Research Document - 2000/140

Assessment of Winter Scate Fishery in Division 4VSW.

By Simon, J.E., Frank, K.T.

Abstract

The experimental skate fishery on the Scotian Shelf began in 1994 with a developmental period of 5 years. This was extended for one year to allow further analysis of the stock and better define the ability of skate to sustain a limited commercial fishery. In 1994, landings in the fishery were 2152t. Since then landings have been progressively lower reflecting reductions in the TAC. In 1999 the TAC was 600t and landings amounted to 623t.

The traffic light approach was used to summarize the several indicators of stock status that were available for this stock in a consistent and unified manner.

Abundance of the fishable component of the winter skate population has been below average for the last three years. Spawning stock biomass (RV Biomass 75+) has been consistently low, whereas the immature fishable biomass (RV Biomas 60-74) has been above average in four out of the last five years. Area occupied has been declining steadily since 1992 and is currently at an historical low (Areaoccupied). The March RV No. indicator has also been low in recent years. Indicators based on the directed fishery and industry/science surveys (CPUE, Industry Spring Biomass, Industry Fall Biomass) have been either stable or increasing but are only available since 1995.

Several indicators suggest that productivity has been low since 1995. Condition factor was high throughout the 1970s and has been in the low part of the range since the mid-1990's (RV Condition @70). Recent recruitment has also tended to be in the low part of the range (RV Biomass 36-59). Total mortality, estimated from the directed fishery, doubled from 1995 to 1997 and has remained at a stable high level (Commercial Z).

There are three indicators associated with mortality based on catch of skate in 4VsW versus RV biomass and biomass estimates from the spring and fall industry surveys. The fishing mortality indicator based on RV survey biomass estimates (RV Relative F) has been in the high part of the range during the past several years. Fishing mortality should not be allowed to increase. The indicators based on biomass estimates from the industry surveys (Industry Spring Relative F, Industry Fall Relative F) available since 1995 suggest a recent reduction in exploitation that is consistent with falling TAC's in that period

The initial developmental period of the experimental skate fishery has ended, but it is uncertain whether or not the fishery is having a negative impact. Due to the uncertainty in the winter skate stock dynamics it will be important to find ways, such as extending the developmental period, to continue to monitor the status of the stock.

Complete document (PDF, 28,589 KB)

Accessibility Notice

This document is available in PDF format. If the document is not accessible to you, please contact the Secretariat to obtain another appropriate format, such as regular print, large print, Braille or audio version.