Propagation Research: Conservation Genetics of Wisconsin Fishes

Objectives of this project are to evaluate the consequences of stock transfers, or movement of fish, among areas where genetic differences have evolved.

Background

Genetic diversity occurs within populations (i.e., individuals from the same population have genetic differences) and among populations (i.e., populations that are geographically isolated accumulate location-specific differences over time). Some differences are adaptive, or beneficial to the survival of individuals at particular locations. Geographically distinct populations may also have co-adapted genes that function well together, but not as well with genes from another locations.

Genetic diversity is important in maintaining a healthy population. Stock transfers, or movement of fish among basins can potentially threaten genetic diversity. However, few field studies have attempted to quantify these potential effects on fish populations.

The first part of this project is a controlled, replicated experiment evaluating fitness traits of bass and bluegill. We will compare the fitness of each fish species of local origin to the fitness of fish crossbred from local and distant stock. Progressively more distant (geographically and genetically) crosses will allow comparison of the relation between genetic distance and potential outbreeding depression (i.e., loss of fitness from in-breeding of distinct populations). The experiment uses fish from Illinois, the Lake Michigan drainage in Wisconsin, the upper Mississippi basin in Wisconsin, and the Hudson Bay drainage in Minnesota. The experimental ponds are located at the Illinois Natural History Survey Aquatic Ecology Field Laboratory in Champaign, Illinois.

The second part of the project will evaluate the long-term consequences of walleye stock transfers. Within a group of experimental lakes having some natural reproduction, walleye from a different geographic area will be stocked. Assuming the stocked fish survive and grow, fitness traits of introduced and local fish will be compared. A genetic marker (e.g. a recognizable piece of DNA) will allow tracking of in-breeding between introduced and native fish. Assuming detectable levels of in-breeding, we will compare fish of different genetic backgrounds, and compare recruitment trends of lakes with in-breeding to a set of control lakes.

The walleye experiment will also attempt to examine stocking success. All stocked fish will be marked with a chemical called oxytetracycline, which permanently stains the otolith, or earstone. By sampling age 0 fingerlings during fall and examining a subsample of otoliths, we can determine the contribution of stocking to the year class. Additionally, we can investigate whether supplemental stocking in lakes with natural reproduction increases the number of fish in the year class. The stocking evaluations will run over a four-year period.

Project partners for this study include: the Illinois Natural History Survey, Minnesota Department of Natural Resources, University of Wisconsin-Stevens Point, National Biological Service, and University of Wisconsin-Eau Claire.

For more information on this topic please contact:
Martin Jennings (715) 635-4160