At least 100 adult walleye died in a recent Otisco Lake fish kill and nobody knows why.
The fish kill occurred two weeks ago, on Thursday, Sept. 8, according to a post on an Otisco Lake community Facebook page from an angler who reported seeing “maybe five” dead walleye floating in the lake.
Dave Marrs retired three years ago to a waterfront house on Fitzgerald Point, on the east side of Otisco Lake. He was fishing in the middle of the lake on Friday, Sept. 9., when he noticed a couple of dead walleye floating around. He didn’t think much of it.
“Over the weekend it was much worse,” Marrs said. “Sunday it was like wow, there’s a lot of them, and they’re all walleyes.”
Marie Thornton, Marrs’ neighbor, was paddle boarding around Fitzgerald Point that Sunday when she counted 17 dead walleye floating near the shore, she said.
Thornton regularly has the water in front of her camp checked for toxic blue-green algae because her dog drinks from the lake and her three children swim in it. She wondered if the walleye die-off might be related to low oxygen levels brought on by excessive algae or weed growth, noting that aquatic weeds have been especially high this year.
“We’ve had a camp here for 26 years,” said Thornton. “We’ve never seen anything like this.”
Marie Thornton counted 17 dead walleye while paddle boarding near her camp on Otisco Lake on Sept. 11. At least 100 walleye died in the fish kill, DEC said.Steve Featherstone
On Sept. 9, Department of Environmental Conservation (DEC) Region 7 Fisheries dispatched a DEC fish biologist to Otisco Lake to collect specimens.
DEC said that the four walleye specimens it collected showed no external signs of lesions, sores, or parasites. DEC sent the specimens for further analysis to Cornell University’s Aquatic Vet Program Laboratory.
No other species impacts were observed or reported, DEC said.
“Safeguarding New York’s freshwater fishery remains a top priority and DEC is investigating the die-off of approximately 100 adult walleye” that occurred in Otisco Lake, said DEC Region 7 Fisheries Manager, Scott Prindle, in a statement released last week.
“At present, it appears to have been an isolated incident and laboratory results are pending,” Prindle said.
DEC stocks Otisco Lake with 44,000 walleye on a biannual basis. Otisco Lake is also an important source of drinking water, supplying nearly 40 million gallons of water per day to 340,000 residents and businesses in five counties, according to the Onondaga County Water Authority (OCWA) website.
“We hadn’t seen any change in any of the parameters that we monitor,” said Jeff Miller, OCWA’s executive director of operations.
Rodney Getchell, Associate Director of Cornell’s Aquatic Animal Health Program, is presently running lab tests on the Otisco Lake walleye specimens collected by DEC. Getchell has not yet issued a final report of his findings.
However, Getchell emailed Syracuse.com with a preliminary analysis, stating that his tests “did not detect any evidence of a bacterial septicemia or a VHSV infection.”
Outbreaks of viral hemorrhagic septicemia virus, or VHSV, are responsible for many large fish kills of various freshwater species since it was first detected in the Great Lakes region in 2005.
Getchell also noted that there were “no signs of swelling or internal hemorrhaging in any of the four fish examined, which you would expect to see if there was an infectious process underway.”
With pathogens such as VHSV likely not a direct cause of the fish kill, sudden environmental changes might provide an answer, said Chris Whipps, a fish health biologist at SUNY College of Environmental Science and Forestry.
“When I think of big die offs like this, I think of a drop in oxygen levels in the lake,” said Whipps. “Why would it aversely effect one species more than another? That’s hard to say. In theory, you’d expect to see more variety of fish in a case like that, showing up on shores.”
“It sounds environmental to me, but that’s based on a hunch,” said Anthony Vandevalk, coordinator of the fisheries program at the Cornell Biological Field Station in Bridgeport. “But low oxygen will kill anything, all species, in that area.”
Vandevalk said he’d never seen a walleye-specific die-off in his 35 years of monitoring Oneida Lake’s walleye population, estimated this year at one million fish, while stressing that Oneida and Otisco are two very different lakes.
Still, Vandevalk said, we may never get to the bottom of what caused the recent Otisco Lake fish kill.
“You can hope for another fish kill” to collect more data, Vandevalk said, “but I think you’ll be a minority.”
Steve Featherstone covers the outdoors for The Post-Standard, syracuse.com and NYUP.com. Contact him at sfeatherstone@syracuse.com or on Twitter @featheroutdoors. You can also follow along with all of our outdoors content at newyorkupstate.com/outdoors/ or follow us on Facebook at facebook.com/upstatenyoutdoors.