Jaenicke and Celewycz: Marine distribution and size of juvenile Pacific salmon 



than pink salmon in each sampling 

 period and were significantly larger 

 than chum salmon in 1984. In both 

 July and August 1984, pink and chum 

 salmon did not differ in size, and in 

 August 1983 chum and sockeye salmon 

 did not differ in size. 



Discussion 



Fish distribution 



Each species of juvenile salmon was 

 highly aggregated rather than dis- 

 persed randomly. In contrast to our 

 results, Hartt and Dell (1986) seldom 

 observed zero catches and therefore 

 concluded that juvenile salmon in the 

 ocean were evenly dispersed. Several 

 differences between our study and 

 theirs may explain the differing conclu- 

 sions. Seines used by Hartt and Dell 

 were longer than ours and were held 

 open for 30 minutes instead of 3-5 

 minutes. Our catches may be more of 

 a point estimate or instantaneous pic- 

 ture of fish abundance, whereas their 

 seines were more likely to intercept at 

 least part of a juvenile salmon school. 

 More importantly, Hartt and Dell did 

 not separate juvenile salmon by species 

 when considering their distribution. 



Species associations 



Juvenile pink, chum 



(4) 



(3) 



(5) (4) 



(2) 



L I  1 1 1 , I  i  



65 



74 



and sockeye 

 salmon were generally closely associ- 

 ated with each other in their distribu- 

 tion. The distribution of these species, 

 however, differed from the distribution 

 of coho salmon, a result consistent with the conclu- 

 sions of Hartt and Dell (1986) and Waddell et al. 

 (1989). In the inside waters and outer coast inlets, 

 we found that pink, chum, and sockeye salmon had 

 a lower FO than coho salmon, indicating that those 

 species were more highly aggregated and sparsely 

 distributed than coho salmon. Paszkowski and Olla 

 ( 1985) found that behavior patterns of juvenile coho 

 salmon promoted dispersion, not aggregation. The 

 utilization of similar areas in this study by juvenile 

 pink, chum, and sockeye salmon correlates with the 

 high degree of diet overlap observed between these 

 species; in contrast, juvenile coho salmon showed 



28 37 46 



Distance offshore (km) 



Figure 4 



Abundance of juvenile salmonids (pink, Oncorhynchus gorbuscha; 

 chum, O. keta; sockeye, O. nerka; coho, O. kisutch ) by distance off- 

 shore in the outside waters of Southeast Alaska in August 1984 

 (36 sets). Abundance is shown in terms of (A) catch per unit of 

 effort (CPUE), (B) the smoothed natural logarithm of CPUE. and 

 (C) the smoothed frequency of occurrence of the catches; number 

 of sets is in parentheses. All distances are rounded to the nearest 

 kilometer. Actual distance between intervals (except the first) 

 is 9.3 km. 



little diet overlap with the other species. 1 Healey 

 ( 1991) reported that juvenile pink, chum, and sockeye 

 salmon in British Columbia were also aggregated. 



Migration 



The migration of juvenile salmon off Southeast Alaska 

 (Hartt and Dell, 1986) consists of two components: 1) 

 fish migrating north from the Pacific Northwest and 

 British Columbia, and 2) fish from Southeast Alaska 

 migrating from inside to outside waters. 



J. H. Landingham, Auke Bay Laboratory. 11305 Glacier High- 

 way, Juneau, AK 99801-8626, pens, commun. Jan. 1992. 



