Proliferation of zebra mussels zebra mussel facts) has caused dramatic changes in the aquatic community of Saginaw Bay, Lake Huron. Filter feeding by zebra mussels has reduced phytoplankton, improved water clarity, and reduced pelagic (mid water) zooplankton. The shift of nutrients to the benthic (bottom dwelling) community has increased benthic algae, and created a novel invertebrate community associated with zebra mussel colonies. Zebra mussel effects on nutrient cycling, phytoplankton, and invertebrates are well documented, but their effects on fish communities are unknown. GLSC and Michigan Department of Natural Resources are investigating effects of zebra mussels on the fish community of Saginaw Bay to help manage the yellow perch population by replicating a portion of a fisheries survey performed in Saginaw Bay during 1986-1988, just prior to zebra mussel invasion. While that study focused on obtaining diet and growth data for walleyes and yellow perch, abundance and biomass were calculated for all fishes, and length frequency information was obtained for the prey fishes. By replicating a portion of the survey, we can make before-and-after comparisons of resource use by native predators, species composition, overall abundance and biomass, and dynamics of prey fishes. Preliminary data suggest that the zebra mussel invasion has favored benthivorous fishes such as yellow perch and freshwater drum, but reduced obligate planktivores such as alewife and gizzard shad. The mechanism appears to be increased food availability within the benthic community. However, yellow perch reproduction has become sporadic, and most year classes since the zebra mussel invasion have been poor. This is likely due to lower zooplankton availability, which creates poor feeding conditions for age-0 yellow perch. However, those that survive grow well because population size is smaller, and fish can take advantage of benthic invertebrates that have proliferated within zebra mussel colonies.

This study will also make the public aware that low numbers of yellow perch are the result of ecological processes beyond control of fisheries managers, and not the result of overharvest by commercial anglers.

Zebra Mussel Factsheet