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Research Document - 2006/096

An assessment of the cod (Gadus morhua) stock in NAFO Subdivision 3Ps in October 2002

By J. Brattey, N.G. Cadigan, B.P. Healey, G.R. Lilly, E.F. Murphy, P.A. Shelton, D.E. Stansbury, J.-C. Mahé

Abstract

This document summarizes scientific information used to determine the status of the cod stock in NAFO Subdivision 3Ps off the south coast of Newfoundland. The current assessment provides revised estimates of the abundance of fish on 1 April 2002. Numbers-at-age are projected to 1 April 2003 by accounting for recorded catch up to the end of August 2002 and assumed catch for the remainder of the season to 31 March 2003. A deterministic medium term (3 yr) projection was also conducted, where numbers were projected to 31 March 2006 under a range of TAC options. Sources of information available for this assessment were: reported landings from commercial fisheries (1959-March 2002), oceanographic data, a time series (1973-2002) of abundance and biomass indices from Canadian winter/spring research vessel (RV) bottom-trawl surveys, an industry offshore bottom-trawl survey, inshore sentinel surveys (1995-2001), science logbooks from vessels <35ft (1997-2001), logbooks from vessels >35ft (1998-2001), and tagging studies (1997-2002). The fishery was still in progress at the time of the assessment and complete information on catch rates and age compositions from the 15,000 t TAC from 1 April 2002 - 31 March 2003 was not available. Several sequential population analyses (SPA) were carried out using reported commercial catches, calibrated with Canadian RV survey data, standardized annual catch rate-at-age indices for line-trawl and gillnet from the sentinel survey, and industry trawl survey data. In some SPA runs, the RV surveys were treated as two indices, one for the eastern and one for the western portion of the stock area, as described in Brattey et al. (2000). Spawner biomass estimates for 1 April 2003 from the various SPA formulations considered covered a wide range, and no single SPA run was considered to best represent absolute population size; however, estimated trends in spawner biomass were similar. All the SPA's indicated that spawner biomass increased during 1993-1998, declined during 1999 to 2001 and increased slightly in 2002. As observed in the previous assessment, the 1997 and 1998 year classes appear to be stronger than those produced during 1991-1996 and these year classes are now entering the fishery. The medium term (3 yr) projection indicated that the spawner biomass is expected to be higher in 2005 compared to 2002 under TAC options of 10,000 t, 15,000 t and 20,000 t. The medium term projection does not take into account any uncertainties, such as those associated with the stock composition of the commercial catch, misreported catches and assumptions about natural mortality. The trends in the 3 yr projection depend heavily on the accuracy of the estimates of the 1997-1999 year classes and their subsequent survival and recruitment to the fishery in 2003-2005.

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