Research Document - 2004/083

Assessment of the cod (Gadus morhua) stock in NAFO Subdivision 3Ps in October 2004

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

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 2004. Numbers-at-age are projected to 1 April 2005 by accounting for recorded catch up to the end of September 2004 and assumed catch for the remainder of the season to 31 March 2005. Sources of information available for this assessment were: reported landings from commercial fisheries (1959 - March 2004), oceanographic data, a time series (1973-2004) of abundance and biomass indices from Canadian winter/spring research vessel (RV) bottom-trawl surveys, an industry offshore bottom-trawl survey (1997-2003), inshore sentinel surveys (1995-2003), science logbooks from vessels <35ft (1997-2003), and tagging studies (1997-2004). 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 2004 – 31 March 2005 was not available. Several sequential population analyses (SPA) were carried out using reported commercial catches, calibrated with various indices. Spawner biomass estimates for 1 April 2004 from the various SPA formulations considered covered a wide range (88,000 to 130,000 t), and as in previous assessments, no single SPA formulation was considered to best represent absolute population size. However, estimated trends in 3+ population numbers and spawner biomass were generally consistent among SPA's; the SPA's indicated 3+ population numbers increased during 1998-2000, but have tended to decline during 2001-2004. Spawner biomass increased during 1993-1998, declined during 1999 to 2001, and increased during 2001-2003 reaching the highest level observed since 1977. The age composition of the current spawner biomass is unusual and in 2002-2004 comprised a high proportion of females that are mature at young ages. Recruitment in 3Ps has shown a long term decline, with a succession of relatively weak year classes produced during the mid-1990s. The year classes produced in 1997 and 1998 are estimated to be relatively strong, but these are followed by weak year classes (2000 and 2001). Medium term (3 yr) deterministic projections were conducted to provide managers with general insights into possible stock trends over the next three years. At a fixed annual TAC of 10,000, 15,000 or 20,000 t the projections suggested that spawner biomass would decline by 1 April 2007, but still remain well above the recommended biological limit reference point (B_rec). At a TAC option of 5,000 t the projections suggested spawner biomass would show a small increase by 1 April 2007. Two strong year classes (1997-1998) are well represented in the 2003 catch and these are likely to dominate the fishery in the coming years. However, these are followed by weak recruitment and current catch levels are unlikely to be sustainable in the long-term unless recruitment improves.

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