FISHERY BULLETIN: VOL. 75, NO. 2 



TABLE 1. — Catches (in metric tons) of Pacific ocean perch by 

 different components of the international trawl fleet, 1966-72. 



research cruise data suggested that the two most 

 significant aggregations of S. alutus in the Van- 

 couver-Oregon region were found at lat. 48°-50°N 

 and lat. 46°-47°N. For all practical purposes then, 

 PMFC Statistical areas 3B and 3C offer a conve- 

 nient unit for studying the WVI stock. 



Data Employed 



Production records used in this study came from 

 the Washington State Department of Fisheries, 

 PMFC, INPFC, and from data furnished during 

 U.S.-U.S.S.R. scientific meetings. 



Landings by Washington trawlers made up a 

 relatively small proportion of the total interna- 

 tional landings during the 1966-72 study period, 

 but the quality of their production records is such 

 that the CPUE data from this fleet offer the best 

 available index of stock abundance. During 

 1966-72, the Washington landings made up 30% of 

 the total international catch from Queen Char- 

 lotte Sound, and 11% of the catch from the INPFC 

 Vancouver area (Table 1). Washington trawlers 

 accounted for the bulk of the North American 

 landings in these areas, however, landing 74% of 

 the Pacific ocean perch caught in Queen Charlotte 

 Sound and 82% of those from the INPFC Van- 

 couver area during 1966-72. 



Most of the data on age composition (as deter- 

 mined from otoliths), length composition, and 

 maturity were obtained by sampling the catches 

 landed by Washington trawlers and were collected 

 during 1967-72. Data from research vessel cruises 

 off Washington and Oregon were used to estimate 

 growth rates and fecundity-length relationships 

 for the WVI stock. 



MIGRATIONS AND AVAILABILITY 



General Features of the Life History 

 Extensive investigations into the life history of 



S. alutus have been carried out in the Bering Sea 

 (Paraketsov 1963; Pautov 1972; Chikuni 1975), 

 Gulf of Alaska (Lyubimova 1963, 1964, 1965; 

 Fadeev 1968; Chikuni 1975), and in the Queen 

 Charlotte Sound-Oregon region (Alverson and 

 Westrheim 1961; Westrheim 1970, 1973, 1975; 

 Gunderson 1971, 1974; Snytko 1971). These 

 studies have shown that there are several basic 

 similarities in the life history and biology of 

 Pacific ocean perch throughout its range. 



Age and growth analyses have shown that S. 

 alutus attain sexual maturity relatively late in 

 life (6-10 yr), grow slowly, and are long-lived. In 

 lightly fished stocks, S. alutus may reach an age of 

 30 yr (Alverson and Westrheim 1961; Paraketsov 

 1963). 



Sebastes alutus is an ovoviviparous species, 

 with three distinct phases in its reproductive cy- 

 cle. These are: mating (when spermatozoa are 

 transferred from males to females), fertilization 

 (when the ova are actually fertilized), and spawn- 

 ing (when the larvae are released). 



Well-defined bathymetric migrations occur in 

 all areas. Pacific ocean perch occupy relatively 

 shallow water during the summer feeding period, 

 then move to deep water during winter. The 

 depths inhabited seem to vary little throughout 

 the geographic range, despite significant differ- 

 ences in thermal conditions (Table 2). Mating oc- 

 curs shortly before or during migration from shal- 

 low water, but fertilization and embryo release do 

 not occur until the fish are in deep water. 



The larvae of S. alutus are pelagic and do not 

 settle into a demersal existence until 2-3 yr old. 

 Juveniles and young adults are confined to the 

 shallowest portions of the adult bathymetric 

 range, so that size and age composition vary 

 widely at different depths. 



Despite these common characteristics, there are 

 substantial geographic differences in life history 

 and migration patterns, even within the relatively 

 restricted region dealt with in this study. For this 

 reason, migration patterns, seasonal availability, 

 age composition, growth, age at maturity, and 



TABLE 2. — Depth and temperature characteristics of Pacific 

 ocean perch habitat. 



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