Date of Award

Spring 1990

Document Type

Thesis

Department

Life & Environmental Sciences

First Advisor

Jean Smith

Second Advisor

John Christenson

Third Advisor

Guido Bugni

Abstract

Flathead Lake has undergone many changes in its flora and fauna due to the introduction of Mvsis relitca. a small freshwater shrimp, from the upper water basin of the lake in 1981. This study was concerned with the effects M. relicta has had on the lake Whitefish (Coregonus clupeaformis). Lake Whitefish were studied using gill nets of two sizes set at two different locations near Yellow Bay on July 11 and 28, 1989. The growth rate was determined using the scale method and length-frequency plot. The health conditions were determined using condition factors and the length-weight relationship, and the diet of the fish was examined. All data were then compared to a study conducted in 1951 and 1952 in Flathead Lake. Lake Whitefish consume M. relicta due to their lake bottom feeding habits. The older age classes (age III and up) consume the most shrimp and are now growing faster than they did in the 1950’s. Age classes I and II of the last 6 years were smaller than those of the 1950’s. However, it appears that the 1989 age class I fish are larger than the age class I fish of 1984-1988.

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