The role of tributaries and river plumes as nursery areas for yellow perch and round gobies in Lake Michigan

Grant: # 1152

Grant Amount: $384,972.00

Board Decision Year: 2010

Purdue University - Dept. of Forestry and Nat. Resources (West Lafayette)

Dept. of Forestry and Nat. Resources

Hook, Tomas (thook@purdue.edu) 765-496-6799

GLFT - Ecosystem Health and Sustainable Fish Populations-C - Ecological and biological fisheries research to inform management

Project Details

To cultivate self-sustaining stocks of fish, fisheries managers need to understand how best to help young fish survive. For example, among all the different habitats in and around Lake Michigan, are there particular ones where larval and juvenile yellow perch—as well as other species, like round gobies and alewives—can find the food and water conditions they need to thrive? And how do these fish use different habitats as they grow?

A team of researchers hypothesized that river plumes—which have unique thermal, light, nutrient, and biological properties—would provide an excellent place for larval yellow perch, round gobies, and alewives to grow. They also wondered how the three species used river mouths, river plumes, and the nearshore waters of southeastern Lake Michigan. Did the young fish function the same regardless of their environment, or were there important differences among habitats?

To test their hypotheses, researchers (1) collected water samples from river plumes and adjacent nonplume areas in southeastern Lake Michigan to compare their physical, chemical, and biotic conditions; (2) estimated the movement of larval fish from tributaries into Lake Michigan; (3) compared the densities, diets, and growth rates of the three species in different areas; and (4) evaluated the extent to which later-stage fish used tributaries and river plumes as early life habitats.

The interdisciplinary research team—which included, among others, a fish ecologist, a physical scientist, and a water isotope specialist—used a number of different tools and methods (including otolith isotopic analysis) to better understand fish movement, as well as habitat contributions and linkages. 

The researchers found that, while river plumes in southeastern Lake Michigan present a somewhat different environment than open lake waters (they are a little bit warmer and more turbid), they are very small and not the hotspots of production that researchers anticipated. Data do suggest, however, that river mouths have greater potential for production, particularly for alewives.

Perhaps the most important finding, though, is that there was a clear distinction between river mouth and nearshore populations of yellow perch and round gobies, but not alewives. An analysis of diets, fatty acids, and stable isotopes, as well as isotopic analyses of otoliths, show that alewives move back and forth between the habitats (the river and the open lake water) with some regularity, while yellow perch and round gobies stay mostly in the same habitat for life.

Additional details for the project will become available as the research team publishes their results.