smolt migration occurs during evening hours. This was l.] ~t_;149 Spa\vning {1950 fry), ~~ shown by Koo in studies of the hourly pattern in timing of seaward mi I gration at Wood River. During 17 days of around-the-clock fishing with n Je m_ajo~ por~ion of the seaward fyke nets in 1951, over 95 per cent of the smolt.s were caught during the v _solj"~f nugrahon the!~ are readil evening period from 2100-0200 hours. Hourly distribution of migration . scl:::! ~ttern. There is no over: during this evening period ~or the years 1955 through 1957, based on .nngratmg yearlings during June data collected by Koo, is shown in Figure 4. re~ed by writer in Koo 1962) Large fluctuations in smolt indexes have been found from 1951 to 1958 ref . water form a smaller pro~ (Table 9, p. 267), but no direct test of the reliability of the smo~t ind.ex !ar .1 !lgs. was made. Evidence as to .reliability of the method has come pnmar1ly from consistency of results: 1"'on Index (1) The seasonal trend of catches of the index net, daily changes in magnitude with fluctuations in water temperature and wind direction, vara: migration of red salmon at and catches in relationship to observed abundance of smolts at the lake l , and the writer. Dr. Koo's ~ork outlet have all shown a pattern of consistency. nel=· tion of young salmon in the (2) The proportion of the catch taken early in the evening has been E tioL ,of an index to show the rei consistent from year to year. During the 1955 through 1959 seasons, he other. His work included in the evening fyke-netting period was extended to include the hours 2100- •1 L95f._~ the year 1952 v..-as used as 0200. Catches for the 2100-2300 period, used in former years, have :ie]r;.s. The method used to ob averaged close to the same percentage of the total catch during the 2100- Wubd River seaward migration 0200 period in each of these years (Koo, 1959, 1960): .ta a;e utilized in discussion of .ge rhanges in the migration. 1955 42.1% ld fl~ obtain samples of seaward 1956 43.4% 1907), the Fisheries Research 1957 39.4% 1958 46.4% m~f·~ns of indexing annual mag 1959 42.0% :rs ,': This gear, installed at the 95 ·;· has been used in the major (3) Magnitude of adult returns has shown a relation to index of abun .., •••.5u.Ln River. At Woo.d River a dance at time of seaward migration. Deviations to date appear to be :luring the seaward migra explainable largely on the basis of recognized changes in ocean mor .. ~he net was set daily for a tality. ion in the same location on the (4) In 1952 a second fyke net identical in structure was fished for 28 ( ' ·T~f: method of fishing was kept days during the season in a position 25-50 feet offshore from the index ~ i~ '.'otal catch for each season net. The total calculated catches of the two nets during the 28-day period were in very close agreement-147,991 fish in the index net, 160,343 fish of :S'eaward migrants. /. on the river bottom in approx- in the offshore net. This was in spite of the fact that two nets could not u be tended as carefully or fished in as favorabls a. location and circum .·.:•J ·. cross section of the river .•·.According to calculations stances as a single net. on June 15, 1955, the net Comparison of fishing results of the two nets fished simultan~ously is /145 of the cross-sectional presented in Table 2 {p. 256). Although differences between days in length 1r:t e. M ax1mum ' current ve- of time the nets were fished somewhat obscure the day-to-day fluctua .Lyke net was set. Average tions in magnitude of migration, high catch of one net was associated with ation on the date stated above high catch in the other, and low catch with low. The coefficient ai cor r~ relation between the unadjusted catches day by day was +0.84tJ.
' ? ... • • ~ ~~·~...... • •.• .. ""'# .. • •• ,!' I, ··"'~ .... r~--..-1 ~ 4!!~:v. -~~~lf~;:ff.~. ::----· \t,.4,J ~~.,.,..._~ ~~~~!;{;':~:;~4A~~*~~:!~,.-€~.f!'t-M:.r""*'! t-• •;J!;•-...... t; • 1 " . ' - ; .
! ' • ·.. • Q, • • Smolts from Wood River Lake 256 Alaska Red Salmon index period, held overnight in 1'ABLE 2. COMPARISON OF FISHING RESULTS BETWEEN THE day. Care was exercised in MOSQUITO POINT INDEX NE-T AND A st;coNil FYKE NET SET 25-50 FEET FURTHER OFFSHORE , 1952 selection resulting from poss · sampling procedure. Tests of Time Fished I Catch of R~d Sm0lts Date -~ .... selection in drawing samples. Hmu·s M:i.p,t;i;~B ~.nqt;;ii; N~'t Offahora Net In 1954 a procedure of mea increase the number of length June }..u 4 40 6,612 13,774 22 3 10 10,780 4,480 killing and preservation of sm( 24 3 10 51,128 51,216 anesthesia. Lengths of these 28 3 30 806 1,096 those of fish measured after 29 2 30 258 342 ments of preserved iish were 30 3 0 13 13 measurements, since by :far ( ~~ July 1 6 40 0 0 and released. • ~! 2 6 40 15,960 28,462 6 4 0 2,590 981 7 2 45 34,020 15,660 Correction for Shrinkage of Fi ... 14 3 25 132 58 ) .. Measurements taken of a s 15 2 25 33 7 , ' lustrate changes in length of r · ;; r. 16 3 15 142 90 17 3 20 1,041 77 10 per cent formalin. Fish · : 18 2 45 2:304 25,698 anesthesia, remeasured appro 19 3 15 12,722 11,957 ~oain after 5 months in formali .. 21 3 15 140 32 TABLE 3. COMPARISO ~· 22 2 5 172 114 UNDER ANESTHE" ··· 23 3 20 2,368 536 I.( ;,...•.• ••• J . " 24 2 0 1,210 350 t':.. 30 3 15 1,193 1,753 31 3 25 1,751 1,534 Aug. 1 3 0 2,383 1,741 __I 2 2 0 41 23 Age I--139 fish ,~ 4 g 45 g7 56 Mean length in Jllillimeters ··. 5 1 53 8 18 Mean decrease in length .' 7 2 0 21 45 Percentage shrinkage ~ ~ .. 10 2 0 136 230 Age II--15 fish r .·.: Mean length in millimeter1··· t.. TOTAL 147,991 160,343 Mean decrease in length · Percentage shrinkage \ RATIO 1 . 1.08 Measurements in Table 3 imf red smolts occurred within a~:· Size and Age of Mig·rants Roughly 80 per cent of decreas; first 24 hours L1 both age grou~~ • I '.!•: Procedure for Proct~ssing Samples '' •' was slightly more in older fist r Preli~n.inary studies were made of seasonal and annual size and age total length was slightly less ·f ; "' ~ompos:tty:m Qp,a:~~~ !'~_?~rr:iii5 1r1 Wu·~ i'iiver smolt§ during the yeru.·s Another sample, taken on Jtm .. 1949--53. Beginnmg 1fi 1954, more complete sampling was initiated, and ~·. n in different length classes. ni:·.: the n~er of ~ples taken annually was increased severalfold. Length, '.' 'rJ' sorted into 5 mm length group , I I rather than weight, was used to measure size of individuals in order that over 5 months later. Tabulati: large samples of smolts could be processed rapidly. All length measure Difference in mean length be ,'1 ments were from tip of snout to fork of tail. around 5 mm for each length J r''!. Samples for study were drawn at the fyke-net site during the ~vening - i ~·· l 1 w·__ ...... _...... _...... -- Alaska Red Salmon Smolts from Wood River Lakes 257
:NG RESULTS BETWEEN THE index period, held overnight in live-boxes, and processed the following OOli;! SECOND FY1
~reasL"'lg with _increased size. Hile (1936) likewise found that shrinkage lings not represented in the U: length of c1scoes was greater on a per cent basis for smaller fish the lake system. The fyke nets H1s specimens, ranging from 150-350 mm, were first pre}3erved i~ rivers between lakes, usually formalin and l~ter transferred to alcohol. Length-frequency study e .. "'"''·L.I·""'"'•" the lakes by this gear were; TABLE 4. SHRINKAGE OF RED SALMON FINGERLINGS IN LENGTH DURING concurrently by fyke net at STORAGE IN 10 PER CENT FORMAL!~* f":'equency were those to be eXll~ and those reds still to migrate. Mean Length (in mm) Difference in Length Class Number of Mean Length More direct information Measured (in mm) Specimens 5i Months obtained in 1954. It had been Alive under After Mill!- Per Cent Anesthetic Preserved meters ior sampling red finger lings in its entirety if the school was 73- 77 4 76.5 71.3 5.2 6.8 The fish were observed to 78- 82 53 80.8 76.0 4.8 5.9 with the seine until they were 83- 87 82 84.6 79.6 5.0 ~.9 Size selectivity was believed 88- 92 17 89.0 84.2 4.8 5.4 rounded by the set. It was ,..,, .. ,n 93- 97 11 94.8 89.5 5.3 5.6 98-102 6 98.5 93.2 5.3 5.4 taneously by beach seine and . 108-112 1 108.0 103.0 5.0 4.6 study of fyke-net selectivity. " The seine used was tapered Total Age I 170 84.61 79.61 5.0 5.9 of 1/8-inch-mesh saran-pla outboard boat a short distanc Total Age II 4 100.75 95.50 5,25 5.2 current than at the site. In or *Measured under anesthetic before killing, remeasured 5l months all fish were removed from the · later. placed, and as soon as a net seine set was begun. The other measurements taken of red smolts show that the initial and most ' . abrupt decrease in length is apparently not due to formalm preservative, were caught in the seme, ... a.~~. ... uq but rather occurs as a result of rigor mortis. Shrinkage in length between manner, two pairs of catches by fish measured alive under anesthesia and remeasured upon reaching of three nights, June 15, 16, a state of rigor mortis without being preserved in formalin averaged live-boxes and a 2-pound oc:~.1u..,r between 2 and 3 per cent. This agrees closely with results reported by in standard manner the Shetter (1936) for brook and brown trout averaging 6-7 inches in length. Runs were relatively light To compensate for total shrinkage of preserved specimens, 5 rom was dividual samples taken by both added to length measurements of yearling smolts preserved several from a few schools. Fyke-net months in 10 per cent formalin. A slightly larger correction was needed siderably longer time, and as for age ll fish which ranged over 100 mm. schools than did seine '-'41.'-'lu;;,;:"l minute fishing periods on Evidence Regarding Selectivity of the Fyke Nets a 29-minute period on June 17. Since the smolt samples taken at the fyke-net site were to be used for seine and no schools cou.ld quencies' obtained by the two !'}II size and age studies, it was necessary to determine whether the nets ~;~•'.... were size selective. This was done by comparing samples with those posite frequencies of all .... -AU ...." t •' taken by other gear. frequencies of June 15 are c Indirect evidence did not indicate that index fyke nets, as used at Mos smolts running on June 16 and· quito Point, tended to select small smolts. Sampling within the lake The feature at once appar system by means of beach seines, lake traps, tow nets and fyke nets geneity in length frequency failed to furnish any evidence of an abundance of larger o~ older finger- results support observations f, I A 1 . f! ~-~ A aska Red Salmon Smolts from Wood River Lakes 259 :·,.: :~ 936) likewise found that Slhrinkage lings not represented in the samples taken by fyke net at the outlet of ·;.a P.t.:· ':' cent basis for smaller fish. the lake system. The fyke nets used within the lake system were set in t:!J 35Ct:nm, were first preserved in rivers between lakes, usually in swifter water than at Mosquito Point. ··:'If Lcoliol • Length-frequency study established that fish in samples captured within ~:\~ FI1'f:':'·ERLINGS IN LENGTH DURING the lakes by this gear were similar in size or smaller than those sampled ..:; l.l !E,. •..,J~OP..MALIN* concurrently by fyke net at Mosquito Point. The differences in length ~1 :=-:.,11 frequency were those to be expected between Mosquito Point migrants ··n•I • ,;·t]! ·ngth (in mm) Difference in a"'1d those reds still to migrate. .1. l, Mean Length t: = 5! Months More direct information regarding possible fyke-net selectivity was .:ll 1 1 erl After Mill!- Per Cent obtained in 1954. It had been observed that beach seines of the type used c ., Preserved meters for sampling red fingerlings in. the lakes tended to capture a school in ~·- its entirety if the school was surrounded initially by the set of the seine. '1·1 71.3 5.2 6.8 The fish were observed to herd toward the beach and to avoid contact 76.0 4.8 5.9 tl/. with the seine until they were finally pocketed in the bag in shallow water .. ~,- 79.6 5.0 ~.9 84.2 4.8 5.4 Size selectivity was believed negligible once the young salmon were sur fi1.l· 89.5 5.3 5.6 rounded by the set. It was decided, therefore, to obtain samples simul •I 93.2 5.3 5.4 taneously by beach seine and standard fyke net at Mosquito Point for ~I \:1 103.0 5.0 4.6 study of fyke-net selectivity. I• Qf .'':': [r.,· 79.61 5.0 5.9 The seine used was tapered, 200 feet long, with a large bunt made ~ l----J:;,I!------1{ ~r,: of 1/8-inch-mesh saran-plastic screen. The sets were made with an .1. ~J·~ 95.50 5.25 5.2 outboard boat a short distance above the fyke-net site and in slower ,l ------~~~ • J current than at the site. In order to make catches at the same time, ·~i~':i1?~ng, remeasured 5l months .1• 'f.• all fish were removed from the cod end of the fyke net, the cod end re ~ ;· 1. .1' placed, and as soon as a sufficient number of fish appeared in the fyke 1:,; JlJ'~how that the initial and most net, seine set was begun. The moment it was determined that smolts : ! not due to formalin preservative were caught in the seine, catches from both gear were removed. In this ;I c; ';! Shrinkage in length 'Yrlf1 betwee~ manner, two pairs of catches by seine and fyke net were obtaine.d on each .· t L au ... remeasured upon reaching of three nights, June 15, 16, and 17. The catches were held overnight in .~t i preserved in formalin averaged live-boxes and a 2-pound sample (about 150-170) processed from each 1: clr;-:;ely with results reported by in standard manner the following day . .i h:t a(}~:~raging 6-7 inches in length. Runs were relatively light during the three evenings of sru.11pling and in ·;.. preserved specimens, 5 mm was dividual samples taken by both beach seine and fyke net were composites : ~:.rlip.;g smolts preserved several from a few schools. Fyke-net catches were obtained by fishing a con ·"r.u:vf.: 1uger correction was needed siderably longer time, and as a result contained components of more . t :n. t~ 1•• S( schools than did seine catches. Fyke-net catches were made during 6- ·.,I minute fishing periods on June 15 and 16, and during a 14-minute and I r' ke !o":'!etS a 29-minute period on June 17. It required less than a minute to set the f' fJ• . , fy~::-net site were to be used for seine, and no schools could enter once the seine was set. Length fre r1y to· determine whether the nets quencies obtained by the two types of gear were compared with com \r comparing samples with those posite frequencies of all samples taken during the same evenings. The ' cr I' t • r, ~ (:·' frequencies of June 15 are compared in Figure 5, those of the smaller ,\in~.r fyke nets, as used at Mos- smolts running on June 16 and 17 in Figure 6. . :rlnolts. Sampling within the lake The feature at once apparent in both figures is the greater hetero I' ·~~ ti'"jPS, tow nets, and fyke nets geneity in length frequency among samples taken by beach seine. The ' ! dal.e of larger or older finger- results support observations that there are marked differences between ~- .
u_r.·m_ h UJ EJ
fl 260 Alaska Red Salmon Smolts from Wood River fl ' til TABLE 5. MEAN WEIGHTS OF schools in size composition of the individual fish. The fyke-net samples DURING THE 2100-2300 were composed of portions of a greater number of schools, hence tended POINT, MAY ~ .... ~;o.· more toward the average size composition of all schools passing, and Time ~-: in Time thus showed less variability size composition between samples. Last Comparisons of individual samples obtained simultaneously by the two Date First ,...... Sample Sample types of gear are presented in Figure 7. The over-all mean length of J," ~•• r L, smolts taken by fyke net was 86.07 mm, by beach seine, 86.95 mm, a llay 30 2240 2300 difference of only 0.88 mm. The two seine hauls made on June 15, cap 31 2117 2300 1 2113 2300 .f. tured several very la1:ge age n smolts of a size range not found in the June i:. 2 2130 2300 fyke-net samples. Fewer fish of this length range (over 105 mm) were 2300 fl J 3 2140 captured by either gear the following two nights. It is not known whether 4 2218 2300 unusually large fish of this size avoided capture by the fyke net on June 5 2200 2300 15 or whether capture of these fish by beach seine and not by fyke net 6 2200 2300 hi 2300 -!' was a chance occurrence. It is unlikely that fish of this size range com 7 2154 tt~ 2300 prised a substantial proportion of the run, since they have never been 8 2106 9 2130 2300 F.::. captured in numbers by any gear used. If selection exists, however, 10 2104 2300 some error would arise in determining the proportion of age II smolts 11 2105 2300 G in the seaward migration in years when sizes of fish in this age group 12 2104 2300 run large. 13 2104 2300 2107 2300 In the size range below 105 mm the samples gave no evidence that the 14 rr,; 15 2120 2300 ~, .. in I'! fyke-net set the current velocities at Mosquito .Point selected smaller 16 2133 2238 fish. There was, then, no evidence that the proportion of yearlings re 17 2200 2243 tained by the fyke net ·was influenced by the size of yearlings migrating. 18 2122 2300 ~:..· Comparison of beach-seine and fyke-net samples did bring out the 19 2107 2300 ,.,I' ,· ,., heterogeneity in length frequency of smolts among schools. As a result of TOTAL these tests, it was decided that when samples for size and age study were ~,. to be drawn from the catch, the fyke net should be fished long enough ~ )! before lifting to make the resultant catch a composite of several schools. ~~: In 1956 and 1957 a Diurnal Changes in Size of Smolts Migrating of age II smolts, and i I During early years of sampling at \Vood River, marked diurnal dif for age II smolts to run I'' fll•' ferences between samples were noted in size of smolts taken. The diurnal consistent. The tendency for differences were first studied in detail in 1954 to determine possible is still under study, for in causes and to evaluate their effect on the sampling schedule adopted. Possible diurnal changs flt carded as a cause of diurnal ~:~~~ Hwrly samples of the run were taken on two evenings of heavy migration. Length frequencies of these samples are presented in Figures 8 and 9. A in efficiency of the net u'"''"'"'"" pattern of general decrease jn the size of smolts during the evening was of increase in efficiency ' pected to increase rather .J'... evident in the samples. This was caused by a decrease in the size of ·~: caught; however, a decrease If' ,J• yearlings, since very few older fish were present in the samples. Evidence that such was a regular feature of the migration in 1954 was Further, as shown in large fish decrease, but F{l indicated by additional samples taken during regular fyke-netting hours, which were from 2100-2300 each evening. The mean weight of fish in the evening samples that were ,;1 ti' first and last samples taken each evening is shown in Table 5. In 20 of 21 avening. The appearance instances, average weight of individual migrants in the first sample was plained by either increase Suggested reasons for the rre gr<'ater than that in the last. l ~ . '
I ~·· n1
Smolts from Wood River f I 260 .Alaska Red Salmon i! ~~~ t TABLE 5 I MEAN WEIGHTS OF schools in size composition of the individual fish. The fyke-net samples DURIIO THE 2100-2300 ..)\ were composed of portions of a greater number of schools, hence tended POINT, MAY ~.·· more toward the average size composition of all schools passing, and Time r·' thus showed lest3 variability in size composition between samples. Time Date First .Last Comparisons of individual samples obtained simultaneously by the two Sample Sample r:·· types of gear are presented in Figure 7. The over-all mean length of t. ;,~1 2240 2300 h.~ smolts taken by fyke net wae 86.07 mm, 'by beach seine, 86.95 mm, a May 30 d:i.ffere..1ce of only 0.88 mm. The two seine hauls made on June 15, cap 31 2117 2300 1 2113 2300 tured several very large age II smolts of a size range not found in the June I 2 2130 2300 t:: fyke-net samples. Fewer fish of this length range (over 105 mm) were ! 3 2140 2300 t'' J captured by either gear the following two nights. It is not known whether 4 2218 2300 unusually large fish of this size avoided capture by the fyke net on ..Tune 5 2200 2300 2300 kl~ 15 or whether capture of these fish by beach seine and not by fyke net 6 2200 ' 1 It 7 2154 2300 [It~ was a chance occurrence. is unlikely that fish of this size range com 2300 prised a substantial proportion of the run, since they have never been 8 2106 9 2130 2300 captured in numbers by any gear used. If selection exists, however, 10 2104 2300 tl· some error would arise in determining the proportion of age II smolts 11 2105 2300 in the seaward migration in years when sizes of fish in this age group 12 2104 2300 run large. 13 2104 2300 2300 In the size range below 105 mm the samples gave no evidence that the 14 2107 P-r'... 15 2120 2300 cu1~r0nt b''l'J .. fyke-net set in the velocities at Mosquito Point selected smaller 16 2133 2238 fish. There was, then, no evidence that the proportion of yearlings re 17 2200 2243 tained by the fyke net was influenced by the size of yearlings migrating. 18 2.122 2300 ;.. ' 19 2.107 2300 ~.t., Comparison of beach-seine and fyke-net samples did bring out the ....: heterogeneity in length frequency of smolts among schools. As a result of TOTAL these tests, it was decided that when samples for size and age study were ~I to be drawn from the catch, the fyke net should be fished long enough MEAN it 11 before lifting to make the resultant catch a composite of several schools. tv In 1951) and 1957 a .-.u.u•oa.a.~ Diurnal Changes in Size of Smolts Migrating of age Il smolts, and alL.uu'ur" 'r lr' l During early years of sampling at Wood River, marked diurnal dif for age H smolts to run e consistet tt. The tendency for t,,..; .. ferences between samples were noted in size of smolts taken. The diurnal differences were first studied in detail in 1954 to determine possible is still u.1der study, for in Possiltle diurnal change I•' causes and to evaluate thetr effect on the sampling schedule adopted. .! l( carded aH a cause of diurnal r\'• Hrurly samples of the run we!re taken on two evenings of heavy migration. Length irequencies of these samples are presented in Figures 8 and 9. A in efficiency of the net oc pattern of general decrease in the size of smolts during the evening was of increase in efficiency ~:! evident in the samples. This was caused by a decrease in the size of pected tc1 increase rather f·:.i ~; caught; h1 ~wever, a decrease ·.l• yearlings, since very few older fish were present in the samples. Evidence that such was a regular feature of the migration in 1954 was Further, as shown in large fish decrease, but (1' indicated by additional samples taken during "'"egular fyke-netting hours, rU evening samples that were 'il which were from 2100-2300 each evening. The t'lean weight of fish in the ..!J, first and last samples taken each evening is shown in Table 5. In 20 of 21 evening. The appearance plained br either incrl-!ir:l.i~I:'!\.U~ instances, average weight of indi;vidual migrants in the first sample was Suggest.~ reasons for the r•r ' ; greater than that in the last.
i'!W' ' • ~ . . . I . . , ..~ l
) f:~ Alaska Red Salmon Smolts from Wood River Lakes 261 \: Tidual fish. The fyke-net samples TABLE 5. MEAN WEIGHTS OF SMOLTS TAKEN IN FIRST AND LAST SAMPI.:ZS ~. ~~~ber of schools, hence tended DURING ~E 2100-2300 EVENING FYKE-NETTING PERIOD, MOSQUITO POINT, MAY 30 THROUGH JUNE 19, 1954 nb :.~t of all schools pas~dng and - ~m 'dsition between sample~. Time Time Difference Mean Weight of Fish ~n Grams · btained simultaneously by the two in First Last Date First Last S j Differenr.e . 7Jl:The over-an mean length of Sample Sample Minutes Sample ampe1 ,::;' Ly beach seine, 86.95 1nm, a May 30 2240 2300 20 7.03 6.55 0.48 .,;/me ha~ls made on June 15, cap 31 2117 2300 103 9.65 6.54 3.11 .~ ~ 0r.f· .a s1ze range ::.1ui: found i.n the June 1 2113 2300 107 6.72 6.05 0.67 1 " ~] 1 en i,ih range (over 105 mm) were 2 2130 2300 90 7.05 5.89 1.14 .., c'.'0 .1ghts. It is not known whether 3 2140 2300 80 6.05 5 .. 93 0.12 'id capture by the fyke net on June 4 2218 2300 42 6.43 6.01 0.42 2200 2300 60 6.61 6.53 0.08 ::J:' ~f·i.r.ch seine and not by fyke net 5 1 6 2200 2300 60 6.67 6.13 0.54 . 1. thb fish of this size range com- ' 11 • 7 2154 2300 66 7.11 5.04 2.07 • v run, smce they have never been 8 2106 2300 114 5.97 5.34 0.63 ~::':ct. tlf selection exists, however, 9 2130 2300 90 6.21 5.21 1.00 ~ :~g t ,;:~ proportion of age !I smolts 10 2104 2300 116 6.06 5.34 0.72 11 2105 2300 115 8.10 7.26 0.84 ·.'i m ~zes of fish in this age group • l 12 2104 2300 116 6.45 5.53 0.92 l·l· 13 2104 2300 116 5.47 5.24 0.23 :ij.arr.l::~es gave no evidence that the 14 2107 2300 113 7.32 6.26 1.06 ··,} M[triquito Point selected smaller 15 2120 2300 100 5.89 5.74 0.15 i ~,:t th~ proportion of yearlings re- 16 2133 2238 65 5.40 6.20 -0.80 17 2200 2243 43 5.2.7 5.10 0.17 : ~ th~ .size of yearlings migrating. 18 2122 2300 98 ii.'t8 5.50 0.28 :fc e-1",,!t1 samples did bring out the 1 19 2107 2300 113 6.05 6.01 0.04 .• 1.~ts lJmong schools. As a. 1·esult of 't 11ples for size and age study were TOTAL 1,827 13,87 J)et{·':rhould be fished long enourrh 1 MEAN 87 5.54 5.88 0.66 • ~ 1l a j'.')mposite of several schools. )'· In 1956 and 1957 a substantial fraction of the migration was composed . ,r~· , ....:~mr-:.,. l : of age II smolts, and although there appeared to be a slight tendency : ','ol,'IRiver, marked diurnal dif- for age smolts to ru:n earlier in the evening, the pattern was far from 1· • •I n : 1,31 ..-,of smolts taken. The diurnal consistent. The tendency for larger smolts to run e~lier in the evening :· ,!.1 in 1954 to determine possible is still under study, for in other years it was not as evident as in 1954. 1 r: th~~i· sampling schedule adopted. Possible diurnal change in selective action of the fyke net was dis · . twt::~venings of heavy migration. carded as a cause of diurnal change in size of fish in the cai:cho If change l' presented in Figures 8 and 9. A in efficiency of the net occurred, it would be expected in the direction :i>f sm.olts during the evening was of increase in efficiency with increasing darkness. This would be ex · (;;eJ::;,Y a decrease in the size of pected to increase rather than decrease the proportion of large fish . ,·,;rerl-.:!1 present in the samples. caught; however, a decrease in proportion of large fish was established. : ,,:ure of the migration in 1954 was Further, as shown in Figures 8 and 9, not only do the proportions of · .:ri~ 1 regular fyke-netting hours, large fish decrease, but size groups of small smolt s are found in late ! : ·• 'f e mean weight of fish in the evening samples that were not present in samples taken earlier in the l is. shown in Table 5. In 20 of 21 evening. The appearance of small fish in later samples cannot be ex nigrants in the first sample was plained by either increased or decreased efficiency of gear. ! Suggested reasons for the phenomenon of diurnal change in sizes caught I'; l Smolts from Wood River Lakes 262 Alaska Red Salmon s averaging well over 1 ,; are .(1) that the larger fish reaching the lake outlet have a greater mi samPle ' du ed t 1 pot 1 sample size was re c o . : gration stimulus because of their more advanced development, and there . ··---""""r of samples and flsh fore,. show .less hesitation in entering the river from the lake; or (2} that To tal rl~ • • frequency and age distrlbutlon arE • the final distance from the qaytime milling area to the lake outlet is TABLE 6. T01'AL NUMSER OE tr~versed more swiftly by larger fish because they tend to be stronger FREQUENCY AND AGE , swimmers. Neither alternative can be explained solely on the basis of behavior Total Seasor . catch of SmoJ~ of i~divi~ual f!sh. R.ed salmon fingerlings exhibit a marked schooling Year during Index P•~ hab~t. It 1s quite unlikely that the faster swimmers or individuals with a greater urge to migrate break away from their unit schools to reach 745,832 1954 the outlet during evening in advance of their slower members. Further 1955 904,236 ~· 1, 325,910 I fingerlings migrating pa...~ Mosquito Point are in definite schools cross~ 1956 ing the shoal areas in distinct waves. The behavior of the sch~~l made 1957 627 ' 884 t~/! up of individua· :s, must therefore be considered in any explan~tion of *DailY fishing hours: 2 •. the phenomenon of diurnal chanr.e rn size frequency. This requires no 1955 through 1957. particular modification of the ~11ggested reasons advanced, for it has During nights of heavy migratif been sh?~n repeatedly by sampling in the lakes that length-frequency the catch occupied the full ef~orti composition varies greatly from one school to the next. Schools com ble it was not at all feas1ble1: posed of larger fish may simply begin migration out of the lake earlier in s ira ' . as a sample. It was the practlcEft the evening or may migrate faster than those composed of smaller fish. Migration of t.he individual is thus apt to be controlled to a considerable spaced at fixed interva:s on a sr each year. This samplmg proct degree by size and impulse of its companions. The explanations advanced, particularly the latter, require the concept urnal changes in size and age \ Samples taken at or of a milling area or reservoir in the lake near the outlet where young between~ study for the 1954 period. The tend to congregate during the course of the day or early evening prior ff to migration out of the lakes. Observations of the behavior of red smolts extended to 0200 beginning in ~ ch'av,;n at approximately 2200, 2r near the outlet o:f Lake Aleknagik, particularly in 1949, support a res ervoir hypothesis. Schools of red fingerlings were observed during cer unless the evening ca~ch was ~!. fish). If the days of hght catc4 tain days feeding and milling in considerable c;:>ncentrJ.tions in the more every three days. Some flexi shallow lower end of the lake near the outlet. Evening observations were 1 made from a boat anchored over submerged light-colored panels near evening run was unusually heay. during an evening were not we\ shore about 300 yards above the lake outlet. During the day only occa evening catch they were tore. sional schools of fingerlings were observed over the panels. During early unwarranted refinement evenL"lg many more schools were observed crossing the panels, but bey~. sampling procedure. Table 7 movement was not decisiveJ.y directional. Schools crossed the panels l L ! 1 1 Alaska Red Salmon Smolts from Wood River Lakes 263 •! tn : ;:r:e laKe outlet have a greater mi- samples, averaging well over 150 fish per pound. In 1957, individual .~ dvanced development, 1 and there sample size was reduced to 1 pound, averaging over 100 fish per pound. ,·e.e . lf::·erB from the lake·1 or (2) that Total number of samples and fish used in determining the season's length ··J tllt: 1g area to the lake outlet is frequency and age distribution a..~e given in Table 6. ~:~ 1~ 1ecause they tend to be stronger 'l'ABLE 6. TOTAL NUMBER OF SMOLT SAMPLES USED FOR LENGTH FREQUENCY AND AGE DETERMINATIONS, 1954-57 '::~;; scr:!ly on the basis of behavior 1 Total Season's Number of Number \:;n. ngs exhibit a marked schooling Catch of Smo1ts Year Samples of Fish .i'l= • swimmers or individuals with during Index Period* ~~·lrol :/ their unit schools to reach .. ,rile~ slower members. Further 1954 745,832 52 8,923 904,236 llO 14,419 •3: are in definite schools, cross~ 1955 1 1956 1,325,910 63 11,134 ·~ ·lte t~havior of the school, made 1957 627,884 94 10,207 '),m,-1,:Iered in any explanation of ···cl,:e ~1-equency. This requires no *Daily fishing hours: 2100-2300 in 1954, 2100-0200 in ~{i r~asons advanced, for ithas 1955 through 1957. :· J,heE!·.lkes that length-frequency During nights of heavy migration, weighing, recording, and releasing of 1 ' .t 1hof:1 to the next. Schools com- the catch occupied the full efforts of the fyke-netting crew. However de ' , t' ~ 9 ra wn out o~ the lake earlier in sirable, it was not at all feasible to draw a uniform fraction ot each catch ,. f ":·• :::lo].composed of smaller fish. as a sample. It was the practice to draw a minimum number of samples ~ :';-;e j;mtrolled to a considerable I . ]l' spaced at fixed intervals on a sampling schedule that could be followed ·. i 10 lo. each year. This sampling procedure did not fully take into account di ·j)~ the _latter, require the concept urnal changes in size and age composition that may have occurred. 'j.e 4t ar the outlet where young Samples taken at or between 2200 and 2300 were used in the present :·lheJl~;ay or early evening prior study for the 1954 period. The standard evening fyke-netting period was .: ''; of the behavior of red smolts extended to 0200 beginning in 1955, and three samples were generally : \lla~~ 11 y in 1949, support a res drawn at approximately 2200, 2300, and 2400. All three were proce:.;sed .1 c1tgs 1 rere observed during cer unles~ the evening catch was light (less than one index point, or 4,000 1 ;· >le·Joncentrations in the more fish). If the days of light catches continued, a sample was processed 't =~t. Evening observations were every three days. Some flexibility was exercised, particularly if the i5e~ ~right-colored panels near evening run was unusually heavy early or late in the evening. Samples . ~et.~ {mring the day only occa during an evening were not weighted according to the proportion of the ).over the panels. During early evening catch they were to represent, since this would have been an ·. {ve[ r 1:crossing . the panels, but unwarranted refinement beyond the accuracy of the fyke-netting and · : ·. :1hools crossed the panels sampling procedure. Table 7 (p. 264) gives the proportions of the migra . ='rrd ·..:..1e outlet. However, :from tion each season that were represented by daily samples. :. 1ive and all schools swam de- In computing seasonal length-frequency curves, daily samples were r- ;, weighted by the daily catches they represented to adjust for changes •' ..• r·I' , . 'I . h -~ during the season in the magnitude of catches. From 1954 through 1956 (Age Composition Studies this was done by combining frequencies for adjacent days within five ',i41J:lrough. c, 1956 were 2-pound day periods in which no significant change in size of migrants was ob (r served, then weighting the frequencies by the total fyke-net index catch ll I p p~· ...f.,rsiological development for days included. Since this involved a decision as to which days could )>perly by size or age alone, be grouped, the procedure was modified in 1957 so that each daily fre l ?f rthysioiogical age. If quency was simply weighted by magnitude of daily catch. ! 264 Alaska. Red Salmon Smolts from Wood River Lakes TABLE 7. PROPORTION OF THE WOOD RIVER SMOLT MIGRATION REPRESENTED not extreme. This may be J..u.,u.i:>• BY DAILY LENGI'H-FREQID~CY SAMPLES, 1954-57 age n fish obtained in this J.J.J."Io.lU.I.• weight to each day on which No Sample At Least One Sample Two or More made in Table 8 for two years from Daily Catch from Daily Catch Samples Daily Year Per Cent Per Cant Per Cent high. Number Number Number of Season of Se1son of Season TABLE 8. EFFECT OF of Days of Days of Days Catch Catch Catch 1954 5 1.0 30 99.0 20 73.7 Method 1955 18 ) 12.9 36 87.1 23 78.4 1956 31 4.0 32 96.0 19 86.3 1957 25 2.8 34 97.2 29 88.4 Samples weighted by magni ! of fyke-net catch Method of Age Determination Daily samples given equal weight Beginning i~1 1954, nearly ,"'1 samples of smolts drawn during evening fyke-net sampling were. proc-essed alive and released, necessitating an age-sampling technique adaptable to this procedure. Groups of age I Relationship between and age II smolts could generally be separated by length frequencies at the beginning of the migration season. Later in the season sizes of the Previous investigators have two age groups overlapped. In order to determine age composition it was water survival rates of red necessary to preserve for scale study those fish which fell in the range Lake on Kodiak Island this in which lengths of age I and age II fish over lapped. Those fish in the tions of fresh-water survival length frequency well outside this overlapping range needed merely to determined through fin- be counted if age composition of the sample was the only information 1944). More direct measure desired. British Columbia lakes, with The zone of overlap in length frequency of the two age groups was From 1925 through 1936 test determined in the field at intervals during the season by examination were conducted there. In of smolt scales under a microscope. As shifts in length frequency were spawners entering the lake observed, scale samples were examined to detect shifts in the overlap produced were cou..nted, range. Sample fish in the range of overlap were preserved at the time of adult females, and oo·teilLtJ the daily live-smolt samples were measur~d. Complete smolt samples, was calculated for each year. preserved at frequent intervals during the season, provided a check numbers of eggs spawned against the range of overlap designated in the field. By this method, an periments conducted prior to adequate age breakdown of a large number of samples was obtained with (Foerster, 1938). However, a minimum of preserved specimens. certain of the years involved, Scales from fish in the preserved samples were mounted on glass during the experimental slides and projected for age reading with methods and equipment de ditions in Cultus Lake even ':, 1951) . ,..... scribed by Koo (1962). Age readings of smolt scales for the years 1951- l,, 57 were made by the writer, the 1958 age readings by Koo. At Lakelse Lake, British An index to annual age composition of smolts in the Wood River sea Cultus Lake were used to vu·-~ ward migration was obtained by weighting samples by the ma~itude of ing (Brett and McConnell, 195 the catches which they were to represent. Grouping of daily age samples seven brood years is given and catches was the same as used in weighting length frequencies. Al Fisheries Research Board, . though changes during the season in age composition and in magnitude tionship between the number of migration were considerable, corrections in the season's age com duced ...." position attained by weighting the samples by magnitude of catch were Fresh-water survival r ' ' r Alaska Red Salmon Smolts from Wood River Lakes 265 ffi f DLT MIGRATION REPRESENTED not extreme. This may be illustrated by comparing the per.centages of . «r st tiPLES, 1954-57 ··r======r===== age ll fish obtained in this manner with values obtained by giving equal ::. One Sample Two or lfore weight to each day on which samples were taken. This comparison is .~ ly ".atch Samples Daily made in Table 8 for two years when the percentages of age ll fish were •e P 3·~~-r----=-===~~;;::~~, Cent Per Cent · .,J._of ._. eason Number high. of Season '.'i Catch 0 f Days TABLE 8. EFFECT OF WEIGHTING ON AGE DETERMINATIONS, .:f~ Catch 1956 AND 1957 ·~~;J1r. :.111 o 20 '} 73~ 7 Percentage of Age II Smolts 00 :~1 23 78.4 Method :::: 96.0 19 86 3 1956 1957 1] 07 2 . ;1~i :,,-·--..1.__2_9 _ _J___:8:.:.8..:_·4.:__ Samples weighted by magnitude 21.6 19.3 of fyke-net catch . Daily samples given aqua! 17.6 20.3 /~of srnolts drawn during evening weight ::1 'I ~t·t released, necessitating an :}LisJj ll'rocedure. Groups of age I 1 Relationship between Parent Escapement and Seaward Migration ,1arated by length frequencies at ,.J .. in the season sizes of the 1~d 3~r"'!' • Previous investigators have found considerable variability in fresh ,., te !(.llne age composition it was water survival rates of red salmon under natural conditions. At Karluk ; 1 ~os ·fish which fell in the range Lake on Kodiak Island this variability was detected by indirect calcula ,. Ql overlapped. Those fish in the tions of fresh-water survival after measures of marine survival had been 1 1·~rtP~_.r ?g range needed merely to determined through fin-clipping experiments (Holmes, 1934; Barnaby, 1 1 ~!lllf~J t~ was the only infot·mation 1944). ?¥lore direct measurements have been ma.de by investigators in . 1 ' l British Columbia lakes, with the most extensive work at Cultus Lake. !1~~c~.,:of the two age groups was From 1925 through 1936 tests of artificial versus natural propagation !_ ;m :'·,:he season by examination were conducted there. In experiments on natural propagation, adult :l~'l..:r l·... • I f ~ ~,,.uL...:-o m ength requency were spawners entering the lake and resultant numbers of seaward migrants ; ! to detect shifts in the overlap produced were counted, average fecundity was determined from samples ,, ip ,;~ ere preserved at the time of adult females, and potential number of eggs available for deposition .'. creq,) Complete smolt samples, was calculated for each year. Survival to smolt stage from calculated :1 ithe season, provided a check numbers of eggs spawned varied from 1. 05 to 3. 23 per cent in three ex ··1·f!.· 1 field. By this method an periments conducted prior to initiation of predator control experiments t ' ' ; ,· o i ':lamples was obtained with (Foerster, 1938). However, natural spawning was permitted only in .t 1 certain of the years involved, and eggs were shipped to other watersheds . ~nples were mounted on glass during the experimental period, which may have disturbed natural con 1 • .:1h ~ ~thods and equipment de ditions in Cultus Lake even prior to predator control (Thompson, 1950, tolibJicales for the years 1951- 1951). . =readings by Koo. At Lakelse Lake, British Columbia, the same procedures as those at ; }mt.~~s in the Wood River sea Cultus Lake were used to obtain calculated survivals from natural spawn : r • s a.~lples by the magnitude of ing (Brett and McConnell, 1950). Range in survival from egg to smolt for ~r · ;.tping of daily age ~amples seven brood years is given as between 1.0 and 4.9 per cent (Canada, C,hting length frequencies. AI- Fisheries Research Board, 1957): "There has been no obvious rela . !Olfc.\'osition and in magnitude tionship between the number of eggs laid and the number of smolts pro ~ontJin the season's age com duced ...." I·. \; by magnitude of catch were Fresh-water survival rates for a small sockeye population at Port L -. ' . ~ .- . t~:• 1 $ Sii 444 CUAJSCA Wi, A 412 rccaaaa a 4 ...... *RW I ------.,..------,_. -·~- r fl 266 Alaska Red Salmon Smolts from T¥ood River Lake { tl John Lake in the central coastal region of British Columbia were studied age composition in the 1953 !o l-1.-..:.;:..o,! . ,' . ) . . . ~ ' ' . ··.· ....· .. ' ··~ . .... ·. . . . . · ..·. , . . " ·. -~ ~ Alaska Red Salmon Smolts from Wood River Lakes 267 e ;.: . \'~'! 3·· • ,3.; B _.1sh Columb1a were studied age co~;r.>sition in the 1953 seaward migration was more complete, and :llPOrted survival values of 0.5 the ·v-alue of 4. 7 per cent age II smolts is believed to be a reasonable •\ouc~~on was reported as havin~ approximation. .:;r e.~~:·: depos. itions of 300,000 to f: h ~~~ard, 1957). TABLE 9. INDEXES OF ABUNDANCE OF WOOD RIVER SMOLTS 0 BY AGE (1952 = 100) /:ltem the number of smolts was - by Year of Wood River Smelt 'iOCW :rather than means of a Per Cent Seaward Abundance Ind<.:!x ) lati;; '! ratios of smolts produced Age II ?n range from 0.49 to 2.49 per Migration Age I Age II Total ::!I} (yanada, Fisheries Research 1951 <20.0 9.9 ~ 1 bfJii~t'een initial }X>pulation size 1952 < 1.0 100.0 i':cgeJl runs produce more smolts; 1953 app. 4.7 282.2 13.9 296.1 'lal from eggs to smolts, indi- 1954 4.2 420.4 18.4 438.6 1955 2.0 217.3 4.4 221.7 1:J b~!~xpected from still larger 1956 21.6 258.2 71.2 329.4 ,•ll J( 1957 19.3 133.6 31.9 165.5 ' 1 .,eru.rl.sula, Krogius and Krokhin 9 1958 35.0 150.0 80.8 230.8 ':..f sockeye over 17 brood years :! ·fonfr?. 04 to 1.3 per cent of eggs 1i) ~·;Jve an even wider range of r : ne lake. Krogius and Krokhin TABLE 10 . WOOD RIVER ESCAPEMENTS AND SMOLTS PRODUCED .I r ·lJ j wr;: much more constant than Index Values of Index Units Wood River .. :. oas~·~~:o correlation between es Year Smelts Produced per 1,000 . Escapement :l'I .. i ~, that the four parent spawning Age I Age II Total Spawners I ·-·.. ; ~r of smolts per spawner were 1949 101,000 9.9* .10 •,, (. j·f_, 1 :n5o 452,000 100.0 13.9 113.9* .25 ;·tva · r survival have succeeded 1951 458,000 282.2 18.4 300.6 .66 :1 trs in survival. No consistent 1952 227,000 420.4 4.4 424.8 1.87 -po~ttation and percentage sur 1953 516,000 217.3 71.2 288.5 .56 •ns i ated. 1954 571,000 258.2 31.9 290.1 .51 r • I 1955 1,383,000 133.6 80.8 214.4 .16 ·;.nee of smolts, 1951-58, clas- - : .w;e II smolts (Table 9), provide *Using maximum values of 20 per cent age II smelts in 1951 ,: '"reef :parent escapement of red migration and 1 per cent age II smelts in ~952, the smelt _Ritr'r lakes and relative num index values would be: . ~years, 1951 through 1953, age 1949 year class 8.9 1950 year class 11~.9 1 f01f.~9lete sampling and require '· : s~ -.:~pies taken during the 1951 During the years 1949-52 Wood River escapement data were obtained adwt returns of 1953 and 1954 by comprehensive ground sur\reys of the spawning areas, supplemented (e percentage age II fish in the by aerial survey estimates. Since 1953 total escapement estimates have :. J' .c1e smolt samples and sub been obtained by the much more accurate method of trunk stream enu ~ lJration iPdicated less than meration from towers situated on Wood River. The spawning ground these years were assigned as surveys were continued after 1953, and provided a basis for adjusting ·; •· Tf.pi s does not serious_ly al!er the 1949-52 escapement estimates to represent total escapement esti l ;e 18 the small total m1gratlon mates for the system. Values given in Table 10 were determined and . ! IT bimolts in 1952. The maxi- provided by John R. Gilbert, who has summarized the Fisheries Re ... (Table 10). Determination of search Institute spawning-survey data for this period. f L 1 an ;:a •• eae:uu t ;a M ntiiat•c~,.. f I 268 Alaska Red Salmon Smolts from Wood River Lakes The relations between values representing parent escapement of red riod of nine years, a close salmon to the Wood River spawning grounds and smolts produced are f:mperatures in Sweitzer Cre given in Table 10 3..t,d graphed in Figure 10. The rate of reproduction is H tated. "When surface represented by the number of smolt-index units per 1,000 pa..t'ent snwn s:c~eye ~ppears to be inhibited ers. While survival values !or the brood years 1951, 1953, and 1954 cation is set up and the are closely gr.ouped, values for the remaining four years fail to :fall in ...,,.,.e they form a temperature ~.~ ' k " line. The best rate of reproduction, that of 1952, was 19 times that J.Uigration of soc eye 4 of the poorest, 1949. No definite reh.tion between size of escapement to seaward migration o~ ~ed and smolt index is seen. The two extremes of escapement provided the attem{t to explain the or1gm of poorest reproduction r-=ale. It appears that conditions for survival were mgton. His comment l·s·· ''When more important than abundance of spawners in determining abundance the migrators which J.mve been of smolts. to desert that level and _withdraw Minor changes in the relation between years would be expected il Striking differences m . survival values were corrected for differences between years il1 average tiems have occurred during fecundity of females and in sex ratio. The primary factor influencing were measured by daily '\o,,., ... rrt:.~cat, average fecundity would be marine-age composition of female spawners. the index fyke net at the outlet Mathisen (1962) showed an average fecundity of 3,639 eggs for female cateh curves of Figure 11 show red salmon returning to Pick Creek, Lake NeJrlr..a, after two winters in years in seasonal timing of ~g~•~. the ocean, and an average fecundity of 4,290 for those returning after , At least four influences had a three Winters. The proportions of the two groups, small and large fe in the wood River lakes. The males;- in the Wood River escapement varied between 23 and 84 per cent ever, changes in relative num small females during the years 1949-55. Sex ratio of escapement during smolts from the lakes, differ these years could not be determined with accuracy. Values obtained smolts, and differences in ranged between 52 and 60 per cent females. Approximated corrections contribute. The last three .I.Q.'-•"'&,· for se;x ratio and fecundity were applied to the data but were found to Changes. in smolt behavior modify only slightly the highly variable relation between parent escape ture have been observed .Lu.'""'• ment and smolts produced. The start of substantial s until lake outlet temperatures Influence of Climate on Timing of Seaward lr1igratirm ice in late May or early June. associated with breakup of ic .lc [~E Causes for fluctuations in fresh-water survival rate must be sought shown in Table 11. where the .• r' in changes in the ecosystem to which salmon are susceptible. Varia and dates by which time 5, 'I bility in seasonal timing of seaward migration and in growth attained catch had been made. For the 1 ! by smolts is a reflection of differences between years in conditions of tially in the same order as :i 1 r r~( fresh-water environment. Foerster (1937) demonstrated that differ sequence was modified by the . ) . ) ences between years in timing of seaward migration at Cultus Lake were factors; yet by the ttme 20 per • o; largely associated with water temperatures in months immediately pre lation to date of breakup was .. l 1 ,, f..: ceding and during migration. As to lakes that freeze over, it was soon Cessation of seaward ...... !: I learned that seaward migration of sockeye followed shortly after breakup to over 50° F (10° C) of the ;I 1 of lake ice (Babcock, 1904; Chamberlain, 1907), so that differences in Nerka weather station. R 1 seasons 1952 through 1957 .f' timing of migration were associated with differences between years in ~ dates of breakup of lake ice. time the lake-surface temper 'I ~ and remained above 50° F c Cessation of seaward migration has also been associated with rising water temperatures (Chamberlain, 1907; Ward, 1932; Foerster, 1937; from June 16 in 1954 to July 21 Parker and Vincent [1956]). At Cultus Lake, Foerster found, over a dates by which time 90 per c I ( tc: .• :•• ' . l• t'!l' JIB Alaska R•~d Salmon Smolts from Wood River Lakes 269 .: en~_, tg parent escapement of red . ': ro~;ds and smolts produced are period of nine years, a close relationship between rising mean daily temperatures in Sweitzer Creek and cessation of seaward migration. .'ex ~.'1 .. itThe rate1 of reproduct·Ion Is. ,,,: ~~. s per -:;000 parent spawn- He stated: "When surface waters rise above 10° C the passage of young ·}o ."-=:ears 1951, 1953, and 1954 sockeye appears to be inhibited and consequently, as summer stratifi ::nammg four years fail to fall . cation is set up and the epilimnial v.--aters rapidly increase in tempera f m ··th~.::. ·•.. :> 19_5_2 , was 19 times that ture, they form a temperature barrier or blanket to terminate the further •'10 J'' t . ,;: '.:.. e ween size of escapement migration of sockeye" (Foerster, 1937). This ntemperature barrier" ...rnes of escapement provided th to seaward migration of red salmon was first d~scribed by Ward in an attem].X to explai,n the origin af landlocked sockeye in Baker Lake, Wash :\'l_at .conditions for !:lurv1·val e / e)r.. . "" were ington. His cornrnent is: ''When the surface water of the lake passes 10° C :.' m ) =» m determining abund~!ce 1 1 the ptigrators which have been continuously at or near the surface appear ./en years would be expected if to desert that level and withdraw into deeper layers" (Wa,rd, 1932) . } env,ts ~tween years in average Striking differences in seasonal timing of Wood River seaward migra .:: Thf~J P~l~ary factor influencing tions have occurred during the year~ un9,er study. These differences ·, om~slbon of female spawners were measured by daily changes in magnitude of smolt catches made by /n~:t!' of 3,639 e~gs fo·r femal; the index iyke net at the outlet of the Wood River lakes. The cumulative ,.,ikef.!(erka, after two wintel,"s in catch curves of Figure 11 show as much as a month's difference between ·,4,21 J for those returning after years i..tl seasonal timing of pe'ak catches. had \~? ~roups, small and Iai.. ge fe- At least four influences a significant effect on timing of migration :: .Ieft,:rbet:veen ~3 and 84. per cent in t..~e Wood River lakes. The most influential factor was climate: How ever, changes in rel~tive numbers in the component s'ubpopulations of , 1~~ ~{at10 of escapement during : lth accuracy. Values obtainsd smelts from the lakes, differences between years in size and age of smolts, and differences in rate of growth in early summer appeared to Ji esJ~'~pproximatad corrections ~. i t{·;,~-he data but we:-e found to contribute. The last three factors will be discussed i.p a later section. ·!sla'· >n between parent escape- Changes in smolt behavior associated with changes in water tempera ture have been observed since the beginning of these studies in 1949. ' The start of substantial seaward migration has been consistently delayed ·I r...~ ·.off award Migratlon until lake outlet temperatures reach 38°-39° F following breakup of lake ice in late May or early June. Timing of initial migration was closely :I su:r;vival rate must be sought associated with breakup of ice on Lake Aleknagik in spring. This is shown in Table 11 where the years are listed in order of date of breah.~p ;lrnfi t are susceptible. Varia I . . ~ra · on and in growth attained and dates by which time 5, 10, and 20 per cent of the season's index . •etween years in conditions of catch had been made. For the 5 per cent dates, the years fell essen : 37f,.; iemonstrated that differ- tially in the same orde:r as the date of lake ice breakup. This initial ~ r:-ation at Cultus Lake were sequence was modified by the continuing influence of weather and other 3 in months immediately pre fac~ors; yet by the time 20 per cent of the .mtgration was over, the re lation to date of brealrup was still ~Lpparent. ' th~~l freeze over, it was soon . fo1!-.:1Ved shortly after breakup Cessation of seaward migration coincided quite closely with warming 1 ... _7), so that differences in to over 50o F (10° C) of the lake-su.rface waters m.?asured at the Lake differences between years in Nerka weather station. Records of lake-surface temperature for the seasons 1952 through 1957 are graphed in Figure 12. Dates bv which o ~/:m associated with rising time the lake-surface temperatures at the Lake Nerka station"passed Ward, 1932; Foerster, 1937; and remained above 50° F varied over: a month between years ranging ,ak~,. Foerster found, over a from June 16 in 1954 to July 21 in 1955. These dat~.s were comp:U.ed with .~1 ' dates by which time 90 per cent of the season's cumulative-index catch [IE! I j li -. 270 Alaska Red Salmon Smolts from Wood River Lake: tant to pass. No such reluctanc TABLE 11. REI.ATION bETWEEN DATES OF BREAKu"P OF LAKE ICE ON LAKE ALEKN.<\GIK AND EARLY-SEASON SEAWARD MIGRATION OF observed in the Wood River lal ... RED SALMON SMOLTS AT WOOD RIVER INDEX SITE served inshore and near the s . . ' the week or ten days after ~urf~ .. . Date 5% of Date 10% of Date 20% of ll' Breakup Dt~.te, The record catch of red fmget ~ Year* Migration Migration Migration Lake Aleknagik o-ver Over Over for siX years at Lake Nerka V: f ture at the trap site read 61 o • ~·~ 1954 May 26 June 1 June 2 June 2 1953 May 27 May 31 June 3 June 11 Summer Grawth of Yea1 1957 May 28 June 2 June 7 June 12 1951 May 30 June 4 June 7 June 9 Growth as Indicated by Scales . 1956 June 1- 3 June 10 June 12 June 15 1952 June 7 June 11 June 12 June 14 While temperature has been : ': 1955 June 10 June 23 June 26 June 29 gration, and is ~own to affect~, lished data showmg that temper, : *Years listed in order of breakup date. I aff.ect growth of young sockeye f .:1 in size of smolts are usually : .,, had been taken at Mosquito Point. The smolt catch each year falls off I density or in food level rathe:J· I ~ t!·1- :a-?idly beginning at about this time of year (see Fig. 11). In Table 12 1.:. t.l the effect of climate on growthf,. '. 1t lS demonstrated that in five of the six years, the 90 per cent level I l was passed within a very few days of the date the lake-surface temper 1956a), who stated that at Lak .·. I . ,I " of plankton were closely assoc ~ rt ature reached 50° F. Cessation of migration is probably closely as ~:• I J:!( sociated with a general thermal ((!hangs in the lake epilimnion. intensity of spring overturn . 1'1 elements were considered to 1;· ',• ',. TABLE 12. RELATION BETWEE:N' LAKE-SURFACE TEMPERATURES more complete overturn and n · ', . '. 1:! ~trr AT LAKE NERKA WEAT"rlER S'l'A'l'ION AND SEASONAL TIMING limnion if the epilimnion was t · 1.1 - •l OF SMOLT SEAWARD MIGRATION AT WOOD RIVER tude of the plarikton crop affe : 1· Date Surface TempeJ:-atures Date C"Umu1ative dence given does not appear .J• I ~!; • at Cabin Bay, Lake Nerka Smolt Catch Reached In the preceding sectiQ!l it w •· Year 11 r·:)·l First Rose over 50 F for 90% at Wood River affected timing of seaward mi . Longer Than One-day Period Index Site to follow that differences in c . I' upon the amount of growth ga; I' ~· 1954 Jwte 16 June 15 ~ I ' c ~arly July prior to seaward l I' 'tf.'"' 1957 June 16 June 26 ~' 1.• 1953 June 21 June 23 The amount of ~ew summer 1,, 1956 July B July 12 migration is indicated on a sc Lt 1952 July 19 July 19 new growth formed beyond th•t. ,•. 1~55 ,July 21 July 16 j!, 1 is negligible in the spring P~ break-un and warming of lake '\ The relation between a~.nnual timing of smolt migration, breakup of s; h: • I lS .,. lake ice, and la..lte temp~r~mres following breakup is shown in Figure 13 occurs in the .lake~. ! ll '• band of wide c1rcuh lru.d down~. itJ for the years 1952 through 1957. For each year, the time interval be .. r- tween breakup and attainment of 50° Flake-surface temperature is com of the annulus (Fig. 14). ~ Increase in scale radius, l pared with the 5 per cent and 90 per cent levels of migration. Delay in ~!~l ice breakup and warming of the lake resulted in delay in smolt migration not strictly proportional to in~·. t: ..: with which we are concerne~ ~- from the lakes. As to sockeye yearlings remaining behind in the lake, Ward (1932) of many different species of l and Foerster (1937) suggested that rising temperatures create an epi formation when the linear dr t:G . limniallayer of warm water through which the fingerlings are reluc- tively faster rate than does j } j\•".11 l l ~{8 ' . . . .. - ...... • : " ·. i ·" . :· . . . . .• ., -~ . . . . : .-~-~~~~--~ ~ . . . . .· . . . : ..: . . . . . J ~ "' . . ' . ~ . . . . ' ~ , • ' '·. ·,..-. _ •• ., "., .. __,. ~~'.&.u<., ..~'\- W•oa.••' ~.,. --:"t'.. JI-:-.."f* .. ·~~~.._... ,.,·_.;,•p.,~....._~~""'""t:;'"~..-_...... ;7~" 'ii;"",.,_,..._'l:r_~;"~"'~ar~;-,..,.:'\!\H"'~' ~ ~e'l'<"'f"'"<.~~~ • ~· '~""'"~ Alaska Red Salmon Smolts from Wood River Lakes 271 : )F BREAKUP OF LAKE ICE ON tant to pass. No such reluctance on the part of red fingerlings has been · i ~r::.~WARD M-IGRATION OF , Rl .. ~3R INDEX SITE observed in the Wood River lakes, for the greatest concentrations ob . -- i!:.___ .. served inshore and near the surface at Lake Nerka were seen during Date 10% of Date 20% of the week or ten days after surface temperatures exceeded 50° F (10° C). JJlfigration Migration The record catch of red fingerlings made in surface lake traps fished Jl: Over Over '. for six years at Lake Nerka was made on a day the surface tempera ~ - ture at the trap site read 61° F (16.1° C). June 2 June 2 June 3 June 11 ~I June 7 June 12 Summer Grawth of Yearlings Prior to Seaward Migration f}:lJune 7 June 9 June 12 June 15 Growth as Indicated by Scales June 12 June 14 !June 26 While temperature has been shown to influence timing of seaward mi : _,,";----....1...-,. ____June 29 _ gration, and is known to affect growth as well, there seems to be no pub ·;'ate.~ lished data showing that temperature differences between seasons directly I affect growth of young sockeye in the lakes. Differences between years ;: m~~~t catch each year falls off in size of smolts are usually associated with differences in population :nru ,.!(see Fig. 11). In Table 12 I density or in food level rather than with climate. Indirect evidence of .' years, the 90 per cent level the effect of climate on growth was given by Krogius and Krokhin (1948, •: latf, the lake-surface temper 1956a), who stated that at Lake Dalnee annual fluctuations in abundance ~ at ~'t!:n is probably closely as- of plankton were closely associated with variations in completeness and 1 tbL Hake epilimnion. intensity of spring overturn and with depth of thermocline. Biogenic J; SUF?\'ACE TEMPERATURES elements were considered to be more thoroughly circulated in years of , ANrl~ SEASONAL TIMING more complete overturn and more available to phytoplankton in the epi ;· AJ !'WOOD RIVER limnion if the epilimnion was thick. It was suggested further that magni tude of the plankton . rop affected the size of smolts, although the evi I Date Cumulative dence given does not appear to be at all clear-cut. ff.'iSmo1t Catch Reached In the preceding section it was shown that seasonal climatic conditions r. 90% at Wood River Index Site affected timjng of seaward migration. It will be shown in the discussion I to follow that differences in climatic conditions have a definite bearing ..,: June 15 upon the amount of growth gained by red salmon yearlings :in June and ~;j June 26 early July prior to seaward migration. June 23 The amount of new summer growth that has occurred prior to seaward July 12 July 19 migration is .indicated on a scale of a yearling smolt by the increment of .J:• J July 16 new growth formed beyond the annulus. As shown by the scales, growth ·r------is negligible in the spring prior to breakup of lake ice, but following · ;molt migration, breakup of breakup and warming of lake waters a rapid increase in size of yearlings • ~e~.~~p is shown in Figure 13 occurs in the lakes. This is indicated on the scales of yearlings by a : Yfljlr, the time interval be-· band of wide circuli laid down beyond the broken, narrowly spaced rings 3urtace temperature is com of the annulus (Fig. 14) . . ave~s of migration. Delay in Increase in scale radius, measured from the focus of the scale, is ·. l l,.: delay in smolt migration not strictly proportional to increase in length of fish over the size ranges ~-l with which we are concerned. Investigators have found that in juveniles nd in the lake, Ward (1932) of many different species of tish there is an extended period after scale e~·J.1-:>eratures create an. epi formation when the linear dimensions of the scale increase at a rela .!lfe: 18 finger lings are reluc- tively faster rate than does the length of the fish. Dunlop (1924) det.:t;r- "1 l 1 ·l I 272 Alaska Red Salmon mined that sockeye of the lower Fraser River show a fairly constant L. increase in scale radius relative to length of fish between 35 and 100 mm, a lessening rate to 115 mm, a.'ld a decreasing ratio above 115 mm. Meas urements were presu.mably made from preserved specimens. Clutter and Whitesel (1956) gave tht: relation between mean scale radius (greatest scale radius, magnified 200x, measured from focus to edge of scale) and .mean fork length as established by 12 samples of preserved Fraser River sockeye smolts with mean lengths ranging from approximately 50-150 mm. Their linear equation for the regression line was: radius = 1.323 fork length - 33.11 The writer has also found a proportionately greater increase in scale 1~+---~~------1 ~· radius than in body length of preserved fish over lengths encountered in age I and age II groups of fingerlings from Wood .River lakes. The per centage increase in scale radius was about one-third greater than the .-i('l) Length of June 16 June 22 June 28 ~'ish in Number Average Per Cent Number Average Per Cent Number Average Per Cent Millimeters of Fish Summ.er Growth I of Fish Summer Growth of Fish Summer Growth 73- 77 8 3.6 8 10.1 6 15.7 78- 82 10 1.9 9 12.3 9 16.8 83- 87 8 4.5 9 14.4 9 15.8 88- 92 18 2.7 10 11.7 8 14.7 93- 97 4 3.4 8 10.2 7 15.3 98-102 1 o.o - - - - 103-101 ------TOTAL 49 44 39 AVERAGE 3.0 11.8 15.7 Length of July 4 July 9 July 15 Fish in Number Average Per Cent Number Average Per Cent Number Average Per Cent· 'Hi1limeters of Fish Summer Growth of Fish Su;mner Growth of Fish Summer Growth 73- 77 - - 1 27.6 - - 78- 82 8 22.4 2 24.5 5 32.8 83- 87 7 19.1 7 28.0 10 30.7 I 88- 92 9 20.0 11 26.7 7 30.4 93- 97 5 23.5 7 21.3 2 22.8 98-102 4 23.8 2 22.7 2 30.6 103-107 - - 1 22.8 9 31.4 108-112 - - - - 1 33.6 113-117 _,... - - - 1 35.8 TOTAL 33 31 37 AVERAGE 21.4 25.3 30.9 n 274 Alaska E!ed Salmon Smolts from Wood R·iver Lake the dates involved are shown graphically in Figure 15. The delay in first Wood River chain. The second appearance of summer growth is very similar to that found by Dombroski breakup and the time when r.. (1952) for 1951 Babine Lake smolts. case, daily mean air Measurements of new growth on the scales illustrate summer growth atures, first, because daily increments are to be found in smolt samples taken at successive dates able for all years, and second, during the migration period. The inc:t'ement pattern is not necessarily the expeclted to reflect too closely same as would be obtained by repeated sampling of a single population of able that mean air te fish within the lakes prior to migration, but does represent growth as ob warming than do water surface · served in successive groups of seaward migrants. As will be discussed sons in air temperature wer 11 later, main seaward migration is generally completed before substantial air "temperature units be summer growth appears on scales of migrating yearlings. The number of temperature tween the mean temperature Relationship between Scale-Growth Increments and Seasonal Climate In Table 15 the years 195 The time of the appearance of summer growth on scales V'a.ried between breakup. Included, in i:tU'""·"'·... v"''• years. Much of the difference in timing could be related to differences was drawn for scale measur in climate between years, just as the time of seaward migration was in found on the scales, number fluenced by climatic factors. and cumulative number of The difference between years in time of appearance of summer growth of sampling. The years 1953 is illustrated by comparing the average amount of growth beyond the an of early breakup with a nulus present on scales of yearling smelts sampled on the same date and a la:rge amount of new each season. In this instance July 5 was selected, since by this date the late breakup years 1952 summer growth is normally well differentiated on scal~s, yet some temperature units and little migraUon is still in progress. Smolt samples which had been preserved linear relation appears to on or very close to July 5 were available for the years 1952 through scale growth than between 1957. Dates of samples, numbers of scales measured, and average (Figs 16A, 16B). percentages of summer growth found along the longest axis of the scale TABI..E 15. RELATION radius are given in Table 14. ON SMOLT SCALES, ?ABLE 14. PERCENTAGE OF NEW SEASON GRO~T.H ON SMOLT SCALES, 1952-57* Date of Year l{t•:!nber Per Cent New Season Sample Date of Year of Scales Growth on Scales Saniple Measured Mean Standard Error 1954 July 5 1953 July 4 1952 July 7 30 7,9 1.15 1957 July 6 1953 July 4 33 21.5 1.13 1952 July 7 1954 July 5 55 19.9 0.70 1956 July 5 July s). July 6} U' 1955 50 6.0 1.02 1955 ~~ July sf July B ~. 1956 July 5 22 4.5 1.26 1957 July 6 32 20.7 0.88 The existence of the I of red fingerlings should *Samples taken at Wood River fyke-net site on or near effect. Temperature rec July 5. ferences in environment Two rather simple measures of late spring climatic differences among breakup in Bristol Bay lakes,.: these years are used for compu-ison with scale growth. The first meas the water below from incr urement is date of lake-ice breakup at Lake Nerka, central lake in the light, and mixing action of '' .<."''- .;JJ:'.,.-.;L•tt#~ ·~ It~~,.,'Jj'':r'•r, ,.,~~•..,.t~"'j :f -~~~!""'1!"•~~..,,.':1 l ···-~~~· ~.·. . - ·~ ' . . . • ' . - . . . \ - l ...... ' ' • ' • - • • • - w , • - ~ :t ~ ' . • '! ·. ' . . . n . r Alaska Red Salmon Smolts from Wood River Lakes 275 ::m.~.· .r.gure 15. The delay in first Wood River chain. The second is based on temperature records be• ween rllar to that found by Dombroski breakup and the time when samples were drawn in earJy July. I.1 this rt·· case daily mean air temperatures were used rather than water tenper ali~ illustrate summer growth atur~s, first, because daily water temperature records were not avail pies taken at successive dates able for all years, and second, because surface temperatures can: 10t be ,:1t is not n('cessarily the expected to reflect too closely transfer of heat into the lake. It is prob ,...••.• ,..,... ".£'"" of a single population of able that mean air temperatures give a more accurate index t >lake , represent growth as ob warming than do water surface temperatures. Differences betweell sea :nigrants. As will be discussed sons in air temperature were measured by the cumulative number of '·ty ".~ 1 mpleted before substantial air "temperature units" beginning with the date of breakup of lal:e ice. ,.·attJ;:5 yearlings. The number of temperature units per day was set as the differen::e be tween the mean temperature for the day and 32° F. ..1ejf• f' and Seasonal Climate In Table 15 the years 1952-57 are listed in order Df time of l~ke-ice ·~· ;ro 9)n. on scales varied between breakup. Included, in addition, are the date on which the smolt flample ;::oU;.:d be related to differences was drawn for scale measurement, average percentage summer ~owth of seaward migration was in- found on the scales, number of days from breakup to date of sample, ~: ; '(lf and cumulative number of air temperature units from breakup to date · a iJ:'arance of summer growth J of sampling. The years 1953, 1954, and 1957 group together a~. years nount of growth beyond the an of early breakup with a large number of cumulative temperatuxe units 'ltslsampled on the same date and a large amount of new growth on smolt scales by July 5. Convarsely, ::; i\u:ected, since by this date the late breakup years 1952, 1955, and 1956 show fewer curr;ulative ,en .. !...l.ted on scales, yet some temperatm·B- units ;md little summer growth on smelt scales. A closer )les which had been preserved linear relation appea:rs to exist between cumulative temperat1re and le ~1~r the years 1952 through scale growth than between length of time after breakup and scale growth :alt ;, measured, and average (Figs. 16A, 16B). g longest axis of the scale the TABLE 15. RELATION BETWEEN AMOUNT OF NEW SUMMER GROWTH ftil ON SMOLT SCALES, TIME OF LAKE-ICE BREAKUP~ AND SO~t1!1ROWTH ON SMOLT TEMPERATURE FOLLOWING BREAKUP 7* IT. Per Cent New Number of Cumulat .ve Air Date of Year Season Growth Days from Lake TU's to Pate 1 Cent New Season Sample h on Scales on Scale Radius Nerka Breakup of Sat 1ple Standard Error 1954 July 5 19.9 40 844 1.15 1953 July 4 21.5 35 805 1.13 1957 July 6 20.7 34 863 0.70 1952 July 7 7.9 30 548 1956 July 5 4.5 24 44& 1.02 ].955 July 6 } 6.0 22-24 382 1.26 1 July 8 0.88 The existence of t.l).e relation betweAn spring temperatu:..·es and g·rowth -net site on or near of red fingerlings should not be regarded as proof of direct camle and s; I effect. Tempe.t'ature records are simply one measure of gener2.1 dif j: ferences in environment caused by climatic conditions. Prior to spring c ,..1natic differences among i breakup in Bristol Bay lakes, the surface layer of snow and ice insttlates growth. rrhe first meas the water below from increasing warmth of spring air, penetrat .on of ~l'~rka, cfmtral1ake in the light, and mixing action of wind. Following breakup, surface tern.. >era- .k ' t ----·------)I '1 I ------~======~~~!~!=·~-=··=··=·=····~==~------~~~ ( m smolts from Wood River Lakes ,I n 276 Alaska Red Salmon system outlet, but which tend to tures r~se quickly to 38°-39° F. Spring overturn of the lake occurs ac of po~lation density (JohnSon, 195 compame~ ~y r~se of nutrients from fue lake bottom, and the amount of hypoUlesized that differential tim· . solar radiat1on 1nc:reases steadily toward a maximurn in Jtme. At break .. ~ was the cause of some of the seas , up, and for about two and ..:me-half weeka, there is no indication of re cent growth on fingerling scales. This is to be expected since the plank at Lake Kitoi in 1955. ~ t(~ ton bloom associated with sprjng overturn and increased light and tem L11 the Wood River lakes, study.·: ,; ·.a during the season revealed that the.· I perature is not instantaneous. Lag in abqndance of copepod and cladoceran ·~ feed, combined with reduced metabolism and activUy of the fish until mon passing Mosquito Point was by ~· " stock of fish, and that distinct s;: i' r, warming of their environment occurs, results in no growth on finger ling ·~;. ltJ! scales until an accumulation of about 300 temperature units has occurred. Seasonal patterns of change in nurq i i Weather .and temperature before breakup have little apparent eifect were of special interest in that thr ! ~ 1 then, on suosequent summer growth and activity of young red salmon in the marked differences found, a1 t~t the lakes except by their influence on time of breakup of lake ice. How indicated between size and survil t_.: Length frequencies of smolt , ever, air te~peratures after breakup are shown to bear a relationship to growth attamed by young salmon. The amount of sunshine the 84'ttent weighted as described previously (p) I• direction, and timing of wind action, and the amount of rai~all are ad: in Figures 17 to 20. These grap* r1}.1 ditional factors known to influence the summer temperature regimen in Cl.Irred in numbers, sizes, and aJ 1954-57. In the graphs, the firstf the lakes. These also affect to some degree the growth of phytoplankton 1 zooplankton, insect, and fish populations within the lakes. all four years have been extended t of low levels of migration at these I 1.'. H;~ quencies for the four years are N Seasanal Changes in Length Frequency of Srnolts for 1958 and 1959, provided by ~ Pattern of Seasonal Changes Features to be noted in these g~ gration {already explained in part }l! Seasonal changes in length frequency and age of smolts have been de r mate), differences in age composl· scribed by a number of biologists. In many red salmon pooulations ences in size of smolts in the mi~ smolts migrating earli&r in the season tend to be larger than iater mi ~ ' • f bimodal size frequency of age I Sj tl€t grants of the same year. class. Ba't"naby (1944) found a ma.th.ed decrease - Migration during the years 195~, . in average size of age ill smolts du.t,ing successive weeks of sampling at tern. YearlLTtg migrants (age I) p~ Kar~;,lk Lake in the years 1925-36. A less marked difference in age n smo.::.ts was attributed to the fact that L'l.ter rrligrants had added new sum several days of the season wer€ r.. mer growth. He concluded that "the urge to migrate seaward is related yearlings reached Mosquito Poin~ ~ gun. Grouped frequencies of 19a to the size a.nd growth rate of fingerlings ...." Gilbert (1916, 1918) this phenomenon (Fig. 20). also found a consistent seasonal decrease in yearling smolt size of Rivers Pa~' .. Inlet sockeye durl11g the yea.i:'s 1914 through 1916. Clutter and Vlhitesel range was great, as in 1955 and ! t·'l1! tinctly bimodal. The difference il (1956) reported that ~.,_ various sockeye populations of the Fraser River syr::tem, yearling smolts were of fairly consi.stent size dur]ng the main ferencras in amount of recent sumn: migratory period but frequently exhibited some trend towards size de yearlings at the lake outlet occu ~~I'' r·.. crease during the season. An exception to seasonal decrease in size was registered on the scales, and the reported by Dombroski (1954), who found a definite seasonal trend of in was over before appreciable su:9 crease in length and weight of Babint~ Lake yearlings in the years 1950 1951, and 1953. The eases were probably ascribable to additionai ta~~ ;::r'!~~~::~:r~=~ ;r~~~dd t·l inc.~. in average length during the seasj ~~= growth gains in the summer shortly before migration, shown by Dom versed the trend. However, the m~ broski. (1952) for the later migrants of 1951, or to th,~ contribution to th.e migration made by Nilkitkwa Lake smolts, which may be first to . to :appear at the outlet of the lak t~1j: pattern that larger smolts tend to -· appear in numbers in the migration because of close proximity to the ' t· t ·----~1 tL .. ·=--="-=""""''='="'-=------...... ~~~ ...... ------~------·--- 1 Alaska Red Salmon Smolts from Wood River Lakes 277 l :>verturn of the lake occurs ac- system outlet, but which tend to be smaller in certain years because lake bottom, and the amount of of po~lation density (Joh.'1Son, 1956, 1958). Parker and Vincent [ 1956] a f:j~l.Ximum in June. At break- hypothesized that differential timing of migration of two different races 1:S, t~ere is no indication of re was the cause of some of the seasonal changes found in size of smolts to be expected since the plank at Lake Kitoi in 1955. increased light and tem In thf' Wood River lakes, study of size changes in smolts occurring ;-..-...... of copepod and cladoceran during the season revealed that the seaward migration of young red sal activity of the fish until mon pa.ssing Mosquito Point was by no means composed of a homogeneous Jults in no growth on fingerling stock of fish, and that distinct seasonal patterns of change occurred. ··~nf~;erature units has occurred. Seasonal patterns of change in numbers of different size and age groups ~have little apparent effect were of special interest in that they provided an insight into causes of activity of young red salmon ~ the marked differences found, and particularly in that a relation was 1e fl1 ~ breakup of lake ice. How indicat~ d between size and survival rates. :e J:~town to bear a relationship Length frequencies of smolt samples taken at Mosquito· Point and :unount of Sl.mshine, the extent, weighted as described previously (p. 263) are graphed by five-day periods the amount of rainfall are ad in Figures 17 to 20. These graphs present seasonal changes that oc temperature regimen in curred in numbers, sizes, and ages of smolts migrating in the years • growth of phytoplankton, 1954-57. In the graphs, the first period in 1955 and the last period in within the lakes. all four years have been extended to include more than five days because fl of low levels of migration at these times. In Figure 21 the season's fre =re~:~uency of Smolts quencies for the four years are presented. The season's frequencies for 1958 and 1959, provided by Koo, are also included. Features to be noted in these graphs are differences in timing of mi nd ~ 11goe of smolts have been de gration (already explained in part by differences between years in cli ~: y red salmon populations, mate), differences in age composition, and seasonal and annual differ to be larger than later mi- ences in size of smolts in the migrations. Especially noteworthy is the 19lr~l) found a marked decrease bimodal size frequency of age I smolts in 1955, 1957, and 1958. 1C1·t13S1Ve weeks of sampling at Migration during the years 1952 through 1957 followed a general pat s marked difference in age II tern. Yearling migrants (age I) passing Mosquito Point during the first · migrants had added new sum several days of the season werG small, and the first waves of large tcfN;nigrate seaward is related yearlings reached Mosquito Point several days after migration had be .lf1l . ." Gilbert (1916, 1918) gun. Grouped frequencies of 1957 provide the dearest illustration of yearling smolt size of Rivers this phenomenon (Fig. 20}. Particu!~r 1y in the years when the size ~:1.916. Clutter and Whitesel range was great, as in 1955 and 1957, yearlin.g frequencies were dis ations of the Frasc.r River tinctly bimodal. The difference in size cannot be accmmted for by dif vu."" ... ""'"¥11 .. size during the main ferences in amount of recent summer growth. Initial appearance of large some trend towards size de- yearllngs at the lake outlet occurred well before summer growth was sEf,.· ·;onal decrease in size was registered on the scales, and the major share of the season's migration cl.Cinite seasonal trend of in was over before appreciable summer growth on the scales was found. e yearlings in the years 1950, In the Wood River lakes a tendency was apparent, pronounced in cer ly ascribable to additional tain years, for the modal group of large yearling migrants to decrease , shown by Dom in average length during the season until rapid new summer growth re , or to the contribution to versed th~ trend. However, the modal group of small yearlings was first olts, which may be first to to appear at the outlet of the la..~e system-an apparent reversal of the r of close proximity to the pattern that larger smolts tend to migrate first (Barnaby, 1944; Gilbert, k.. ID { Alaska Red Salmon Smolts from Wood River Lakes 277 ::>verturn of the lake occurs ac system outlet, but which tend to be smaller in certain years because lake bottom, and the amount of of poplla.tion density (Jolmson, 1956, 1958). Parker and Vincent [1956] a l(aximum in June. At break hypothesized that differential timing of migration of two different races ·s, taere is no indication of re was the cause of some of the seasonal changes found in size of smolts to be expected since the plank at Lake Kitoi in 1955. increased light and tem- In the Wood River lakes, study of size changes in smolts occurring .,~...... of copepod and cladoceran during the season revealed that the seaward migration of young red sal activity of the fish until mon passing Mosquito Point was by no means composed of a homogeneous .rults in no growth on fingerling stock of fish, and that distinct seasonal patterns of change occurred. ·enft~erature units has occurred. Seasonal patterns of change in numbers of different size and age groups ·.kuti:r have little apparent effect were of special interest in that they provided an insight into causes of activity of young red salmon~ the marked duferences found, and particularly in that a relation was ·le ~~: breakup of lake ice. How indicated between size and survival rates. ~e #i~own to b.;::Rr a relationship Length frequencies of smolt samples taken at Mosquito· Point and amount of sunshiiie,. the extent, weighted as described previously (p. 263) are graphed by five-day periods the amount t;i rainfall are a.d- in Figures 17 to 20. These graphs present seasonal changes that oc temperature regimen in curred in numbers, sizes, and ages of smolts migrating in the years · he growth of phytoplankton, 1954-57. In the graphs, the first period in 1955 and the last period in ,within th/8 lakes. all four years have been extended to include more than five days because of low levels of migration at these times. In Figure 21 the season's fre f :reHt!ency of Snwlts quencies for the four years are presented. The season's frequencies for 1958 and 1959, provided by Koo, are also included. ':~· I Features to be noted in these graphs are differences in timing of mi [I I nd[11!5e of smolts have been de gration (already explained in part by differences between years in cli m~. y red salmon populations, mate), differences in age composition, and seasonal and annual differ 3nd to be larger than later mi- ences in size of smolts in the migrations. Especially noteworthy is the 19f:~,) found a marked decrease bimodal size frequency of age I smolts in 1955, 1957, and 1958. lCittssive we~ks of sampling at Migration during the years 1952 through 1957 followed a general pat ss marked difference in age IT tern. Yearling migrants (age I) passing Mosquito Point during the first · migrants had added new sum- several days of the season were small, and the first waves of large t size during the main ferences in amount of recent summer growth. Initial appearance of large I some trend towards size de- yearlings at the lake outlet occurred well before summer growth was ~I sef1 ·sonal decrease in size was registered on the scales, and the major share of the season's migration 4.t;:inite seasonal trend of in was over before appreciable summer growth on the scales was found. yearlings in the years 1950, In the Wood River lakes a tendency was apparent, pronounced in cer ly ascribable to additional tain years, for the modal group of large yearling migrants to decrease :ligration, shov.'Il by Dom-· in average length during the season until rapid new summer growth re , or to the contribution to versed the trend. However, the modal group of small yearlings was first molts, which may be first to to appear at the outlet of the lake system-an apparent reversal of the t;· of close proximity to the pattern that larger smolts tend to migrate first (Barnaby, 1944; Gilbert, I tf( f l '( l l 1 l J f I 278 Alaska Red Salmon Smolts from Wood River Lakes 1916, 1918; Clutter and Whitesel, 1956). Furthermore, smaller smolts (Lake Nerka) lake trap was . . c•h were observed the folloWlng te~ded t~ complete migration earlier in the season. This, in addition to fhi . t 0 f other ~VIdence, led to the hypothesis that the migrations commonly are ta:nce of 5 miles from pom comprised of numerous groups of smolts which have experienced dif experiments on red fingerlings ferent growing conditions in different parts of the several lakes. The subSequently recaptured at the minimum length of time befor s~ early migrants were believed to be fl~om Lake Aleknagik, the lower lake m the system, and the waves of larg:er migrants from Lake Nerka lapse of time between r_elease ~d o~er u~per lakes. It was of particular interest to test this hypothe Nerka lake trap and thelr of 34 miles; was 8 days. These SIS, smce 1t would aid in determining what conditions are responsible for size achieved by the smolts. · of travel, measured in a direct Although the migration rates Effect of Lake-Ice Braakup and Distance from of the small numbers of r ~~···~·..... Outlet on Pattern of Seasonal Migration on normal behavior, it is to be The timing of ice breakup in the various lakes of the Wood River sys nagik before breakup would be i:hat over-all timing of seaward tenl ~gest~ that smolts from the upper la#:~'S would be later in reaching Mosquito Pomt. Substantial seaward migration has never been observed fected to some degree by during spring fyke-netting operations at Wood River, Little Togiak River mating in different lake areas. and Aguluk.pak. River until the lake outlet temperatures have reached at Substantiating evidence that r- least 39o F following breakup of the lake ice. This is in agreement with seaward was presented by Koo 1 d: migration threshold temperatures of approximately 40° F, reported for yearling smolts had more sockeye fingerlings in lakes with winter t,emperatures falling below this and that the amount of fre level (Chamberlain, 1907; Foerster, 1937 1952· Parker and Vincent turning adults was directly to the outlet of the system at [1956)). Any delay in ice breakup of the up~er lakes in the Wood Rive; syste1n might therefore be expected to delay arrival of upper-lake mi grants at Mosquito Point. Lake Aleknagik has in every year been the first to become ice free, although brealrup on Lake Nerka may occur the same day. The contrast between years in breakup sequence is some In a search for additional times rnarked; for example, 1954 versus Jl956 (Table 16). groups in the Wood River lakes, 1953 year class of Wood River · TABLE 16. SEQUENCE OF LAKE-ICE BREAKUP IN 1954 AND 1956 because yearlings migrating in. dality in size frequency (Fig. Breakup Date Lake 1954 1956 recognition in later life stages In the 1955 yearling migration Aleknagik May 26 June 1-3 first to appear at Mosquito Nerka May 26 June 11 netting no other yearling sizes Little Togiak Before May 30 June 15 tion of this small size group (No record) June 20 (approx.) Kulik the season, there was no The colder 1956 season extended the breakup period, and the ice cover on upper-lake areas. No small encountered in samples from the lakes delayed the arrival of threshold temperatures for migration in r,. the upper lakes areas. River fyke-net samples in 1 lings remained an extra year h: The rate of smolt migration between the outlet of Lake Nerka and particularly heavy migration the outlet of Lake Aleknagik at Mosquito Point a distance of 18 miles . . ' 1s not known. How.ever, marking and recovery experiments conducted, the 1956 season (Fig. 19}. tered in samples from the upper in 1956 shed some light on possible rates of migration. The maximum Lake Nerka, and Lake Kulik. rate of movement. of red fingerlings released from the Catherine Cove ..... Alaska Red Salmon Smolts from Wood River Lakes 279 . Furthermore, smaller smolts (Lake Nerka) lake trap was recorded on July 23. Seven of these tattooed · th~:~;ea~n. ~his, in addition to fish were observed the following day in Cabin Bay, Lake Nerka, a dis ~.. a rmgrat10ns commonly are t~ce of 5 miles from point of release. Thirteen fish tattooed .in marking ,Its which have experienced dif- experiments on red fingerlings migrating out of Little Togiak Lake were 9~.? of the sever~ lakes. The subsequently recaptured at the outlet of Aleknagik, 40 miles distant. The fr~;ltll Lake Aleknagik, the lower minimum length of time before ,"ecapture was 11 days. The shortest ·ger~ migrants from Lake Nerka lapse of time between release of h~ttooed red fingerlings from a Lake .ar interest to test this hypothe Nerka lake trap and their hrrival at the outlet of Aleknagik, a distance .vhtp; conditions are responsible of 34 miles, was 8 days. Tl:i.3Se experiments indicated a maximum rate ' .!. _.. of travel, measured in a direct water route, of 4-5 miles per day. Although the migration rates should not be taken too seriously because roiJ.1,1 of the small numbers of !'ecoveries and the possible effect of tattooing ~0~·!1 on normal behavior, it is to be expected that fingerlings already in Alek ts ilikes of the Wood River sys nagik before breakup woulcl be first to pass Mosquito Point, and also .ak~s would be later in reaching that over-all timing of seaward migration durir~ a season would be af raf~~m has never been observed fected to some degree by relative numbers in 1nigrant populations orig iocltRiver, Little Togiak River, inating in different lake areas. temperatures have reached at Substantiating evidence that Aleknagik smolts are first to migrate .L This is in agreement with seaward was presented by Koo (1962), who showed that later-migrating ~mately 40° F, reported for yearling smolts had more new-season, or ''plus," growth on their scales, falling below this and that the amount of fresh-water plus growth found on scales of re 7 ~ 1952; Parker and Vincent, turning adults was directly related to distance from their lake of origin upf.11!r lakes in the Wood River to the outlet of the system at Mosquito Point. eJ.~ arrival of upper-lake mi ;ik has in every year been the Origin of Size Groups in the 1955 Seaward Migration ku~-;lion Lake Nerka may occur · ·}•reakup sequence is some- In a search for additional evidence of origin of different smolt size 19 o (Table 16). groups in the Wood River lakes, the writer made detailed studies of the 1953 year class of Wood River red salmon. This year class was chosen because yearlings migrating in 1955 exhibited the most striking bimo dality in size frequency (Fig. 21) and hence offered the best chance of recognition in later life stages available for examination. In the 1955 yearling migration (1953 year class), small yearlings were June 1-3 June 11 first to appear at Mosquito Point, and during the first 10 days of fyke June 15 netting no other yearling sizes were caught. Although the largest migra June 20 (approx.) tion of this small size group did not occur until July 10, fairly late in the season, there was no evidence that this group had moved down from and the ice cover on upper-lake areas. No small yearlings of the size group in question were es for migration in encountered in samples from Lake Nerka lake traps or Little Togiak River fyke-net samples in 1955. A large contingent of small 1955 year lings remained an extra year in the lakes, the survivors maldng up the a distance of 18 miles, particularly heavy migration of small age II smolts at the beginning of .,... ,, .... u experiments conducted the 1956 season (Fig. 19). These small age II fish also were not encoun . nigration. The maximum tered in samples from the upper lakes area, including Little Togiak Lake, from the Catherine Cove Lake Nerka, and Lake Kulik. Presumably they grew in Lake Aleknagik. h.J - I 280 Alaska Red Salmon Smolts from Wood River Lakes To ~ettle the question oi the origin of small smolts migrating in 1955 as on the various spawning grounds [ yearlmgs and in 1956 as age II fish, it was necessary to examine scales supervision of J. R. Gilbert. In from adults of the 1953 year class returning to spawning grounds in adult scales were too resorbed to 1957 through 1959. H the small smolts did indeed originate only in Lake annuli. Therefore, individuals Aleknagik and· the large smolts in the upper lakes of the Wood River identified by length measurem.em:,; system, the nuGlear area of the scales of adult reds from the 1953 year influenced by the number of class taken on the spawning beds in the different lakes should show dif smaller adults of both sexes are ferences in amount of fresh-water growth because of the strong tendency in the ocean; th~ larger fish ha. of red salmon to return to their original birthplace for spawnifig. four winters in the ocean (Koo, Scales used in this study were taken from the fish just above the lateral in l~ngth of the two groups, it line and between dorsal and adipose fins, shown by Koo (1962) and Clutter falling well below the intercept of and Whitesel (1956) to be in the area of first :.; .. ;3le formation. The meas to be reasonably certain that urement chosen for comparison of scales from 1955 yearling smolts with only two winters at sea. Males of scales from returning adults was the anterior radius from focus to outer males between 400 and 490 mm, edge of the fresh-water annulus. Tf.Js measurement was chosen in pref of 25 of these fish from each erence to the radius from focus to edge of fresh-water growth because measured if available. Sexes of the possibility that additional growth appearing after the fish migrated preciable difference in amount from the lakss may not always be distinguishable from the widening between sexes of red salmon ( r circuli of summer lacustrine growth. Scale-radius measurements were Several samples, collected t.'~ used instead of circulus counts because the former are a more direct migration period, were utilized ~l index to fish size. For simplicity of procedure the longest radius from scales. Scale measurements wer focus to edge of the first annulus was used. To facilitate measurement, of the fish, and were later c the images of smolt and adult scales were projected onto a table with of lengths between 68 and 77 the apparatus described by Koo (1962) at a magnification of 23 0 times. mode of sm.2ll yearling smolts, In the analysjs presented here, scale samples were utilized from the 83 and 102 mm, inclusive, to first returning contingent of the 1953 year class, i.e., four-year-olds (Fig. 23). taken on the spawning grounds in 1957 that had Iiligrated seaward as Radius-measurement yearlings in 1955 and returned as adults after two winters in the ocean. 2 to 5-millimeter intervals, are Koo (1962) found that the fresh-water growth pattern determined from the frequency of small-yearling. scales of adults returning after twc· winters in the ocean does not differ frequencies ta..~en from from that of those returning to the same spawning area after three win quency of large-yearling scale ters in the ocean, if the scales have been collected from a single year from returnees to the other I class .migrating seaward in the same year. Therefore, it was assumed in amount of scale growth to f·J··· ~·. that comparison of the scales of yearling smolts of the two size groups returning spawners to ~~·en.' I ~~~i encountered in 1955 with scales of the single age group of adults that re lakes spawners establishes turned in 1957 would provide reliable data. (Analysis of scales of adults 1955 did inhabit Lake ~~·-.r..,,Q.f')...., t.: returning in 1958, after three winters in the ocean, has since confirmed Radius measurements of ' 1.'.'i.. this assumption.) The scale photomicrographs in Figure 22 illustrate dif water annulus are presented ferences between the two smolt sizes in scale growth and the similarity Locations of spawning areas to be found in scale pattern of smolts and adults of the same year clasE:i. will be discussed later, few s The 1957 scale samples from adult reds were collected from dead fish were available so these are adults sampled from Agulowak 2 Scale formula 1.2 (Koo, 1962) or 42 (Gilbert and Rich, 1927). This is in the small size category, the one of the two main age groups in the Nushagak District, the other the tirely of five-year-old fish five-year-olds, scale formula 1.3, or :52 • The greatest number of scwe ,,,t ~€ ., ·: • -··.::;··~-, • . ·, ~~. ' . • ~~~.\!i~!i , . . ' ::Ow ~_"~~ ~· .. -~,.· •• ·- •·" ~. ' -r. ><,·' • '• :·- '"'i' .'•'"::- ' f • • • • • r Alaska Red Salmon Smolts from Wood River Lakes 281 'smolts migr~ing in 1955 as on the various spawning grounds during spawning area studies under the necessary to examine scales supervision of J. R. Gilbert. In most instances, the marginal portions of tUlF iing to spawning grounds in adult scales were too resorbed to permit counting the number of marine kl~deed originate only in Lake annuli. Therefore, individuals that had spent but two winters at sea were ·upper lakes of the Wood River identified by length measurement. This was possible bet~ause length is >f f!~ult reds from the 1953 year influenced by the number of winters the fish remain in the ocean. The djjfjl~rent lakes should show dif smaller adults of both sexes are those fish that have spent two winters !1 ifl:!cau.se of the strong tendency in the ocean; the larger fish have spent primarily thrue, occasionally birthplace for spawning. four winters in the ocean (Koo, 1962). Because there is some overlap >mp111e fish just above the lateral in length of the two groups, it was necessary to select fish of lengths stf!;'f'll by Koo (1962) and Clutter falling well below the intercept of the two modal length-frequency groups rst scale formation. The meas to be reasonably certain that the adults used for scale study had spent fr~:m 1955 yearling smolts with only two winters at sea. Males of lengths between 430 and 510 mm and fe ~r:f~ i:- radius from focus to outer males between 400 and 490 mm, mid-eye to tail fork, were used. Scales le~hre:ment was chosen in pref of 25 of these fish from each of the spawning ground~ sampled were of fresh-water growth be~ause measured if available. Sexes were combined in treatment since no ap ,Lring after the fish migrated preciable difference in amount of lacustrine scale growth has been found Uishable from the widening between sexes of red salmon (Clutter and Whitesel, 1956). radius measurements were Several samples, collected at intervals throughout the main smolt the former are a more direct migration period, were utilized for measurement of 1955 yearling smolt >ctf., ure the longest radius from scales. Scale measurements were first made without reference to length e&'" To facilitate measurement, of the fish, and were later classified by fish length. Scales from fish ere projected onto a table with of lengths between 68 and 77 mm, inclusive, were used to represent the aJ1nagnification of 230 times. mode of small yearling smolts, and scales from fish of lengths between s::t}ples were utilized from the 83 and 102 mm, inclusive, to represent the mode of large 1955 yearlings •ar class, i.e., four-year-olds (Fig. 23). hat had migrated seaward as Radius-measurement frequencies of 1955 yearling smolt scales, grouped two winters in the ocean. 2 to 5-millimeter intervals, are presented in Figure 24. Superimposed on pattern determined from the frequency of small-yearling scale measurements are corresponding ers in the ocean does not differ frequencies taken from returning Aleknagik spawners, and on the fre twning area after three win quency of large-yearling scale measurements, corresponding ft~equencies !'!ollected from a single year from returnees to the other Wood River lakes. The close correspondence · . Therefore, it was assumed in amount of scale growth to the first annulus between small smolts and ~molts of the two size groups returning spawners to Aleknagik and between large smolts and upper 1 age group of adults that re lakes spawners establishes the fact that the small smolts migrating in of scales of adults 1955 did inhabit Lake Aleknagik during their fresh-water growth. the ocean, has since confirmed Radius measurements of adult scales from focus to edge of the fresh s in Figure 22 illustrate dif water armulus are presented classified by spawning ground in Figure 25. growth and the similarity Locations of spawning areas repre3ented are shown in Figure 26. As g.y~u.a.c of the same year class. will be discussed later, few scales of small adults from Lake Aleknagik were collected from dead fish were available so these are grouped 1:ogether in the graph. None of the adults sampled from Agulowak River, tributary to Lake Aleknagik, fell and Rich, 1927). This is in the small size category, the 1957 escapement there being almost en shagak District, the other the tirely of five-year-old Lsh with three years of ocean residence. 2fl The greatest number of scale samples were collected from Lake Nerka jjl I ' l ,1 282 Alaska Red Salmon Smolts fram Wood River Lakes where the majority of salmon spawned in 1957. Scale measurement data consideration. Results of the for samples from this lake were examined to determine whether there 18. was any relation between type or location of spawning area and amount of growth achieved during the first year. An F test was first applied to TABLE lB. stll!MARV SHEET OF MULTIPLE I MEANS, SCALZ ;.'IAD!US TO FIRST test homogeneity of the set of scale measurement means of the samples from the Lake Nerka spawning areas (Table 17). A very large F ratio, Standard error mean, s. = 1.253 significant at the 1 per cent level, was obtained; hence the hypothesis Number of means in range 2 of homogeneity was rejected, indicating that one or more of the differ Shortest significant range, 5 per cent level 3.47 ences between means was significant. TABLE 17. MEASUREMENT* DATA FROM SCALES OF ADULT RED SALMON, SCALE FORMULA 1.2, LAKE NERKA, 1957, SHOWING ANALYSIS OF VARIANCE TEST 10 Area numbers 11 Agu-lukpak Kema Spawning Area lti :LXii X;. I; x;j Localities River Creek 91.9 ldeanst 89.4 River Bay 25 2,529 101.2 258,649 I~ Fenno Creek 25 2,608 104.3 275,414 l j Allah Beach 25 2,568 102.7 265,388 :) Stovall Creek 25 2,725 109.0 298,539 '~ N-4 Beach 25 2,456 98.2 244,430 *Measurement: £ocus to first annulus Pick Creek 25 2,624 105.0 277,088 tAnY two means not underscored by thl! Anvil Bay 25 2,348 93.9 223,334 underscored by the same solid line are Kema Creek 25 2,297 91.9 214,281 Agulukpak River 25 2,234 89.4 201,204 The underscorings in TablEl TOTAL 225 22,389 2,258,327 not significantly different. were significantly larger t *Measurement: focus to outer edge of first annulus in mm; magnifica spawning populations in tion 230x. the two sections of the lake first year, and that the Analysis of Variance of Scale Measurements growing conditions. Amo?g the three beach-spawnmg Degrees of Sum of Mean Source of F year than did the three Variation Freedom Squares Square tion between samples from ... 1• , . Between areas 8 21,722 2,715.25 69.23 stream. For this year c [:·~ Within areas 216 8,573 39.22 exerted more influence on --· development. TOTAL 224 30,295 In a comparison between 1' - and Kulik suggest that ·.l" F.99 :::::: 2.60 1.~I were similar to those in In order to reach a decision as to which of the differences among the however, between Lake means could be considered significant and which not, a multiple-range scale growth of Aleknagik test proposed by Duncan (1955) was applied. Values from his table of r early life. "special significant studentized ranges" were multiplied by the standard error to obtain a series of "shortest significant ranges" between means. Causes of Difference The means are ranked in order, and the difference between any two means is considered significant if it exceeds the corresponding shortest Climate significant range for the number of means involved in the range under Yearling smolts 1\ ~ • • • .or•j 4 ~~~~~ ;.,. ~~ • • .. ~·. ~"'"- !''~:f::l.ii . ~~~...... ~. ,.~~.t\ l • . '> ' • ' • ' " • • ' 'Iii ' • ' • ' ' . ...;; ...... ,!-... ~.... {'; .' - ...... , • • ' R • ' . . ' ' • q . \ . li .. ~ f • .. • \ ...... '. - .. ~·...,·~~- - . ) ~· ~ .,.__ . -- - . - Alaska Red Salmon L Smolts fram Wood R:iver Lakes 283 19_5 7. Scale measurement data consideration. Results of the multiple range test are presented in Table f~o dete~mine whether there on l;. spawmng area and amount 18. · An F test was first applied to TABLE 18. SI.Jm!ARY SHEE'r OF MULTIPLE RANGE TEST FOR SIGNIFICANCE OF DIFFERENCES llETWEEN SAMPLE stlljj~ ment means of the samples MEANS, SCAL:>: RADIUS TO FIRST ANNULUS, OF RED SALMON IN LAKE NERKA SPAWNING AREAS* abl::l! .17). A very large F ratio, Standard error of mean, ol)tctmed; hence the hypothesis s~ = 1.253 that one or more of the differ Number of means in range 2 3 4 5 6 7 8 9 Shortest significant range, f.jl: 5 per cent level 3.17 3,66 3.78 3.87 3.95 4.00 4,05 4.08 ADULT RED SALMoN, SCALE L:t~ Lower Lake Nerka ANALYSIS OF VARIANCE TEST U~per Lake Nerka Beacn Spawning Creek Spawning Area nwnbers 11 10 9 6 2 4 3 7 5 Agulukpak Kema Anvil N-4 River Allah Fenno Pick Stovall Localities River Creek llay Beach Bay Beach Creek Creek Creek 89,4 91.9 93.9 98.2 101.2 102.7 104,3 105.0 109.0 101.2 258,649 Heanst 104.3 275,414 102.7 265,388 109.0 298,539 98,2 244,430 105.C 277,088 *Measurement: focus to first annulus x 230. After Duncan, 1955, Table 4. 93.9 223,334 tAny two means not und~rscored by the same solid line are significantly different, Any two means underscored by the same ~olid line are not significantly different. 91.9 214,281 89.4 201,204 The underscorings in Table 18 indicate which means are and which are 1. 2,258,327 not significantly different. All six means of Lower La!ce Nerka samples were significantly larger than the means of samples from the three annulus in mm; magni:fica- spawning populations in Upper Lake Nerka. This suggests that young in the two sections of the lake remained somewhat segregated during their first year, and that the Lower Lake Nerka feeding area provided better growing conditions. Among the six spawning groups of Lower Lake Nerka, Mean the three beach-spawning groups showed less growth during the first Square F year than did the three stream groups, but there was no clear demarca tion between samples from the two spawning-area types: lake-beach and 2,715.25 69.23 stream. For this year class, it is evident that rearing-area conditions 39 •. 22 exerted more influence on growth than did conditions for embryonic development. In a comparison between lakes (Fig. 27), samples from Lakes Beverley and Kulik suggest that growth conditions for young during their first year were similar to those in Lake Nerka. The contrast was very striking, o~ 1.!he differences among the v.f:lch not, a multiple-range however, between Lake Aleknagik and the other Wood River lakes. The . Values from his table of scale growth of Aleknagik adults was markedly less for this period of early life. e~·1Jlultiplied by the standard a~. !I ranges" between means. d Herence between any two Causes of Difference Between Lakes in Size of Smozts Produced the corresponding shortest Climate i1'·.~~:olved in the range under ..."l Yearling smolts migrating in June or July have achieved most of their r Smolts from Wood River Lake 284 Alaska Red Salmon tion was inverse between size gro~h during the previous summer. For the 1955 smolts, the pr~yious of plankton consumers both ~rowrng season, 1954, was characterized by early breakup of the lake rce and warm lake temperatures. New summer growth appeared early pop1lation density and size of on the scales of yearlings migrating in 1954 (Table 14). As shown in a seven brood years beginning in previous section, differenceR between years in climate resulted in dif 1957). ferenc:s in growth rate of you..1g salmon. However, within a single year Studies at Babine Lake the entire lake system is subjected to much the same climatic conditions sockeye in a single lake can 1956, 1958). Lake areas adj hence poor grovv-th of fry in one lake area , such as Aleknagik in 1954', would not be expected unless it was caused by conditions other than eli found by tow-net sampling to ling" young. Marked differenc mate. Differences between lakes in level of key nutrients or in degrees l:p: of competition for food are suggested. in these areas were attri tt·' consequent density of young. Level of Basic Nutrients be reduced in areas where Fisheries Research Board, 1 It has been proposed that in red-salmon lakes, levels of nitrogen, With regard to intraspecific phosphorus, or other biogenic elements may be limiting factors in pro was evidence that changes ~uction of phytoplankton, hence indirectly of zooplankton and young salmon young red salmon were ~Barnaby, 1944; Nelson and Edmondson 1955· Nelson 1958· Goldman quency of smolts. In various. 1958; Kr?khi~, 1957~ Alaska Department' of Fish' and Game,' ' 1959). No' comparative information on levels of critical nutrients has been collected .... available measure of for the Wood River chain. The lakes are basically quite similar in mor was magnitude of parent esc it is necessary that in a given phometric features, but Lake Alel:Jlllgik as the lowest lake in the series be reasonably paralleled b may have the greatest amount of dissolved nutrients flowing through. It is slightly more turbid in summer and there is no reason to suspect a divisions of the lake system. lower level of basic nutrients. sential, that difference in their first year not be large. Competition for Food escapement and seaward Chamberlain (1907) was first to suggest that differences between years differences in mortality fresh-wa:ter life. However, ....1; in population density of young sockeye during lake residence might be of spawning populations have ..··! the cause of observed annual differences in yearling smolt sizes. Foer I.. _, t. stelr {1944) demonstrated the effect of population density on size of mi the data on parent e grating smolts. He correlated weights of Cultus Lake yearlings in the tion between parent The red fry population (age migratio11 years 1927 through 1935 with lake population densities based on Pumbers and ages of seaward migrants. His conclusions were sup only of fish originating ; Agulowak River connecting ported by the inverse correlation found by Ricker (1937) between zoo plankton abundance and population size of sockeye salmon in Cultus Lake lakes. Emerging fry in the !"egl.!ctim~ in plankton being assumed to be the result of grazing by youn~ ~ by the swift current from sockeye. Rounsefell (1958) used additional Cultus Lake data from more sequently must descend recent ye:a.rs to correlate biomass of smolts versus the logarithm of the downstream fry movem [ so that fry migration from rnJmb~r P! smolts produced. He concluded that "the closeness of the 1 semilogarithmic fit suggests-that the increasing competition between to be negligible. Two major area smolt~} as their numbers increase sets an asymptotic level on the bio mass." Analyzing Karluk Lake data, he interpreted a linear relation Lake Nerka-Little Togiak "I between Lake Nerka and !I betwP.en numbers and biomass of the annual smolt migrations as indi I:...~ cating no intraspecific competition for food in the years studied. Krogilis Kulik area. Data on de and Krokhin (1956) stated that in Lake Dalnee, Kamchatka, the correla- Wood River system have ~ Alaska Red Salmon Smolts from Wood River Lakes 285 t~e 1955 smolts, the previous tion was inverse between size and weight of red smolts and the number ~Y early breakup of the lake of plankton consumers both intra- and interspecific. No relation between ner growth appeared early pop1lation density and size of migrants was found at L.akelse Lake for the .: (Table 14). As shown in a seven brood years beginrJ.ing in 1946 (Canada, Fisheries Research Board, in climate resulted in dif _ 1957). ~fl~rever, within '"'; single year Studies at Babine Lake were first to show that unequal distribution of I I[::l! same cliinF.dc conditions, sockeye in a single lake can result in overcrowding and stunting (Johnson, such as Aleknagik in 1954. 1956, 1958). Lake areas adjacent to main spawning concentrations were ~Y conditions other than eli:.. found by tow-net sampling to be more densely populated by "underyear 1 ot:j!~ey nutrients or in degrees ling" young. Marked differences between years in size of young sockeye .[ in these areas were attributed to differences in spawning density and consequent density of young. Abundance of zooplankton was re!ported to !It be reduced in areas where density of young salmon was high (Canada, lakes, levels of nitrogen Fisheries Research Board, 1958). be limiting factors in pro~ With regard to intraspecific competition in the Wood River lakes, there ~oplankton and young salmon was evidence that changes between lakes in relative population £i.ze of 1flil·15; Nelson, 1958; Goldman young red salmon were correlated with observed changes in length fre O~J.:li'ish and Game, 1959). N~ quency of smolts. In various areas of the Wood River lakes, the only nutrients !"..as been collected available measure of population size of young for the years concerned quite similar in mor- was magnitude of parent escapement. For this measure to be reliable, :::·3 lowest lake in the series it is necessary that in a given year class, mortality rates. of young reds trients flowing through. It be reasonably paralleled between population groups defined by major !3 is no reason to suspect a divisions of the lake system. It would also be desirable, but not as es sential, that difference in mortality rates between year classes during [~ their first year not be large. Since the relation between magnit1·des of escapement and seaward migration has been shown to be erratic, definite ;nq~:,.aru,erl:mc~es between years differences in mortality rate must exist between year classes during l :·~ lake residence might be fresh-water life. However, changes among lakes in relative magnitude 1 · smolt sizes. Foer- of spawning populations have been large, and it is pertinent to examine density on size of mi the data on parent escapement and smolt size for indications of a rela Lake year lings in the tion between parent population size and growth attained by young salmon. ~'11•• PV'!JU.La.t..tuu densities based The red fry population (age 0) in Lake Aleknagik is assumed to consist rI His conclusions were sup only of fish originating within the lake and its tributaries, including the ·I . ~cker (1937) between zoo Agulowak River connecting Lake Aleknagik with the upper Wood River ,,y-e salmon in Cultus Lake lakes. Emerging fry in the Agulowak River spawning area are prevented I . of grazing by young' by the swift current from migrating upstream into Lake Nerka, and con ,, Cultus Lake data from more sequently must descend into Lake Aleknagik to feed. No appreciable ! 1!rsus the logarithm of the downstream fry movements between the major lakes has been found, !. ·· hat "the closeness of the so that fry migration from Lake Nerka to Lake Aleknagik is assumed ing competition between to be negligible. .I.HL,LULJc level on the bio Two major area groupings will be used for the upper lakes~ (1) the !rpreted a linear relation Lake Nerka-Little Togiak Lake area, including the Agulukpak River ~molt migrations as indi between Lake Nerka and Lake Beverley, and (2) the Lake Beverle)'-Lake the ye?.rs studied. Krogius Kulik area. Data on density of spawning in the separate lakes of the •ltKamcnatka, the correla- Wood River system have been compiled by J. R. Gilbert Irom Fisheries l: ri l l l I !' .,: -- .. 286 Alaska Red Salmon Smolts from Wood River Research Institute records of aerial and ground surveys conducted an 1955 and the over-all size of nually since 1946.3 Estimates are presented in Table 1 of Report of Op distinct bimodality of. yearling erations, 1958 (Fisheries Research Institute, 1959). This information cause of the much greater from 1946 through 195'! is expressed in Table 19 in terms of number Thus, the smallest Alekn of parent spawners per surface square mile of lake rearing area for duced by the largest es'"'""'J<;;J..LJ. young in the three lake regions. The parent years 1952-57, for which of the same magnitude h~ 1953 smolt length frequencies are presented, are indicated below the broken in average size. The par-ent line in Figure 21. in the Aleknagik-Agulowak . not as much contrast in size •.( TABLE 19. ESTIMATED ESCAPEMENT OF RED SALMON PER SURFACE r.. SQUARE MILE OF LAKE REARING AREA, 1946-57 evident, and the large strong evidence that the ~ ...... , .... Lake Nerka- Lake Beverley- Escapement Lake Aleknagik taxed by the progeny of large !:p Little Togiak Lake Lake Kulik Year (34 Sqnare Hiles) another paper that stunting ~~.! ~2 Square Miles) (62 Square Miles) similar parent spawning den . 1946 10,600 25,000 21,100 There is danger in · 1947 5,500 10,800 11,400 size simply to population 1948 4,600 11,800 5,900 1949 1,000 700 200 petition caused differences 1950 3,800 2,700 1,600 played an important part. 1951 2,700 2,400 2,800 by the fyke-net index ------!------r------1952 2,000 1,600 500 If early season feeding of 1953* 7,400 2,900 500 i1 the lake's food supplies, the 1954 3,900 3,000 3:100 ' be most affected, since all 1955* 14,500 6,300 6,000 through it. The fry in this 1956* 7,400 5,300 1,400 1957 2,700 2,400 200 ye-ars, 1955 and 1957, would - I an additional year in these *Escapements producing bimodality in yearling smolt length fre pete to some extent with the quencies. there is no consistent The heaviest spawning density shown in Table 19 for the years 1952- ing since the yearling uv,...... ,Jf' 57 occurred in the Aleknagik-Agulovtak rearing area in 1953, 1955, and moderate, that in 1957 heavy. .,:.. not be as heavy as within f! 1956. These were parent years of the yearling smolt groups that ex l.'•,. t,._ hibited the most pronounced bimodality in length frequency. The small feeding area, particularly yearlings were offspring of heavy spawning populations in Lake Alek toral areas more heavily. nagik and tributaries. There is additional The greatest contrast between growth of Aleknagik smolts and those differences are the result from. upper lakes occurred in the 1953 year class (Fig. 21) when the group. This evidence is pr escapement reached the highest percentage of the Wood Hiver lakes amount of fresh-water total. Although spawning was particularly heavy in all three lake areas in parent spawning population year-old adult salmon, 1953 3Each seaso.1' s escapement estiniates were based on aerial estimates the initial year achieved by and ground coWlts taken at or near peak of spawning. Data most directly was much superior to that comparable were used to determine differences between lakes and be however, is exactly the tween years. Estimates since 1953 are considered more accurate, since adults of the 1948 year class trunk stream enumeration of the runs by use of towers in Wood River the writer for scale LU"''"'0' ...... IJ was begun in that year and provided a more accurate annual estimate returning to spawn in 1950. ! classes was better in .n."'''"'"""u,;.. t.<., of total escapement to the system. Alaska Red Salmon Smolts from Wood River Lakes 287 surveys conducted an 1955 and the over-all size of smolts in the 1957 migration was reduced, : in Table 1 of Report of Op distinct bimodality of yearling smolt sizes in 1957 was still present be ' 1959). This information cause of the much greater parent spawning density in Lake Aleknagik. Table 19 in terms of number Thus, the smallest Aleknagik smolts observed in any year were pro rfi:Ie of lake rearing area for duced by the largest escapement, that of 1955. The large escapements ,:·;t years 1952-57, for which of the same magnitude in 1953 and 1956 produced stunted smolts similar are indicated below the broken in average size. The parent populations of the other recent year classes in the Aleknagik-Agulowa,k area had been at a lower level, and there was :j D SALMON PER SURF ACE 1946-57 not as much contrast in size between the small, early migrants, when evident, and the large migrants. The consistency of these results is Lake Beverley strong evidence that the capacity of Lake Aleknagik nursery area was Lake Kulik taxed by the progeny of large spawning populations. It will be shown in (62 Square Miles) another paper that stunting occurs in other lakes of the system under 21, 10,{) similar parent spawning densities. 11,400 There is danger in attempting to assign marked differences in smolt 5,900 size simply to population pressures of fry alone. If intraspecific com 200 petition caused differences in growth, older age groups may well have 1,600 played an important part. The largest migration of smolts measured ______2,800 , ___ _ by the fyke-net index method occurred in 1954 and 1956 (see Table 9). 500 If early season feeding of these fish prior to migration seriously affected 500 the lake\s food supplies, the lower lake in the system would presumably 3,100 6,000 be most affected, since all migrants must either originate in or pass 1,400 through it. The fry in this area migrating as yearlings the following 200 years, 1955 and 1957, would thus be affected. Also yearlings remaining ! an additional year in L.'lese lake C'..reas and migrating at age n would com I length ire- pete to some extent with the fry for food. On this latter point, however, there is no consistent relation between yearling holdover and fry stunt 19 for the years 1952- ing since the yearling holdover in 1954 was very slight, that in 1956 area in 1953, 19"-~ and moderate, that in 1957 heavy. The competition between year classes may ;:1.ng smolt groups that ex not be as heavy as within year classes because of differences in food and 'I:I frequency. The small feeding area, particularly early in the summer when fry utilize the lit l populations in Lake Alek- toral areas more heavily. j There is additional evidence supporting the hypothesis that smolt size , !eknagik smolts and those differences are the result of intraspecific competition within the year :l class (Fig. 21) when the group. This evidence is provided by a comparison between areas in of the Wood River lakes amount of fresh-water growth associated with relative magnitude of ·1 1. in all three lake areas in parent spawning populations. Scale measurements presented of four year-old adult salmon, 1953 year class, have indicated that growth during based on aerial estimates the initial year achieved by salmon originating in other ·wood River lakes . Data most directly was much superior to that obtained in Lake Aleknagik {Fig. 25). This, ~s between lakes and be however, is exactly the reverse of the relation found by Koo {1962) for more accurate, since adults of the 1948 year class returrJng to spawn in 1952 and 1953, and by e of towers in Wood River the writer for scale measurements made of adults of the 1946 year class J,·lccurate annual estimate returning to spav,'n in 1950. The first year's growth in those two year t !: classes was better in Aleknagik than in the Beverley-Kulik area. Fol- Smolts from ·wood River fl 288 AJ.aska Red Salmon t affect young red salmon. At lowing the hypothesis of population pressure, an explanation of this re plerocercoids of T. crassus versal in rates of early growth lies in relative population sizes of young mortality of young rainbow sal~on pre~ent in the two areas during the years in question. Referring the years 1921 through 1923 agam to Table 19, the spawners were relatively much more numerous (1945) reported the cestode in the Beverley-Kulik area than in the AleknagLlt-Agulowak area in the mon whitefish (Coregonus .,'·, . years 1946 through 1948. In the years to follow the Aleknagik-Agulowak ··: at Lesser Slave Lake. I area population increased greatly in relative overshadowing 1\ . i~portance, In young red salmon the ~hat of the Beverley-Kulik area in eight out of nine years, particularly 1n the years 1953, 1955, and 1956, which produced the bimodality of erable tis sue during The plerocercoids first smolt sizes seen in 1955, 1957, and 1958, respectively. Weakening of young salmon The relation discussed above between magnitude of adult populations and growth of smolts produced is surprisingly consistent. fu view of fish is very small, since a . the very large changes in relative magnitude of adult spawning popula destroyed by a single tions between the areas under discussion, it appears that spawning popu the cestode is a serious is prevalent enough to be lation estimates were a sufficiently sensitive index of relative size of of parasitism by T. fry populations produced within the major divisions of the lake system; crassus Point was found to be 66.0 and, therefore, that intraspecific competition of the young does play a determining role in growth achieved during the first year of lake life. 20). In TABLR 20. PERCENTAGES OF WOOD RIVER view of other possibilities, yet unmeasured the relation found be TilE CESTODE, tween initial populations and smolt size in Wo~d River lakes must be Total Numbel' !{umber of further tested. The very real possibility of interspecific competition Year of Fish Samples shoul? not be overlooked, for a prominent competitor, rivaling the young Examined Examined reds m abundance, exists in the threespine stickleback fow1d in the Wood 1948 100 2 1949 504 8 River lakes. This species is closely associated with young red salmon 1950 350 7 1951 423 8 in the lakes and was found by the writer to feed on the same organisms. 7 ~952 350 8 It will be shown in a later report that r•eduction in growth of sticklebacks ~953 393 1954 445 7 also occurs when population density of young salmon is high. Increase or 1955 810 7 4 ~956 400 decrease in ge.1erallevel of abundance of sticklebacks or annual fluc 1957 263 3 3 tuations in their abundance would be expected to influence growth of young ~958 276 ....,. salmon if competition for food is indeed responsible for a major share I,•. of the size fluctuations observed. *Only samples taken between dates of ..~·,:· Relation of Growth Rate to Survival Delay in seaward slower-growing young """"'"· ...... Fresh-water Survival an additional year or m Young red salmon that grow more slowly are probably subject to greater been well established mortality from a number of sources. Ricker and Foerster (1948) have and Krokhin, 1956a; Kr suggested that lacustrine predation is gnatest while the sockeye are by those fish residing an .l l. small, and that if this vulnerable stage is. passed through rapidly the by increased ocean survival chances for survival are increased. migration. This view is It is likely that slower-growing young salmon may also suffer more emphasized the need to damage from parasites. In Bristol Bay, the cestode, Triaenopho·rus stream migration in order crassus, was foWld by the writer to be. a common parasite of red salmon length of residence in fre (Lawler and Scott, 1954). The plerocercoid stage of this cestode has been In summary, slower g't" found on occasion to be detrimental to other species of fish, and may result in greater over-all ' .. . ~ I '• ' . I ' \ ... Alaska Red Salmon Smolts from Wood River Eakes 289 , an explanation of t.i.is re affect young red salmon. At the fish culture station at Kalerna, s~ eden, po~lation sizes of young plerocercoids of T. crassus were reported to ha.ve caused a widespread y~ars m question. Referring mortality of young rainbow trout, brook trout, and Atlantic salr1on in : ·lVely much more numerous the years 1921 through 1923 (Bergman, 1924; Scheuring, 1930). Ji'liller :nagik-Agulowak area in the (1945) reported the cestode to havl~ affected growth and condition of com . , the Aleknagi.k-Agulowak mon whitefish (Coregonus clupeaformis) and tullibee (Leucichth: 1s sp .) •.. Importance, overshadowing at Lesser Slave Lake. ·1 of nine years, particularly In young red salmon the plerocercoids of T. eras sus destroy c 1nsid _ produced the bimodality of erable tissue during' development and encystment in the museu .ature. ::>8, respectively. The plerocercoids first appear in the flesh of red fry in late su .nmer. 1 :gnitude of adult populations Weakening of young salmon is likely to be severe or even letha i if the consistent. In view of fish is very small, since a high proportion of the musculatt1.re is then of adult spawning popula- destroyed by a single plerocercoid. While direct proof is lacking that fi.pJpe.E U'S that spawning popu the cestode is a serious mortality factor in young salmon, the p uasite Index of relative size of is prevalent enough to be wo:rthy of attention. Average annual in· !idence ...... ,u., of the lake system; of parasitism by T. eras sus in red smolt samples collected at M Jsquito ...... vu of the young does play a Point "'aS found to be 66.0 per cent for the years 1948 through 195S (Table . ·:; the first year of lake life. 20). ~· ' )red, the relation found be TABLE 20. PERCENTAUES OF WOOD RIVER RED SALMON SMOLTS PARASITIZED BY THE PLEROCKRCOID S rAGE OF . Wood River lakes must be THE CESTODE , TRIAENOPHORUS CRASSUS, IN THE YEARS 1948 THROUGH 1958* ! J.·.•. .,,.r-_; j -·-- p.f interspecific competition Total Number Number of I Average Per Cent Range betwe·l!n J\ r' a• t· Year C1f .Fish Samples Samples n Per Cent 1 : ·lpe Itor, rivaling the young '~'''''''''· E:~:aminec Examined ... ,,. All Samples Para itized S:;.'ickleback found in the Wood 1948 100 2 48~ 52 88 8 ·-90 iated with young red salmon 1949 504 8 50-112 81 7 1•92 1950 350 7 50 . 76 e 1-94 ~~.:i~d on the same organisms. 1951 423 8 so- 73 82 e 1-96 '1:1 in growth of sticklebacks 1952 31::0 7 50 82 7 t-:30 1953 393 8 32- 78 78 6 1~90 salmon is high. Increase or 1954 445 7 I 50-110 63 5 -76 1955 810 7 99-152 63 3 -80 ~tickleb: . .!ks or annual fluc- 1956 400 4 100 74 6 -86 1 . infl 1957 263 3 76-104 23 2, -25 ·B .i·) • uence growth of young ., 1958 276 ~ 74-111 16 .-22 ~~,ons1ble for a major share ------M~an annual percentage ------= 6J *Only samples taken between dates of lake breakup and July 31 are included, Delay in seaward migration is another probable cause of mort a.lity in slower-growing ycung salmon. The tendency for smaller fish to remain an additional year or more in the lake before migrating seaw~ ~rd has ltrobably subject to greater been well established (Foerster, 1937; Barnaby, 1944; Koo, 1962; l(rogius ·;and Foerster (1948) have and Krokhin, 1956a; Krogius, 1957). The additional mortality s .tffered test while the sockeye are by those fish residing an extra year .in the lakes is not apt to bE offset 11ssed through rapidly the by increased ocean survival gained through their greater size at S•laward migration. This view is shared by Krogius and Krokhin (1956c: ), who ...... vu may also suffer more emphasized the need to understand causes of difference in age at down cestode, Triaenophorus stream migration in order to develop means of management to •educe ·In parasite of red salmon length of residence in fresh water. of this cestode has been In summary, slower growth of young in fresh water is believed to species of fish, and may result in greater over-all mortality during fresh-water stages .. \.ctual I ····- ·,.--~---.. -·-·-·.. ' l ' ! 1 -- •' - _j I 290 Alaska Red Salmon Smolts from Wood River Lakl I proof that such is the case is lacking for red salmon of Wood .l.tive:r lakes. of young reds in fresh water 1 at return. (Table 21 ). 1 I Marine Survival TABLE 21. RATIOS OF S .: ~~ It i,.:; generally accepted that marine survival rates vary dii'ectly with MIGRATION A.TiD IN R t sh!:e of anadromous salmonoids at time of seaward migration. In fin ~,I clipping experiments on Karluk Lake red salmon smelts. higher marine survival values were obtained in four of five years fo~ the older (and ~arger) of the two major cmolt age groups (Barnaby, 1944). However, 1955 seawar•~l migration 1t must be noted that siza alone at seaward migration may not have been 1957 adult .~.·eturn responsible for these results. A close exam:ination uf the Karluk data 1958 adult return indicates that differential S11rvival m the ocean was probably influenced Tctal adult return · by at least three distinct factors oi unknown relrative importance: (1) size The ratio of small to large ~nd. age at seaward migration, older smolts being larger in size; (2) l tnmng of entry into I!".a.rine environment, older 'Smolts tending to migrate cu1ated to be 7:93 and in the 1q, earlier in the season; and (3) length of stay in the ocean, older smolts ratio of 15:85. This indicatesf~ having a greater tendency to remain only two years at sea, but at the ·was about half that of large t same time ter.rHng to return later in t:hot=.! season in the year of return. Riw~r system, and that there r Strong evidence that size of smolts at time of seaward migration is to remain an eid:ra year at sel actually an important qualitative factor in survival during seaTVard mi It should be not~1~ that tht gration and ocean residence was presented by Foerster (1954) for Cultus smolt age composu.1.on, spai • Lake sockeye. Data were presented gi ring numbers and mean size of of catch and escapem..3nt, a~: "•I'!' • .. smolts in the 1927 through 1944 seaward migrations, and the number of River fish in the antire Nuslti Il.:. '• adults in return spawning escapements t0 the lake. Through analysis also have been affected by dif~! of these data by multiple-correlation treatment, Foerster concluded high-seas fishery. Selection 1c that the negative correlation between magnj:ude of smolt migration and have had an effect, altho~~! r percentage return of adult spawners to the lake. was related principally Fisheries persmmel haS mdicl ' to size nf smolts at time of seaward migration. the fishery does not differ fr ·. Krogius ~nd Krokhin (1956a) did not find a relation between size and There was also no indi·-ati{ ':,. marine survival of Lake Dalnee sockeye smoits, but considered that adult fish differed in size fJi ~ ' this lack of coincidence with Foerster's findin;;ri;; may be explained by mainder of the system. Alth! d t the larger size of Dalnee smolts and less size varlaoility between years sented cannot be determine i than at Cultus Lake. Further, the 1959 and 1960f Distinct bimodality of sizes at Wood; iver in the 1955 vearling mi seaward migration again in gration presnnted a unique opportunity to study the effeci: o~· a jifference from Lake Aleknagi-k. in smolt size on marine survival and length of stay in the t ...... ean, for in this instance ~he size difference existed within a single year class en Effect of Smolt Size on Ad~· tering the nl:iu:lne environment in the same season. Peretmtages of small 1,he above discussion tot and large migrants found in the 1955 seaward migration were compared custrine growth conditions l wlth percentages of returning adults in catch and escapement possessing salmon. The inverse relatio1 the fresh-water scale pattern characteristic of small and of la.1'ge sea s. ize in subdivisions of the.~l ward migrants. Small smolts, originating in the Aleknagik.-Agulowak mechanism of some fluctua area, were calculated to have totaled 29 per cent of the 1955 yearling When spawning populations 1 !j l seaward migration, and were produced by a parent escapement calculated of a lake rACU'ing area, st~, at approximately 49 ,r,ar cent of the Wood River lakes total. Adult returns 1·eturn from the ocean may, in catch and escapement in 1957 and 1958 provided evidence that stunting drop in numbers and fl"V ~. [ l Alaska Red Salmon Smolts from Wood River Lakes 291 Ralmon of Wood River lakes. of young reds in fresh water had affected both marine survival and age at return (Table 21 ). rates vary directly with TABLE 21. RATIOS OF SMALL A.~D LARGE YEARLINGS IN 1955 SEAWARD f .eaward migration. In fin- MIGRATION A..~D IN RETURN AB ADULTS IN 1957 A.lffi 1958 :Jon smolts, higher marine Small Large t years for the older (and Yearlings Yearlings {Barnaby,.. . 1944). However t ·tgrahon may not have been' 1955 seaward migration 29 71 t 1957 adult return 7 93 ...~",;;;;.I,.UlQ.t.;Lvu of th.~ Karluk data 1958 adult retm"n 18 82 cean was probably influenced Tbtal adult return 15 85 !lative importance: (1) size .!s being larger in size; (2) The ratio of small to large yearlings in the 1957 adult return was cal smolts tending to migrate culated to be 7:93 and in the 1958 adult return, 18:82, for a total weighted In the ocean, older smolts ratio of 15:85. This indicates that survival of small Aleknagik yearlings .?o years at sea, but at the was about half that of large yearlings from the remainder of the Wood ~!son in the year of return. River system, and that there was a definite tendency for smaller smolts of seaward migration is to rc,main an extra year at sea. 1 · SJ · ~vival during seaward mi It should be noted that the computations involve determinations of }Foerster (1954) for Cultus smolt age composition, spawning population estimates, age analysis .u•.uuu1:::..1 s and mean size of of catch al!ld escapement, and an assumption as to percentage of Wood . , and the number of River fish in the entire Nushagak red salmon cat\!h. Return ratios may ! .e lake. Through analysis also have been affected by differential fishing mortality from the Japanese ' ent, F'oe:rster concluded high-seas fishery. Selection by the Bristol Bay fishery may conceivably of smelt migration and have had an effect, although tagging conducted by Bureau of Commercial 1~1 ~~e was rel~ted principally has that l Fishf'ries personnel in·li.cated timing of the Aleknagik run through ,:1. the fishery does not differ hom the remainder of the Wood River race.s. between size and There was also no indicathm from length frequencies that Aleknagik l.:;).ll.Lu.u.;::), but considered that adult fish differed in size from those of the same age group in there ;ings may be explained by mainder of the system. Although confidence intervals of the ratios pre ·.variability between years sented cannot be determined, the trend of results is strongly suggestive. Further, the 1959 and 1960 :.:·eturns of adult red salmon from the 1S57 in the 1955 yearling mi seaward migration again indicated a lower survival of sh,nted smolts . the effect of a difference from Lake Aleknagik. stay in the ocean> for in a single year class en- Effect of Smolt Size on Adult Popu:i.ation Size . 1on. Percentages of small The above discussion touches on possible effects of changes in la nigration were compared c.ustrine growth conditions on fresh-water and marine survival of red and escapement possesFlng salmon. The inverse -r.elation observed between population size and smolt ,1-r small anti of large sea size in subdivisions of tr1e Wood River lakes system may explain the . the Aleknagik-Agulowak mechanism of some fluctuations in population level that have occurred. 'cent of the 1955 yearling When spawning· populations produce numbers of young beyond the capacity ·'3Scapement calcuJ ~tP.Ci of a lake rearing area, stunting of yc,ung, low survival, and delay in retu:.~"l.tJ .ak.es total. Adult return from the o~ean may follow. With low survival, the return runs : . led evidence that stundng d:rop in numbers and fry production may decrease, again permitting /'. {) : ~.. ll-1) .. ' • • • • •• •J Smolts from Wood River Lake 292 Alaska Red Salmon of seasonal migration. Timin go~ growth. Individual rearing areas may thus tend to fluctuate in popu lahon level somewh&t 1Gdependently of other rearing areas in the lake associated with breakuP of lak rise of lake surface tempera ~ystem. This sequen~e of events appears to have held in recent years 9. Seasonal increase in ne ·. I 1n the Wood River la...l{es. U;, smolts was demonstrated, a SUMMARY of new growth attained by a gi shown to be related to time o 1. The ear~y lif~ hist?ry studies discussed in this paper are an integral tures. part of the F1shenes Research Institute program on red salmon runs of 10. The pattern of seasonal the Nushagak District in Bristol Bay, Alaska. The research described River, 1954 througl11957, sug PI deals with smolts in ·wood River seaward migrations of 1951 through from the lowest lake in the W q 1[' these fish were smaller. in s}J f-' 1959. from lakes above. Delay 1n mli. . 2. A .smolt enumeration system adaptable to large rivers was estab attributed to delay in ice bre11 {~ {;, . .. l~shed m 1951 at the outlet of Lake Aleknagik. A winged fyke net was and Wood River. J ~J f1sh~d t?roughout the migration seasons: 1951 through 1958, its catch 11. Length-frequency and 1 furn1shmg the annual migration index. A comparison of catches made in size of yearling smolts in i1 '11 by two nets fished simultaneously during the same period as well as indirect evidence attest to reliability of the index method. tions. SmallEr yearlings were 1 r 'Il groups .was studied by compar! t.. ; 3. Smolts used for length frequency study were measured alive under ling smolts with measurem.en\ anes~esia. Those fish preserved in 10 par cent formalin undergo shrink the same year class returnmg \ age m length. Shrinkage is greater in percentage for smaller fish. A correction of +5 mm in length was determined necessary to convert The small smolts were found ~ lengths of pr9served yearling smol1:s to correspond to measurements the hypothesis based on the i I of live fish. Mosquito Point. \ I 12. In Lake Nerka, scale 1 4. Size selectivity of the index fyke net was tested by comparison of nf class established the existenq 1 smolt samples taken simultaneously at Mosquito Point by beach seine growth between fish spawningi 1 and fyke net. Heterogeneity between schools in size composition was indicated limited I made evident by the tests. There was no indication that larger yearling circulatio~! in conditions for growth. S1g I smolts are less likely to be caught by tr.e fyke net than smaller fish. were also found between adulllf .I .5. A yattern of dec.rease in size of yearling smolts during evening in Lower Lake Nerka. 1 1 m~grahon was established. Net selectivity was ruled out as a causa. 13. Small size attained bYj 1 It 1s proposed that the phenomenon of diurnal change in size was due to 1957 and 1958 was related tt I difference in swimming speed or migration .stimulus related to fish size tions' in the Lake l and that schools of larger fish tended to reach the outlet earlier in Alekn~-J th~ lakes in degree of competltJ evening from the daytime milling area. major source of differences 6. Agr. determination of smolts was based on a combination of length petition between age classe 1 frequenc.:ll' a.11d scale study. In determining age it was necessary to pre threespine sticklebacks its ~. serv,e for scale study only those fish of lengths which fell in the range 14. Change in smolt size} 1 of overlap between age I and age II fish. rate, is suggested as one ca~ 1. 7. No definite relationship was found between magnitudes of parent ulation levels among the rea:> I esc~pement of red salmon :.n Wo~d River lakes and seaward migrants The low returns of adults i! I proauced for the year classes 1S.t:~.9 through 1955 .. Rates of survival of of smolts migr~ting seawar~l.\ young in fresh water varied as mu~h as 19 times. on marine surv1val and ag.a. 8. Climate was determined to be a dominant factor in over-a~l1 timing J I !(· ~" f.h Alaska Red Salmon Smolts from Wood River Lakes 293 !h'us tend to fluctuate in popu _ of seasonal migration. Timing of early season migration was closely . rearing areas in the lake associated with breakup of lake ice, and termination of migration with ~·;.? have held in recent years rise of lake surface temperatures above 50° F. 9. Seasonal increase in new ~ummer growth on scales of yearling smolts was demonstrated, and differences between years in amount of new growth attained by a given calendar date during the season was shown to be related to time of breakup and subsequent lake tempera this paper are an integral tures. on red salmon runs of 10. The pattern of seasonal changes in smolt length frequency at Wood The research described River, 1954 through 1957, suggests that L~e first smolts to migrate were ons of 1951 through from the lowest lake in the Wood River chain, and that in certain years these fish were smaller in size at time of migration than were those , 1 to large rivers was estab from lakes above. Delay in migration of smolts from the upper lakes is }ik. A winged fyke net was attributed to delay in ice oreakup and distance between lake of origin ~51 through 1958, its catch and Wood River. c . i! JJ.!U ,._ p Uk:Q(UI®AL£ .. t.- 294 Alaska Red Salmon Smalts from Wood River Lakes .\ 1952 Sockeyt.1 smo : ACKNOWLEDGMENT nom bros ki , E · · eries Research Board of Cana - It is a pleasure to express my sincere appreciation toW. F. Thomp (91):21-26. . " -----. 1954. The sizes of Bab1 1 son, who, as the first director 7 organized and developed the Fisheries Research lnstltute. It was he who foresaw the need for the early life his grants, 1950-1953. Fisheries Re ll Sta. Progr. Rept., (99):30-34. ,~ tory studies as a part of the basic program of research on red salmon in Bristol Bay. His constant encouragement, inspiration, and helpful advice nuncan, D. B. 1955. Multiple ran are gratefully acknowledged. 11(1):1-42. l)un].op, H. A. 1924. The growth-rat. ~ring the course of the studies I received valuable cooperation and as:;;astance from other memberto:. oi the staff working on closely integrated Oncorhynchus nerka. Contrib. C problems. Th~se inclu~ed ty.v:i.tcularly, Ted S. Y. Koo, Ole A. Mathisen, Fisheries Research Institute. 195 and John R. Gilbert. Wilb,.1~ A. Church gave competent assistance in the \''ashington. 24 P· . I conduct of the sampling pr•Jg;ram at Lake Nerka. Foerster, R. E. 1937. The relah I grati~n of yo~ng sockeye salmon I also wish to thank Miss Pea;rl Mooney Institute librarian for her f 1 . t ' ' Canada 3(5).421-38. ass1s ance in .preparation C!f my original thesis, and William F. Royce 1 1 ----- '1938. An investigation l for his review and criticism of the revised manuscript. 1 This study was financed by the Bristol Bay salmon canning industry. and a~tificial propagation of s1 at Cultus Lake, Britinh Columbl' 4(3):151-61. . ----- 1944. The relation of lat LITERATURE CITED . . ;, sockeye salmon (Oncorhynch:u.s ,• ada 6(3):267-80. Alaska Department of Fish and Game. 1959. Annual Report for 1957. ' d . 1 Juneau. 124 p. -----• 1952.- . The seawar -m1gJI Lakelse Lake, 1952. Fisherij Babcock, J. P. 1904. Fisheries Commissioner's Report for 1903, British 1 l . Bioi. Sta. Progr. Rept., (93):v Columbia Dept. of Fisheries, Victoria. 15 p. 1 -----. 1954. on the relation ot, -----. 1905. Fisheries Commissioner's Report for 1904. BriUsh Co 1 lumbia Dept. of Fisheries, Victoria. 12 p. nerka) returns to known smolt sj 1 Barnaby, J. T. 1944. Fluctuations in abundance of red salmon, Onco Board Can.:1.da, 11(4):339-50. I '• rlz;,nchus nerka (Walbaum), of the Karluk River, Alaska. U.S. Fish ----. 1955. The Pacific salmo' and Wildl. Serv., Fishery Bull., 50(39):237-95. Pacific coast, with particula{ Bergman, A. M. 1924. Larven von Triaenoplzor.ts robustus Olsson und near fresh water. Int. North! einer Dibothriocephalusart als Ursache eines Massensterbenr.; unter '· 1-s6. I Gilbert, C. H. 1914. Contribut jungen Lachsfischen. Deutsche tiedirztliche Wochschr., 32(21):292-~a; 32(22):311-16. salmon. (No. 1) p. 53-57. In Brett, J. R., and J. A. McConnel. 1950. Lakelse Lake sockeye survival. 1913. British Columbia Dept. I J. Fish. Research Board Canada, 8(2):103-10. -----. 1915. Ccdributions to j Canada, Fisheries Research Board. 1957. Annual Report for 1955. Ot·· (No, 2) p. 45-75. In }fisheries t ish Columbia Dept. Fisheries.[ tawa. 182 p. 1 -----. 1957a. Annual Report for 1956/1957. Ottawa. 195 p. --.--- • 1916. Contributions to ! I -----. 1958. Annual Report for 1957/1958. ottawa. 195 p. (No. 3) p. 27-64. In Fisheries · Chamberlain, F. M. 1907. Some observations on sa1mon and trout in ish Columbia Dept. Fisheries. 1 Alaska, 112 p, In Rept. U.S. Commissioner of Fisheries for 1906. -----. 1918. Contributions to 1 Clutter, R. I., and L. E. Whitesel. 1956. Collection and interpretation (No. 4) p. 33-80. In Fisheries l ,. of sockeye salmon scales. Int. Pacific Salmon Fisheries Comm., Bull. ish Columbia Dept. Fisher~es.j J f Gilbert, C. H •. and W. H. Rich. 9, 159 p. New Westminster, B. C. ' I 1 •. '· ..-. ' . .., :... ~: ' .... - . Alaska Red Salmon Smolts from Wood River Lakes 295 Dombroski, E. 1952. Sockeye smolts from Babi!te Lal~e· in 1951. Fish cries Research Board of Canada, Pacific Bioi. Sta. Progr. Rept., ...· (91):21-26. . j -----. 1954. The sizes of Babine Lake sockeye salmon smolt emi grants, 1950-1953. Fisheries Research Board of Canada, Pacific Bioi. Sta. Progr. Rept., (99):30-34. Duncan1 D. B. 1955. Multiple range and multiple F tests. Biom~trics, 11(1):1-42. J Dunlop, H. A. 1924. The growth-rate of the scales in the sockeye salmon, ] Oncorhynchus n.erka. Contrib. Canaclian BioL, 2(10):151-59. j Fisheries Research Institute .. 1959. Report of Operations, 1958. Univ. ) Washington. 24 p. Foerster, R. E. 1937. The relation of temperature to the seaward mi i 1stitute librarian, for her gration of young sockeye salmon (0nc(;rhynchus nerka). J. Bioi. Board 1 I ..1 .s, and William F. R'Jyce manuscript. · Canada, 3(5):421-38. ------. 1938. An investigation of the relative efficiencies of natural vl:almon cann;.,-,g industry. and artificial propagation of sockeye salmon (Oncorhynchus nerka) at Cultus Lake, British Columbia. J. Fish. Research Board Canada, 4(3):151-61. -----. 1944. The relation of lake population density to size of young sockeye salmon (Oncorhynchus nerka). J. Fish. Research Board Can Annual Report for 1957. ada, 6(3):267-80. -----. 1952. The seaward-migrating sockeye and coho oalmon from '·~Report for 1903. British ..ol Lakelse Lake 1952. Fisheries Research Board of Canada, Pacific Bioi. Sta. Progr.' Rept., (93):30-32. for 1904. British Co------. 1954. On the relation of adult sockeye salmon (Oncm~hynchus nerka) returns to known smolt seaward migrations. J. Fish. Research · l,:e of red salmon, Onco Boat'd Canada, 11(4):339-50. o'ver~ Alaska. U.S. Fish -95. -----. 1955. The Pacific salmon (genus Oncorhynchus) of the Canadian Pacific coast, with particular reference to their occurrence in or robustus Olsson und near fresh water. Int. North Pacific Fisheries Comm. Bull., (1): ·~. :; Massensterbens unter 1-56. :l.Jchschr., 32(21):292-98; Gilbert, C. H. 1914. Contributions to the life-history of the sockeye salmon. (:No. 1) p. 53-57 . .Jn Fisheries Commissioner's Report for Lake sockeye survival. 1913. British Columbia Dept. Fisheries. Victoria. -----. 1915. Contributiong to the life-history of the sockeye salmon. Ot- (No. ?.) p. 45-75. In Fisheries Commissioner's Report for 1914. Brit t t ~' ish Columbia Dept. Fisheries. Victoria. · ttawa. 195 p. -----. 1916. Contributions to the life-history of the sockeye s~lmon. 195 p. (No. 3) p. 27-64. Jn Fisheries Commissioner's Report for 1915. Brit s on salmon and trout in ish Columbia Dept. Fisheries. Victoria. i. of Fisheries for 1906. -----. 1918. Contributions to the life-history of the sockeye salmon. il 'tion and interpretation J (No.4) p. 33-80. In Fisheries Commissioner's Report for 1917. Brit Fisheries Comm., Bull. ish Columbia Dept. Fisheries. Victoria. Gilbert C. H., and W. H. Rich. 1927. Investigations concerning the red ' ... IW l( i .J. - IISilliMii-lm.!lai•M•••"Iii'M'- -·• ••· 1 a~·ii.::.•""'lllii''"iliii•-'·~P"C""C'S!iiiii· • •• ••••• ~-•··•·~""ae.:.w- •. ""iirlililililliiii:liWi-81111111--•••••••••··~··~-r.::!""!f!'==' '""!-- n-·sr··x:r==<$===-----""'"'··--··-· ~.., =· .I· ' - I Alaska Red Salmon smolts from Wood River Lak1· salmon runs tn the Karluk River, Alaska. Bull. U.S. Bur,. Fisheriess chatka.] Fisheries Researc i~ 1':: 1959. Ottawa. I 43(Pl. 2):1-69. • • Goldman, C. R. 1960. Primary productivity and limiting factors in three Krok...~Ln, E. M. 1957. Istoch· lakes of the Alaska Peninsula. Ecol. Monographs, 30:207-30. gennymi elementami. Izves r Hile, R. 0. 1936. Age and growth of the cisco Leu.cichthys artedi (Le telskovo Inst. Rybnovo Khoj Sueur), in the lakes of the northeastern highlands, Wisconsin. Bull. enrichment of spawning 1:1 U.S. Bur. Fisheries, 48(19):211-317. search Board of Canada, Tri Holmes, H. B. 1934. Natural propagation of salmon in Alaska. Fifth Pa Lawler, G. H. , and W. B. Seal· cific Science Congress, Victoria and Vancouver, B. C., Proc. for 1933, bution and the hosts of the cer 5:3585-92. ica. J. Fish. Research Bq Johnson, W. E. 1956. On the distribution of young sockeye salmon (On Mathisen 0. A. 1962. The eff[ corhynchus nerka) in Babine and Nilkitkwa Lakes, B. C. J. Fish. Re red sa.imon. See elsewhere ~ search Board Canada, 13(5):695-708. Mertie, J. B., Jr. 1938. Tlil: -----. 1958. Density and distribution of young sockeye saimon (On Survey, Bull. 903. 96 p. corh:ynchus nerka) throughout a multibasin lake system. J. Fish. Re Miller, R. B. 1945. Effects I J. Fish. Research Board~ search Board Canada1 15(5):961-82. Koo, T. S. Y. 1959. Red salmon smolt enumeration in the Wood River Nelson, P. R. 1958. Relati~, system. Report of field operations and results, 1958. Univ. Wash growth of juvenile red sa~l! Nelson P. R., and W. T. · ington, Fisheries Research Inst. Circ. 103. 11 p. ' . -----. 1960. Abundance, size and age of red salmon smolts from the fertilizing Bare Lake, Ala Wood. River system, 1959. Univ. Washington Fisheries Research Inst. :1 Bull. 56(102):415-36. .! Circ. 118. 9 p. Parker, R. R. , and R. E. Vil ----. 1962. Age and growth studies of red salmon scales by graphical studies at.the ~itoi Bay Re~ ment of Fisheries Ann. Re.J:., means. See elsewhere in this volume. r Krogius, F. V. 1951. 0 dinamike chislennosti krasnoi. [Oncorhynchus Ricker, W. E. 1937. The fj nerka (Walbaum)]. !zvestiia Tikhookeanskovo Nauchno-issledovatel (Oncorhynchus nerka V/alb. skovo Inst. Rybnovo Khoziaistva i Okeana~., 35:1-16. [On the dynamics Biol. Board Canada,_ 3 (5 )~:1 of abundance of the sockeye salmon Oncorhynchus nerka (Walbaum) .] Ricker, W. E., and R. E. Fo Bull. Bingham Oceanog. C Fishe~ies Research Board of Canada, Transl. Ser., No. 101, 1957. ottawa. Rounsefell, G. A. 1958. F~ I· Krogius, F. V., and Eo M. Krokhin. 1948. Ob urozhainosti molodi kras Karluk River, Alaska. 11 noi (Oncorhynchus nerka Walb. ). Izvestiia Tikhookeanskovo Nauchno 58(130}:83-169. I issledovat~lsiwvo Inst. Rybnovo Khoziaistva i Okeanog. 28:3-27. [On Scheuring, L. 1930. Beobach~ the productlon of young sockeye salmon Oncarhym:h~t.s nerka (Wan· .:.urn).] und Betrachtungen uber dal Fisheries Research Board of Canada, Transl. Ser., No. 109, 1958. ern. Z. Parasitenkunde, 2 Ottawa. Shetter, D. S. 1936. Shri~ -----. 1956. Rezultaty issledovanii biologii nerki-krasnoi, sostoianiia Copeia, (1}:60-61. 1 ee saposov i kolebanii chislennosti v vodakh Kamchatki. Voprosy Ikhtio Sv~dson, G. 1955. Salmon logii. (7):3-20. [Results ~fa study of the biology of sockeye salmon, ningholm, Sweden. S the conditions of the stocks and the fluctuations in numbers in Kam sotvattensfisket. Ann. chatka waters.] Fisheries Research Board of Canada, Transl. Ser., Thompson, W. F. 1950. No. 176, 1958. Ottawa. pared for the meeting -----. 1956a. Prichiny kolebanii chislennosti krasnoi na Kamchatke. tific research in Alas..tm. . Trudy Problemnekh i Tematicheskikh Sovesbchanii ZIN, (6): 144-49. Washington Fisheries Re [Causes of the fluctuations in abundance of sockeye salmon in Kam~ -----. 1951. An outline Alaska Red Salmon Smolts from Wood River Lakes 297 .BulL U.S. Bur. Fishertes, chatka.] Fisheries Research Board of Canada, Transl. Ser., No. 92, 1959. Ottawa. Kroki1in, E. M. 1957. Istochiki obogashcheniya nerestovykh ozer bio gennymi elementami. Izvestiia Tikhookeanskovo Nauchno-issledova telskovo Inst. Rybnovo Khoziaistva i Okeanog., 45:29-35. [Sources of enrichment of spawning lakes in biogenic elements.] Fisheries Re search Board of Canada, Trans!. Ser., No. 207, 1959. Ottawa...... ,,.. vu in Alaska. Fifth Pa Lawler, G. H., and W. B. Scott. 1954. Notes on the geographical distri ' B. C., Proc. for 1933 bution and the hosts of the cestode genus Triaenophorus in North Amer ' ica. J. Fish. Research Board Canada, 11(6):884-93. ·· young sockeye salmon (On Mathisen, 0. A. 1962. The effect of altered sex ratios on the spawning of Lakes, B. C. J. Fish. Re- red salmon. See elsewhere in this volume. Mertie, J. B., Jr. 1938. The Nushagak District, Alaska. !r S. Geol. young sockeye salmon (On Survey, Bull. 903. 96 p. j lake system. J. Fish. Re- Miller, R. B. 1945. Effects of Triae1Wphorus on growth of two fishes. J. Fish. Research Board Canada, 6(4}:334-37. in the Wood River Nelson, P. R. 1958. Relationship between rate of photosynthesis and .,esults, 1958. Univ. Wash grov.rth of juvenile red salmon. Science, 128(3317):205-7. l03. 11 p. Nelson, P. R., and W. T. Edmondson. 1955. Limnological effects of red salmon smolts from the fertilizing Bare Lake, Alaska. U.S. Fish and Wildl. Serv., Fishery Fisheries Research Inst. Bull. 56(102):415-36. Parker, R. R. , and R. E. Vincent. [1956]. Progress report on research studies at the Kitoi Bay Research Station, p. 25-67. In Alaska Depart .. salmon scales by graphical I ; ment of Fisheries Ann. Rep:. for 1955. i sti krasnoi. [OnCfYI"hynchus Ricker, W. E. 1937. The food and the food supply of sockeye salmon ~ovo Nauchno-issledovatel (Oncorhynchus nerka Walbaum) in Cultus Lake, British Columbia. J. ' 35:1-16. [On the dynamics Biol. Board Canada, 3(5):450-68. vnLnu. •.., nerka (Walbaum) .] Ricker, W. E. , and R. E. Foerster. 1948. Computation of fish production. . ansi. Ser., No. 101, 1957. Bull. Bingham Oceanog. Collection, 11(7):173-211. Rounsefell, G. A. 1958. Factors causing decline in sockeye salmon of Ob urozhamosti molodi kras Karluk River, Alaska. U.S. Fish and Wild!. Serv., Fishery Bull., ~, Tikhookeanskovo Nauchno- 58{130):83-169. 1ra i Okeanog. 28:3-27. [On Scheuring, L. 1930. Beobachtungen zur Biologie des Genus Triae~wphorus rtcc.rrnvm-:m~S p...::, • 1?£.. {Walbaum}.] und Betrachtungen iiber das Jahreszeitliche Auftreten von Bandwiirm ansi. Ser., f·lo. :n9, 1958. ern. Z. Parasitenkunde, 2:157-77. Shetter, D. S. 1936. Shrinkage of trout at death and on preservation. · nerki -krasnut, sostoianiia Copeia, (1}:60-61. Kamchatki. Voprosy Ikhtio- SW!'dson; G. 19.55. Salmon stock fluctuations in the Baltic Sea. Drott 1 biology of sockaye salmon, ningholm, Sweden. Statens undersoknings- och forsoksanstalt for . \ ations in numbers in Kam sotvattensfisket. Ann. Rept. and Short Papers for 1954. (36): 226-62 . of Canada, Transl. Ser., Thompson, W. F. 1950. Some salmon research problems in Alaska; pre pared for the meeting held by the National Research Council on scien .li ::>sti krasnoi na Kamchatke. tific research in Alaska. Washington; D. C., November 9, 1950. Univ .. veshchanii ZIN, {6): 144-~9. Washington Fisheries Research Inst., Circ. 11. 19 p. of sockeye salmon in Kam------. 1951. An outline for -salmon research in Alaska; prepared for l [ r J Alaska Red Salmon Smolts from Wood River Lakes 297 U.S. Bur. Fisheries chatka.] Fisheries Research Board of Canada, Transl. Ser., No. 92, ' 1959. ottawa. and limiting factors in three Krokhin, E. M. 1957. Istochiki obogashcheniya nerestovykh ozer bio- ' 30:207-30. gennymi elementami. Izvestiia Tikhookeanskovo Nauchno-issledova _ Leucichthys artedi {Le telskovo Inst. Rybnovo Khoziaistva i Okeanog., 45:29-35. (Sources of :.d.ghlands, Wisconsin. Bull. enrichment of spawning lakes in biogenic elements.] Fisheries Re search Board of Canada, Trans!. Ser., No. 207, 1959. ottawa. ':a!mon in Alaska. Fifth Pa Lawler, G. H. , and W. B. Scott. 1954. Notes on the geographical distri ' B. C., Proc. for 1933 bution and the hosts of the cestode genus Triaenophorus in North Amer ' ica. J. Fish. Research Board Canada, 11{6):884-93. young sockeye salmon (On Mathisen, 0. A. 1962. The effect of altered sex ratios on the spawning of Lakes, B. C. J. Fish. Re- red salmon. See elsewhere in this volume. Mertie, J. B., Jr. 1938. The Nushagak District, Alaska. U.S. Geol. iVoung sockeye salmon (On Survey, Bull. 903. 96 p. lake system. J. Fish. Re- Miller, R. B. 1945. Effects of Triaenophorus on growth of two fishes. l J. Fish. Research Board Canada, 6(4):334-37. in the Wood River Nelson, P. R. 1958. Relationship between rate of photosynthesis and ·}esults, 1958. Univ. Wash growth of juvenile red salmon. Science, 128(3317):205-7. L03. 11 p. Nelson, P. R., and W. T. Edmondson. 1955. Limnological effects of red salmon smolts from the fertilizing Bare Lake, Alaska. U.S. Fish and Wild!. Serv. , Fishery Fisheries Research Inst. Bull. 56(102):415-36. Parker, R. R., and R. E. Vincent. (1956]. Progress report on research salmon scales by graphical studies at the Kitoi Bay Research Station, p. 25-67. In Alaska Depart ment of Fisheries Ann. Rept. for 1955. ! sti krasnoi. [Oncorhynchus Ricker, W. E. 1937. The food and the food supply of sockeye salmon ~ovo Nauchno-issledovatel (Oncarhynchus nerka Walbaum) in Cultus Lake, British Columbia. J. ' 35:1-16. [On the dynamics Bioi. Board Canada; 3{5):450-68 . . ! hynchus nerka {Walbaum).] Ricker, W. E., and R. E. Foerster. 1948. Computation of fish production. ansl. Ser., No. 101, 1957. Bull. Bingham Oceanog. Collection, 11(7):173-211. Rounsefell, G. A. 1958. Factors causing decline in sockeye salmon of Ob urozhainosti molodi kras Karluk River, Alaska. U.S. Fish and Wildl. Serv., Fishery Bull., • Tikhookeanskovo Nauchno 58(130):83-169. Fa i Okeanog. 28:3-27. [On Scheuring, L. 1930. Beobachtungen zur Biologie des Genus Triamwphorus zcm.,.nwvu:il2'.lS nerka (Walbaum) .] und Betrachtungen iiber das Jahreszeitliche Auftreten von Bandwiirm ,! ansl. Ser., No. 109, 1958. ern. Z. Parasitenkunde, 2:157-77. !j Shetter, D. S. 1936. Shrinkage of trout at death and on preservation. nerki -krasnoi, sostoianiia Copeia, (1):60=61. Kamchatki. Voprosy lkhtio- Svil.rdson, G. 1955. Salmon stock fluctuations in the Baltic Sea. Drott 1 biology of sockeye salmon, ningholm, Sweden. Statens undersoknings- och forsoksanstalt for ations in numbers in Kam sotvattensfisket. Ann. Rept. and Short Papers for 1954. (36): 226-62. of Canada, Trans!. Ser., Thompson, W. F. 1950. Some salman rasaa.Feh pFoblems in .Alask~; pre ~EK.! [Q!' th~ m~~t!ng held by the National Research Council on scien ..1 ' :>sti krasnoi na Kamchatke. tific research in Alaska. Washington, D. C., November 9, 1950. Univ. eshchanii ZIN, {6): 144-49. Washington Fisheries Research Inst., Circ. 11. 19 p. .of sockeye salmon in Kam------. 1951, An outline for -salmon research in Alaska; prepared for I J .L 298 Alaska Red Salmon .. ,. the meeting of the International Council for the Exploration of the Sea ~t.il·:J, at Amsterdam, October 1-9, 1951. Univ. Washington Fisheries Re search Inst., Circ. 18. 49 p. U.S. Army Corps of Engineers. 1957. Harbors and rivers in southwest ern Alaska. U.S. GO",;i:. Printing Office, Washington. 89 p. (House ll Document No. 390] Ward, H. B. 1932. The origin of the landlocked habit in salmon. Proc. Nat. Acad. Sci. 18(9):569-80. Withler, F. C. 1952. Estimation of the size of the sockeye smolt run, Babine Lake, 1951. Fisheries Research Board of Canada, Pacific Bioi. Sta. Progr. Rept., (91):17-19. L.itt !! Togili b . .·: t ,.•• . ' ' l ' BPI STO L tAY, ALASKA I &.--1.1' t I 0 I. 2 3 4 !I WILES I I Alaska Red Salmon il for the Exploration of the Sea '~ 1·· Washington Fisheries Re- t :trbors and rivers in southwest- ~rj• Washington. 89 p. [House cf1dcked habit in salmon. Proc. ~' {ze of the sockeye smolt run, ft!i1)ard of Canada, Pacific Bioi. ' \ R. .·:t 1.~ '.. .. ri I I 1 ' I N WOOD RIVER LAKE SYSTEM BIUSTOL BAY, ALASKA : I' 'I 01.2345 •. -:t fA I LE 5 I i; Fig. 1. Wood River lake system, Bristol Bay, Alaska. !, - Fig. 2. The fyke net used at Mosquito Point index site, Wood River, for smolt sampling. (Photo by W. F. Thompson) 0 I I r r r I I Fig. 3. The outlet of Lake Aleknagik, showing fyke-net VI 0 location (arrow) in the river current at Mosquito Point; Wood River is in the foreground. (Photo from color transparency by Ole A. Mathisen) o m en 0 .g ::r' ~ .... 0 ~~ M-8"$.! ,-3M- t-j ..... 8' !j• ::soaqIll I'd ::s .:~J en ..... :g~ >t;j::S-<' en e: ~r; it ::som ..... I m&~, - ..err 1 C'l ::s '< ~ ·~ c.8 Jl:! 'It J ------,, 'i - ~ " I '1 S ~ 25 Tttn• -2lJ5 20 """215(1 IS 5 10 leoeb-tel.•toompl.., ;. •- '•;>, .;.,_;,~...,~~~-<;~ s L ~-->-<"=> I 0 ol Tim• n ·-2135 10 ...... ,2150 1956 25 .... I r-- r-- 20 t- -;,. s s IS ...--- 0 l'yke-oet oompl.,, 1- . dmultaoto~~~~ wltb above ~ !: :1o i- ~ 5 !- ~ oj ,. I 0 .. •~ 10 1957 .. 25 r-- 20 - 5 - r---"'1 Compudtt, alloampi•a, Jun• IS r-- (i sample1 15 907 flab 1? 0 1 • ,/ 1 1 ,...... _ • 1 I s 70 80 90 100 I l 0 I 20 "' Longth Ia mllllm•tua 0 2100- 2200- 2300- z,j()O. 0100- 2200 2300 2400 0100 0lOO Houu Fig. 5. Length-frequency samples of red smolts taken at Mosquito Point, June 15, 1954. (All fish measured Fig. 4. Mean percentage distribution of hourly alive. All frequencies smv..>thed by moving averages of fyke-r.et catches during daily fishing period, threes. Frequencies at each millimeter interval graphed 2100-0200 hours, at Mosquito Point smelt as per cent of total sample.) enumeration site 1955-57. l' :/; ·1 .._..IJO ""'r' u:, ~ --~,0. .Ill~.:.. ... ~ .. -o ~r .._, .._ I!. -\.~ I ,..---.-.---- '" - Time - 2205 June 16 -- 2238 June 16 10 ·-·- 2214 Jun~ l7 ...... 2240 June 17 5 Beach-teine samplea I • t I 'J ,.,, '·. ,,,;. • .J 0 J!llbe.=•..... ,,.,... Time -2~5June 16 ---2238 June 16 IO ·-·-~21_. June 17 •••••••• 2240 Junt- 17 ~ -sg., tl ,. "' -tl Jl~ ... 5 ~ ..Q Fyke-net samples, simultaneo1.11 .... witli aba->1e r 0 ... ~ ~ .. =Ill 0 u.. '"6' Ill ...... 0 II. 0 ~ i ....·"' 10 0 10 .... s:: Cll (J 5 ):" ... Cll t p.. ''t 0 Composiee, all samples, Junr 16-17 10 samples 10 1132 fiah 5 110 120 Length in millimeters Fig. 6. Length-frequency samples of red smolts taken at Mos quito I?oint1 June 16 and 17, 1954. (All fish measured alive. All frequencies at each millimeter interval graphed as per cent of total sample.) Fig. 7. Comparison simultaneously by b Lake Aleknagik, Ju11e Ti~e -2205 June 16 Fyke net -- 223eJune 16 Beach seine Xf= 88.72 mm ·-·-221• June t7 5 ········2~June 17 "Xb • 88.99 mm 2135, June 15 Xf= 87.94 mm mm Beach-s~ine sampl~s xb•93.70 5 2150, Junf" IS - 10 ~fm84.76 mm Time xb= 82.62 mm 'r! - 2a:IS June 16 1. ---2238 June 16 2205, June 16 ~: ·-·-221• June 17 5 ...... 2<.'40 June 17 I'! :l ,,.• Xf• 85.23 mm xb=86.19 mm 5 2238, June 16 ....Ill p. 0 E :::..., ,... -, tl ...... -~----.---.;;;·.;;;·~~ . "' 10 mm .}~ .... ~=85.77 ...0 xb ""'86.60 mm ~ (lj s 2214, June 17 ·. ..0 (lj ll., 0 ' all sampies, ]unr 16-17 I 10 xf= 84.44 mm l 732 fish . • 0 10mples .---.,--.~I xb=85.07 mm 5 2240, June 17 l I I ::~------~~~----110 12:0 ~ 1 smolts ta..lten at Mos Xf:::r 86.07 mm t measured alive. All xb =86.95 mm J'aphed aa per cent of 5 Composite of above liamples, June 15-17 Fig. 7. Comparison of pairs of length-frequency samples taken simultaneously by beach seine and fyke net at Mosquito Point, Lake Aleknagik, June 15-17, 1954. lr ·~ ------~------~== ,, ,-,~ t.., 2100-2106 D • 152 w=s.'97 lO 10 1 .. 88.50 5 5 0 t • 2120-2156 q 0 10 D .157 i 'il. 5. 78 ?t r. 87.87 10 5 0 5 •' t • 2259-2300 10 ·= D • ,, 170 j w c 5.34 j 0 l ... T. ss.n "llo .. 5 0. .t e - :·~ 1:1 s. ; .. s 0 ... .. 0 d ... Hr--; ... 0 .. , 0 lO t & 2358-2400 ...... 1,1 0 n • 183 ,., ... = 0 u.. w- 4.95 ~ 10 r- 83.04 ~ .. 5 n g. p u I ., " I ,.f .. 5 I· 0 i a." IJ '~ t • 0058..0100 lil D • 178 0 '. w •5.10 T • 84.17 i1 10 ;i ~ 5 I', :~ , ·' .. ,';'·~ ~- J 10 t. 0158-0m I ] ~'· I ~1 ~ l l ~~ \ ·I... i I ~ .~ I ...... ·. ,. . ". . ~ ' . ~. "' . -...... t 2 2100-2105 11 • 152 t '" 2'100-2"104 w=-s:97 1-ss.so n = 125 10 w. 6.45 T = 90.34 s t • 21CD-2156 n .157 or-~~-----4------~------~~-----L--~ w -5.78 r. 87.87 t = 2159-2200 10 n • 157 w: 5.78 T • 88. ·14 t • 2259-2300 5 11 • 170 wc 5.34 \ r. as.12 .. 0 t = 2259-2300 -Q, s n • 164 • a n w = 5.53 5 T = 86.81 ...0 t & 2358-2400 0 n • 183 ... 0 4.96 ... w .. 0 r. 83.04 ... 10 n t :: 2359-2.(00 II n • 157 u .. w :11:5.78 5 r. 87.99 0:." t • 0058-0100 n • 178 \ w. s. '10 0 T-84.17 t 0059-Q 100 10 = n • '134 w. 5.27 r = 85. J5 5 -I t. 0158-QCDQ n •179 w •5.07 0 r. 84.65 80 100 110 length in millimeters Fig. 9. Length frequencies of red smolts in st~.mples ca¢ured by fyke 120 net at Mosquito Point at hourly intervals during evening of June 12 and early morning of June 13, 1954. (Measured under anesthesia. Fre r n samples captured by fyke quencies smoothed' by moving averages of threes. All fish under 100 e mm were yearlings.) evening of June 8 and early 1( mare yearlings •.Measured t =fishing period w = mean weight in g n sample size l = mean length in mm averages of threes.) = lE mean weight in g )( me&.n length in mm l ! j I -··I Index of smolts produced e Ag" II ..0 rzm "E :s D Ag" I =... :f .:: 300 ·•' :s.. ~ " 200 100 0 Parent escapement 1000 j .5 ~ 500 E.. ~ ...0 Ill 0 1949 1950 1951 1952 1953 !954 1955 Year af escap.,ment Fig. 10. Wood River escapement countpr and indexes of smolts 1 produced. Fig. 12. Daily lake June-september, 195.2-. l' ~ 80 I i c 60 195Z j u.. I _j ,. .../ 1954 .."c...... l...... 11956 > ,.~ 1953 ~ 40 :; ...... 1 E 1957 u" ...... --~ [ zo 1956 195Z J 1955 May June July U-__...1--~s---i,I Fig. 11. Cumulative daily fyke-net catches, Mosquito Point, ir> I per cent of season's total. Fig. 13. Relationshit red smolt migration} (Years arranged in seq. l ,, ' TOduced I '{]]J "9 ~ II i',·...... , ____, A9" I 1,1 ~'·-~'--...__--1..--L.. L 1 ,,. I j J954 1955 J1de."'l:es of smolts E Fig. 12. Daily lake-surface temperatures: Lake Nerka station, June-Septennber, 1952-57. -- Fniod brtwun lGlc~ hrt>ekup and ·. wormlo.g of tm.,_. tutfac~ to so• F ntllllllll ?rriod brtw~rn date-s then S cmd 90 ! pPr c:rnt of the ucucus'• cumulatlvr indtx; catch orr frocbtd. 1954 1111111111111111111 I ,..I I 1953 IIIIIIIIIIIIIIIIIIIIIIIIUIIIIII 1957 ? 11111111 ,...... 1956 II IIIIIIIIIIIIIIIIIIIIIIIUIIIIIIIIIIIIIIIII 195Z tlllllllllllllltlillllllltllllllltlll"'''''''"''''' 1955 111111111111111 f:,!lllll I IIIII ..... IS a. squito Point, in i Fig. 13. Relationship between spring climate and timing of the red smolt migration, Wood River lakes, 1952 through 1957. (Years arranged in sequence of breakup dates at Lake Aleknagik.) ,, m~ q " ~ ~ I' I '.I ~;!, ' . ~ --~ ~ """'"' il,1 ~\ I ! ~P ~-~ J ,.'. ,'·.. ;•. , SlJOUll '·;j Fig. 14. Scale of a red salmon yearling 99 mm long, collected at Mosquito Point on July 5, 1954, showing new summer growth beyond the narrow rings of the annulus. Magnification 113x. ·. .. a 20 E .. r:; u.. 10 20 30 10 20 Jun .. July Fig. 15. Changes during 1953 migration season in amount of new summer growth on scales of yearling smolts sampled at Mosquito Point, Lake Aleknagik. (Summer growth is shown as percentage of total anterior scale radius.) rn (0 q:}rn ·--"--...... -.w -·""·W~YA PM¢. ¥%40i9..hi4QJ. (IPJIJ$ IIJIIIII 25 - ngrl ---a~~ U t~ May 2!1-Jun~ 2 sfi 15 il ~ i 10 u -'~>~·-""'-~ J! 5 0 .. "' •n Number of dayt Irom date of lee breakup to date of mmple, w" 0 s 25 " "'0 1953 / .a-.. • ~ 20 ~1957 s G. ·19~ "~ ~ ll > e 15 w ~ -" lt a:" :! 10 i.. t c>. s 0o·L------~200~--~--~~------~------~~----~ June 18-22 Number of aJ.r TU11 accumulated from date ~ lee breakup to date of ~ample Jun• 23•July l 60 120 Fig. 16. A. Relation between time of ice breakup, Length In mllllmet•n Lake Nerka, and percentage new summer growth on scales of red yearlings in above samples. B. Relation Fig. 17. Length frequencies of red smolts, i.n between cumulative air temperature following ice 1954 Wood River seaw, rd migration, weighted breakup and percentage of new summer growth on by magnitude of 2100-2300 catches in index fyke scales of red yearlings in samples collected on or net and grouped by five-day periods. (Frequen about July 5 in the years 1952-57. cies smoothed by moving averages of threes.) ~·.-,.- ..... ,.._,._...... _.~--->< ~..,....,_. ______·<::- ~ _j,r-- crt 'f'W n ... ) .. +...,., .. -,¥! •''t• m ... _..,._._, --~------...,._.,., ____' --- :...... :;. __ ..,....:.;_ __ ~-----~· _.....,.._....,_ ...... __,...,,~~-.---~ Jun• 1-22 ''\ --Age[ I ,! ' \ ---Agel& / \ Ju,.7- U ' ' I ' .. June 18-22 -- Agd --- Ag•ll June 23- V El '"" ~ ...... _. d I 0 li July 8-12 ... June 28 - July 2 0 ::I , ..e 0 ...u li e ... ~ July 3- 7 0 A M .... E ~ ~ ..u ~ ..:. July 8- 12 ~ ..... ~~·'*' July ll - Augwt 8 60 120 60 so 100 120 Length In mliUmeters Fig. 18. Length frequencies of red smolts in Fig. 19. Length frequencies of red smolts in 1955 Wood River seaward migration, weighted 1956 Wood River seaward migration, we ... ghted by magnitude of 2100-0200 catches in index fyke by magnitude of 2100-0200 catches in index fyke i net and grouped by five-day periods. (Frequen net and grouped by five-day periods. (Frequen cies smoothed by moving averages of threes.) cies smoothed by moving averages of threes.) i we ;acwa P4iZW a a.. a z.u~. &!J1U'~·~!'.O,'JJI,::::J; J... JJtl',if!d~tittaltU'ifZ~' I Mny :Ill- Juno 2 -Agel rt 6 ----Ao• 11 I, 4 1954 It 2 ! l); r l .w ...a ~ I -K ,...,_-~I -...._.. ___ I -1 l_ ~~! ,,{I \ I Lrngth ln mllllmrters 150 120 ,j Length ln •nllUmete11 t ! ! Fig. 18. Length frequencies of red smolts in 1955 Wood. River seaward migration, weighted Fig. 19. Length frequencies of :red smolts in by magnitude of 2100-0200 catches in index fyke 1956 Wood River seaward migration, we,.ghted j net and grouped by five-day periods. (Frequen by magnitude of 2100-0200 catches in index fyke !!les smoothed by moving averages of threes.) net and grouped by five-day periods. (Frequen l cies smoothed by moving averages of threes.) I 4 1954 2 ...... _ 2 "-"~··--t ~ N 0 ...~I .¥ ,...,--,~I --~--... I I 0 ]1111< 18- 22 4 ...... 19!56 I ~, J- ~...... I I ~ d -Agel ~ 2 : A ---·Age~ .., ... ~ 0 N ! ~ 4 . ~ a: 'II) 1957 ..... 2 (l jUDe2l-'J:l ~ 0 ~ 4 .... «1: 2 1958 0 ]tme 28 - July 2 4 19!59 Jlllr3 ·28 2 150 80 100 120 0 Length In m11Umeten 6'0 Fig. 20. Length frequencies of red smolts in 1957 Wood River seaward migration, weighted Fig. 21. Season composite length frequencies by magnitude of 2100-0200 catches in index fyke of red salmon smolts, 1954-57, Wood River. net and grouped by five-day periods. (Frequen cies smoothed by moving 2.verages of threes.) t~·~-- ! .,.,._ ... ,,_I I\ J I I I\ \ , ~--,-, _ ___..... --.,...,..-....-..-...... _ ___ ,__ ...... ,_..______·--·u---- ___ _ '-:----.--.~~ n' '~' ;.,.:...oJI -· r ~ Ll ·f-'' ~ l ~~·-~ A B ., 'l' f s Fig. '22. Photomicrographs of scales from small and large yearling smolts in the 1955 seaward migration, and of nuclear areas of scales from adults in the 1957 return escapement, Wood River lakes (magnification 43x): A. Scale from smolt 72 mm long; B. Nuclear area of scale from adult female, Hansen Creek, Lake Aleknagik, showing small amount of growth to first annulus; C. Scale from smolt 90 mm long; D: Nv.clear area of scale from adult female, Fenno Creek, Lake Nerka, showing good growth to first annulus. I : II uI ' !' 1. lu 1 1 0 l& ~ ~ ...0 llU~W~H1JD;>Ul JO U 5u ll "" Length In mllUmetm J Fig. 23. Season composite length frequency of red salmon year-. l ling migrants, Wood River, 1955, showing length groups from which scale radius measurements were taken, and number of scale measurements made. I ! t I I - ._. .. AatMUWJ!!IIJ U&IISC!!li££_Q.ii£&6 ..-.(~,~-:,_,_ _:.;;.,,~i~~:..--·~htcG'' r'" '- -,,~•~'"'?r ~· ...... _f 'l'~rwwiiir > "~i'--··~·~...;-.... ,~.¥J~t.- ... ---"-....;...~_.,_tt!! '}' J f no:29 A --- Alrknaglk adults n•29 ..,.zs- Rlvrr Bay a) - Small y.,arllngs D"S6 I~ 3-L. Nrrka ~ --- .... .,.zs .. 10 Frnno Crerk 4-t. N.,rka .A. ..-zs o 1-' ="""" I Allah Brach B . ---- adults Jram lakrs above S-L. N~rka -- naZS I 'il60 Al.,knaglk n=29Z Stovall Creok .. - l.Grg., yearlings ll"lZZ E .. • 6-L. Nrrka n-ZS ;so It-, , __\ ;; 1 N-4 B~ach - 0 .. .. , \ e E I \ .. I 7-L. N~rka ./"o.. ,.,zs -40 I ' .. Pick Crr~i< I 0 . \ ..= .. I \ 0 .. I \ .. .D 6 I 8-Llttlr Togiak l.Gke n•ZS E30 I ' \ \ W~rt end I \ . :z:" I \ .," 0 I 9-L. Nrrka -. n•ZS 20 II 'l .. Anvil Bay I l ... 0 .. Nerka .. I 10-L, .A nmZS 10 ' .D 'l 6 I :z:" 11-Agu!Ukpok ~ no nLJ 9 : L.J WOOD ,liVER i L_j 0tC34& lilllllltt L..J Fig. 26. Spawning grounds represented in t.1e study of first-year growth attained by adults, t 1953 year class, returning 1957. (See Figure 25 l for names of numbered at"eas.) l t :r laco Altluwsglk I -·t u 10 l· 0 I J..own lab H•th and a a 170 Linlt TQ91ak lot..- ~ I 30 t :%) J .E t I ~ JO : ~' E !' 'i: 0 U~LahN'ttka r ' ...= Contribution No. 111, Cold ' ~211 i ' ;z: ington, Seattle, Washingtc·(· L:..1 second of two installment 10 1 1958 by the University of 'h r , 0 requirements for the degref 1.4k• kvotl")'·l.oh Kullk 10 0 so 140 I I' Fig. 27. Difference between lake areas in l scale radius measurements of four-year-old adult red salmon, scale formula 1.2, 1953 yf:ar ,-{! class.