Saginaw Bay Fish Survey

The abundance of newly hatched walleye and yellow perch in Saginaw Bay was again high, according to preliminary review of 2004 fall survey data by the Michigan Department of Natural Resources (MDNR) Fisheries Division.

For walleye, 2004 constitutes the third strong year class in a row. The 2004 yellow perch year class (this year’s young-of-the-year) were again very abundant although not as great as last year, according to MDNR data.

Two main factors contribute to the successful reproduction of both walleye and yellow perch, collectively called percids, says MDNR biologist Dave Fielder, who coordinates the annual survey. One reason is ideal climactic conditions that favored egg hatch and survival of fry.
“What favors good percid production is gradually warming water, not peaks and valleys in temperature,” says Fielder, who also notes that the presence or absence of big storms also plays a role.

The second reason is a low abundance of alewife in 2003 and 2004, according to survey data. The low numbers mean less predation on newly hatched fish by alewife when they typically enter Saginaw Bay for spawning in the spring.

Surviving Winter
As the fish grow, however, they face other challenges. Of the record numbers of walleye and yellow perch that hatched in Saginaw Bay in 2003, only a fraction of the young fish survived the winter, according to 2004 data. Survey data indicates that walleye yearlings had “suffered considerable mortality,” while yellow perch yearlings were reduced by more than 90 percent.

While some over-winter mortality was expected, the resulting 2003 walleye year class is still strong, says Fielder, and the overall trend toward greater percid production bodes well for the future of perch and walleye fisheries in the bay.

Analysis of the 2004 survey data will continue, with an emphasis on understanding the factors limiting percid survival. The MDNR currently has a Walleye Recovery Plan in place for Saginaw Bay. The goal of the plan is to boost the walleye population to be more in line with historic numbers and achieve a predator-prey balance.

For more information contact
Dave Fielder at fielderd@michigan.gov or (989) 356-3232.