Benchmark workshop on selected elasmobranch stocks (WKBELASMO)

Type Article
Date 2023
Language English
Author(s) ICES
Contributor(s) Biseau Alain, Baulier LoicORCID, Lorance PascalORCID
Source ICES Scientific Reports/Rapports scientifiques du CIEM (2618-1371) (ICES), 2023 , Vol. 5 , N. 45 , P. 117pp.
DOI 10.17895/ices.pub.22760042
Abstract

A Benchmark Workshop for selected elasmobranch stocks (WKBELASMO) was convened to evaluate the appropriateness of data and methods to assess and provide short-term forecast for three rays stocks in the greater North Sea: thornback ray in the North Sea, Skagerrak, Kat-tegat, and eastern English Channel (rjc.27.3a47d), spotted ray in the North Sea, Skagerrak, Kattegat, and eastern English Channel (rjm.27.3a47d), and blonde ray in the southern North Sea and eastern English Channel (rjh.27.4c7d).

For thornback ray in the North Sea, Skagerrak, Kattegat, and eastern English Channel, a SPiCT assessment using removals since 1999 and two series of biomass indices (NS-IBTS-Q1 and FR-CGFS-Q4 combined, and NS-IBTS-Q3, BTS-ENG-Q3, BTS-BEL-Q3 combined) since 1989 was accepted. The workshop also agreed on the settings for the short-term forecast, allowing the stock to be assessed as category 2. This stock is estimated to be harvested well below Fmsy with a biomass just above BMSY. The 15th percentile of the removals at Fmsy is slightly below MSY and corresponds to landings higher (~3 times) than the previous landings advice.

For spotted ray in the North Sea, Skagerrak, Kattegat, and eastern English Channel, a SPiCT assessment using removals since 1999 and two series of biomass indices (NS-IBTS-Q1 and FR-CGFS-Q4 combined, and NS-IBTS-Q3, BTS-ENG-Q3, BTS-BEL-Q3 and BTS-NL-Q3 com-bined) since 1989 was accepted. The workshop also agreed on the settings for the short-term forecast, allowing the stock to be assessed as category 2. This stock is estimated to be harvest-ed well below Fmsy with a biomass above BMSY. The 15th percentile of the removals at Fmsy is just above MSY and corresponds to landings higher (~5 times) than the previous landings advice.

For blonde ray in the North Sea and eastern English Channel, a synthesis of stock ID infor-mation (tagging, surveys) was presented, indicating that the stock unit for blonde ray should cover Division 4.b. Therefore, WKBELASMO has considered a new stock unit (rjh.27.4bc7d) for the assessment. A SPiCT assessment using removals since 1999 and one series of biomass indices (NS-IBTS-Q1, Q3 and FR-CGFS-Q4 combined) since 1997 was accepted. The workshop also agreed on the settings for the short-term forecast, allowing the stock to be assessed as category 2. This stock is estimated to be harvested well below Fmsy with a biomass above BMSY, both with a relatively wide confidence interval. The 15th percentile of the removals at FMSY is above MSY and corresponds to landings largely higher (~6 times) than the previous advice.

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