Recruitment, pre-recruit survival and mortality in three Newfoundland cod stocks : northern (2J3KL), southern Grand Banks (3NO) and St. Pierre Bank (3Ps) / John T. Anderson and Eugene Colbourne. : Fs70-1/2000-116E-PDF

Indices of recruitment (R), spawning stock biomass (SSB) and pre-recruit survival (R/SSB) were examined and compared among three Newfoundland cod stocks: northern (2J3KL); Grand Banks (3NO); and St. Pierre Bank (3Ps). Survival generally has been lower during recent time periods compared to earlier time periods for similar levels of SSB. Survival was most strongly linked with warm temperature conditions for the Grand Banks cod stock during several pre-recruit stages and less weakly linked with the northern cod stock. There was no detectable relationship between environmental conditions and survival for the St. Pierre Bank cod stock. Estimates of mortality based on research vessel (RV) data demonstrated that mortality remained anomalously high for several years following the implementation of fishing moratoria for the northern and Grand Banks cod stocks. However, during the most recent time periods there has been a trend to decreasing mortality. Estimates of RV mortality for the St. Pierre Bank cod stock were highly variable and at times positive. It is difficult to distinguish environmental effects on survival and recruitment in the different cod stocks due to the changes in the physical environment that have varied throughout all time periods examined. Unraveling the perplexity between natural and anthropogenic factors on cod production will require new measures of the ecosystem and stock performance than are currently available for these stocks.

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