Science Advisory Report 2021/001

Harvest allocation modelling for Baffin Bay Narwhal (Monodon monoceros) stocks

Summary

• Hunt management for Baffin Bay narwhal is based on summering stocks, but these stocks mix during migrations and in wintering areas, such that some stocks are harvested at multiple locations in both Canada and Greenland, and some locations harvest from multiple stocks.
• A two-step model was developed by the Canada/Greenland Joint Commission on the Management and Conservation of Narwhal and Beluga (JCNB) to allocate catches to different stocks (stock exchange model) and to analyze the impact of these catches on the dynamics of the eight narwhal stocks (population dynamics model). These models work together to define stock catch levels for all stocks. It is an improvement over previous models since it considers stocks shared between Canada and Greenland.
• The stock exchange model uses satellite telemetry data from Canada and Greenland, and expert opinion to determine the availability of narwhal stocks in the different hunting regions for each season.
• The population dynamics model combines available data on narwhal life-history, catches, and abundance from Greenland and Canada, but is limited by the available data for many stocks.
• The outputs of the population dynamics model for each stock should be evaluated using the precautionary approach framework developed for marine mammals in Canada.
• For stocks with sufficient input data, and where the population dynamics are captured by the model, the stock exchange and population dynamics models could be used to identify stock catch levels for Canadian communities based upon Canadian management objectives.
• If the level of stock knowledge is limited and the population dynamics not captured by the model, the Potential Biological Removal (PBR) for the stock should be estimated, and used with the stock exchange model to assign catches in relation to the availability of narwhals to the different hunting regions and seasons. This is consistent with the current approach for Data Poor species in Canada.
• We support continued development of this approach by JCNB with further consideration of how it can accommodate the Canadian Precautionary Approach Framework, particularly when the dynamics of a stock are not captured by the population dynamics model. Further sensitivity testing should also be conducted.

This Science Advisory Report is from the October 17–21, 2016 meeting on Baffin Bay Narwhal – Review of a harvest allocation model. Additional publications from this meeting will be posted on the Fisheries and Oceans Canada (DFO) Science Advisory Schedule as they become available.

Science Advisory Report 2021/001 (PDF, 324 KB)

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