Science Advisory Report 2018/032

Assessment of Redfish Stocks (Sebastes mentella and S. fasciatus) in Units 1 and 2 in 2017

Summary

• During the management year 2017-2018 (preliminary data as of February 26^th 2018), Redfish landings reached 192 t in Unit 1 under an index fishery of 2,000 t. In Unit 2, 2,077 t of Redfish were landed on a total allowable catch (TAC) of 8,500 t. Landings were below the average annual reported landings from 2010 to 2016 of 499 t and 3,592 t in Units 1 and 2, respectively.
• Based on the main stakeholder input, management measures, market conditions, small Redfish size and moratorium impact limited fishing effort in the past few years in Unit 1. In Unit 2, market conditions represented the main factor limiting fishing effort.
• Bycatch landings in the directed Redfish fishery using mobile bottom gears represent 9% of Redfish landings in Unit 1 and 4% in Unit 2 from 2010 to 2017. The most common bycatch species in Unit 1 were Greenland Halibut, White Hake, and Atlantic Cod, whereas Atlantic Cod and Witch Flounder were the most common in Unit 2.
• Juvenile Redfish abundance from the 2011 to 2013 cohorts has increased dramatically in both DFO (Unit 1) and GEAC (Unit 2) research surveys. These cohorts are the most abundant ever observed in the research surveys. These individuals are largely dominated by S. mentella and show the genetic signature of the Units 1 and 2 adult population.
• In the summer 2017, the 2011 to 2013 Redfish cohorts’ modal size was 20 cm. If the anticipated growth of these cohorts continues, close to 50% of the individuals (59% biomass) of the 2011 cohort should be larger than 22 cm in 2018, the minimum commercial size. By 2020, 51% of the cohort (62% biomass) should be larger than 25 cm.
• According to research survey in Unit 1 in 2017, total minimum trawlable biomass was estimated to be 2,166,000 t for S. mentella, the highest value observed since 1984. Total biomass of S. fasciatus estimated to be 346,000 t is of the same order of magnitude as the highest value observed since 1984.
• In Unit 1, total minimum trawlable biomass of Redfish greater than 22 cm in length began to increase in 2017. It was estimated to be 349,000 t and 89,000 t for S. mentella and S. fasciatus, respectively. However, biomass of Redfish greater than 25 cm in length has not yet started to increase in the survey. By 2019, biomass of Redfish greater than 25 cm is expected to increase substantially.
• In Unit 2, total minimum trawlable biomass of Redfish greater than 22 cm in length has been stable since 2005. In 2016, it was estimated to be 86,000 t for S. mentella and 167,000 t for S. fasciatus. Biomass of Redfish greater than 25 cm in length remained stable and should increase substantially by 2019.
• Based on August bottom trawl research survey in Unit 1, both Redfish species are distributed according to depth. In addition, as they grow, larger Redfish appear to concentrate in Laurentian channel deeper areas. Currently, the strong recruitment of new cohorts means that the biomass of individuals smaller than 22 cm dominates at all depths.
• Redfish summer diet in Unit 1 varies according to fish size. Redfish less than 20 cm consume mostly zooplankton, and primarily shrimps (Northern Shrimp and Pink Glass Shrimp) when they are over 20 cm. When Redfish reach a size of 25 cm, they start consuming fish.
• The massive increase in Redfish has important repercussions for the ecosystem. Increasing predation among other things is contributing to the Northern Shrimp decline in the Estuary and Gulf of St. Lawrence.
• Prospects for Redfish stocks in Units 1 and 2 are extremely positive. The strong recruitment and biomass increase may allow higher catches of S. mentella in Unit 1 by 2018, while it is preferable to remain cautious for S. fasciatus.

This Science Advisory Report is from the March 14-15, 2018 Assessment of Redfish stocks (Sebastes mentella and Sebastes fasciatus) in Units 1 and 2. Additional publications from this meeting will be posted on the Fisheries and Oceans Canada (DFO) Science Advisory Schedule as they become available.

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