Landingham et a I.: Feeding habits of juvenile Pacific salmon 
299 
Table 7 
Neuston and zooplankton organisms (number per 100 m 3 ) from outside- and inside-water habitats in British Columbia (BC) and 
Alaska, collected in July 1984. 
Neuston 
Zooplankton 
Outside 
Outside BC 
Combined Alaska 
BC 
Alaska 
Inside Alaska 
Number of samples 
20 
16 
3 
9 
5 
Invertebrate eggs 
— 
— 
343.00 
1,449,78 
304.20 
Polychaeta 
0.13 
0.13 
— 
— 
— 
Gastropoda 
Limacina helicina 
124.67 
243.67 
62.80 
Bivalvia 
— 
— 
— 
— 
26.60 
Cephalopoda 
0.05 
0.13 
31.00 
— 
— 
Cladocera 
— 
— 
145.33 
524.00 
234.20 
Calanoida 
39.77 
114.56 
48,672.34 
60,074.67 
25,956.00 
Harpacticoida 
0.50 
4.31 
0 
34.33 
5.20 
Cirripedia 
1.90 
0.75 
187.00 
3,203.44 
543.40 
Mysidacea 
— 
0.13 
0 
579.89 
— 
Gammariidea 
0.92 
18.17 
0 
2.22 
— 
Hyperiidea 
126.12 
5.21 
436.33 
566.33 
1,142.00 
Euphausiacea 
8.86 
0.17 
4,072.70 
126.78 
164.80 
Decapoda 
873.11 
40.18 
363.67 
510.33 
230.00 
Insecta 
0.21 
0.21 
— 
- 
3.00 
Chaetognatha 
0.34 
5.63 
249.33 
171.67 
42.20 
Larvacea 
0.15 
5.00 
62.33 
262.78 
204.00 
Teleosts 2 
1.46 
0.79 
31.00 
6.11 
— 
1 Eggs, larvae, and juveniles combined. 
salmon in our study (seined during the day); of 2,216 
stomachs examined, only 32 (1.4%) were empty. Al- 
though we found few empty stomachs, we did find 
evidence of decreased feeding in the 0-37 km region 
of outside waters, which includes the region of peak 
catches of pink and chum salmon (Jaenicke and 
Celewycz, 1994); fullness was lower for all species, 
and empty stomachs were most common for pink and 
chum salmon collected in these outside waters. 
Juvenile coho salmon diet rarely showed signifi- 
cant overlap with pink, chum, and sockeye salmon 
diets. Coho salmon differed in distribution and size 
from the other three species (Jaenicke and Celewycz, 
1994) and were more piscivorous. Curves of cumula- 
tive number of taxa (Fig. 3) sloped more steeply for 
coho salmon than for the other species; this rapid 
rate of increase in prey types may reflect opportu- 
nistic feeding of juvenile coho salmon. Diets are even 
more diverse among coho salmon individuals than 
among pink salmon individuals, which consumed a 
similarly broad array of prey taxa. Less aggregation 
and lower densities (CPUE) than those for other 
salmon (Jaenicke and Celewycz, 1994) allow coho 
salmon to exploit fully all locations within a habitat 
type. The other three species tended to occur in fewer 
Table 8 
Mean percent similarity index (PSI) values indicating 
amount of overlap between prey fields and juvenile salmon 
diet. Stations where prey were collected were included in 
the analysis for a particular salmon species if at least five 
stomachs were collected at the station. 
Similarity values 
Number of 
stations 
Mean 
Range 
Neuston collection 
Pink 
8 
10.8 
0-24.6 
Chum 
2 
9.3 
0-18.5 
Sockeye 
8 
9.1 
0-37.8 
Coho 
2 
16.7 
0-33.3 
Zooplankton collection 
Pink 
8 
8.0 
1.0-22.7 
Chum 
5 
2.2 
0.2-6. 8 
Sockeye 
4 
9.3 
1.0-24.9 
Coho 
6 
6.2 
0.7-11.7 
locations (although they were well represented 
within habitat types) and tended to be more highly 
aggregated, increasing the tendency toward more 
