Landingham et al.: Feeding habits of juvenile Pacific salmon 
301 
Table 10 
Principal prey of juvenile sockeye salmon in southeastern 
Alaska and northern British Columbia in 1983 and 1984 
and in the Gulf of Alaska and Bering Sea in 1967 and 1968 
(Hartt and Dell, 1986). Values are percent biomass of total 
diet. The number of fish sampled is shown in parantheses, 
followed by fork length ranges (mm). 
Prey 
Pooled 
1967-68 
(996) 
130-180 
Pooled 
1983-84 
(361) 
100-300 
August 
1983 
(55) 
130-249 
July 
1984 
(159) 
100-209 
August 
1984 
(147) 
110-300 
Copepods 
5.1 
0.5 
4.6 
0.4 
0.5 
Decapod 
larvae 

2.6 
8.3 
0.8 
5.3 
Euphausiids 
42.0 
4.3 
39.0 
3.4 
3.8 
Amphipods 
1.6 
3.7 
30.7 
2.0 
5.1 
Pteropods 
6.2 
— 
— 
— 
— 
Larval fish 
30.8 
87.2 
16.7 
92.0 
83.1 
teleost prey increased in all diets — pink, chum, and 
sockeye salmon readily switched from small zoo- 
plankton to larger teleost prey in response to an ap- 
parent increase of available larval fish prey. The abil- 
ity of salmon species to maintain plasticity in their 
diets may be an adaptation to changing ocean condi- 
tions — one that may improve marine survival. 
On the basis of our comparisons between the prey 
composition of juvenile salmonids and the taxa found 
in neuston and plankton tows, we conclude that these 
juveniles are selecting a limited subset of available 
prey. Although other factors besides feeding prefer- 
ences (e.g. prey patchiness, gear selectivity, differ- 
ential digestion rates of prey) could lead to low se- 
lectivity values, certain taxa do appear to be con- 
sumed in high proportions in relation to their abun- 
dance. Our results suggest that juvenile salmon are 
visual predators and select prey on the basis of prey 
size and visibility and not on local abundance. For 
example, relatively rare hyperiid amphipods were se- 
lected by most salmon, whereas slightly smaller but 
much more numerous copepods were ignored. As ob- 
served by Peterson et al. (1982), this prey selection 
may be due to the heavy pigmentation and unusual 
swimming motion of hyperiids in contrast to the light 
pigmentation and fast swimming motion of copepods. 
Although the diets of both chum and coho salmon 
appear to be more similar to the neuston than the 
zooplankton catches, a reliance on neustonic fauna, 
as suggested by Brodeur (1989) for coho salmon off 
Washington and Oregon, is not conclusively demon- 
strated because of the small number of comparisons 
that we were able to make. More detailed field and 
laboratory studies are required to determine whether 
juvenile salmon show a reliance on certain prey or 
an inability to switch to alternate prey when pre- 
ferred prey resources are depleted. Under these con- 
ditions, the availability of the right kinds of prey may 
have more important implications for the survival of 
juvenile salmon in coastal waters than the overall 
production of prey. 
Acknowledgments 
We thank the biologists and technicians who helped 
in the field and laboratory, particularly P. D. 
Mothershead. We also thank the crews on the NOAA 
RV John N. Cobb and FV Bering Sea for their coop- 
eration during seining operations. The FV Bering Sea 
cruise was part of a cooperative coastwide survey 
from California to southeastern Alaska with W. 
Pearcy, Oregon State University. We especially ac- 
knowledge the review of the manuscript by A. Wer- 
theimer and significant editorial assistance from 
G. Duker. 
Literature cited 
Andrievskaya, L. D. 
1968. Feeding of Pacific salmon fry in the sea. Izv. 
Tikhookean. Nauchno-Issled. Inst. Rybn. Khoz. Okeanogr. 
(TINRO) 64:73-80. [In Russ.; Engl, transl. 1970, Fish. Res. 
Board Can. Transl. Ser. 1423, 16 p.] 
1970. Feeding of Pacific salmon juveniles in the Sea of 
Okhotsk. Izv. Tikhookean. Nauchno-Issled. Inst. Rybn. 
Khoz. Okeanogr. (TINRO) 78:105-115. [In Russ.; Engl, 
transl. 1973, Fish. Res. Board Can. Transl. Ser.2441, 20 p. I 
Bailey, K. M., and L. S. Incze. 
1985. El Nino and the early life history and recruitment of 
fishes in temperate marine waters. In W. S. Wooster and 
D. L. Fluharty (eds.), El Nino North: Nino effects in the 
eastern subarctic Pacific Ocean, p.143-165. Washington 
Sea Grant WSG-WO-85-30, Univ. Washington, Seattle, WA, 
312 p. 
Beacham, T. D. 
1986. Type, quantity, and size of food of Pacific salmon 
( Oncorhynchus ) in the Strait of Juan de Fuca, British 
Columbia. Fish. Bull. 84:77-89. 
Beamish, R. J., and D. R. Bouillon. 
1993. Pacific salmon production trends in relation to 
climate. Can. J. Fish. Aquat. Sci. 50:1002-1016. 
Birman, I. B. 
1969. Distribution and growth of young Pacific salmon of 
the genus Oncorhynchus in the sea. Probl. Ichthyol. 
9:651-666. 
Brodeur, R. D. 
1989. Neustonic feeding by juvenile salmonids in coastal 
waters of the Northeast Pacific. Can. J. Zool. 67:1995- 
2007. 
1991. Ontogenetic variations in the type and size of prey 
consumed by juvenile coho, Oncorhynchus kisutch, and 
chinook, O. tshawytscha, salmon. Env. Biol. Fishes 
30:303-315. 
