Research Document - 2005/018
An assessment of the cod (Gadus morhua) stock in NAFO Divisions 2J3KL in March 2005
By Lilly, G.R., J. Brattey, N.G. Cadigan, B.P. Healey, E.F. Murphy
Abstract
The directed commercial fishery for northern (2J3KL) cod was closed in 1992, reopened for small boats in the inshore alone during 1998-2002, and closed again in 2003. Landings in 2003 came mainly from a mass mortality of cod in Smith Sound during April, and landings in 2004 were mainly from by-catch during a winter (blackback) flounder fishery in summer. Because of differences in the dynamics of offshore and inshore populations of northern cod since the mid-1990s, information is provided for the offshore and inshore separately. Populations in the offshore remain broadly distributed at very low density. The indices of biomass from research bottom-trawl surveys in autumn (2J3KL) and spring (3L only) are at less than 2% of their levels during the 1980s. Recruitment in the offshore has been very low and total mortality has been very high since at least the mid-1990s. Few fish survive beyond age 5. In the inshore, catch rates in sentinel surveys (1995-2004) and commercial fisheries (1998-2002), as well as cod by-catch in fisheries targeted at other species (2003-2004), indicate that there has been relatively few cod in 2J and northern 3K since at least the mid-1990s. However, there have been high catch rates at various times and places in southern 3K and in 3L. Inshore catch-rate indices from linetrawl and gillnet sentinel surveys increased from 1995 to a peak in 1997 and 1998 respectively, declined by the early 2000s, and then increased during recent years to levels similar to those in 1995. For the purpose of this assessment, the inshore is subdivided into three areas: 1) a northern area (2J and northern 3K) that contains relatively few cod; 2) a central area (southern 3K and northern 3L) where most of the resident inshore fish are located; and 3) a southern area (southern 3L) that is, at present, largely dependent on cod that overwinter in inshore and offshore areas of 3Ps, move into southern 3L in the spring-summer and return to 3Ps in the autumn. A sequential population analysis (SPA) was conducted for the resident cod in the inshore central area. SPA estimates indicate that spawner biomass in this area increased from 10,000 t in 1995 to 22,000 t in 1998, declined during 1998-2002 (when there was a commercial fishery) to 7,000 t in 2003, and has subsequently increased to 13,000 t by the beginning of 2005. The estimate of age 4+ biomass at the beginning of 2005 is about 20,000 t. Fishing mortality increased from 1998 to a peak of about 35% in 2001 and 2002 and has subsequently declined to relatively low levels. Deterministic projections from 2005 to 2008 were conducted for the inshore central area under three annual catch options and three recruitment assumptions (low, medium, high). No such projections could be performed for the northern and southern areas. The inshore northern area appears to have very low densities of cod. Any catch option would likely impose high fishing mortality and further reduce stock size in this area. The inshore southern area is primarily dependent on seasonal immigration of fish, the magnitude of which cannot be predicted. Therefore, the effect of removals of various levels cannot be estimated. There is a risk that fishing in the inshore will impede recovery in the offshore. The spawner biomass of the stock as a whole remains far below any conservation limit reference level as generally applied through the precautionary approach to fisheries management. Although such a level has not been defined precisely for 2J3KL cod, it is anticipated to lie above 300,000 t.
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