300 
Fishery Bulletin 96(2), 1998 
Table 9 
Prey selection frequencies (Strauss’s linear index of food selection (L); Strauss 1979) in juvenile salmon diet for neuston and 
zooplankton collections, July and August 1984. A positive (pos. ) value indicates that a prey was more abundant in the diet than in 
the environment at a level of >0.10. A negative (neg.) value indicates that a prey was less abundant in the diet than in the 
environment at a level of <0.10. A random (ran.) value indicates that a prey was about equally abundant in the diet and in the 
environment. Absent indicates that a prey item was absent from the diet and from the environment in a particular location. 
N = number of groups tested, where group size was 5 or more of a species. 
Prey selection frequency 
Pink salmon 
Chum salmon 
Sockeye salmon 
Coho salmon 
Taxon 
Pos. 
Neg. 
Ran. 
Absent 
Pos. 
Neg. 
Ran. 
Absent 
Pos. 
Neg. 
Ran. 
Absent 
Pos. 
Neg. 
Ran. 
Absent 
Neuston 
Polychaetes 
0 
0 
1 
7 
0 
0 
0 
2 
0 
0 
0 
8 
0 
0 
0 
2 
Pteropods 
1 
0 
2 
5 
0 
0 
2 
2 
0 
0 
0 
8 
0 
0 
0 
2 
Squid 
0 
1 
0 
7 
0 
0 
0 
2 
0 
0 
0 
8 
0 
0 
0 
2 
Calanoid copepods 
1 
1 
4 
2 
0 
0 
0 
2 
4 
2 
1 
1 
0 
0 
0 
2 
Barnacle larvae 
0 
0 
0 
8 
0 
0 
0 
2 
0 
1 
0 
7 
0 
0 
0 
2 
Gammarid amphipods 
0 
2 
2 
4 
0 
1 
0 
1 
0 
1 
1 
6 
0 
1 
0 
1 
Hyperiid amphipods 
5 
1 
1 
1 
1 
0 
0 
1 
6 
2 
0 
0 
0 
1 
0 
1 
Euphausiids 
4 
1 
1 
2 
0 
0 
1 
1 
3 
1 
1 
3 
0 
0 
1 
1 
Decapod larvae 
2 
4 
1 
1 
0 
2 
0 
0 
2 
3 
1 
2 
1 
1 
0 
0 
Insects 
0 
0 
1 
7 
0 
0 
0 
2 
0 
0 
0 
8 
0 
0 
0 
2 
Chaetognaths 
0 
0 
2 
6 
1 
0 
0 
2 
0 
0 
1 
7 
0 
0 
0 
2 
Salps 
0 
0 
0 
8 
0 
0 
0 
2 
0 
0 
0 
8 
0 
0 
1 
1 
Larvaceans 
1 
0 
3 
4 
1 
0 
0 
1 
1 
0 
0 
7 
1 
0 
1 
0 
Teleosts 
1 
0 
5 
2 
0 
0 
1 
1 
0 
0 
5 
3 
1 
0 
0 
1 
Percent selection 
13.5 
9.0 
20.7 
57.4 
7.2 
10.7 
14.3 
74.8 
14.4 
9.0 
9.0 
67.9 
10.8 
10.8 
10.8 
67.7 
Plankton 
Cnidaria 
0 
0 
3 
5 
0 
0 
2 
3 
0 
0 
2 
2 
0 
0 
1 
5 
Polychaetes 
0 
0 
0 
8 
0 
0 
1 
4 
0 
0 
0 
4 
0 
0 
1 
5 
Pteropods 
1 
0 
1 
6 
0 
0 
0 
5 
0 
0 
1 
3 
0 
0 
1 
5 
Bivalve larvae 
0 
0 
0 
8 
0 
0 
0 
5 
0 
0 
0 
4 
0 
1 
1 
4 
Squid 
0 
0 
0 
8 
0 
0 
0 
5 
0 
0 
1 
3 
0 
0 
0 
6 
Invertebrate eggs 
0 
2 
1 
5 
0 
1 
0 
4 
0 
1 
0 
3 
0 
0 
1 
5 
Calanoid copepods 
0 
7 
0 
1 
0 
4 
0 
1 
0 
4 
0 
0 
0 
6 
0 
0 
Barnacle larvae 
0 
0 
2 
6 
0 
0 
1 
4 
0 
1 
1 
2 
0 
1 
1 
4 
Mysids 
0 
0 
0 
8 
0 
0 
0 
5 
0 
0 
0 
4 
0 
0 
0 
6 
Hyperiid amphipods 
2 
0 
2 
4 
2 
0 
1 
2 
2 
0 
1 
1 
1 
0 
4 
1 
Euphausiids 
2 
0 
2 
4 
1 
0 
1 
3 
1 
0 
1 
2 
2 
0 
3 
1 
Decapod larvae 
4 
0 
1 
3 
1 
0 
2 
2 
2 
0 
1 
1 
5 
0 
1 
0 
Insects 
0 
0 
0 
8 
0 
0 
0 
5 
0 
0 
0 
4 
0 
0 
2 
4 
Cladocera 
0 
0 
0 
8 
0 
0 
0 
5 
0 
0 
1 
3 
0 
0 
2 
4 
Chaetognaths 
0 
0 
2 
6 
0 
0 
0 
5 
0 
0 
2 
2 
0 
0 
1 
5 
Salps 
0 
0 
1 
7 
0 
0 
1 
4 
0 
0 
0 
4 
0 
0 
1 
5 
Larvaceans 
2 
0 
1 
5 
2 
0 
1 
2 
0 
0 
2 
2 
1 
0 
3 
2 
Teleosts 
1 
0 
2 
5 
1 
0 
1 
3 
1 
0 
3 
0 
3 
0 
2 
1 
Percent selection 
8.4 
6.3 
12.6 
73.5 
7.7 
5.5 
12.1 
73.7 
8.4 
8.4 
21.0 
61.6 
11.1 
7.4 
23.1 
58.2 
similar diets. Many seine sets caught only coho 
salmon, whereas catches of the more highly aggre- 
gated species often also contained coho salmon. In 
laboratory experiments, coho salmon smolts in sea- 
water demonstrated agonistic behavior which, if oc- 
curring in the wild, would maintain discrete feeding 
territories and a dispersed population (Paszkowski 
and Olla, 1985). 
Differences in diet, distribution, and size indicate 
that juvenile coho salmon have a distinct feeding 
ecology in comparison with these other, more plank- 
tivorous, juvenile salmon co-occurring in the south- 
ern Gulf of Alaska. In both our study and that of 
Brodeur and Pearcy (1990), fish were more impor- 
tant in the diets of juvenile coho salmon than in other 
species. During the second year of our study — when 
