Comparison Of Fatty Acids And Proximate Composition Between Southern And Northern Stocks Of Lake Michigan Lake Whitefish
Eric T. Volkman, Purdue University, Department of Forestry and Natural Resources, 195 Marstellar Street, West Lafayette, IN 47907-1159; (765) 494-3581; FAX (765) 496-2422; evolkman@purdue.edu
Trent M. Sutton, Purdue University, Department of Forestry and Natural Resources, 195 Marstellar Street, West Lafayette, IN 47907-1159
Bruce A. Watkins, Purdue University, Department of Food Science, 745 Agriculture Mall Drive, West Lafayette, IN 47907-2009
Yong Li, Purdue University, Department of Food Science, 745 Agriculture Mall Drive, West Lafayette, IN 47907- 2009
Food-web alterations in Lake Michigan are thought to be responsible for recently detected differences in lake whitefish Coregonus clupeaformis body size and condition between southern and northern stocks. To determine the magnitude of these differences and possible impacts on the fitness of eggs, sexually mature females (N = 32) and eggs were collected from southern (Muskegon, Michigan) and northern (Naubinway, Michigan) sites. Fatty-acid (FA) analysis was conducted on eggs and fish muscle tissue, while proximate-composition analyses were conducted on eggs and whole-body fish. Although the percentage of total n-3 FA in fish was significantly lower in the southern than the northern population, there was no difference in total n-3 in eggs between populations. Similarly, northern lake whitefish had a significantly higher docosahexaenoic acid (DHA)/eicosapentaenoic acid (EPA) ratio than southern fish; however, there was no significant difference detected in the eggs. Fish collected from the southern site had a higher mean condition factor (1.13) than fish collected from the northern site (1.09), but the difference was not statistically significant. Although southern fish had higher total-lipid content than northern fish, there was no difference in total lipids detected in the eggs from either site. Our results indicate that environmental variation appears to have led to differences in the FA profile and proximate composition of lake whitefish between southern and northern stocks. However, many of these differences were not passed to the eggs, indicating that eggs from both populations may have similar fitness levels.