Research Document 2024/031

Potential Removals of Redfish (Sebastes mentella and S. fasciatus) in Unit 1

By Senay, C. and Duplisea, D.

Abstract

Redfish biomass in Unit 1 increased significantly in the past decade, as supported by the strong cohorts of 2011-2013. Since then, no important recruitment has been observed in the Gulf of St. Lawrence. The growth rate of the 2011-2013 cohorts has been low since 2021. The goal of the present document is to determine a range of potential removals for Unit 1 Redfish. To do so, 17 estimation methods of natural mortality rate based on temperature and/or life history traits were applied to Unit 1 Redfish stocks. To determine a range of potential removals consistent with a precautionary target using natural mortality in the estimation of fishing pressure, natural mortality rates were halved and multiplied by species-specific estimates of biomass for fish larger than 22 cm. Given that extreme values of natural mortality are the most unlikely, a realistic range of potential removals was determined between the 25^th and 75^th percentiles of these estimates, corresponding to 88 and 318 kt for S. mentella. S. mentella will very likely remain in the healthy zone in 2024 given this range of removals for the 2024-2025 fishing season. Considering the uncertainty over the status of the S. fasciatus stock in Unit 1 and the assumptions underlying the proposed approach, a range of potential removals could not be determined with certainty. The available evidence suggests that fishing deeper than 300 m would target the more abundant species, S. mentella, and reduce catches of undersized Redfish. Taking into account the low recruitment and growth observed in recent years, and even in the absence of fishing, Redfish biomass is expected to decrease in upcoming years, mainly due to natural mortality.

Research Document 2024/031 (PDF, 1,710 KB)

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