Science Advisory Report 2012/043
Advice on an allocation model for landed catches from Baffin Bay narwhal stocks
- A community landed catch allocation tool for Baffin Bay narwhals in Canadian waters was developed using an allocation model and risk analysis. It was structured around a spatial and temporal model of narwhal mixtures based on available information on narwhal seasonal distribution.
- Co-managers can explore the impact of allocation decisions by varying the amounts of landed catches by communities at both ends of the range of the four stocks and setting the proportions of the catch that are to be taken in the summer season. A structured optimization version and a simpler, iterative version of the allocation model are available.
- The allocation tool produces possible solutions that maximize community catches, particularly for those with large historic narwhal catches, while minimizing the risk of over-exploitation of any one stock. Four sets of scenarios were run to illustrate the types of results that can be produced.
- As the proportion of animals belonging to any particular stock in the non-summer community harvest is unknown, the model assumes that non-summer catches are taken in proportion to the size of each stock relative to the total number of animals in the mixture of stocks.
- Sensitivity analyses, run to test this assumption, resulted in a medium to high risk of exceeding Total Allowable Landed Catches (TALCs) for Admiralty Inlet, Eclipse Sound and East Baffin Island if the entire optimized catches are taken.
- In general, reducing the community allocations to 80-90% of the optimized catches significantly lowered the risk of exceeding a stock’s TALC.
This Science Advisory Report is from the May 6, 2011 meeting of the National Marine Mammal Peer Review Committee (NMMPRC): advice on community allocations for harvesting Baffin Bay Narwhals. Additional publications from this process will be posted as they become available on the Fisheries and Oceans Canada Science Advisory Schedule.
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