Terms of Reference

Northern Gulf of St. Lawrence Cod (3Pn, 4RS) Assessment Framework

Regional Peer Review – Quebec Region

Part 1: April 21-23, 2021
Part 2: May 24-26, 2022
Virtual Meeting

Chairperson: Daniel Duplisea

Context

The assessment framework meeting will focus on the available data and methodology for estimating the population size and other indicators of the stock status of Atlantic cod in the northern Gulf of St. Lawrence (Subdivision 3Pn and NAFO Divisions 4R and 4S) (DFO 2019; Brassard et al. 2020).

For more than 30 years, the assessment of this stock has included a virtual population analysis (VPA). As of 2015, the ASP has been performed using the National Oceanic and Atmospheric Administration's Virtual Population Analysis, VPA / ADAPT (NOAA 2014). This program is a model for estimating the age structure of a population, it was developed from the model of Gavaris (1988), in which features from other versions of ADAPT were incorporated. This tool makes it possible to estimate several parameters of population dynamics as well as an indirect estimate of natural mortality (M). The pattern of residuals obtained for this stock suggests a lack of fit of the model.

A new model should allow; 1) estimate the variability of catches, and possibly include modeling censored catches; 2) estimate natural mortality; 3) have the ability to integrate multiple data sources, including tagging, to improve the estimation of vital stock parameters; 4) to provide the opportunity to make projections and ultimately to turn it into a custom model with fully integrated analyzes.

This assessment framework meeting will review the data available for the establishment of a new model (Part 1) and examine models of population dynamics of 3Pn, 4RS cod, in particular those that may incorporate unaccounted for catches and estimation of natural mortality (Part 2).

Part 1: Review of data available for modeling

Objectives

The objective of this first part is to examine the available data, and their statistical treatment, which would be used for the population estimation models including:

• Catches at age in the commercial fishery;
• Unaccounted catches;
• Catches at age and standardized indices for scientific surveys:
• DFO research vessel surveys,
• Mobile sentinel fisheries,
• Sentinel fisheries with gillnets, and
• Sentinel longline fisheries.

Part 2: Revision of the estimation models (at age) of the population

Objectives

Evaluate potential assessment models for possible use as the basis for providing science advice on cod in the northern Gulf. If a model is found to be appropriate for the assessment of 3Pn, 4RS cod, it would be used subsequently during the next stock assessment and could be used in the development of a recovery plan. Specifically, the framework meeting will address the following:

• Evaluate potential assessment models to determine if they provide a sufficient framework for providing scientific advice on the impact of exploitation on 3Pn, 4RS cod, in particular estimating the stock size (biomass and abundance), recruitment, fishing mortality, and potentially natural mortality of the population.
• Provide direction on projection methods for future catch options.
• Provide direction for an approach to estimating reference points for this stock.
• Discuss whether the assessment methodology has the potential to support quantitative evaluation of harvest control rules.
• Identify uncertainties and knowledge gaps.
• Identify priority short and medium-term research recommendations to improve data sources, assessment model formulation and estimation, and projection methods.

Expected Publications

• Proceedings
• Research document(s)

Expected Participation

• Fisheries and Oceans Canada (DFO) (Science and Fisheries Management Branches)
• Industry
• Academia
• Non-Governmental Organizations

References

• Brassard, C., Lussier, J-F., Benoît, H, Way, M. and Collier, F. 2020. The status of the northern Gulf of St. Lawrence (3Pn, 4RS) Atlantic cod (Gadus morhua) stock in 2018. DFO Can. Sci. Advis. Sec. Res. Doc. 2019/075. x + 117 p.
• Gavaris, S. 1988. An adaptive framework for the estimation of population size, CAFSAC Res. Doc. 1988/029.
• DFO. 2019. Assessment of the Northern Gulf of St. Lawrence (3Pn, 4RS) Atlantic Cod Stock in 2018. DFO Can. Sci. Advis. Sec. Sci. Advis. Rep. 2019/032.
• NOAA Fisheries Toolbox. 2014. Virtual Population Analysis Model (VPA/ADAPT), Version 3.4.5.