Research Document - 2003/027

Assessment of 4VsW cod to 2002

By Fanning, L.P., Mohn, R.K. and MacEachern, W.J.

Abstract

The last complete assessment of 4VsW cod included data to 1997. This assessment includes new information from 1998 to 2002 as well as a new treatment of research survey data. There has been no commercial fishery since 1993 however the cod stock has continued to decline. The lack of catch makes sequential population analysis relatively uninformative and the research survey data has been used as the primary source of information on recent trends. The July RV data has been adjusted to account for estimated catchability at length by the survey gear however it is apparent that the existing estimates are only partially effective in this regard. The spring survey series was used to re-estimate the maturity schedule. The new estimates indicate that the age of 50% maturity has fallen to 3 years old. Mortality remains high in spite of the closed fishery and, while seals may be a factor for younger age groups, there is no clear explanation for the high adult mortality. The 1999 yearclass index is the largest since 1990 but is still below the long-term average. Since the closure of the fishery in 1993 the surplus production has averaged -2000 t/yr, i.e. the SSB has been declining steadily for 10 years without fishing. The population biomass has declined to very low levels and the SSB is currently estimated to be less than 5,000 t, a 97% decline from the peak in 1984.  Biological reference points for spawning stock biomass limits were derived for three methods of stock size estimation. All three methods estimate the current SSB to be below the lowest applicable reference point value. The bottom line is that, in spite of 10 years with virtually no fishery and a return to normal environmental conditions, the cod in 4VsW are continuing to decline. There is no evidence that this will change  any time soon.

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