Research Document - 2003/031

The status of Thorny skate (Amblyraja radiata Donovan, 1808) in NAFO Divisions 3L, 3N, 3O and Subdivision 3Ps

By Kulka, D.W. and Miri, C.M.

Abstract

This evaluation of thorny skate (Amblyraja radiata)represents the fourth assessment of this relatively new fishery. The stock biomass indices, following a decline to their lowest historic level in the early 1990s have stabilized since the mid1990s. However, a change in research survey gear (in the fall of 1995) with different catch characteristics has created a discontinuity in the survey time series, thereby preventing a comparison between two periods: 1986 to 1994, and 1995 to date. The spring survey, previously used to estimate biomass and abundance, may not include a substantial portion of the population, and thus represents only the portion of the stock that occurs within the surveyed area. On average (1990-2002), fall survey estimates of biomass for the comparable area (NAFO Divisions 3LNO) were 41%. Analysis of lengths taken during research surveys have covered a consistent range since 1985, with main modes occurring at 15-32 cm and 65-83 cm in both spring and fall; the latter mode comprising mature skates. Since 1996, a single mode in the 30-60 cm range (a mix of mature and immature fish) has been observed. A recent increase in the proportion of larger skates in survey catches is noted. Since the mid1980s, Spain, Portugal, and Russia have prosecuted a directed fishery for skate (Raja sp.) outside Canada's 200- mile-limit on the Tail of the Grand Banks. However, Canada only established a limited directed fishery for skate on the southwestern Grand Banks and southern St. Pierre Bank after the decline of traditionally exploited groundfish resources. Prior to 1993, skates in Canadian waters were taken only as bycatch, most of which were discarded. Reported catches of all countries combined have averaged 12 191 t (23 948-7 626 t) since 1985. In 2002, the (preliminary) reported catch was 9 838 t (3 342 t for Canada; including discards). A comparison of skate distribution from research survey data with commercial grounds indicates that the Canadian fleet fishes about one third of the area where skate are greatly aggregated in the spring; primarily along the shelf edge where skate are largest. Non-Canadian fleets fish a separate area on the Tail of the Grand Banks (outside 200 miles) in the fall, catching smaller skates.

Complete document (PDF, 4737 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.