Research Document - 2010/021
Survey Index of the Northern Hudson Bay Narwhals, August 2008
By P.R. Richard
Abstract
The Northern Hudson Bay narwhal stock size was previously indexed by aerial photographic surveys of the summering aggregation area in 1984 and 2000. A new survey was done in August of 2008 to add to the series and allow a full assessment of the stock. The plan was to use a tandem of digital medium format cameras but one broke down so a single digital medium format camera was used instead. A first survey was completed on 21-22 August with a target altitude of 914 m, but cloud cover limited survey altitude in some parts to 549 - 762 m. Another survey was flown at higher altitude the next day, ahead of a storm, but the resulting photographic resolution did not allow adequate detection of narwhals. No survey could be flown in the rest of the aircraft charter period, due to poor weather. The estimate obtained from the 21-22 August survey was 610 narwhals (95% CI: 377 - 988). This survey index is less than half of those obtained in 1984 and 2000. Several factors which may have affected the estimate are discussed. Nevertheless the low index comes after a period of more intense hunting so it is also plausible that the population has declined. A full assessment using population indices and the catch history should be done to inform future co-management of this stock.
Accessibility Notice
This document is available in PDF format. If the document is not accessible to you, please contact the Secretariat to obtain another appropriate format, such as regular print, large print, Braille or audio version.
- Date modified: