Our Bay: The search for perch
Volunteers monitor status of yellow perch in Severn River
By PAMELA WOOD, Staff Writer
Magnifying glass in hand, Catherine Stirling is an expert at spotting teeny-tiny yellow perch larvae.
She leans over a container full of Severn River water and trains her eyes on the various specks and dots floating in the water. She's looking for a nearly translucent critter with two black eyes.
"It's moving! We got another one!" she calls out to fellow volunteers aboard the Lady Echo who are conducting twice-weekly monitoring for the miniscule yellow perch larvae.
The volunteers, organized by the Arlington Echo Outdoor Education Center and the Severn Riverkeeper Program, will send their data to state biologists.
More often than not, their monitoring is turning up hardly any yellow perch larvae - a sign that something is going wrong in the reproduction process. Sometimes they find motionless, dead larvae.
In 2008, just 4 percent of the samples had any perch larvae. That's down from survey results that showed greater than 20 percent recorded in the past several years.
To look for yellow perch, a team of volunteers motors out to 10 sites in the Severn, from Round Bay heading north to where the river begins to narrow into Severn Run.
They've gone out twice a week for four weeks already, and will continue "until we stop seeing them," said Steve Barry, director of Arlington Echo and captain of the Lady Echo.
The team deploys a cone-shaped net with super-fine mesh behind the boat. A jar at the end collects the water and tiny critters trapped in the net during the two-minute trawl.
The contents are then dumped into a clear bucket and examined - sometimes using a magnifying glass, because the larvae are so small.
During a trip this week, the team struggled to find many perch larvae. Several samples came up empty.
But at the last site, far upstream on the river, they hit the jackpot. Vast amounts of tiny larvae wiggled at the surface, giving the water sample a shimmery cast.
"They're all over the place," said Stirling, who works for the Maryland League of Conservation Voters.
Pierre Henkart, who also volunteers with the Severn Riverkeeper's water-quality testing program, was impressed.
"I think this is about the best haul I've seen," he said. "They're just all over the place."
The volunteers estimated perhaps two dozen yellow perch larvae, a good sign.
The struggling yellow perch population has received some special attention in the Severn recently. Yellow perch are a striking fish with yellow and green bands, found in mostly fresh water. It's often the first fish caught by anglers in the spring.
The first-ever report card for the Severn River issued this spring gave the yellow perch its own grade, and it wasn't a good one: an F.
Even though there are concerns about the reproduction of yellow perch in the Severn, the Maryland Department of Natural Resources recently reopened the river and other rivers on the Western Shore to limited recreational fishing this spring for the first time in years.
DNR fisheries officials are convinced the adult yellow perch population is robust enough - and reproducing enough baby fish in other rivers - that it can support a certain amount of fishing in Anne Arundel's rivers.
The decision earned mixed reviews from environmentalists and fishermen. Some said they don't think there are enough fish to support reopening the fishery. Others said if more people are catching yellow perch, they might become invested in improving the health of the rivers.
Officials are keeping an eye on how the fishing for yellow perch works out. In addition to reviewing citizen monitoring data on the yellow perch eggs and larvae, the DNR conducts its own seine surveys for juvenile fish.
Several factors could be influencing the yellow perch's problems. Some could be simple factors in nature, such as the weather not being ideal for successful egg hatching.
Others could be caused by humans: sediment washing down from the land can coat and smother perch eggs, which hang in the water for several days before hatching.
Barry from Arlington Echo wondered if septic systems might be leaching human drugs into the water that could affect reproduction.
Barry's staff also monitors the status of eggs in the Severn before they hatch. They used to collect the eggs and send them out to schools for children to raise in their classrooms, but so few eggs were successful that Arlington Echo has largely switched to eels instead.
Arlington Echo still collects some eggs - the center has a special state permit to do so - and monitors them in tanks. This year, most eggs failed, Barry said.
"The science is clear, this is a stressed species," he said.
(Revised April 2009)