Research Document - 2015/023

Genetic stock identification and mixed-stock fishery analysis of Arctic Char (Salvelinus alpinus) in Darnley Bay, Northwest Territories

By David A. Boguski, Colin P. Gallagher, Kimberly L. Howland, and Les N. Harris

Abstract

Genetic mixed-stock fishery analysis (MSFA) is applied to resolve the proportional contribution of populations to a fishery where a mixture of populations is known to be harvested. Here, we examine the genetic composition of 882 Arctic Char (Salvelinus alpinus) collected from two important coastal subsistence fisheries (mouths of Hornaday River and Lasard Creek) in eastern Darnley Bay, Northwest Territories. Specifically, we assayed genetic variation at 18 microsatellite loci to determine whether:

1. stock components (baseline) can be genetically identified;
2. population structure is temporally stable;
3. stock components are always separated and, if not, where they mixed; and
4. the proportional stock contributions to areas identified as mixed-stock fisheries can be estimated.

The results indicated population subdivision was low (Global FST; θ = 0.010). Estimates of genetic structure (θ) revealed few significant differences between coastal harvesting locations with little interannual variation (with the notable exception of char collected from Lasard Creek in 2010). According to the realistic fishery simulations using empirical baseline sizes, between the years 2009 and 2012 the Hornaday River contributed 84.4%, 80.9%, 92.7%, and 88.8%, respectively, to the Hornaday River fishery, and between the years 2010 and 2012 it contributed 64.3%, 89.9%, and 81.5%, respectively, to the Lasard Creek fishery. Furthermore, these simulations indicated that both harvest locations were dominated by the Hornaday River stock (88.9% and 87.7%, respectively and pooled across years). The co-management partners for Arctic Char in Darnley Bay can utilize the results from the genetic MSFA to build upon previously established management plans.

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