The status of redfish (S. mentella and S. fasciatus) in Divisions 3LN at present and the likelihood its follow up in the near future (under the ongoing the Management Strategy or a status quo TAC scenario)

Abstract

There are two species of redfish in Divisions 3L and 3N, the deep-sea redfish (Sebastes mentella) and the Acadian redfish (Sebastes fasciatus) that have been commercially fished and reported collectively as redfish in fishery statistics. Both species, occurring on Div. 3LN and managed as a single stock, don’t belong to isolated local populations but, on the contrary, are part of a large Northwest Atlantic complex ranging from the Gulf of Maine to south of Baffin Island. The ASPIC assessment of this stock is based on the logistic form of a non-equilibrium surplus production model (Schaeffer, 1954; Prager, 1994), adjusted to a standardized catch rate series (Power, 1997) and to all stratified-random bottom trawl surveys conducted in various years and seasons in Div. 3L and Div. 3N from 1978 onwards. Both CPUE and surveys were used with all observations within each series. The 2018 assessment proceed on the threshold of the new 2014 approach, the main features of the previous input framework were kept, with MSY fixed at 1960-1985 average catch and the rest of the approved 2014 assessment framework updated. Despite its poor performance the 3L Spanish survey has been kept in the analysis due to its high correlation with the autumn 3LN Canadian survey, one of the two backbone series of the assessment. ASPIC results confirm a stable stock from the 1960’s to the first half of the 1980’s, sustaining an average yield of 21 000t. Stock declined with a sudden rise of the catch over the late 1980’s first half of the 1990’s, and started to gradually recover after catches fell to a residual level when the stock collapse. The maximum observed sustainable yield (MSY) of 21 000 t can be a long term sustainable yield if fishing mortality stands at 0.11/year, exploiting a correspondent Bmsy at 187 000 t. From assessment results there is a high probability (CL’s 80%) that the stock was at the beginning of 2018 above Bmsy, after crossing 2017 under a fishing mortality most likely below 34% Fmsy