The post-impoundment commercial whitefish fishery of Southern Indian Lake, Manitoba : summer 1980 and 1981 results / by R.A. Bodaly, T.W.D. Johnson and R.J.P. Fudge. : Fs97-4/1686E-PDF

"The results of this study extend the period of detailed observation of the post-impoundment summer commercial whitefish (Coregonus clupeaformis (Mitchill)) fishery on Southern Indian Lake and confirm the existence of severe declines in catch per unit of effort (CPE) and market quality of the catch. Mean whitefish CPE on traditional fishing grounds decreased from 23 kg/net/night in 1972, prior to impoundment, to 14 kg/net/night in 1979, and this study documents further declines to 10.5 and 7.5 kg/net/night in 1980 and 1981. As a result of these lower catches on traditional fishing grounds, a large proportion of fishing effort was relocated away from traditional areas to the area north of Sand Point. This effort comprised 30 and 33% of the total sampled effort in 1980 and 1981. Fishing north of Sand Point was attractive to fishermen because of 17-26% higher whitefish CPE, shorter wind fetches and shallower fishing depths than on traditional fishing grounds. Whitefish caught north of Sand Point were of lower commercial value than fish from traditional fishing areas because of darker external coloration and higher Triaenophorus cyst counts. Dark whitefish, which were largely absent from the commercial catch prior to impoundment, comprised 12-72% of production from 1976 to 1979 and 34 and 81% in 1980 and 1981. The lake was reclassified to Continental (#2) grade from Export (#1) grade in the summer of 1981 because average Triaenophorus cyst counts from sampled commercial shipments continued to be above the Export limit of 40 cysts/45 kg in 1980 and 1981"--Abstract, page iv.

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