PEARCY ET AL.: JUVENILE CHUM SALMON 



1984 



OlMAR 01APR 



JUL 



10 12 14 16 18 20 22 

 UPPER BAY TEMPERATURE 



24 



MAR OlAPR OlMAY OIJUN 01JUL 



10 12 14 15 18 20 22 24 

 UPPER BAY TEMPERATURE 



OlMAR OlAPR OlMAY OIJUN OIJUL 



p 100 



E 



R 80 



10 12 14 15 18 20 22 24 

 UPPER BAY TEMPERATURE 



Figure 5. — (Left) average temperatures occupied by chum salmon (triangles), average upper bay temper- 

 atures (squares) and maximum and minimum temperatures temperatures per collection period (solid lines), 

 and (Right) the percent of juvenile chum salmon collected in upper bay stations vs. average upper bay 

 temperatures (lines connect sequential sampling periods) for 1984, 1985, and 1986. Reference lines indicate 

 14°C. 



Residence Times - Loss Rates 



Population estimates based on the total catch 

 showed that the number of marks present, and 

 numbers of marked fish recaptured (Equation 

 (D), rapidly declined during 1984 and 1986 (Fig. 

 3 dashed lines; Table 2). The trends shown by 

 mark and recapture estimates and by median 

 seine haul catches were similar in 1984 (Fig. 3). 



Population estimates on 17 and 18 April 1984 and 

 3 and 4 May 1985 (1-2 days and 7-8 days after 

 release of all marked fish) were 30'7f and 57% 

 smaller than the actual numbers offish released, 

 suggesting rapid decline in numbers soon after 

 release. In 1986, however, the initial population 

 estimate was 55% larger than the number of fish 

 released a week earlier. Marked fish released in 

 April 1986 probably experienced higher mortal- 



561 



