hauling) and 129 min in the last set. Five to eight 

 minutes were required to set the nets, 12-20 min to 

 retrieve them. 



The study area was between lat. 54° 51. 5' and 

 54°57.9'N, long. 144°55.1' and 14511.3' W. On con- 

 secutive sets the gill nets were set 1.5-30 km apart 

 to reduce the possibility of one net influencing the 

 catch of another. Gill nets were set along a ship 

 course of 040°, except for the first two nets which 

 were set along 230°. In general, nets drifted 0.4-6.5 

 km northeastward during the sets. 



The vertical location in the gill net (upper, mid- 

 dle, and lower 2 m) and species of each captured 

 salmon were noted as the gill net was hauled 

 aboard. Fish were removed from the gill nets, 

 measured (fork length), and weighed with a beam 

 balance. Stomachs were removed, weighed to the 

 nearest gram with a beam balance, placed in a 

 tray, and cut open with scissors. The fullness of 

 cardiac and pyloric portions of the stomach was 

 estimated visually as a) empty, b) trace amounts 

 (few individual organisms with cumulative 

 weights of a gram or less), c) <Mj full, d) %-% full, 

 and e) full (rugae fully distended, stomach lining 

 thin and translucent). The degree of digestion was 

 estimated as a) fresh (prey intact, no obvious di- 

 gestion; fishes and squids with intact skin, 

 euphausiids translucent), b) partially digested 

 (fishes and squids identifiable, their skin, but not 

 flesh, largely digested; euphausiids opaque, ap- 

 pendages often absent), and c) digested (fishes 

 consisting of pieces of white flesh and vertebrae, 

 crustaceans in pieces, euphausiids sometimes 

 identifiable from fragments, especially their eyes). 



The percentage composition by volume of prey 

 taxa (euphausiids, amphipods, squids, fishes, 

 salps, pteropods, copepods) was visually estimated 

 for the cardiac and pyloric portions of each 

 stomach. Stratification of food taxa in the cardiac 

 portion was noted. Stomachs with diverse prey 

 taxa were flushed into a petri dish to facilitate 

 identification and estimation of prey composi- 

 tions. Samples of prey organisms were preserved 

 in Formalin 4 for verification and identification to 

 lower taxa. Stomachs with more than trace 

 amounts of food were then rinsed with water to 

 remove adhering food items, blotted, and re- 

 weighed to the nearest gram. 



The data were all obtained during the 2-h 

 periods after setting one gill net and hauling the 

 other. 



FISHERY BULLETIN: VOL. 82, NO. 2 



RESULTS 



Catches of Salmon 



A total of 107 sockeye, 68 pink, 51 coho, and 44 

 chum salmon and 6 steelhead trout were caught in 

 the 12 sets (Table 1). In general, the catches of each 

 species were highest between sunset (2113 h) and 

 sunrise (0420 h). This trend is clearly shown in 

 Table 1. Catches were several times larger during 

 night sets (1957-0627 h, sets 5-9) than sets that 

 fished during daylight periods. 



To illustrate diel trends in the vertical distribu- 

 tion of the salmon captured in the gill net, catches 

 of a species were combined (because of the low 

 numbers of individual species caught per set in 

 each vertical section of the net) for afternoon (sets 

 1-5), night (sets 6-8), and morning (sets 9-12). Fig- 

 ure 1 shows that the average percentage of all 

 species of salmon caught in the upper 2 m of the 

 gill net was highest at night. Moreover, as the 

 lower part of Figure 1 illustrates, peak catches of 

 all species combined occurred at night. 



Length-frequency distributions of the four 

 species of salmon from the catches at all sets com- 

 bined are shown in Figure 2. Fish of several ocean 



100 



SET NUMBER 

 I 234 56 789 10 II 12 



E 



CM 



tr 



Ld 



50 



or 



Ld 

 CD 



3 



O 



30 



20 



10 



"i i i i r 



"i i 1 r 



..<—>::•.. 





COHO 

 S ^'•- CHUM - 



1-5 



6-8 



9-12 



200 



TIME (hrs) 



- 1 Reference to trade names does not imply endorsement by the 

 National Marine Fisheries Service, NOAA. 



FIGURE 1. — Average percent of the total catch of the four species 

 of salmon caught in the upper 2 m of the gill net during afternoon 

 (sets 1-5), nighttime (sets 6-8), and morning hours (sets 9-12) 

 (upper panel), and the total number of all species of salmon 

 caught in the upper 2 m of the gill nets per set during the 24-h 

 period (lower panel). 



392 



