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Research Document - 2009/037

Assessment of the southern Gulf of St. Lawrence cod stock, February 2009

By D.P. Swain, L. Savoie, T. Hurlbut, T. Surette, and D. Daigle

Abstract

The cod (Gadus morhua) stock of the southern Gulf of St. Lawrence (NAFO 4T and 4Vn (November to April)) has not recovered since it collapsed in the early 1990s. In 2008, the TAC for the stock was 2,000 t, the same level as in 2007. Estimated landings from all sources amounted to 1,648 t up to December 31, 2008, including 121 t landed from 4Vn mainly in January-February 2008. About 70% of the landings were of fish 6 to 8 years old. In a telephone survey of fishermen active in 2008, the most common opinion was that the abundance of the stock in 2008 was about the same as in 2007. The abundance indices for this stock indicate that it is at a record low level. The indices of abundance and biomass from the September bottom-trawl survey of the southern Gulf, conducted since 1971, have been at a record-low level since 2005. The abundance index from the sentinel trawl survey, conducted since 2003, declined in 2005 and has remained below the 2003-2004 level since then. Catch rates in the sentinel longline survey, conducted since 1995, declined to a record low level in 2005 and have declined further each year since then. Based on the survey data, the total mortality rate (Z) was estimated to be 0.57 during the fishing moratorium in 1994-1997, indicating that natural mortality (M) was 0.4 or higher, well above the estimates of 0.2 or less in studies using data from the 1970s and earlier. Estimated Z increased to higher levels in the 2000s, indicating further increases in M in recent years. Population models indicate that abundance and biomass have been steadily declining for several years. Spawning stock biomass (SSB) is estimated to be 28,000 t at the beginning of 2009, the lowest level observed in the 60-year record. SSB is estimated to now be about one-third of the 2000 level, and is well below the limit reference point for the stock (80,000 t or higher). Recent year-classes are estimated to be extremely weak, the lowest on record. SSB is almost certain to decline further in 2009, even with no fishery. With no catch in 2009, there is a 94% probability of a decline of 5% or more, and a 54% probability of a decline of 10% or more. The stock currently has a production deficit, mainly due to elevated natural mortality. The population is expected to continue to decline even in the absence of fishing unless productivity improves. Given the status of the stock relative to the limit reference point, the application of the precautionary approach would require catches in 2009 to be at the lowest level possible. While elevated natural mortality is the main reason for the current decline of this stock, actions to preserve the remaining spawning biomass would increase the chance for the stock to recover if productivity improves.

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