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DNR Says Die Off Of Yellow Bass On Lower Chain Of Iowa Great Lakes Is Likely Natural And Cyclical In Nature

Thu 6-4-2020

(Spirit Lake)-- A fish kill on East Lake Okoboji is affecting a large number of yellow bass. Mike Hawkins, a fisheries biologist with the Iowa Department of Natural Resources says the fish kill is the result of natural causes, and is cyclical in nature...Fish Kill01 

"Their populations do kind of do get really large and then we'll experience something like what's going on where the yellow bass will die off. It's also associated with their spawning time which is also a very tough time for some fish species. It's a time where they're putting a lot of energy into egg production and that spawning process so they can succomb to that stress as well and that's not uncommon."

Hawkins says most of the dead fish have been found in the lower half of East Lake Okoboji and down through the lower chain...Fish Kill02 
"I wouldn't be surprised if they showed up in some other areas as well. Most of the fish that I saw had been dead for a little while, so I didn't see any real new fish that were dying so that's a good sign it might be fairly short lived."

He says it appears to be affecting primarily that one species...Fish Kill03 

"We have been out, just as a side, we have been out doing quite a bit of fisheries sampling on East Lake Okoboji and the lower chain and right now the fishery looks very, very healthy. Lots of pan fish and bass and northern pike. The fish that are there look very healthy."

Hawkins says anyone who sees dead yellow bass don't need to report it. He says the fish may be disposed by burying them or using them in gardens.

Hawkins says a chemical treatment for curly leaf pond weed was used in a very limited fashion along the shorline of those areas in early May. He says they aren't associating it with the fish kill...Fish Kill04 

"You know the herbicide that is used for the curly leaf pond weed has a half life of 10 days and we've shown that it's basically undetectable after just a couple days through some testing that we've done, so. And it is not known to have negative affects on aquatic life at all other than the plants that we're treating."

Hawkins says the treatment and mechanical harvesting have both since ended and that there's sign the curly leaf pond weed is dying off earlier than usual this year.