Research Document 1998/19
An assessment of the cod stock in NAFO Subdivision 3Ps
By D.E. Stansbury, P.A. Shelton, J. Brattey, G. R. Lilly, G. Winters, E. F. Murphy, M. B Davis, and D.W. Kulka
Abstract
The current assessment attempts to determine the status of the stock on 1 January 1997 and evaluates alternative TAC options for 1998. Separate analyses are carried out on the inshore and offshore. For the offshore an ADAPT is calibrated with Canadian and French research vessel trawl indices. In addition a SPA based on quasi-likelihood theory is applied to the same indices. In a final analysis on offshore catch data, separate catchabilities were estimated for Canadian surveys carried out in winter and spring. No SPA was attempted on the inshore catch data. However, an estimate of the abundance of cod in Placentia Bay from an in-season tagging experiment was extrapolated across the whole of the inshore area based on commercial gillnet catch rates and relative area. From an offshore spawner biomass estimate of about 100,000 t and an inshore extrapolation from the tagging study of about 115,000 t, a total spawner biomass for 1 January 1998 of about 215,000 t was obtained (subsequently revised to 183,000 t because of a revised inshore estimate of 82,765 t). This would equate to an F0.1 TAC of about 40,000 t. In the absence of a full risk analysis for both the inshore and the offshore, it was considered that exploitation not exceeding about 50% of the F0.1 level would provide an adequate margin of safety for this stock and be in keeping with the precautionary approach, indicating a TAC of about 20,000 t. It was noted however that for a 10,000 t offshore quota in 1998 there is about a 30% probability that the offshore spawner biomass would not increase from 1998 to 1999.
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