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Stock Identification, Abundance, Hunt Sustainability, and Tracking and Movements of Canadian Narwhal

Zonal Peer Review – Central and Arctic and National Capital regions

10-11 May 2012
Winnipeg, Manitoba and teleconference/WebEx

Chairperson: Don Bowen

Context

The two narwhal populations in Canada (Northern Hudson Bay (NHB) and Baffin Bay) are comprised of five stocks which are named for the locations of their known summering aggregations: Northern Hudson Bay, Somerset Island, Admiralty Inlet, Eclipse Sound and East Baffin Island. DFO has recommended that narwhal be managed according to summering aggregations. The purpose of this meeting is to peer review the latest scientific findings on stock identification, abundance, hunt sustainability, and tracking and movements for the five stocks of narwhal in Canadian waters. Determining the sustainability of the narwhal hunt is important for making decisions related to the management of narwhal, such as determining harvest levels, Integrated Fisheries Management planning and issuance of non-detriment findings (NDF) under the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES).

Canadian narwhal stock identification

Identification of stock structure is needed to facilitate management of narwhal. Various methods are being investigated to see how well they can be used to define stock identity in narwhals. Using chemical tracers of narwhal feeding ecology (i.e., carbon and nitrogen isotope ratios) can help delineate summering stocks and their relative contributions to Inuit harvests. Stable isotope analysis of narwhal samples, collected from Canada (NHB and Baffin Bay populations) and Greenland, has been conducted.

Northern Hudson Bay narwhal abundance and hunt sustainability

The Northern Hudson Bay narwhal population is an important regional subsistence fishery. The population was previously assessed from aerial photographic surveys of summer aggregations in 1984, 2000 and 2008. The August 2008 survey was intended to provide information necessary for a full assessment of the population. However, it provided only a partial estimate owing to camera malfunction, sea ice conditions and poor weather conditions. That partial estimate of population size was only a fraction of the 2000 estimate.

After the 2008 survey results were reviewed, a stock-dynamic model using Bayesian methods was run to assess whether the low estimate derived from the 2008 survey might be explained by a decrease in stock size due in part or in whole to either recent increases in reported takes or by increased predation, and to estimate a sustainable harvest from the population. Based on the analysis it was concluded that it would be difficult to estimate stock trend and future sustainable catches for the NHB narwhal population using the available data. It was recommended that a new survey be conducted as soon as possible to inform the population modelling and advice.

Central and Arctic Resource Management requested a current abundance estimate and sustainable harvest level recommendation for the Northern Hudson Bay narwhal population. A new aerial survey was flown in August 2011 and the data analyzed. A stock-dynamic model was used to evaluate the most recent survey in light of previous surveys and review the sustainability of hunting for different catch scenarios taking into account the current and predicted impact of killer whale predation on narwhals.

Tracking and movements of narwhal (Eclipse Sound and Admiralty Inlet)

Satellite tracking of narwhals in Canadian waters in recent years has provided a better understanding of the distribution and movements of this species and has provided useful information to assist with resource management decisions related to stock discrimination. The most recent results were obtained from narwhals tagged in summer in Admiralty Inlet (2009) and Eclipse Sound (2010 and 2011).

Evaluation of Baffin Bay narwhal hunt sustainability

Each of the four Baffin Bay stocks (Somerset Island, Admiralty Inlet, Eclipse Sound and East Baffin Island) has been identified as a separate management unit, with a sustainable harvest recommendation derived from aerial survey abundance estimates.  A harvest allocation model was used to conduct a retrospective analysis of the 2011 Canadian narwhal hunts from these four Baffin Bay stocks, to determine their sustainability.

A fifth management unit comprises narwhal found seasonally in Jones Sound, Smith Sound and Parry Channel, but their abundance and relationship to the Baffin Bay population is not known. Sustainability of narwhal hunts in this management unit will also be reviewed.

Objectives

Canadian narwhal stock identification
  1. Review the use of stable isotopes for stock identification of narwhal on the basis of samples collected in Canada and Greenland.
Northern Hudson Bay narwhal abundance and hunt sustainability
  1. Determine the population estimate for Northern Hudson Bay narwhal based on an analysis of the 2011 aerial survey data.
  2. Determine the sustainable harvest recommendation for Northern Hudson Bay narwhal taking into account the current and predicted impact of killer whale predation on narwhals. Evaluate sustainability of recent harvest levels. (The meeting will not include management discussions about harvest allocations.)
Tracking and movements of narwhal (Eclipse Sound and Admiralty Inlet)
  1. Review the most recent satellite tracking results for narwhals tagged in Admiralty Inlet and Eclipse Sound in 2009-2011.
Evaluation of Baffin Bay narwhal hunt sustainability
  1. Evaluate the sustainability of Canadian harvests of Baffin Bay and other High Arctic narwhal in 2011.

Expected Publications

Participation

Notice

Participation to CSAS peer review meetings is by invitation only.

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