Research Document - 2012/069

Information in support of Assessment of Buffalo River Inconnu, (Stenodus leucichthys), Great Slave Lake, Northwest Territories, 1945-2009

By M. VanGerwen-Toyne, C. Day, F. Taptuna, D. Leonard, S. Frame, and R. Tallman

Abstract

Inconnu have been caught primarily as bycatch in the Lake Whitefish commercial fishery in Great Slave Lake (GSL) since 1945. However, targeting has occurred in some years, including the late 1970s; after which time harvests declined and have remained low. Currently, harvests of Inconnu remain low due to reduced stocks, non-targeting, implementation of closure zones, and decreased fishing effort.

Periodically since 1947, research to document Inconnu distribution and stock status has been undertaken. Results of several mark-recapture studies and a fishery-independent harvest study have shown that the south shore of GSL is an important area for the Buffalo River Inconnu stock. Results of a gillnet sampling program at the mouth of Buffalo River has shown that the targeting of Inconnu in the late 1970s had a profound negative impact on the Buffalo River stock and its biological parameters, and that the status of the stock is still dependent on harvest levels. Fish fork length, age frequency, and size-at-age all showed a reduction after the late 1970s when Inconnu harvests were high. In addition, the percentage of mature individuals caught, especially females, dropped dramatically in the early 1980s. Similarly, catch-per-unit-effort (CPUE) was highest prior to the fishery targeting Inconnu, after which it dropped dramatically. These metrics showed periods of improvement when harvests were lowest, but have not returned to their original state.

Fishing closures implemented by DFO Fisheries and Aquaculture Management have been successful in areas applied, but total Inconnu harvest in the west basin remained above 10,000 kg in 2008-2009. Further recommendations for closure zones based on risk to the Inconnu stock are presented.

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