Post-impoundment changes in commercial fishing patterns and catch of lake whitefish (Coregonus clupeaformis) in Southern Indian Lake, Manitoba / by R.A. Bodaly, T.W.D. Johnson, and R.J.P. Fudge. : Fs97-4/1555E-PDF

"Prior to flooding, the commercial lake whitefish (Coregonus clupeaformis (Mitchill)) catch from Southern Indian Lake was composed almost totally of light colored, export or A grade fish. Since flooding in late 1976, dark colored lake whitefish have made up from 12 to 72% of the catch. Dark colored lake whitefish are graded as continental or B grade fish on the basis of darker external coloration and higher average Triaenophorus crassus cyst counts than light lake whitefish. These dark lake whitefish are entering the commercial catch because of a major shift in the geographical location of the majority of fishing effort in the Loon Narrows area of the lake. In 1972, almost all fishing effort was located south of Sand Point while in 1979 a majority of fishing effort was deployed north of Sand Point. In 1979, the proportion of dark fish in lake whitefish catches south of Sand Point was usually low whereas dark fish generally made up 100% of catches north of Sand Point. The shift in fishing effort has apparently been the result of decreased catches in traditional fishing areas. The average lake whitefish catch per unit of effort for fish landed at Loon Narrows decreased 30% from 1972 to 1979 while the average catch per unit effort for traditional (pre-flooding) fishing areas south of Sand Point decreased 40%. It is hypothesized that this decrease in catch per unit effort on traditional fishing grounds has been due to changes in the movement of fish brought about by decreased light penetration due to higher post-impoundment turbidity levels from extensive shore erosion"--Abstract, page iv.

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