Landingham et al.: Feeding habits of juvenile Pacific salmon 
297 
Table 5 
Diet overlap values ( C A , Morisita’s index for prey numbers; Horn, 1966) for inside and outside waters of British Columbia (BC) 
and Alaska by sampling period and pooled over time. Nearshore = 0-37 km; offshore = >37 km. An asterisk indicates a significant 
value. 
Diet overlap ( C A ) 
July 1984 August 1984 
Pooled 
Comparison 
Aug 1983 
BC 
Alaska 
Nearshore 
Offshore 
over time 
Inside inlets 
Pink-chum 
0.55 
0.87* 
0.56 
0.66* 
Pink-coho 
0.89* 
0.04 
0.29 
0.41 
Pink-sockeye 
— 
0.21 
0.15 
0.37 
Chum-coho 
0.47 
0.11 
0.14 
0.24 
Chum-sockeye 
— 
0.25 
0.85* 
0.51 
Coho-sockeye 
Inside passages 
— 
0.64* 
0.01 
0.55 
Pink-chum 
0.94* 
— 
0.91* 
0.91* 
Pink-coho 
0.54 
0.11 
0.09 
0.25 
Pink-sockeye 
0.85* 
0.49 
— 
0.58 
Chum-coho 
0.45 
— 
0.20 
0.25 
Chum-sockeye 
0.74* 
— 
— 
0.73* 
Coho-sockeye 
Outside waters 
0.65* 
0.46 
— 
0.49 
Pink-chum 
— 
0.44 
0.82* 
1.00* 
0.85* 
0.67* 
Pink-coho 
0.26 
0.24 
0.10 
0.12 
0.11 
0.20 
Pink-sockeye 
0.77* 
0.85* 
0.97* 
0.67* 
0.79* 
0.83* 
Chum-coho 
— 
0.96* 
0.10 
0.10 
0.09 
0.32 
Chum-sockeye 
— 
0.39 
0.82* 
0.53 
0.97* 
0.68* 
Coho-sockeye 
All habitats 
0.16 
0.20 
0.17 
0.13 
0.09 
0.17 
Pink-chum 
0.95* 
0.80* 
0.88* 
0.91* 
Pink-coho 
0.43 
0.21 
0.18 
0.38 
Pink-sockeye 
0.72* 
0.79* 
0.99* 
0.93* 
Chum-coho 
0.31 
0.15 
0.25 
0.24 
Chum-sockeye 
0.58 
0.73* 
0.85* 
0.73* 
Coho-sockeye 
0.62* 
0.37 
0.18 
0.49 
chum, and sockeye salmon in the Sea of Okhotsk and 
the Bering Sea (Andrievskaya, 1968). In our study, 
temporal patterns based on seasonal (monthly) dif- 
ferences in the FO of fish prey were rare; the diets of 
pink, chum, or sockeye salmon included fish as fre- 
quently in July 1984 (when transects extended only 
to 37 km) as in August 1984. However, interannual 
differences were observed: all species, except chum 
salmon, ate fish more frequently in August 1984 than 
in August 1983. These observations suggest that in- 
creased frequency of fish prey in salmon diets is re- 
lated more to annual variations in teleost prey abun- 
dance than to distance offshore. 
Juvenile fishes are often identified as important 
prey for juvenile salmon, although seldom to the ex- 
tent that we observed in 1984 in northern southeast- 
ern Alaska. Comparison of our results with other 
studies of juvenile salmon diet in Alaska suggests 
that, although pink, chum, and sockeye salmon feed 
principally on planktonic taxa, they readily switch 
to teleost prey when available. For example, crusta- 
ceans were the principal prey of pink, chum, and sock- 
eye salmon in the outside waters of southeastern 
Alaska in 1982, whereas fish were the principal prey 
of coho salmon ( Jaenicke etal., 1984). In our study in 
southeastern Alaska in 1983, prey fish made up only 
half as much biomass as that observed in juvenile 
sockeye salmon stomachs collected from the Gulf of 
Alaska and Bering Sea in 1967 and 1968 (Hartt and 
Bell, 1986); in 1984, however, we recorded substan- 
tially higher teleost prey biomass than that observed 
by Hartt and Dell (TablelO). Although we found that 
sockeye salmon diet varied more than that of the 
other species, increases in the FO of predation on 
teleosts were consistent among pink, chum, and sock- 
eye salmon. 
