The reason for the drop appears as clear as the lake's water on this tranquil evening: As invasive species have altered the Lake Michigan food web, the population of perch has plummeted. With fewer perch and restrictive regulations to protect the remaining population, anglers have either stopped fishing or are pursuing other species.erch have suffered from too many years of extremely poor recruitment, or survival of young fish, since the early 1990s.
Though comprehensive research on the cause of the perch decline is lacking, most biologists implicate the drastic changes in the lake's food web brought on by invasive zebra and quagga mussels. Once larval perch absorb their yolk sac, they don't seem to find enough food to survive. There is an abundance of data, however, to detail the fish's decline.
The Wisconsin Department of Natural Resources conducts annual spawning, young-of-the-year and graded mesh assessments. In December 2011, DNR crews caught just 300 perch in the department's annual graded mesh assessment off Milwaukee.
It was common to catch many thousands of fish in assessments in the 1980s and '90s. The recent results are alarming not only because of the low catch but because of the population's old age structure.
Nearly half of perch caught (48.6%) were from the 2005 year-class (7 years old), followed by the 2003 (10%) and 2006 (9%) year-classes.
Very few younger yellow perch (ages 2 and 3) were present in the sample. Female perch dominated the catch, comprising 77%.
A normal, healthy population with good recruitment would be dominated by fish in younger age classes.
The Lake Michigan (excluding Green Bay) perch harvest in 2011 was 16,982 fish, the lowest since 2000 and 66% below the 10-year average.
To give some perspective, in 1988 anglers landed 869,164 perch in Lake Michigan, including 408,438 perch in Milwaukee County waters alone.The species' decline caused serious concern and prompted lakewide conferences in the 1990s. These days, however, scientists and fisheries managers appear resigned to the new reality of a smaller perch population.
There have been several pleas by anglers for state agencies or the federal government to stock Lake Michigan with perch.
Some researchers have pointed to the low number of breeding stock as a critical impediment to a perch recovery in the lake.