Landingham et a I.: Feeding habits of juvenile Pacific salmon 
293 
Inside water (IRI) 
(partitioned into inlets and passages) 
Outside waters and 
outer coast inlets (IRI) 
80 60 40 20 0 20 40 60 80 
Calanoid copepods 
Decapod larvae 
F TTT 1 Euphausiids CZU Hyperiid amphipods 
E23 Fishes I" 1 "3 Tunicates 
Figure 5 
Index of relative importance (IRI) of principal prey of juvenile chum salmon in inside and outside waters and 
outer coast inlets of southeastern Alaska in 1983 and 1984 and outside waters and outer coast inlets of northern 
British Columbia in 1984. 
completely ( (A =0.99); prey composition and IRI for each 
prey category were highly similar (Table 2). Pink and 
chum salmon diets ( (^=0.88) and sockeye and chum 
salmon diets ( C x = 0.85) had almost identical prey spe- 
cies compositions, although proportions of prey catego- 
ries differed (Table 2). 
Spatial diet overlap Diet overlap was more com- 
mon for species comparisons in outside waters than 
in inside waters. Of all possible habitat comparisons, 
diet overlap was significant ( C A >0.60) in 42% of the 
outside-waters comparisons, 39% of inside-passage 
comparisons, and 29% of inside-inlet comparisons 
(Table 5). Within each habitat, mean overlap (all pe- 
riods) was significant in inside inlets for pink and 
chum salmon ( C A =0.66), inside passages for pink and 
chum salmon (C A =0.91), and chum and sockeye 
salmon ( C A =0.73), and outside waters for pink and 
sockeye salmon ( C A =0.83), chum and sockeye salmon 
( C A =0.68), and pink and chum salmon ( C A =0.67). 
Fullness and digestion 
Most salmon stomachs were evaluated to be at least 
half full (fullness index of 3); coho salmon stomachs 
were more full than those of other species (Table 6). 
Stomach fullness was always greater for fish from 
the inside waters than from outside waters; stom- 
achs of fish caught 0-37 km offshore were less full 
than those of fish caught >37 km offshore. Only 32 of 
2,210 (1.4%) stomachs sampled were empty: 72% in 
outside waters, 3% in coastal inlets, and 25% in in- 
side waters. The contents of most stomachs were 
“partly digested” (digestion index of 2). Pink, chum, 
and coho salmon from inside waters had stomach 
contents in an earlier stage of digestion than fish 
