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Research Document 1998/135

Assessement of Cod in Division 4X in 1998

By D. Clark

Abstract

Landings of cod from Division 4X have fluctuated since 1948 between 35,500t and the 1995 value of 8,800t. The quota for 1997 was increased to 13,000t, of which 11,500 were landed. The quota for 1998 is 9,300t, 6,500t of which had been landed by the beginning of October. Landings in both 1997 and the first half of 1998 were divided fairly evenly amongst the 1992, 1993 and 1994 year classes. The summer RV survey was higher than in 1997, and continues to indicate that the 1992 year class is particularly strong. The indices for all other ages, however, were below average. The ITQ survey was down substantially from 1997 in weight, but up in numbers, due to relatively good catches of the 1996 year-class.

Based on analyses which indicated either natural mortality (m) or survey catchability (q) may have increased in recent years, a variety of ADAPT formulations were explored. A standard formulation including the Research Vessel (RV) survey and the ITQ survey as indices estimates a 1999 4+ biomass of 36,000t, similar to 1998. A formulation which estimates natural mortality in the 1990's suggests that m may have increased to 0.4 from 0.2. This formulation estimates biomass higher, but F0.1 yield 20% lower than the standard. The most troubling results come from an analysis which suggests with some support from observations of fishing patterns, that survey catchability (q) may have increased in recent years. This analysis estimates age 4+ biomass for the beginning of 1999 of 20,000t, and estimates the F0.1 yield for 1999 as 4,300t.

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