Fish kills, cooling lakes: Update on 7-9-20 on fish kills (better than first look) at LaSalle and Braidwood lakes

The Thursday update on the fish kills at LaSalle and Braidwood lakes: Not nearly as bad as first looked and there’s hope wind and storms will help.

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The boat launch area of LaSalle Lake showed the worst of the fish kill Wednesday morning, but a survey showed the rest of the lake was not as impacted. Credit: Dale Bowman

The boat launch area of LaSalle Lake showed the worst of the fish kill Wednesday morning, but a survey showed the rest of the lake was not as impacted.

Dale Bowman

I decided to push the initial version down and lead with the update from Thursday evening.

UPDATE from the evening of 07-08-20

The good news is the fish kill this week at LaSalle Lake looks worse than it is and appears thermal related rather than one related to a crash of dissolved oxygen (DO).

“This is not the 2008 Braidwood kill,” fisheries biologist David Wyffels said Thursday evening. “Definitely not that type of a kill.”

The imfamous 2008 Braidwood kill was related to an odd crashing of DO.

That is not what appears to be going on at LaSalle, though the launch area in particular looked brutal earlier this week.

Earlier Thursday, Wyffels emailed this explanation, “The situation at LaSalle is related to increased cooling pond temperatures due to the high air temps and lack of wind not dissolved oxygen issues on the main lake. Areas hardest hit are the boat launch area.

The boat launch area is cooler than the cooling loop (main lake) and many fish are congregating in that area trying to get into cooler water. Problem is that the boat launch area is outside the cooling loop (little to no circulation) and had lower dissolved oxygen. So in that area fish are really stressed. Fish from all species were observed in this die off with gizzard shad and thread fin accounting for most of dead fish. Hybrid, white and yellow bass would be second.

“From observations made yesterday I do not see it as a total kill. I fully expect the fishery to recover. Looking at the weather I am hopeful for some rain, cooler weather and wind. Forecast look favorable for decreased cooling pond temperatures. I will continue to monitor the situation.”

I did a follow-up call Thursday evening with Wyffels.

“At some point, there was one of every species,” Wyffels said. But he also noted that they saw some bass, blue catfish and channel catfish swimming in the boat launch area while they were assessing things.

“Definitely not a DO issue, it was definitely thermal. You worry about the DO crashing. Blue cats are a little more thermal tolerant. The fish are used to it getting warm at some point, this was a little out of the norm.

“It was not a total kill. I don’t see any reason this fishery will crash or suffer.”

As to Braidwood, fisheries biologist Seth Love said Thursday evening, “From what I was talking to people, threadfin and gizzard shad and some hybrid stripers are popping up, but it is nothing close to the stories of 2008.” 

He is hopeful that the weather change will provide some assistance.

Part of the problem, especially at a perched lake such as LaSalle, is that wind really helps and this week has been relatively calm, especially Tuesday.

“I will be checking as often as possible,” Love said. “I like to come by every day if I can.”

Wyffels and Love will be definitely be checking again on Friday.

“Hopefully, a good storm rolling in and we should be good to go, hopefully,” Wyffels said. 

(Initial posting from 7-8-20)

MARSEILLES, Ill.—The stench of a serious fish kill clutches your nostrils, then hangs on like a bad memory.

As of Wednesday, a serious fish kill is occurring or occurred at LaSalle Lake, the cooling lake south of Seneca. A minor one of mostly shad is occurring or occurred at Braidwood Lake, the cooling lake in southwestern Will County.

Jeremiah Haas, the principal aquatic biologist for Exelon’s Quad Cities Generating Station, arrived to check LaSalle shortly after I did Wednesday morning.

Thousands of small shad were the primary dead fish easily seen, but I also spotted nearly everything swimming in the lake: big common carp, big blue catfish, largemouth bass, drum, channel catfish, bluegill and bullhead.

The kill extending across all species is a bad sign; as were the dead bullheads.

IDNR fisheries biologist David Wyffels will also be assessing the fish kill today and I expect to follow up with him later on the severity and the future.

I also drove to check Braidwood and found nothing more than a few shad floating. Fisheries biologist Seth Love expected to swing by Braidwood this evening.

Here’s the reality, you can fish both cooling lakes and people were Wednesday morning.

At LaSalle, when I arrived, Don Guier was just launching through the dead fish and said, “I drove all the way here, I am going to fish.”

He was targeting blue catfish.

This online story will be updated, maybe several times over the next few days. Unfortunately, this has the looks of a potentially major kill fish at LaSalle.

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