'No obvious quick fix' for declining yellow perch: study
Richard Howard fishes for yellow perch off a Lake Erie break wall east of downtown Cleveland Tuesday, Oct. 6, 2009. (AP/Mark Duncan)
Published Thursday, July 16, 2015 11:29AM EDT
The yellow perch has been an easy catch for Canadian fishers for more than a century, the fisheries department says. But a new report suggests rising water temperatures are threatening the fish.
According to the Department of Fisheries and Oceans, perch are "abundant" in North America, living as far west as British Columbia, as far east as Nova Scotia, and as far north as the Northwest Territories.
The greatest concentration live in the Great Lakes, but according to a study from Ohio State University, climate change is threatening the perch population in Lake Erie.
According to the study's authors, the number of yellow perch in Lake Erie has halved since the '60s and '70s, and been especially low since 2003.
The study, released Wednesday, suggests that warmer water temperatures are to blame.
According to the study, rising temperatures and shorter winters are causing weaker eggs and larvae that struggle to survive into adulthood.
Findings also showed that yellow perch haven't adjusted their spawning schedule to match shorter winters and early springs. And growth patterns of zooplankton, the main source of food for young perch, have changed too. As a result, when the young perch have hatched and are ready to start feeding, plankton are in short supply.
"If not enough food is available, the larvae will grow slowly and be vulnerable to predators," Stuart Ludsin, the study's principal investigator, said in a statement.
To test how temperatures affect yellow perch, the team of researchers collected eggs from the wild, and then raised them in a lab.
Scientists kept some of the eggs in historic cool temperatures, and others in the warmer temperatures seen today. They also adjusted the length of time fish were in winter conditions, to simulate longer and shorter seasons.
Researchers found that, on average, eggs raised in long, cold winter conditions were up to 40 per cent bigger than eggs in warm, short winter environments. They were also two to four times more likely to hatch.
According to the study's authors, the perch that did hatch in warmer conditions were weaker, putting them in danger of being eaten by predators, particularly the white perch.
In the face of increased pollution and harmful algae blooms in the lake, the study's authors say there may be little humans can now do to preserve the yellow perch population.
As temperatures continue to rise, the fate of the yellow perch may rest on its own ability to adjust and evolve, Ludsin said.
"It could be we'll have to wait for adaptation to occur," he said. "There is no obvious quick fix."