Research Document 2017/023

The status of the redfish stocks (Sebastes fasciatus and S. mentella) in Unit 1 (Gulf of St. Lawrence) in 2015

By Brassard, C., Bourdages, H., Duplisea, D., Gauthier, J., and Valentin, A.

Abstract

Redfish fishing in the Gulf of St. Lawrence (Unit 1) targets two species, Sebastes mentella and S. fasciatus. Between the mid-1950s and 1993, it was marked by three more intense exploitation episodes that were closely linked to recruitment of one or several strong year-classes. A sudden drop in landings and the absence of recruitment led to the imposition of a moratorium in 1995. Redfish fishing is still under a moratorium in Unit 1 and an index fishery has been authorized there since 1998. Total allowable catches have been 2,000 t per year since 2006.

According to surveys conducted in the Gulf of St. Lawrence, abundance and biomass indices for Sebastes fasciatus and S. mentella were low and stable since the mid-1990s. Since 2013, we have seen a significant increase in the abundance of small redfish in the surveys, which meant an increase in the abundance and biomass indices of the immature portion of redfish stocks in 2014 and 2015.
Genetic testing showed that these new strong redfish cohorts (2011, 2012 and 2013) are made up of the S. mentella species, whose genetic signature indicates that these cohorts belong to stock from the Gulf of St. Lawrence.

In recent years, we have seen a significant arrival of young specimens, in particular the 2011 cohort. This one is far more abundant than those seen in the past. Based on redfish growth estimates and assuming the population is balanced, 12% of the 2011 year-class would be more than 20 cm and nearly 50% of the fish in this cohort should be over 22 cm, the minimum harvest size, by 2018. By 2020, 51% of fish in the 2011 cohort should be over 25 cm, size at sexual maturity. There should also be large quantities of fish less than 25 cm from the 2011, 2012 and 2013 cohorts.

According to the reference points of the precautionary approach of 2011, both stocks have improved. However, the mature biomasses are still in the critical zone and this fact should not change over the course of the next three years.

In support of the redfish stock assessment survey (S. fasciatus and S. mentella) of Units 1 and 2 in 2015, this document describes the data and methods use for the stocks of Unit 1 under the responsibility of the Science Branch, Quebec Region of the Department of Fisheries and Oceans.

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