Research Document 1998/145

Assessment of the Winter Skate Fishery In Division 4VsW

By J.E. Simon, and K.T. Frank

Abstract

The skate fishery on the Scotian Shelf began in 1994 with landings of 2152t. Since then landings have been progressively lower reflecting reductions in the TAC. In 1997 the TAC was 1200t and landings amounted to 1048t. There are indications that the Div. 4VsW winter skate stock is currently overexploited.

Abundance of winter skate from the summer research vessel (RV) survey has been below the long-term mean for the last four years. The spring RV survey suggests a progressive shift in the distribution towards the edge of the shelf. Both the spring and summer surveys show a reduction in the number of winter skate greater than 85cm. This was reflected in the commercial landings where a marked decline in the percentage of winter skate greater than 90 cm has occurred. The industry/science surveys have also shown a decline in abundance of larger winter skate.

Previous maturity studies suggested that female winter skate reached 50% maturity between 65 to 70 cm. Further research showed that 50% maturity of female winter skate was closer to 75cm. Estimates of total mortality (Z) of winter skate were derived from an analysis of commercial catches using a growth model of Scotian Shelf winter skate to convert lengths to ages. The resulting Z’s were low in 1995 (0.35), reached a maximum in 1997 (0.76), and levelled off at 0.73 in 1998. In the previous assessments of this stock, no reduction in the length range of winter skate was evident. This situation no longer holds true: declines in the abundance of all sizes of skate especially the larger sizes have occurred, and the estimates of total mortality are very high. Therefore, it is considered that either the developmental fishery continue in 1999 at a very much reduced level or the skate fishery be closed entirely.

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