Research Document - 2005/070
An assessment of the cod (Gadus morhua) stock in NAFO Subdiv. 3Ps in October 2005
By Brattey, J., N.G. Cadigan, B.P. Healey, G.R. Lilly, E.F. Murphy, P.A. Shelton, and 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 estimates of the abundance of fish on 1 April 2005. Numbers-at-age are projected to 1 April 2006 by accounting for recorded catch up to the end of September 2005 and assumed catch for the remainder of the season to 31 March 2006. Principal sources of information available for this assessment were: reported landings from commercial fisheries (1959-March 2005), oceanographic data, a time series (1973-2005) of abundance and biomass indices from Canadian winter/spring research vessel (RV) bottom-trawl surveys, an industry offshore bottom-trawl survey (1997-2004), inshore sentinel surveys (1995-2004), science logbooks from vessels <35ft (1997-2004), industry logbooks for larger (>35 ft) vessels (1998-2004), and tagging studies (1997 onwards). 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 2005 – 31 March 2006 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 2005 from the various SPA formulations considered covered a wide range and as in previous assessments, no single SPA formulation was considered to best represent absolute population size. Catches of cod in the 2004 GEAC survey and the 2005 DFO RV survey, particularly for the 1997 and 1998 year classes, were much lower than the preceding years. Also, sentinel line-trawl catches of the 1997 and 1998 year classes were not markedly different from those of other recent cohorts at the same age. These findings had a considerable effect on the stock size estimates for the recent portion of the time period and stock size estimates for the past 4-6 years were revised downward. The age composition of the spawner biomass in 2002-2004 comprised a high proportion of females that are mature at young ages. The spawner biomass still has many older females that are thought to be more effective at producing eggs, but the stock has produced only two strong year classes (1997-1998) in the period 1990-2002. Several of the most recent year classes (1999-2002) are estimated to be weak and these will feed into the fishery in the coming years. Medium term deterministic projections were conducted to provide managers with general insights into possible stock trends over the next three years. At fixed annual catch options ranging from 7,500 to 15,000 t projections indicated that spawner biomass would decline by 1 April 2008, but still remain well above the recommended biological limit reference point (Brec). At a catch option of 5,000 t both formulations indicated a small increase (5-8%) in spawner biomass by 1 April 2008.
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