FISHERY BULLETIN: VOL. 75, NO. 2 



TABLE 3. — Number of age-length observations, mean length (centimeters), and fitted length at each age for QCS and WVI stocks 



of Pacific Ocean perch. 



Data from the 120-, 160-, and 200-fm (219-, 293-, 

 and 366-m) sampling stations were combined by 

 weighting the mean length at each age by the 

 catch rate of Pacific ocean perch in that depth 

 stratum and arriving at an overall weighted mean 

 length for each age group (Table 3). The calcula- 

 tions were carried out separately for males and 

 females, and the resulting age-length data were 

 then fitted to the von Bertalanffy growth model 

 using the technique described previously. 



The results (Table 3) suggest that fish off 

 Washington grow somewhat slower than those in 

 Queen Charlotte Sound. In order for the results 

 from the two stocks to be strictly comparable, 

 however, several research cruises should have 

 been made in Queen Charlotte Sound during 

 September-December. The age-length data from 

 those cruises where availability was maximal 

 could then have been weighted in proportion to the 

 catch rate for each depth stratum, as was done for 

 the WVI stock. If fishermen effectively "sample" in 

 proportion to abundance, however, the results 

 from commercial fisheries data should agree well 

 with those from research cruises. 



FIGURE 12. — Changes in the size composition (sexes combined) 

 of Pacific ocean perch in commercial catches, 1956-73. N = 

 number of fish sampled. 



ANNUAL CHANGES IN SIZE AND 

 AGE COMPOSITION 



Size Composition 



Queen Charlotte Sound 



The Washington State Department of Fisheries 

 has obtained size composition data on landings 

 from Queen Charlotte Sound since 1956. Collec- 

 tion of such data was limited and sporadic prior to 



QUEEN CHARLOTTE SOUND 



WASHINGTON -VANCOUVER IS 



378 



