by Sarah Coomber
MADISON ( 4/16/97) -- Lake Michigan’s yellow perch population has crashed, and no one knows exactly why.
Yellow perch numbers appear to have decreased 80 percent since 1990. Wisconsin banned commercial fishing for Lake Michigan’s yellow perch and cut the daily bag limit to five, effective Jan. 1.
This is not the first time Lake Michigan’s yellow perch population has dwindled, but it is the most severe. Biologists from the four states bordering the lake are teaming up to find out what happened to the yellow perch.
University of Wisconsin Sea Grant researcher Fred Binkowski said the Great Lakes Fishery Commission's Yellow Perch Task Group has named many possible culprits and is focusing on six ways to approach the problem: alewife preying on larval perch; synergistic factors killing the fish; pre-demersal survival limiting recruitment; weather limiting pre-demersal survival; larval fish starving; and decreasing sampling deficiency due to increased water clarity. Binkowski said a combination of these – and possibly other – factors is causing the decline of yellow perch in Lake Michigan.
"Fish in general can tolerate stress," Binkowski said. "They can compensate for one or two stressors, but maybe that third level of stress is the one that will put them on the decline, and the fourth one will usually take them to the mat."
UW Sea Grant Advisory Services fisheries specialist Clifford Kraft said the yellow perch problem seems to be concentrated in southern Lake Michigan.
"We should try to understand what’s going on to know whether it’s something that’s going to happen elsewhere," Kraft said.
Michigan, Indiana and Illinois also are taking action to alleviate pressure on Lake Michigan’s yellow perch. Michigan has not had a commercial fishery for many years, but last year the state reduced its daily bag limit to 35. Indiana instituted an emergency ruling Jan. 1 that closed the state’s commercial fishery and cut the sport limit to 15. Illinois’ Department of Natural Resources has recommended closing the commercial fishery and reducing the sport limit to 15; only 8- to 10-inch-long fish could be kept, if the recommendation is approved.
See also our EARTHWATCH radio report (1/22/97).
Created in 1966, Sea Grant is a national network of 29 university-based programs of research, outreach and education dedicated to the protection and sustainable use of the United States' coastal, ocean and Great Lakes resources. The National Sea Grant Network is a partnership of participating coastal states, private industry and the National Sea Grant College Program , National Oceanic & Atmospheric Administration , U.S. Department of Commerce . The University of Wisconsin Sea Grant College Program is administered by the Sea Grant Institute on the UW-Madison campus in Madison, Wisconsin.
Last revised 12/07/00 by Wittman
Copyright 1997 University of Wisconsin Sea Grant Institute
http://www.seagrant.wisc.edu/communications/news/perchnew.htm
