Science Advisory Report 2014/036
Assessment of Dolly Varden (Salvelinus malma) from the Rat River, Northwest Territories, 2002-2007
Summary
- Sea-run Dolly Varden, known locally as “char”, inhabits the Rat River and its tributaries.
- Abundance of the mature segment of this stock declined from around 8,500 fish during the period between 1995 and 2001 to around 2,700 in 2004. Following a voluntary closure of the river in 2006 and 2007 by co-management partners, harvest of Dolly Varden was limited to 40 fish by each of three fish monitors (total 120 fish) involved in the community-based sampling program.
- The current status of the stock at the time of this assessment was uncertain as there were no abundance estimates since 2004.
- Future prospects for Rat River Dolly Varden were encouraging with evidence of increases in fork length of spawning fish, improved condition, relatively stable sex and maturity composition and the recent observed pulse of juvenile production in 2007.
- Nevertheless, uncertainties remain including potential changes in Dolly Varden habitat and carrying capacity of the Rat River, low numbers of spawning males and the contribution of Rat River Dolly Varden to the mixed stock coastal fishery.
- Harvesters should be encouraged to release live any Dolly Varden that they think could be a sea-run male as the proportion of spawning males in the stock is very low.
- Harvest levels from all sources, including research activities, mixed stock coastal fisheries and the Rat River directed fishery, are recommended to remain at or below 5% (i.e., 120 fish).
- Examination of approximately 400 fish (>400 mm fork length) is recommended in 2008 to increase precision of the 2007 stock estimate based on mark-recapture analysis.
This Science Advisory Report is from the March 17-19, 2008, Assessment of Rat River Dolly Varden. 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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