Research Document 1997/105
Status of 4X winter flounder, yellowtail flounder, and American plaice
By W.T. Stobo, G.M. Fowler, and S.J. Smith
Abstract
The management of Scotian Shelf flatfish (winter flounder, American plaice, yellowtail flounder and witch flounder) during the past several years has largely been based on an evaluation of the resilience of the stock complex to commercial catch levels. In 1994 the flatfish stocks were split into a 4VW and a 4X unit for management purposes, although there was not a strong biological basis for that partitioning. The current evaluation considers only winter flounder, American plaice and yellowtail flounder, although the TAC for 4X in the past always included witch flounder in the management complex. Comparison of distributions of winter flounder, American plaice and yellowtail flounder as derived from research vessels surveys conducted in the spring, summer and fall from 1978-84 suggest such a partition is appropriate for winter flounder, but does not provide as strong an indication of the appropriateness for the other two species. Partitioning the species into two management units is however, a more conservative approach and distributes the fishery across the shelf.
Stock status evaluations were based on research vessel survey abundance indices and size compositions and commercial catch rates. A new time series, the ITQ annual survey, was reviewed, but the time series was too short (3 years) to provide trend information.
Total landings of flatfish in 4X in 1996 was 2453t, a slight decrease from 1994. To mid-summer 1997, catches appeared to cover a similar geographic range. The proportion of the total landings reported as 'unspecified flounder' continues to be problematic with this fishery. Although that proportion has been decreasing since 1993 (>80%), it was >36% in 1996 and >25% to mid-summer 1997. Research vessel survey results for winter flounder, American plaice and yellowtail flounder suggest that all three populations are not undergoing serious declines in their abundance. While there has been a decline in the abundance of large fish and no signs of significant recruitment for any of the three species, for yellowtail, the RV surveys indicate a modest increase in abundance of fish over all length groups. This was in contrast to the decline observed in the commercial catch rate for yellowtail, which along with the other two flounder species, indicate a decline over the last few years.
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