Science Advisory Report  2011/044

Recovery potential assessment of redfish (Sebastes fasciatus and S. mentella) in the northwest Atlantic

Summary

• COSEWIC identified two designatable units (DU) for deepwater redfish (Sebastes mentella): Gulf of St. Lawrence/Laurencian Channel (Unit 1+2) and northern population (SA0+2+3KLNO). Due to a lack of data in the north, the areas considered here for the northern population are  2+3KLNO. These two DU’s match assessment units.
• In the case of Acadian redfish (Sebastes fasciatus), two designatable units were identified by COSEWIC: Bonne Bay and Atlantic populations. The latter included three assessment units for the purpose of this RPA: (1) Unit 3, (2) Unit 1+2, 3LNO, and (3) 2J3K. Bonne Bay was not examined here.
• Long term projections were undertaken for the five above assessment units using Bayesian surplus production models. While the Bayesian approach used in the assessment provides a mechanism to include uncertainty in estimating the current status of the population, managers and stakeholders are advised that not all sources of uncertainty have been addressed and the true uncertainty is even greater with the 20-year and 60-year forecasting. These projections assume the population will respond to the future environment as it did to the past environment, an assumption which may not hold due to the effects of cyclical or long-term climate change and/or other external processes.
• Projections are illustrated using the median and the 5th and 95th percentiles, as well as alternatives for model inputs and historic catch scenarios. The full range of uncertainty should be considered when interpreting these projections.
• DFO fishery decision making framework incorporating the Precautionary Approach states that 40% of BMSY is the default critical zone boundary. This is used here as a reconstruction target for the purpose of this RPA.

Deepwater redfish (Unit 1+2; Gulf of St. Lawrence/Laurentian Channel DU)

• The estimated biomass in 2010 is 19,000 t, with 90% probability intervals ranging from 11,000 t to 35,000 t, which is 2-6% of BMSY. With a catch level of 1000 t, the stock has a 46% chance of exceeding 40% of BMSY in three generations (60 years, i.e., in 2070).

Deepwater redfish (2+3KLNO; northern population DU)

• The estimated biomass in 2010 is 54,000 t, with 90% probability intervals ranging from 27,000 t to 118,000 t, which is at 7-29% of BMSY. With current catch levels of 3000 t, the stock has a 90% chance of exceeding 40% of BMSY by 2070.

Acadian redfish (Unit 3)

• The estimated biomass in 2010 is 2,254,000 t, with 90% probability intervals ranging from 325,000 t to 8,642,000 t, which is 150-230% of BMSY. With catch levels of 6000 t (slightly above current catch), the stock has a 99% chance of staying above 40% of BMSY by 2070.

Acadian redfish (Unit 1+2+3LNO)

• The estimated biomass in 2010 is 1,876,000 t, with 90% probability intervals ranging from 175,000 t to 8,778,000 t, which is 30-225% of BMSY. With catch levels of 9000 t (slightly above current catch), the stock has a 99% chance of staying above 40% of BMSY by 2070.

Acadian redfish (2GHJ3K)

• The estimated biomass in 2010 is 8,000 t, with 90% probability intervals ranging from 3,000 t to 23,000 t, which is 4-32% of BMSY. With no catch (about equivalent to current minimal catches), the stock has a 95% chance of exceeding 40% of BMSY by 2070.

Acadian redfish (Atlantic Canada DU)

• Population reconstructions of two of the three assessed areas within the DU suggest that there is a low probability that there has been a 30% decline in spawning stock abundance across the DU since the 1960s. Analyses suggest that most of the biomass resides in these two stock areas.

This Science Advisory Report is from the Fisheries and Oceans Canada, Canadian Science Advisory Secretariat, zonal advisory meeting of March 8-9, 2011 on Recovery Potential Assessment for Acadian redfish (S. fasciatus), Atlantic Canada Designatable Unit (DU) and Deepwater redfish (S. mentella), Northern and Gulf of St. Lawrence - Laurentian Channel DU). Additional publications from this process will be posted as they become available on the DFO Science Advisory Schedule.

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