Science Advisory Report  2016/047

Assessment of Redfish Stocks (Sebastes fasciatus and S. mentella) in Units 1 and 2 in 2015

Summary

• Both species of Redfish are distributed according to depth. In summer surveys, Sebastes fasciatus dominates in water depths of less than 300 m, along the slopes of channels and on banks, except in the Laurentian Fan where it is found in deeper waters. Sebastes mentella mostly predominates in the main channels at depths of over 300 m.
• From 2010 to 2015 (2014 and 2015 data are preliminary), average annual landings were 481 t in Unit 1 (annual 2000-tonne Total Allowable Catch (TAC). During the same period, average landings in Unit 2 were 3775 t (annual 8500-tonne TAC). Industry reported that market conditions and restrictions related to management measures had a major impact on taking all of the TAC.
• Since 2004, the performance index for the bottom trawl index fishery has been stable and comparable to the average in Unit 1. There is no performance index available for Unit 2.
• The abundance of juvenile Redfish, largely dominated by S. mentella, increased significantly in research surveys starting in 2013. In the Northern Gulf of St. Lawrence, the abundance of juvenile S. mentella and S. fasciatuswas 80 and 4 times higher, respectively, than their average abundance for 1993–2012. The first large cohort, from 2011, had a modal size of 17 cm in summer 2015.
• The strong 2011 and 2012 year-classes of S. mentella have the genetic signature of the adult population of Units 1 and 2. The 2011 cohort seems to be as abundant as the last large cohort of S. mentella (1980) that contributed significantly to the fishery and adult population in Units 1 and 2.
• S. fasciatus juveniles observed in recent surveys have the genetic signature of the adult population of Units 1 and 2. In comparison, the large cohorts of S. fasciatus from 1973, 1985, 1988 and 2003 observed at the juvenile stage in Unit 1 had the genetic signature of the population along the southern edge of the Grand Banks.
• Based on Redfish growth estimates and assuming the population is balanced, almost 50% of the fish in the 2011 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.
• The biomass of S. mentella and S. fasciatus spawning stocks estimated in research surveys fell in the early 1990s to its lowest observed values and has remained stable to date. The species in the Unit 2 survey could not be separated in 2014.
• Despite the potential for strong recruitment, the spawning stock biomass for both species is still in the critical zone, based on the 2011 precautionary approach.
• The Redfish stock outlook for Units 1 and 2 is very encouraging in the short term due to the large cohorts from 2011, 2012 and 2013. Large numbers of these fish will start recruiting to the fishery from 2018 to 2020, which could lead to a rapid increase in the spawning biomass. Until then, bycatch of Redfish under 22 cm should be minimized.
• The arrival of large Redfish cohorts will most likely have a significant impact on the ecosystem in the area, especially due to increased predation on small invertebrates and fish.
• Current harvesting has not led to an additional decrease in the spawning biomass since the last assessment. The outlook is good for recruitment to the fishery for 2018 and an increase in the 2020 mature biomass for both species. Currently, the main concern is to maximize the survival of this potential recruitment for the next five years.

This Science Advisory Report is from the March 3, 2016 meeting on the Assessment of Redfish stocks (Sebastes mentella and Sebastes fasciatus) in Units 1+2. Additional publications from this meeting will be posted on the Fisheries and Oceans Canada Science Advisory Schedule as they become available.

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