NOAA Technical Memorandum NMFS-AFSC-28

U.S. DEPARTMENT OF COMMERCE

National Oceanic and Atmospheric Administration

National Marine Fisheries Service

Alaska Fisheries Science Center

December 1993

Effects of Water Temperature

on Growth of Juvenile Pink Salmon

(Oncorhynchus gorbuscha)

by

Donald G. Mortensen and Herman Savikko
NOAA Technical Memorandum NMFS

The National Marine Fisheries Service's Alaska Fisheries Science Center

uses the NOAA Technical Memorandum series to issue informal scientific and

technical publications when complete formal review and editorial processing

are not appropriate or feasible. Documents within this series reflect sound

professional work and may be referenced in the formal scientific and technical

literature.

The NMFS-AFSC Technical Memorandum series of the Alaska Fisheries

Science Center continues the NMFS-F/NWC series established in 1970 by the

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the Northwest Fisheries Science Center.

This document should be cited as follows:

Mortensen, D.G., and H. Savikko. 1993. Effects of water temperature 

on growth of juvenile pink salmon (Oncorhynchus gorbuscha). U.S.

Dep. Commer., NOAA Tech. Memo. NMFS-AFSC-28, 12 p. 

 

Reference in this document to trade names does not imply endorsement by

the National Marine Fisheries Service, NOAA.
Effects of Water Temperature

on Growth of Juvenile Pink Salmon

(Oncorhynchus goibuscha)

by

Donald G. Mortensen1 and Herman Savikko2

Auke Bay Laboratory’

Alaska Fisheries Science Center

11305 Glacier Highway

Juneau AK 99801-8626

Alaska Department of Fish and Game2

1255 W. Eighth Street

Juneau, AK 99801-8626

 U.S. DEPARTMENT OF COMMERCE

Ronald H. Brown, Secretary

National Oceanic and Atmospheric Administration

D. James Baker, Under Secretary and Administrator

National Marine Fisheries Service

Rolland A. Schmitten, Assistant Adminstrator for Fisheries

December 1993
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Growth rates were calculated for recently emerged

juvenile pink salmon (Oncorhynchus gorbuscha) held at constant

water temperatures of 4°, 8°, and 12°_C for 6 weeks. The

juveniles in all treatments were fed live zooplankton to

excess, and exhibited a minimum growth rate of 1.64% body

weight per day (bw/d) at 4°C and maximum growth rate of 3.25%

bw/d at 12°C. Growth rates were significantly different

(P < 0.05) between 4°, 8°, and 12°C treatment groups. A

linear model of juvenile pink salmon growth was developed

using data from this and five other studies. This model

provides a simple and reliable means to project the potential

growth rate of juvenile pink salmon when natural zooplankton

prey is abundant and estuarine water temperatures are between

4.0° and 18.3°C.
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INTRODUCTION

METHODS . . .

RESULTS . . .

DISCUSSION .

CITATIONS . .

V

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INTRODUCTION

The pink salmon (Oncorhynchus gorbuscha) is the smallest

and most abundant of the five species of Pacific salmon found

in Alaska. After spending 12-14 months at sea, adult pink

salmon return from the pelagic zones of the North Pacific,

Ocean between July and September to spawn-in coastal streams 

(Bailey 1969). The eggs and alevins develop with-in

interstices of the streambed gravel for several months. From

mid-March to mid-June, the pink salmon emerge as fry and

migrate downstream to the marine environment (Bailey et al.

1975). Once in the estuary, the pink salmon fry form tight

schools in the nearshore surface waters and generally feed on

small zooplankters (Bailey et al. 1975). During this period,

surface water temperaturesrange from about 3.5° to 13°C

(Ziemann et al. 1990) and prey-abundance ranges from 5 to 55

organisms per liter (Coyle and Paul 1990). Rapid growth of

juvenile pink salmon (>4% body weight per day [bw/d]) during

their early marine residence may be-an important mechanism

that evolved to reduce size-dependent predation by larger fish

(Parker 1971; Healey 1982; Hargreaves and LeBrasseur-1985).

This rapid growth is-thought to be related to environmental

conditions and food- availability. Water temperature is a

significant environmental factor influencing the growth of

juvenile chum salmon (0. keta) and sockeye salmon (O. nerka)

(Paloheimo and Dickie 1966; Brett et al. 1969,; Brett 1979;

Weatherley and Gill 1987). However, little work-has been done

to isolate and assess the effects of water temperature on the

growth of juvenile pink salmon.

Our objectives were to determine the maximum growth rate

of recently emerged juvenile pink salmon over a range of-water

temperatures most likely to be encountered. in the wild and to

provide resource managers with a simple-'model of growth rate

as a function of water temperature.

METHODS

Juvenile pink salmon were captured between late April and

mid-May at a weir at the mouth of Auke Creek in Southeast

Alaska.

stream.

These fish were actively emigrating from their natal

The captured fish were reared at three different

temperatures, with two aquaria for each temperature treatment.

We prepared the aquaria by pumping seawater (salinity

29%) directly from the 30 mm level (depth) of Auke Bay through

a 10 μm sand filter to three head tanks at 5 l/min. A

submersible electric water heater in each head tank warmed the

water to 4°, 8°, or 12°.C (+ 0.l°C). Each head tank supplied a

pair of 60 1 aquaria with warmed water at a rate of 1.0 l/min.

Two broad-spectrum 25 W fluorescent lamps fitted with plastic

light-diffuser panels provided each pair of aquaria with a

water surface light intensity of 0.900 μW cm nm ,
2

approximating the natural light intensity (1 hour after

sunrise on an overcast day at Auke Bay in mid-April) and day

length (18 hours light) matched to the season and latitude.

Each aquarium was stocked with 250 juvenile pink salmon

(4.2 fish/l). After the first 24 hours, any dead fish were

replaced with live fish. Initially,

ranged from 266 to 290 mg (Table 1).

average fish weight

The fish were fed zooplankton collected from nearshore

areas (3 to 20 m from shore) of Auke Bay by towing a 0.233 mm

mesh, 1 m diameter conical net about 1 m below the water

surface behind a small skiff. The live zooplankton were

immediately placed in a 250 1 holding tank with about 200 1 of

6°C filtered and aerated seawater. Zooplankton were collected

continuously during the day to ensure an adequate supply of

prey for the experiment. The collected zooplankton consisted

primarily of small calanoid copepods (Pseudocalanus sp. and

Acartia sp.), copepodids and copepod nauplii, euphausiid

larvae; polychaetes, barnacle nauplii and cyprids, and bivalve

larvae. The relative number of each of the zooplankters was

not determined. Occasionally when the amount of live

zooplankton collected was not sufficient to feed the fish to

satiation, the diet was supplemented with frozen zooplankton

concentrate collected in Auke Bay before the experiment.

Zooplankton were placed in each aquarium at 2-hour

intervals during the 18-hour light cycle, providing a standing

zooplankton crop of at least 100 plankters per liter (pl/l).

For 6 weeks, 25 juvenile salmon were removed weekly from

each tank (15 from each 12°C tank for weeks 5 and 6) and

immobilized with a solution of MS-222 (methane tricainesulfonate) at the appropriate water temperature. The salmon

were then weighed to the nearest milligram and allowed to

recover in a tank of seawater held at the appropriate

temperature before being returned to-the test aquaria.

The growth rate of the fish in each aquarium was

described using an exponential model,

(Eq. 1)

where d is time in days, G is the daily growth rate, and Wo

and W1 are the fish weight at the beginning and end of the

time-period. Using this model, weight can be expressed as a

linear function of time,

Linear regression was used to fit the natural log of

observed weights to this equation. The computed slope of the

regression equation is then the specific growth rate over the

interval, which, when multiplied by 100, can be expressed as

percent body weight gained per day (%bw/d).
Table l.--Mean weights (mg) and standard deviations (in parentheses) of juvenile pink

salmon reared at water temperatures of 4°, 8°, and 12°C over a 42-day period

(n = 25).

4°c 8°C

Replicate Replicate

12°C

Replicate
4

An analysis of covariance (ANCOVA) was used to determine

whether growth rates (slopes of the regression lines) among

different treatment groups of fish were equal (Zar 1974). If

the growth rates were significantly different (P < 0.05), then

the Newman-Keuls multiple-range-test was used to test for

differences between each pair of growth rates (Zar 1974).

A simple linear model,

G = a + bt, (Eq. 3)

where G is growth rate (%bw/d), a is the water temperature at

a zero growth rate, b is growth acceleration rate, and t is

water temperature was then used to predict maximum growth

rates of juvenile pink salmon fed at maximum rations at

various water temperatures between 4° and 18.3°C. Data were

incorporated into the analysis from five additional studies

which cultured juvenile pink salmon: two studies involved

short-term rearing in seawater net-pens (Martin et al. 1981;

A. C. Wertheimer, Fisheries Biologist, Auke Bay Lab. Pers.

commun., September 1989), and three involved culture of

juvenile pink salmon in laboratory aquaria (Brett 1974;

Kepshire 1976; Moles and Rice 1983). In all five studies the

fish were fed to excess with a commercially prepared fish

food, and water temperatures were calculated as meanvalues

over the rearing period.

RESULT S

Growth rates of juvenile pink salmon in each treatment

group in our study ranged from 1.64% to 3.25% bw/d (Table 2).

Fish held at 12°C grew significantly faster (3.25% bw/d)

(P < 0.05) than those at 4°C and 8°C, and fish held at 8°C

(2.77% bw/d) grew significantly faster than those at 4°C

(1.71% bw/d). There was no significant difference (P < 0.05)

between paired temperature groups.

remain constant,

Assuming these rates

it would-take 41-42 days for a juvenile pink

salmon to double in weight at 4°C; at 12°C it would take 21-22

days.

During the experiment,

diseased. This epizootic,

fish in both 12°C aquaria became

diagnosed as a combination of

several stress-related bacterial infections, began at day 33

of the experiment with the death of a few fish in each

aquarium. At this point each of the tanks was treated with

Diquat at levels recommended by personnel at the State of

Alaska Fish Pathology Laboratory in Juneau, Alaska.

within a week,

However,

the 12°C aquaria lost 102 and 107 fish,

'Reference to trade names does not imply endorsement by the National

Marine Fisheries Service, NOAA.
5

respectively. The remaining fish continued to feed actively

but exhibited a low-level chronic infection rate. Dissolved

oxygen levels in each tank averaged about 5.5 ppm throughout

the epizootic. The 4°C and 8°C aquaria each lost fewer than

20 fish over the 42-day study period.

The simple linear growth model, based on data from our

study and five others (Table 3), provided a satisfactory fit

(r2 = 0.92, P = 0.00, Fig. 1). The parameters of the linear

regression were G = 0.925 + 0.224t, where G = growth as %bw/d

and t = water temperature.

Table 2. --Growth rates with upper and lower confidence limits

(CL) for juvenile pink salmon held at 4°, 8°, and

12°C. Growth rate was determined as the slope

resulting from the regression of the natural log of

weights of individual fish as a function of time in

days and expressed as percent body weight gained per

day (%bw/d). The coefficients of determination (r2

)

are also presented.

Growth rate

Water

temperature Lower Upper 

(°C) Replicate % bw/d CL CL r

2

4 1 1.64 1.59 1.68 0.72

4 2 1.71 1.67 1.74 0..83

8 1 2.71 2.68 2.75 0.91

8 2 2.77 2.73 2.81 0.92

12 1 3.11 3.07 3.15 0.88

12 2 3.25 3.21 3.30 0.88

DISCUSSION

The growth pattern displayed by juvenile pink salmon was

similar to that documented for juvenile sockeye salmon (Brett

et al. 1969) and for juvenile rainbow trout (0. mykiss)

(Hokanson et al. 1977). The growth rates of the juvenile

sockeye and rainbow trout were roughly linear between lo and

12°C but declined to an asymptote near 15°C. Observed growth

rates of juvenile pink salmon from our study seemed to

approach an asymptote at 12°C but it may be an artifact of the

disease outbreak in these groups. The actual temperature

where an asymptote is reached could be higher.
Table 3. --Daily growth

growth rates

rates of juvenile pink salmon from this study compared to the

of juvenile pink salmon from other studies. Water temperatures

remained constant except where parentheses enclose temperature range during

the study period. All juvenile salmon were fed near maximum ration with wild

zooplankton or a prepared diet.
Figure 1. --Predicted growth rate (%bw/d) and 95% confidence

interval (CI) for growth data presented in Table 3.

= growth rate; t = water temperature; observed

data = data solely from our study; calculated data

= combined data from our study and Brett 1974,

Kepshire 1976, Martin et al. 1981, Moles and Rice

1983, and Wertheimer (pers. commun.).
8

Several studies-have computed growth rates of wild

juvenile pink salmon during seaward migration. Phillips and

Barrclough (1978) found that juvenile pink salmon sampled in

the Straits of Georgia, British Columbia, grew about 3.6-4.5%

bw/d during 70-88 days between April and June. Lebrasseur and 

Parker (1964) established that in the marine waters of central

British. Columbia the juvenile pink salmon grew about l.8-5.5%

bw/d between mid-April and mid-July. Although neither study

presented water temperature data, Healey (1979) reports that

estuarine temperatures in British Columbia can range from l0o

to 15°C during these months. Coded-wire tagged juvenile pink

salmon in Auke Bay, Alaska, grew from 3.6% bw/d (over 63 days,

mean temperature 8.1°C) to 4.9% bw/d (over 71 days, mean temperature l1.4°C) from April to June (Mortensen and Wertheimer

1988).

In comparison, the observed growth rates and those

predicted by the simple linear model for juvenile pink salmon

in our study were lower than growth rates calculated from

juveniles actually captured in estuarine rearing areas.

Higher growth rates of the fry captured in estuaries may

result from several factors. The simple linear model that we

developed by including data from other studies may not

accurately predict the growth of juvenile salmon. Those

studies were not originally designed to determine growth rates

of juvenile pink salmon at various temperatures under

controlled conditions. The juvenile pink salmon in the

estuary were probably a mixture of ages, resulting in mixed

growth rates which would differ from juveniles in our study.

Size-selective predation (Parker 1971) may eliminate smaller

fish-from the natural population, resulting in artificially

high calculated growth rates. Also, at times the water

temperatures may have exceeded 12°C, resulting in higher

growth rates during those studies.

Alternatively, lower growth rates may have been

precipitated by the types of prey fed to juvenile pink salmon

reared in tanks and net-pens. For example, Volk et al. (1984)

found that the epibenthic harpacticoid copepod Tigriopus

californicus was converted more efficiently than the pelagic

calanoid copepod Pseudocalanus minutus. Therefore, the

consistently lower growth rates indicated by. our prediction

model may have resulted from the use of small pelagic

organisms and commercially prepared food.

A fifth explanation may be that stress from crowding,

confinement, and handling may have reduced growth rates of

cultured pink salmon relative to free-ranging fish. T h e

disease problem observed at 12°C in our study is evidence of

stress-related complications of crowding or confinement.

Although the data presented in our study may not reflect

the exact growth rates of juvenile pink salmon under natural
conditions,

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10

CITATIONS

Bailey, J. E. 1969. Alaska's fishery resources: the pink

salmon. U.S. Fish and Wildl. Serv., Bur. Commer. Fish.

Leafl. 619, 8 p.

Bailey, J. E., B. L. Wing, and C. R. Mattson. 1975.

Zooplankton abundance and feeding habits of fry of pink

salmon, Oncorhynchus gorbuscha, and chum salmon,

Oncorhynchus keta, in Traitors Cove, Alaska, with

speculations on the carrying capacity of the area. Fish.

Bull., U.S. 73:846-861.

Brett, J. R. 1974. Tank experiments on the culture of

pan-size sockeye (Oncorhynchus nerka) and pink salmon (0.

gorbuscha) using environmental control. Aquaculture

4.:341-352.

Brett, J. R. '1979. Environmental factors and growth. In

W. S. Hoar, D. J. Randall, and J. R. Brett (editors),

Fish physiology, vol. VIII, p. 599-675. Academic Press,

New York.

Brett, J. R., J. E. Shelbourn, and C. T. Shoop. 1969: Growth

rate and body composition of fingerling sockeye salmon,

Oncorhynchus nerka, in relation to temperature and ration

size. J. Fish. Res. Board Can. 26:2363-2394.

Coyle, K. O., and A. J. Paul. 1990. Interannual variations in zooplankton population and biomass during

the spring bloom in an Alaskan subarctic embayment.

In D. A. Ziemann and K. W. Fulton-Bennett (editors),

APPRISE - Interannual variability and fisheries

recruitment, p. 179-228. The Oceanic Institute,

Makapuu Point, Waimanalo, HI 96795.

Hargreaves, N. B., and R. J. LeBrasseur. 1985. Species

selective predation on juvenile pink (Oncorhynchus

gorbuscha) and chum salmon (0. keta) by coho salmon

(0. kisutch). Can. J. Fish. Aquat. Sci. 42:659-668.

Healey, M. C. 1979. Detritus and juvenile salmon production

in the Nanaimo Estuary: I. Production and feeding"rates

of juvenile chum salmon (Oncorhynchus keta). J. Fish.

Res. Board Can. 36:488-496.

Healey, M. C. 1982. Timing and relative intensity of

size-selective mortality of juvenile chum salmon

(Oncorhynchus keta) during early sea life. Can. J. Fish.

Aquat., Sci. 39:952-957.

Heard, W. R., R. M. Martin, and A. C. Wertheimer. 1977 .

Estuarine and freshwater culture of 1974 brbod coho

salmon in net pens and floating raceways at Little Port

Walter, Alaska. NWAFC Processed Rep., 55 p. Available
11

Auke Bay Lab., Alaska Fish. Sci. Cent.; 11305 Glacier

Hwy., Juneau, AK 99801-8626.

Hokanson, K. E. F., C.F. Kleiner, and T. W. Thorslund. 1977.

Effects of constant temperatures and diel temperature

fluctuations on specific growth and mortality rates and

yield of juvenile rainbow trout, Salmo gairdneri. J.

Fish. Res. Board Can. 34:639-648.

Kepshire, B. M. 1976. Bioenergetics and survival of chum

(Oncorhynchus keta) and pink (0. gorbuscha) salmon in

heated seawater. Ph.D. Thesis, Oregon State Univ.,

Corvallis, 112 p.

LeBrasseur, R. J., and R. R. Parker. 1964. Growth rate of

central British Columbia pink salmon (Oncorhynchus

gorbuscha). J. Fish. Res. Board Can. 21:1101-1128.

Martin, R. M., W. R. Heard, and A. C. Wertheimer. 1981.

Short-term rearing of pink salmon (Oncorhynchus

gorbuscha) fry: effect on survival and biomass of

returning adults. Can. J. Fish. Aquat. Sci. 38:554-558.

Moles, A., and S. D. Rice. 1983. Effects of crude oil and

naphthalene on growth, caloric content, and fat content

of pink salmon juveniles in seawater. Trans. Am. Fish.

soc. 112:205-211.

Mortensen, D. G., and A. C. Wertheimer. 1988. Residency and

growth of juvenile pink salmon (Oncorhynchus gorbuscha).

in Auke Bay. In APPRISE annual report, volume I, SFOS

APP87-100, p. 501-544. School of Fisheries and Ocean

Sciences, Univ. Alaska Fairbanks, Fairbanks, AK.

Paloheimo, J. E., and L. M. Dickie. 1966. Food and growth of

fishes. III. Relations among food, body size, and

growth efficiency. J. Fish. Res. Board Can. 23:1209-

1248.

Parker, R. R. 1971. Size selective predation among juvenile

salmonid fishes in a British Columbia inlet. J. Fish.

Res. Board Can. 28:1503-1510.

Phillips, A. C., and W. E. Barraclough. 1978. Early marine

growth of juvenile Pacific salmon in-the Strait of

Georgia and Saanich Inlet, British Columbia. Can. Fish.

Mar. Serv. Tech. Rep. 830, 19 p. Nanaimo, BC.

Volk, E. C., R. C. Wissmar, C. A. Simenstad, and D. M. Eggers.

1984. Relationship between otolith microstructure and

the, growth of juvenile chum salmon (Oncorhynchus.keta)

under different prey rations. Can. J. Fish. Aquat. Sci.

41:126-133.

Weatherley, A. H., and H. S. Gill. 1987. The biology of

fish growth. Academic Press, London, 443 p.
12

Zar, J. H. 1974. Biostatistical analysis. Prentice-Hall,

Englewood Cliffs, NJ, 620 p.

Ziemann, D. A., L. D. Conquest, K. W. Fulton-Bennett, and P.

K. Bienfang. 1990. Interannual variability in the

physical environment of Auke Bay, Alaska. In D. A.

Ziemann and K. W. Fulton-Bennett (editors), APPRISE -

Interannual variability and fisheries recruitment, p. 99-

128. The Oceanic Institute, Makapuu Point, Waimanalo, HI

96795.
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