Research Document - 2001/091
Taxonomic Issues, Life History and Stock Discrimination - Rat River Dolly Varden
By Jim Reist
Abstract
The populations of northern form Dolly Varden that occur in Arctic Canada (Firth R./Joe Creek, Babbage R., Big Fish R., Rat R., and Vittrekwa R.) represent the only populations of this distinct taxon known to be present in Canada. Thus, these fish are of interest as a unique part of the Canadian fish fauna and care in conservation and management of these populations and their habitats are high priorities. The six populations of the northern form Dolly Varden known to be anadromous appear to represent distinct biological populations or stocks. Studies using both morphology and genetic characters have confirmed the discreteness of fish from four river systems (Firth, Babbage, Big Fish and Rat) as well as indicating that fish from Joe Creek may be distinct from those that spawn in the Firth River (Reist, 1989). Preliminary analysis of stock structure using otolith microchemistry for Firth R./Joe Creek, and Babbage R. confirms the structuring of Dolly Varden populations as determined by other methods (Babaluk et al., 1998; unpublished data). Analyses of mitochondrial DNA supports the distinctness of Rat R. fish from the north slope populations. High diversity observed within the Rat R. stock, is unexpected given diversity found in other systems in the area, and especially in view of the level of exploitation sustained by this population (the typical effects of exploitation are to reduce such variability). This finding suggests that hidden structuring may be present in the Rat R. and is consistent with the suggestion of temporally different spawning stocks.
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