Science Advisory Report 2020/051
Estimated Abundance and Total Allowable Landed Catch for the Eclipse Sound Narwhal Stock
- Aerial photographic surveys were flown by DFO in August 2016 to estimate the abundance of the Eclipse Sound narwhal stock. Sightings in the fiords were analysed using density surface modelling, while sightings in other strata were analysed using a strip transect design.
- On August 7, 9 and 10, 2016 all survey strata were covered. These data were analysed to provide a corrected total abundance estimate of 12,039 narwhals (Coefficient of Variation [CV] = 0.23).
- DFO also obtained data from visual surveys of the Eclipse Sound narwhal stock conducted by the environmental consulting company LGL Environmental Research Associates in 2013–2015 to evaluate the impact of shipping in narwhal distribution. These data were evaluated to assess their suitability for estimating abundance of Eclipse Sound narwhals.
- The LGL data were not considered suitable for estimating stock abundance for a number of reasons, including: 1) incomplete coverage of the survey area; 2) the high proportions of sightings missing perpendicular distances required to estimate narwhal abundance; and, 3) failure of fiord survey design to meet distance analysis assumptions.
- Harvest advice was generated using the Potential Biological Removal (PBR) method. Using the 2016 DFO survey results and a recovery factor of 0.75, the estimated PBR is 150 narwhals. The PBR estimate includes all sources of human-caused mortality, such as landings, struck and lost, non-reporting, and bycatch.
- The PBR value was adjusted to account for the current estimate of narwhal hunting losses (28%), resulting in a Total Allowable Landed Catch (TALC) of 117 narwhals for the Eclipse Sound stock.
This Science Advisory Report is from the February 26 – March 2, 2018 National Marine Mammal Peer Review meeting on Estimated abundance of the Eclipse Sound narwhal stock from the 2016 aerial photographic survey. Additional publications from this meeting will be posted on the Fisheries and Oceans Canada (DFO) Science Advisory Schedule as they become available.
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