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Fishery Bulletin 98(2) 



Table 3 



Simple and partial (S/P) correlation coefficients between the instantaneous growth rate of juvenile pink salmon and average water 

 temperature; average harpacticoid biomass; average biomass of prey integrated from 40 m to surface; average biomass of prey in 

 the upper 5 m; and average biomass of harpacticoids + prey from the integrated water column. An * indicates a significant (P<0.05i 

 correlation. NA = not available. 



Year 



Average water 

 temperature 



Average harpacticoid 

 biomass 



Average integrated 

 column biomass 



Average biomass 

 in upper 5 m 



1986 

 1987 

 1988 

 1989 



0.696*70.696* 

 0.312*/0.312* 

 0.423*/0.047* 

 0.354*/0.354* 



NA 

 -0.201*/-0.017* 



0.337/0.000 

 -0.226*/-0.118* 



0.630*70.187* 

 0.193/0.248 

 0.505*/0.505* 

 0.057/0.003 



-0.187/-0.046 

 0.228/0.046 

 0.472/0.228 

 0.254/0.128* 



The 5-m depth zooplankton biomass was not signifi- 

 cantly related to growth in any year, whereas biomass 

 from the 40-m integrated water column was signifi- 

 cantly correlated in two of the four years. In 1988, the 

 biomass from the 40-m integrated water column was 

 the parameter most correlated with growth. 



The biomass of littoral harpacticoids was signifi- 

 cantly correlated with juvenile pink salmon growth 

 for two of the three years for which data were avail- 

 able. In both cases, the relationship was negative 

 (Table 3). Because feeding habits showed that the 

 pink salmon were switching between epibenthic and 

 zooplankton resources during the nearshore phase, 

 growth rate was also correlated with a combined 

 index of the biomass of littoral harpacticoids and the 

 40-m depth zooplankton. This combined index did 

 not fit the growth data as well as either water tem- 

 perature or zooplankton biomass considered inde- 

 pendently (Table 3). 



Growth and survival 



Mid- to late April emigrants had significantly higher 

 survival than the earliest emigrants within a year 

 (Table 1). Brood year is specified in the following 

 paragraphs unless otherwise noted. When emigra- 

 tion extended into May ( 1985 and 1988 brood years), 

 survival decreased by as much as 2% from the groups 

 released from mid- to late April. The last emigi-ants 

 from both the 1985 and 1988 broods, which had the 

 lowest growth rates of those years, also had signifi- 

 cantly lower survival than emigrants from mid- to 

 late April. 



The intra-annual survival of cwt juvenile pink 

 salmon exhibited a pattern similar to that for growth 

 rates. Regression of growth rate against survival 

 (as proportions within each year) indicated a highly 

 significant relationship (r2=0.65, P<0.003; Fig. 8). 

 Within-year survival generally increased with growth 

 rate. 



To examine the relation between growth and 

 survival interannually, growth rate (%bwd) was 

 regressed against survival rate of each release group. 

 Although survival appears to increase with increas- 

 ing growth rate, there was no relationship when all 

 years were considered (r'-=0.02, P>0.397). Fish from 

 the 1987 brood year (1988 emigrants, 1989 adults) 

 had a distinctly different growth versus survival 

 trajectory than fish for other years (Fig. 9). Data 

 from brood years 1985, 1986, and 1988 fitted well 

 (r~0.88, slope=1.82, P=0.001). Survivals of the 1987 

 brood were also significantly related to growth when 

 considered separately from the other years (r''^=0.93, 

 slope=0.40.P=0.001). 



Discussion 



Pink salmon juveniles were abundant in the near- 

 shore areas of Auke Bay in April and May; by the 

 end of May or early June, the fish had moved farther 

 offshore. This pattern is typical for juvenile pink 

 salmon, which generally follow shorelines during 

 their first weeks in the marine environment, then 

 migrate offshore as they grow (Heard, 1991; Celew- 

 ycz and Wertheimer, 1996a). We found water tem- 

 perature to be the main factor that determined the 

 growth rate of juvenile pink salmon during their 

 early marine existence. The metabolism and growth 

 offish are influenced extensively by water tempera- 

 ture and prey density (Brett et al., 1969; Weather- 

 ley and Gill, 1995). To attain maximum growth at 

 a particular temperature, prey concentrations must 

 be adequate (Bailey et al., 1975; Cooney et al., 1981). 

 In our study there were indications in early spring 

 of each year that the growth of juvenile pink salmon 

 was limited by abundance of prey. These early fish 

 enter the Auke Bay estuary before the spring zoo- 

 plankton bloom and rely on overwintering epiben- 

 thic prey organisms such as harpacticoid copepods. 



