Research Document 2021/015
Unit 1 Redfish (Sebastes mentella and S. fasciatus) stock status in 2019 and updated information on population structure, biology, ecology, and current fishery closures
By Senay, C., Ouellette-Plante, J., Bourdages, H., Bermingham, T., Gauthier, J., Parent, G., Chabot, D., and Duplisea, D.
The Redfish fishery in the Gulf of St. Lawrence (Unit 1) targets two species, Sebastes mentella and S. fasciatus. Between the mid-1950s and 1993, the fishery was marked by three intense exploitation episodes that were closely linked to the recruitment of one or several strong year-classes. A sudden drop in landings and the absence of strong recruitment led to the establishment of a moratorium in 1995. Redfish fishing is still under moratorium in Unit 1 and an index fishery has been authorized since 1998. The total allowable catch (TAC) for this fishery has been 2,000 tonnes (t) per management year since 1999. Since 2018, an experimental fishery was established with an additional TAC of 2,500 t for 2018-2019 and 3,950 t for 2019-2020, which can be harvested all year round. The objectives of the experimental fishery were to target S. mentella, which is actually more abundant than S. fasciatus, to investigate ways to limit bycatch and the harvesting of undersize Redfish, and to better understand the spatio-temporal distribution of Redfish and bycatch species.
According to surveys conducted in the northern Gulf of St. Lawrence (nGSL), abundance and biomass indices for S. mentella and S. fasciatus were low and stable since the mid-1990s. Abundance of juvenile Redfish from the 2011 to 2013 cohorts has increased substantially in the Fisheries and Oceans Canada (DFO) research surveys. These cohorts are the most abundant ever observed in the nGSL.The minimum trawlable biomass of both species combined increased by 72% since the last biomass estimate in 2017, to reach 4.3 million t in 2019. These individuals are largely dominated by S. mentella with a genetic identity specific to Units 1 and 2. Unit 1 includes Divisions 4RST and from January to May Subdivisions 3Pn4Vn while Unit 2 includes Subdivisions 3Ps4Vs, Subdivisions 4Wfgj, and from June to December Subdivisions 3Pn4Vn. In the summer of 2019, the modal length of Redfish was 23 cm, slightly over the regulatory minimum size of 22 cm. If the anticipated growth of these cohorts continues, by 2020, 51% of the individuals of the 2011 cohort (62% biomass) should be larger than 25 cm.
In support of the Redfish stock assessments (S. mentella and S. fasciatus) of Units 1 and 2 in 2020, this document describes the data and methods used to analyse the status of the stocks found in Unit 1 and updates information on population structure, biology, ecology, and current fishery closures, which fall under the responsibility of the Science Branch of DFO Quebec Region.
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