Pilot program seeks to ensure long-term viability of longear sunfish in Wisconsin
MUKWANAGO, Wis. – A breeding population of a sunfish listed as a threatened species in Wisconsin may be established at a pond at the Milwaukee County Zoo as part of a pilot program to protect the long-term viability of the species in the state.
As part of an annual stream survey to capture and document the variety of species living in a short stretch of the Mukwonago River, fish biologists with the Department of Natural Resources and Milwaukee County Zoo found several longear sunfish. The species is found throughout the Mississippi and Great Lakes region but is found in only about 20 Wisconsin counties. They prefer clear, shallow, moderately warm, still water of streams, rivers or lakes with moderate aquatic vegetation. Longear sunfish resemble other sunfish, but their ear flap, or operculum, is much more elongated.
Because the species is intolerant of turbid, cloudy water, it is usually found in shallower, warmer headwaters of streams with a steady flow. The Mukwonago River is one of the most diverse aquatic habitats in in the entire state, according John Lyons, a DNR fisheries research scientist.
“Typically when we see a waterway that has 10 to 20 different species, we consider that ‘excellent;’ the Mukwonago has anywhere from 30 to 40 different species,” Lyons said.
With a healthy population of the state threatened longear sunfish in the river, Lyons worked with Craig Berg, a Milwaukee County Zoo biologist, to capture some immature fish during a regular survey of the Mukwonago River and take them to Milwaukee County Zoo. There they are being held in aquariums to monitor them for disease, before they will be released into a pond at the zoo.
According to Berg, the goal is to create what’s called an ‘assurance population’ for the longear sunfish. In a couple of weeks the zoo will release the sunfish into one of their ponds. The fish are expected to reach maturity within a year and will hopefully establish a breeding population.
Lyons says this breeding population could then be used to re-establish a population should the existing Mukwonago River population be wiped out by disease or fish kill.
The zoo plans to later create signs and educational items to teach visitors about the importance of preserving species native to Wisconsin.