Area whitefish die-off: 'Population is not at risk so not to worry' | BrainerdDispatch.com | Brainerd, Minnesota

Area whitefish die-off: 'Population is not at risk so not to worry'

Posted: August 17, 2012 - 8:18pm

Blame it on the balmy days of winter and dog days of summer.

A good number of whitefish have been found dead in area lakes — the Whitefish Chain in particular — in recent weeks. And while local fisheries types say it’s nothing to get too concerned about, thousands of dead fish floating in the water will have that effect.

The situation was set in motion by the record early ice-out — with the ice gone, lakes started warming up earlier than usual. Then came the recent hot spell in the Brainerd area. That’s a bad combination for cisco — a coldwater fish. Central Minnesota is actually about the southern edge of the range for these fish, according to Andy Carlson, DNR fisheries research biologist in Brainerd.

“It’s the same kind of die-offs we usually see this time of year,” Carlson said Wednesday. “And when you start accumulating (warm) days a lot earlier. Usually the bigger fish die first, but we’ve seen all sizes dying. We got a lot of calls this past weekend.

“There’s no oxygen in the lower water column (because of the heat). We’ve had cooler weather since (the recent stretch of hot weather), but if we get another heat stretch we’ll see other die-offs as well.”

While it’s mostly been on the Whitefish Chain, Carlson said there also have been reports of dead whitefish “on Middle Cullen. And I got a call this morning of (dead) fish on Gull. ... And on Mille Lacs they’ve been dying for three weeks.

“A lot of lakes lost ice so much earlier that started warming up these systems that we haven’t (seen) in a while. It’s similar to 2007. But we’re seeing them die earlier than other years. In previous years it was cooler and didn’t magnify the die-offs. But when that colder water disappears. ... Cisco are at the southern edge of their range (in central Minnesota) and what determines that range is the heat.”

Not many anglers target ciscos, but they are a huge part of the food chain for muskies, northern pike and walleyes.

“This changes some of the population dynamics,” Carlson said. “They (ciscos) are an energetic food source and it will change the dynamics of that system.”

There are indications that this may not be a widespread problem in the northern half of the state. To the far north, Tom Heinrich, large lake specialist for Lake of the Woods, said there have been reports of a few dead whitefish on the lake that boasts a strong cisco population, but nothing of note. And in the recent DNR conservation officers’ report, only Nikki Shoutz, CO in Pine River, noted the whitefish die-off in her weekly report.

“I had many questions on the lake about dead, floating whitefish on Whitefish,” Shoutz said Monday night. “The problem started with the record early ice-out. Lakes were warming up and there were the record temps in July and August, which contributed to it. But Marc Bacigalupi (Brainerd area fisheries supervisor) tells me the population is not at risk so not to worry.”

According to the Weather Channel, high temperatures were expected to be in the low to mid-70s through next week.

“That cold front will give the fish a reprieve,” Carlson said. “Then it probably won’t be until the fall turnover that they’ll see a reprieve.

“Smaller fish can weather those extreme conditions. So the cisco will spawn in the fall and we’ll have good numbers.”