High Lake Temps Stress Fish

Pewaukee Fishermen and true conservationists – The Lake Temperatures are very hard on fish…here’s the scientific data and some words for thought…

When lake temperatures reach 80 degrees it puts great stree on to the fish. The big lake (West Basoin) is 80 degrees down to the thermocline. At the thermocline the fish seek the cooler “quick change” of temperature. However the D.O. (Disolved Oxygen” level is so low it isn’t all usable oxygen and the fish are stressed even though they try to beat the heat.

As the D.O. level gets below 3 mg/l they begin to die. When shallow lakes like the east basin reach this 80 degrees they also stress fish as there is no cooler water refuge. Although we are fortunate enough to have a cold water creek and some natural springs, they are barely flowing so the fish do not have a “safe zone”.  in shallow basins the fishes respiration exceeds the photosynthesis. Photosynthesis is where aquatic plants change carbon dioxide into oxygen through the green leaves and the sunlight. However this doesn’t happen at night and as the oxygen gets used up by the aquatic species, the oxygen released by the plants isn’t enough for the fish. Fortunately we do have a lot of aquatic plants to help produce oxygen. If we can hang on long enough to avoid an algea bloom we be o.k. as long as some cool weather comes along. If an algea bloom hit, the shallow lake would turn colors and not let the sunlight hit the bottom. This in turn cuts off the oxygen production and leads to the big fish kills as seen on Muskego and Koshkongon in 2012 per Ben Huessner our areas fish biologist from the WDNR.

53 and a half inch Muskie

So what can we do? Well if we let the fish be we are doing our part.

To the fishermen that I haven’t seen trolling or casting for Muskies on Pewaukee, how cool is this….that Pewaukee’s finest fishermen respect our fisheries so much that they are protecting the fishery for their future as well as the future generations. From a water quality standpoint Pewaukee Lake is the best it has been for 40 years. With the help of the WDNR, WFT Pewaukee Chapter and the people really practicing good catch and release – the fishery is improving drastically, it is highly respected and it is well on its way to being the best it has ever been.

Dead Muskie 07192016

As far as fishing in the heat….make your own decisions, it is your right.

Thank you for being leaders in conservation….it is recognized, respected and it’s getting contagious!

Lake Temps July 2016

Pewaukee Lake Sanitary District records temperatures, Disolved Oxygen, salinity and other water quality data every Wednesday during the Spring, Summer and Fall. We also take secchi disc readings to record water clarity.

All this information is utilized in determining the best management practices to keep a healthy ecosystem.


Looking forward to cooler temperatures and tight fishing lines….soon











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