Science Advisory Report  2012/065

Assessment of Dolly Varden from the Big Fish River, NT 2009-2011

Summary

• Based on mark-recapture studies, the estimated population abundance of Dolly Varden ≥365 mm from the Big Fish River was 3,853 in 2009 and 4,338 in 2010.
• The count of Dolly Varden ≥365 mm from the Big Fish River using a DIDSON sonar was estimated to be 1,243 in 2010.
• Estimates of effective population size determined using genetic data suggest there are no immediate conservation concerns for the population.
• Using the effective population size results, abundances were estimated to be 2,336 and 2,550.
• Population abundance estimates in 2009 and 2010 remain lower compared to the 1970s, but are comparable to estimates from the 1990s.
• Biological data from the mark-recapture studies indicate a high incidence of consecutive year spawning.
• Current mean and modal length of Dolly Varden are similar to those after the population decline in the 1970s, while the proportion of fish ≥550 mm was greater during 2009-2011.
• Genetic mixed-stock fishery analysis of samples collected along the Beaufort Sea coast in 2011 indicate that Dolly Varden from the Big Fish River only contributed to the harvest at Shingle Point and King Point.
• Dolly Varden from the Big Fish River contributed 13% to the harvest at Shingle Point and King Point.
• It is estimated that the overall harvest rate of Dolly Varden from the Big Fish River in 2011 was approximately 0.75%.
• The population appears stable although the impact of an increase in fishing mortality on population abundance is uncertain.
• Continued sampling of the coastal mixed-stock fishery and implementation of a monitoring program are recommended if there is an increase in harvest for Dolly Varden from the Big Fish River.

This Science Advisory Report was developed following a meeting held February 29, 2012 to consider the assessment of and recommended sustainable harvest level for Dolly Varden from the Big Fish River, NT. 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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