Recently the National Oceanic and Atmospheric Administration (NOAA) National Climatic Data Center published a report confirming what most people already suspected – that the period from January 2012 through June 2012 was the warmest first half of a year ever recorded for the U.S. mainland. According to the report, every single state in the contiguous U.S. except Washington saw warmer-than-average temperatures during this time period.
Southeast Michigan has not escaped the effects of this unprecedented heat wave as evidenced by the recent news that several lakes and rivers have experienced fish die-offs due to sustained periods of high water temperatures. To date, the Michigan Department of Natural Resources has recorded fish kills in Genesee County’s Loon Lake, portions of the Shiawassee River and Oakland County’s Pontiac Lake.
Some of these fish kills have occurred in watersheds under the jurisdiction of Joe Leonardi, DNR Fisheries Biologist for the Southern Lake Huron Management Unit. Leonardi has a deep understanding of the effects of temperature extremes on fish, pointing out that each fish species has a relatively narrow preferred temperature range that promotes optimal survival and growth and a secondary, broader range that while not optimal, can be tolerated. But all fish species have a temperature threshold beyond which they cannot survive for more than a short period of time and it’s this threshold that has been breached on several Michigan waterways.
Northern pike, considered a cool water species, have been particularly impacted by the recent heat wave. Sustained water temperature readings of 90 degrees, considered beyond a pike’s temperature threshold, have been recorded on many southern Michigan watersheds. When confronted with such conditions and unable to find cooler water with sufficient oxygen levels, they perish.
Although fish kills can sometimes be anticipated in watersheds with marginal water quality for some fish species, they typically occur with little warning. Aerators have been used in small lakes and ponds to distribute water temperatures more evenly but also mix low oxygen water with high oxygen water which could lower the lake’s overall oxygen level.
In their July 23rd press release detailing the recent heat related fish kills, the DNR recommends that anglers be extra careful in handling and unhooking fish that are to be released and fishing in the early morning period when the water is coolest in order to minimize stress on the fish.
Jeremy Geist, Watershed Ecologist for the Clinton River Watershed Council echoes the recommendations of the DNR. Although he has not heard any reports of fish die offs in the Clinton River or its tributaries, he feels the unusually warm weather conditions, combined with longer than usual periods of extremely low water flows, are having a negative impact on fish and other aquatics.
The DNR press release goes on to suggest that angler’s not keep fish to be released in livewells for extended periods. That suggestion however could prove to be impractical considering the dozens of fishing tournaments, particularly bass fishing tournaments, held each week on Michigan waterways.
The bass fishing community, led by the Bass Anglers Sportsman Society (B.A.S.S) has stressed the importance of conservation since the inception of its “Don’t Kill Your Catch” program in 1972 and publishes detailed instructions on techniques for maintaining a healthy livewell environment in its Keeping Bass Alive guidebook. In addition, prior to each B.A.S.S. sanctioned event, competitors are given pocket guides containing tips for keeping bass healthy. One factor in their favor is that unlike northern pike, both species of bass are considered warm water species and more tolerant of high water temperatures.
Paul Sacks, President of the Michigan B.A.S.S. Federation Nation adds that tournament anglers employ a variety of tactics to ensure livewells are kept cool, oxygen levels are kept high and the bass’ layer of protective slime is maintained. “We are the guardians of our fishery” says Sacks.
Despite slight differences of opinion in how to respond to extreme ecological events like the current heat wave, the DNR and fishing tournament organizations like B.A.S.S share a common goal to promote sport fishing in Michigan and collaborate often through DNR sponsored advisory groups. This collaboration could prove valuable in the face of changing environmental conditions.