Mortensen et a\ Growth of Oncorhynchus gorbuscha in relation to marine water temperature, secondary production, and survival 325 



1986Nearshore 

 Pink Salmon 83% 



H other 1% 

 Chum Salmon 16% 



1987 Nearshore 

 Pink Salmon 52% 



1987 Offshore 

 Capelin 32% 



Other 3% 

 Sockeye Salmon 2% 



Chum Salmon aWo 



1988 Nearshore 

 Pink Salmon 65% 



>_ Chum Salmon 8% 



Pink Salmon 10% 



Other 6% 



Chum Salmon 17% 



Herring 44% 



1988 Offshore 

 Capelin 46% 



Coho Salmon 1% 

 Other 3% 



Herring 14% 



Herring 28% 



1989 Nearshore 



Pink Salmon 13% 

 1989 Offshore 



Other 3% 



Coho Salmon 1% 



\,-;— Chinook Salmon 2% 

 rK$> Chum Salmon 4% 

 Sockeye Salmon 6% 



Pink Salmon 44% 



J 



\)y^ 



Other 2% 

 Herhng 1% 

 Coho Salmon 1% 



Pink Salmon 1% 

 Other 19% 

 Capelin 1% 



Chum Salmon 52% 



Figure 3 



Species composition of nearshore and ofTshore catches from Auke Bay, Alaska, 1986-89. 



by Coyle and Paul (1990), and we used their data 

 to develop these profiles. Generally the biomass of 

 zooplankton prey in the upper 40 and the upper 5 m 

 of the water column began rising in mid-April and 

 peaked in mid-June. However, in 1986 the biomass 

 of prey in the upper 5 m remained low throughout 

 the spring (Fig. 5). 



Littoral harpacticoids were sampled at Spuhn Island 

 in 1987, 1988, and 1989. Although the sampling method 

 changed between 1987 and 1988, an indication of the 

 dynamics of the hai-pacticoid population is achieved by 

 presenting indices of biomass as a proportion of the 

 highest value within each year In 1987, harpacticoid 

 copepod biomass was characterized by rapid fluctua- 

 tions but remained low, except for a peak in mid-May. 

 The biomass in 1988 again fluctuated rapidly, with 

 peaks in late April and early May. In 1989, the biomass 

 peaked in early April and again in early May. 



Diet 



Harpacticoid copepods and zooplankton (princi- 

 pally calanoid copepods, euphausid larvae, Oiko- 

 pleura sp., and fish eggs and larvae) were eaten 

 by the pink salmon juveniles captured near shore 

 (Fig. 6). Between April and May, pink salmon con- 

 sumed epibenthic prey more than pelagic prey; by 

 mid-May they switched to a predominately pelagic 

 diet. 



Pink salmon juveniles captured offshore in Auke 

 Bay exhibited a predominately pelagic diet, but 

 some epibenthic organisms were still present. This 

 finding may indicate that at times epibenthic prey 

 are transported to offshore areas by water currents, 

 or that the juvenile salmon optimize feeding by 

 moving between pelagic and epibenthic areas in 

 Auke Bay. 



