Research Document - 2010/076

Biological characteristics and population assessment of walleye (Sander vitreus) from Tathlina Lake, Northwest Territories

By Colin P. Gallagher, A. Chris Day, and Ross F. Tallman

Abstract

The commercial walleye fishery in Tathlina Lake, Northwest Territories, collapsed in 2001 from a quota of 20,000 kg per year. The total catch of walleye has fluctuated multiple times since commercial fishing began in the 1950s and past quotas do not appear to have been sustainable. The interaction between harvest levels and the abiotic conditions of the lake is poorly understood and likely has an important effect on recruitment of walleye to the fishery as Tathlina Lake is large, shallow and turbid, with one documented case of winterkill in the 1940s. Biological and catch-per-unit-effort information from experimental gill netting conducted between 2001 and 2007 were used to assess the status of the walleye population. Additionally, commercial plant sampling data collected between 1990 and 1998 were examined. Between 2001 and 2007, the status of the stock appears to have improved although the extent of recovery was unknown. The mean fork length, weight, age and catch-per-unit-effort of walleye increased among years. Additionally, the proportion of walleye in the total catch increased. The growth rate of walleye between 2001 and 2007 did not demonstrate significant changes among sampling years. Compared to results from experimental gill netting in 1946 and 1979, walleye in Tathlina Lake appear to have increased in mean length, age and length-at-age. A recommendation was made to open the fishery with a conservative quota (≤5000 kg). Additional recommendations were made regarding approaches to monitoring the fishery and environmental conditions that likely influence walleye production.

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