Spatial and Temporal Dynamics of Lake Whitefish (Coregonus clupeaformis) Health Indicators: Linking Individual-based Indicators to a Management-relevant Endpoint

Tyler Wagner a*, Michael L. Jones a, Mark P. Ebener b, Michael T. Arts c, Travis O. Brenden a, Dale C. Honeyfield d, Gregory M. Wright e, Mohamed Faisal f,g

Abstract

We examined the spatial and temporal dynamics of health indicators in four lake whitefish (Coregonus clupeaformis) stocks located in northern lakes Michigan and Huron from 2003 to 2006. The specific objectives were to (1) quantify spatial and temporal variability in health indicators; (2) examine relationships among nutritional indicators and stock-specific spatial and temporal dynamics of pathogen prevalence and intensity of infection; and (3) examine relationships between indicators measured on individual fish and stockspecific estimates of natural mortality. The percent of the total variation attributed to spatial and temporal sources varied greatly depending on the health indicator examined. The most notable pattern was a downward trend in the concentration of highly unsaturated fatty acids (HUFAs), observed in all stocks, in the polar lipid fraction of lake whitefish dorsal muscle tissue over the three study years. Variation among stocks and years for some indicators were correlated with the prevalence and intensity of the swimbladder nematode Cystidicola farionis, suggesting that our measures of fish health were related, at some level, with disease dynamics. We did not find relationships between spatial patterns in fish health indicators and estimates of natural mortality rates for the stocks. Our research highlights the complexity of the interactions between fish nutritional status, disease dynamics, and natural mortality in wild fish populations. Additional research that identifies thresholds of health indicators, below (or above) which survival may be reduced, will greatly help in understanding the relationship between indicators measured on individual fish and potential population-level effects.

a Quantitative Fisheries Center, Department of Fisheries and Wildlife, Michigan State University, 153 Giltner Hall, East Lansing, MI 48824-1101, USA

b Chippewa Ottawa Resource Authority, 179 West Three Mile Road, Sault Ste. Marie, MI 49783, USA

c Environment Canada, 867 Lakeshore Rd. Burlington, ON, Canada L7R 4A6

d US Geological Survey, Northern Appalachian Research Laboratory, 176 Straight Run Road, Wellsboro, PA 16901, USA

e Nunns Creek Fishery Enhancement Facility, HC 47, Box 8100, Hessel, MI 49745, USA

f Department of Pathobiology and Diagnostic Investigation College of Veterinary Medicine, Michigan State University S-110 Plant Biology Building East Lansing, Michigan 48824, USA

g Department of Fisheries and Wildlife College of Agriculture and Natural Resources, Michigan State University S-110 Plant Biology Building East Lansing, Michigan 48824, USA