by Sarah Coomber
MADISON, Wis. (Aug. 20, 1997) -- UW Sea Grant fisheries scientist Fred Binkowski and his colleagues made headlines this summer with their yellow perch research. Seven years of weak year classes joining the perch population led to a Lake Michigan commercial fishing ban and sport fishing restrictions beginning several months ago. Now researchers, the fishing community and fish-fry aficionados want some answers.
Binkowski and Wisconsin Department of Natural Resources personnel spent a month off Milwaukee's shores catching yellow perch in the green can reef area, which is known as a perch spawning habitat. Using gill and fyke nets, they caught 14,463 yellow perch but found some disturbing trends: Only 46 of the fish were female. And the males were old — the majority were 8 or 9 years old.
Binkowski and Wisconsin DNR fish technician Matt Coffaro both said it is important not to focus too much on the lack of females.
"People have a misconception that the problem out there is there are so few females," Coffaro said. "It's a problem we're facing now, but it's really the result of the problem -- the problem being the poor reproduction we've had since 1989."
With fewer young fish entering the adult population during the last several years, the fishing community has been working with essentially the same yellow perch population, year after year. Because females grow faster than males, they are more attractive to sport fishermen and are more likely to be caught in commercial gill nets. Selective fishing for large fish could have led to the drastic decrease in numbers of females.
"The number of females is so low, because they've been getting fished on for more years than the males have," Coffaro said.
Now Binkowski is looking for the reason why few yellow perch are surviving long enough to join Lake Michigan's adult perch population. With $92,000 from UW Sea Grant's rapid-response funds, he and his colleagues launched a monumental research project at UW-Milwaukee Center for Great Lakes Studies. They are investigating the early life stages of yellow perch from four different places.
They collected yellow perch eggs from Green Bay, Lake Ontario, Lake Mendota and Lake Michigan, off Milwaukee's shore, and now they are watching how the different strains develop. Staff members are creating optimal conditions for these fish and are carefully monitoring them every step of the way. From prior research, they know the temperatures and foods the fish respond to best at each stage of development. They will watch the four perch populations for at least three years -- until they reach reproductive maturity.
"We want to establish a complete profile on all the life stages of yellow perch," Binkowski said. "Essentially what we're doing is taking a photograph and X-ray from every angle of every critical life stage from the fertilized egg to the reproductive male and female."
Once they have this complete life history picture, Binkowski said scientists from many different disciplines will be able to use the data to look for different trends.
Already Binkowski has found a difference between the Lake Michigan perch and their cousins from other lakes.
"The Lake Michigan fish, when they hatch out of the egg, initially they seem to have a much slower growth rate," Binkowski said. He said this could make them more susceptible to predators. Although this slow growth rate could be normal for the Lake Michigan perch, it could also be the result of something interrupting their normal development.
Surplus eggs not needed for the study are in a mass rearing tank. Binkowski said he hopes to raise these 5,000 to 10,000 fish for preserving the Lake Michigan strain, in case it ever completely bottoms out.
"The problem won't be solved quickly," Binkowski said. "We allowed this thing to go on for seven years, and it's not going to be turned around in one year."
The answers that emerge might not make everyone happy, but Binkowski said his goal is to save the yellow perch. "My client is Perca flavescens -- the yellow perch," he said. "That's who I work for."
UW Sea Grant also allocated $9,600 to support field testing of sampling gear by UW Sea Grant fisheries specialist Clifford Kraft and Wisconsin Department of Natural Resources Green Bay fisheries biologist Brian Belonger.
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.
Posted 20 August 1997 Coomber
All contents copyright 1997 University of Wisconsin Sea Grant Institute
Last updated 03 November 1999 by
Wittman
http://www.seagrant.wisc.edu/communications/news/perch.htm
