There have been numerous fish kills recently reported from around the state, and staff from the Michigan Department of Natural Resources’ Fisheries Division is tracking and monitoring these events.
“We appreciate the public letting us know where they are seeing unusual fish kill events,” said Jim Dexter, Fisheries Division chief. “This can be done by emailing reports to DNR-FISH-Report-Fish-Kills@michigan.gov.”
The combination of very high water temperatures and drought flow conditions have made conditions very stressful for fish and, in many cases, these conditions are beyond lethal temperatures for fish. Additionally, high water temperatures also often result in low oxygen values, particularly where there is a lot of vegetation.
“For example, water temperatures of nearly 90 degrees Fahrenheit were recorded in the lower Shiawassee River last week, which resulted in a small kill of northern pike as temperatures were beyond their physiological ability to handle these conditions,” explained Gary Whelan, DNR fish production manager. “We expect to see more of these fish kills until there are major changes in this summer’s weather.”
The overall fisheries effects of such events are often very local in nature and may not significantly change overall population numbers. However, population level effects are not known at this time and will take some time to fully evaluate.
“We recommend anglers be extra careful in handling and unhooking fish that are to be released to keep stress to a minimum. It is also best for our fish if anglers refrain from fishing during the hottest parts of the day and not keep fish to be released in live wells for very long,” continued Whelan. “Fishing in the early morning period is least stressful for fish, as it has the coolest water temperatures.”
Once most fish lose most of the oxygen in their blood they can’t make up the loss and will die. Some like carp and largemouth bass have a special chemical in their blood that allows them to extract oxygen more readily from the water. At water temperatures of 80 F and above many fish will crossover that critical concentration and become what’s called the living dead. The water can’t hold enough oxygen and the fish can’t absorb it fast enough. So fish in the morning to help the fish and yourself.
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