Terms of Reference

Assessment Framework for Unit 1+2 Deepwater (Sebastes mentella) and Acadian Redfish (Sebastes fasciatus) and for Unit 3 Acadian Redfish

Zonal Peer Review – Quebec, Maritimes and Newfoundland and Labrador Regions

December 8-11, 2015
Mont-Joli (Québec) 

Chairperson: Ghislain Chouinard

Part 1: Data Framework review in Unit 3 for Acadian Redfish (Sebastes fasciatus) – December 8, 2015

Context

Redfish is a long-lived, cold water groundfish species found in both the Atlantic and Pacific oceans. In the Northwest Atlantic, two main redfish species exist: Acadian Redfish (Sebastes fasciatus) and Deepwater Redfish (Sebastes mentella). Acadian Redfish, which is found from the Gulf of Maine to the Labrador Sea, is considered two designated units (DU): Atlantic population and Bonne Bay population. Redfish in Unit 3 constitute that portion of the Atlantic population DU residing on the central and western portions of the Scotian Shelf. In April 2010, both redfish species were assessed by the Committee on the Status of Endangered Wildlife in Canada (COSEWIC) as Threatened and Special Concern, respectively, due to evidence of declines in some stocks. In March 2011, Fisheries and Oceans Canada (DFO) conducted a Recovery Potential Assessment, concluding that Redfish Unit 3 biomass in 2010 was approximately 2,254,000 tonnes, with the stock having a 99% chance of staying above 40% of Biomass at Maximum Sustainable Yield (BMSY) by 2070 based on catch levels at the time (DFO 2011). In October 2011, DFO conducted a second assessment on Redfish with the key objective of defining limit reference points for Atlantic redfish stocks (DFO 2012). It was concluded that Redfish Unit 3 biomass was well above its limit reference point, considered healthy, and exhibiting increased growth. The intent of this science framework meeting is to review data inputs in support of evaluating the Redfish Unit 3 stock. It is intended that a follow-up science framework and assessment meeting would occur in 2016-2017, which would model the stock and assess its current status.

Objectives

• Review and evaluate biological and fishery information on Unit 3 Redfish stock status and characterize the uncertainty of the results.  In particular, provide survey and catch trend information on distribution, biomass, length composition, age composition and condition, highlighting any trends over the long-term (length of assessment) and most recent period (5 years).
• Report on any spatial/temporal component to Unit 3 Redfish age structure.
• Report on frequency and distribution of Observer coverage in the Unit 3 Redfish fishery, identifying adequacy of coverage.
• Report on the bycatch of non-target species in the Unit 3 Redfish fishery and identify any notable changes in the occurrence of these species relative to previous years. In addition, report on Unit 3 Redfish bycatch captured in other fisheries.

Part 2: Assessment Framework for Unit 1+2 Deepwater (Sebastes mentella) and Acadian redfish (Sebastes fasciatus) – December 9-11, 2015

Context

Unit 1 + 2 Redfish (Sebastes spp.) are distributed in the Gulf of St. Lawrence as well as the Laurentian Channel and Laurentian Fan areas off southern Newfoundland and Northeastern Nova Scotia. Both S. fasciatus and S. mentella in these areas are considered to be in a low relative biomass state and a 2012 peer review meeting showed them to be in the precautionary approach critical zone at 44% and 8% of their biomass limit reference points, respectively. These long lived species have proven difficult to age and age based modelling approaches have not as yet been applied successfully to either of these stocks. Reference point estimates from these stocks are the result of fitting a state-space Bayesian implementation of the Schafer surplus production model, BSP (McAllister & Duplisea 2011, 2012). BSP does not make use of the length composition data available for these stocks and it was agreed at the 2012 reference point meeting that further approaches would be considered that could include these data in hopes of more accurately modelling population dynamics and improving management advice. Furthermore, both of these species display spasmodic recruitment characteristics and approaches which can more explicitly model recruitment should be advantageous.

It has become apparent since the last evaluation in March 2012 (DFO 2012), that the 2011 and 2012 year classes of S. fasciatus and especially S. mentella are very strong and S. fasciatus in the south-eastern part of Unit 2 may be more closely related to Redfish in 3LNO than to Unit 1 and the western part of Unit 2. A new assessment should therefore consider how to both protect these year classes as pre-recruits, to avoid compromising yield per recruit potential by harvesting too heavily at relatively younger/smaller ages, and to enhance the level of the spawning stock biomass potential for the purpose of facilitating future recruitment prospects.

Objectives

Review of indices of abundance, fishery data and biological data for both species:

• Review indices of abundance in DFO research vessel surveys, industry surveys and commercial index fisheries
• Review fishery data inputs including spatial and temporal distribution, size composition
• Review comparative fishing experiments and conversion methods for GEAC-Teleost April 2015

Assessment of Model(s) to Monitor Stock Status and Productivity for both species:

• Review plausible method(s) to estimate the current status, specifically, stock size, size composition and fishing mortality, as the basis to provide advice to managers outlining their scope for use, strengths and weaknesses and how advice can be provided from these methods.
• Determine methodology to characterize stock productivity including reference points for fishing mortality and spawning stock biomass and past, current and projected states relative to these points for each species.
• Determine plausible forecasting method(s) for providing advice on a range of harvest levels associated with various fishing strategies including risk of being above or falling below biological reference points at different time frames (e.g. 5 years, 10 years, 25 years). Discuss the reliability of projections over different time periods.
• Discuss the potential and likely contribution of the 2011 and 2012 year classes to the fishery and to reproductive biomass over the cohorts' life spans and strategies for optimising their utilization and contribution towards future recruitment.

Minimal set of diagnostics, sensitivities and justifications expected from model fitting approaches:

• Residuals from survey abundance
• Residuals from composition data
• Retrospective analysis going back at least 10 years
• Sensitivity to main productivity parameters of stock
• Sensitivity to data weighting assumptions
• Sensitivity to fishery and survey selectivity assumptions particularly the proportion of biomass generated from selectivity assumptions if selectivity is considered domed or non-sigmoidal
• For Bayesian assessments, sensitivity to bounds/priors including a clear statement when a posterior median parameter estimate is in improbable areas of the prior or at the bounds
• Justification for all parameters, especially model-scaling parameters (e.g. K and/or q) of model which strongly impact reference point estimates and sustainability of catch scenarios
• Selection of key run and justification. Any sensitivity runs identified as such with its particular purpose stated including a statement of plausibility relative to key run (quantitative or qualitative)
• Sensitivity to catch, especially in the early part of the time series where catches are less certain and likely underestimated

Establish a schedule for future processes and interim year advice:

• Establish a full assessment review period as well as interim-year advice utilizing the guidance provided by the March 2015 document from TESA
• Provide guidance on inter-framework review activities, including the procedure and frequency of providing fisheries management advice and events that would trigger an earlier-than-scheduled assessment
• Discuss data availability and resources required for dealing with potential stock structure issues that would be important for any future peer review process on stock structure

Establish requirements for model output for the assessment meeting in 2016. Minimally:

• Fittings expected
• Diagnostics expected
• Projections expected

Other information relevant to the physical and ecological context of redfish in the Unit 1+2 stock area

Transparency

In the interest enabling full evaluation and reproducibility of approaches explored as well as the longer term goal of continuity of the assessment methodology, contributors are expected to:

• make all data publically available in electronic format upon request
• provide a working document with publication expected as a CSAS research document
• make available all model code and inputs for the meeting and afterwards, upon request in electronic format and ideally should also be provided as a research document appendix. Reasonable conditions of use to protect intellectual property are acceptable as long as they do not compromise scrutiny of methods and/or continuity of the assessment of Unit 1+2 redfish. Non-DFO model code can be provided on the condition that it not be circulated for purposes other than peer review and further assessment of this stock and will be utilized only for these stocks by meeting participants or their designates.

Expected Publications

• CSAS Proceeding
• CSAS Research Document(s)*

*Drafts of documents should be provided at least one week before the scheduled start of the meeting

Participation

• Fisheries and Oceans Canada (DFO) (Science and Ecosystems and Fisheries Management sectors)
• Aboriginal Communities/Organizations
• Provincial Representatives (NS, NB, NL, QC)
• Fishing Industry
• Non-governmental Organizations
• Academics and Other External Experts

References

DFO. 2011. Recovery potential assessment of redfish (Sebastes fasciatus and S. mentella) in the northwest Atlantic. DFO Can. Sci. Advis. Sec. Sci. Advis. Rep. 2011/044. (Erratum: June 2013).

DFO. 2012. Reference points for redfish (Sebastes mentella and Sebastes fasciatus) in the northwest Atlantic. DFO Can. Sci. Advis. Sec. Sci. Advis. Rep. 2012/004. (Erratum: June 2013).

McAllister, M. and Duplisea, D.E. 2011. Production model fitting and projection for Atlantic redfish (Sebastes fasciatus and Sebastes mentella) to assess recovery potential and allowable harm. DFO Can. Sci. Advis. Sec. Res. Doc.2011/057 vi + 75 p.

McAllister, M. and Duplisea, D.E. 2012. Production model fitting and projection for Acadian redfish (Sebastes fasciatus) in Units 1 and 2. DFO Can. Sci. Advis. Sec. Res. Doc.2012/103 iii + 34 p.