Reflections – Heat danger for lakes

Reflections – Heat danger for lakes

Jul 13, 2012

Summer Time and the Livin’s a Beating

By Mike Pehanich

We’re having a heat wave, and reports on waters from South Dakota to South Carolina indicate trouble for our fisheries.

Reports of fish kills and suffocating algae blooms have flooded DNR departments and local lake managers and biologists.

Many areas of the country that go years without recording a 100-degree temperature, reported temperatures over the “century” mark for several consecutive days last week. My northeast Illinois region was one of them, and, after a couple of days of relief, we’re back in the steaming 90s!

Sad sight on the water

On Saturday, I witnessed a fish kill at a 120-acre local lake that left my heart in my shoes.

Many predicted this would be a tough year for our fisheries. Mossy algae emerged on this northern Illinois lake in mid-March, a time when lakes still have ice in some seasons.

I had taken two young anglers out for a morning of bass fishing. They fared well, catching 30 bass between them in only a few short hours. (That’s the “good news” portion of the day. Read about it in an upcoming SWF post!)

But the sight of the white bellies of dead musky and several dozen big northern pike cut into everyone’s elation.

On Father’s Day weekend, I had helped to run a kids’ fishing event at the lake. The fishing was good; the event…a success.

Afterwards, I spent a few minutes fishing with Mike Kajiwara, U.S. distributor for Marukyu’s Nories and Ecogear brands and a sponsor of the event. The lake was so clear that we were able to target bass by “sight fishing” from shore.

But there was no sight fishing on Saturday! Algae had bloomed heavily across the lake, and the healthy vegetation that had given the lake the look of a well-kept aquarium was nowhere to be seen!

Be careful with those chemicals!

No doubt the algae had contributed to the fish kill. But the bloom the young anglers and I had before us was a product of something beyond summer heat.

Lake owners revealed that a chemical herbicide had been applied to the lake several days earlier – right in the middle of the intense heat wave that had lifted water temperatures well into the 90s!

Now the manufacturers of these aquatic herbicides shout loud and strong about their safety to fish, and, in a very literal sense, that is true. But that chemical treatment added serious stress to an ecosystem already stressed by higher-than-normal water temperatures, corresponding algae blooms, and falling water levels.

Dying vegetation precipitated by the chemical treatment consumed dissolved oxygen and also deprived the lake of the much-needed oxygen that living plants themselves would have produced.

We had little idea how many big pike this northern Illinois lake held when Ron Urick landed this young pike last March. Summer fish kill revealed the lake had held a tremendous number of large pike and musky.

The pike in this relatively shallow lake were at risk during this sustained heat wave.

The chemical treatment was their coup de grace.

Make sure they care about your lake!

As drought continues and the heat wave persists, the lives of many fish are already at risk without any assist from human carelessness.

If you have control or say in the management of small waters near your home, make sure that fellow lake owners, lake managers, and pond service personnel understand the pressures that drought and summer heat are putting on our waters and our fisheries.  Make sure that they have the health of the lake and fishery as their foremost priority.

If you have a lake service that cares more about charging you for a herbicide treatment than it does the health of your lake, it’s time to have a very serious discussion with them – or perhaps find a new service altogether.

We all are stewards of our local lakes, ponds and streams. What we do – and don’t do – to protect their health and their fish populations will surely have an impact.

Read more! Nate Herman of Herman Pond Management Service details his guidelines for lake care during drought in severe heat in “Aquatic Plants and Summer Heat.”

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