New study tests temperature in live wells

Many catch-and-release fishing tournaments require anglers to hold fish on board for hours at a time, but do live wells get too hot for fish?

Catch-and-release tournament anglers launch in the morning and bring fish back to the weigh in site after a day’s fishing. Photo: Dan O'Keefe | Michigan Sea Grant

Catch-and-release tournament anglers launch in the morning and bring fish back to the weigh in site after a day’s fishing. Photo: Dan O'Keefe | Michigan Sea Grant

Anyone who has kept fish in an aquarium is well aware of the effect that temperature can have on fish health. When moving fish from one place to another, it is important to “temper” the fish slowly and avoid rapid changes in temperature. According to Michigan State University Extension, this is true when moving tropical fish from the pet store to a home aquarium and it is also important when moving wild fish from the place of capture to a tournament weigh-in site.

Researchers in the Department of Natural Resources and Environmental Sciences at the University of Illinois Urbana-Champaign recently investigated live-well conditions at three separate competitive fishing events in Illinois. They used temperature loggers to compare live-well temperatures to lake temperatures during the course of the tournaments to find out if wide temperature swings might be having a negative impact on bass.

Their study, which was recently published in the North American Journal of Fisheries Management, found that automatically-circulating live wells were similar, but not identical, to ambient lake temperatures. During one tournament, live-well temperatures were slightly (less than 1.8˚F) warmer than lake temperatures, but during the other two tournaments the live-well temperatures were slightly cooler (again differing by less than 1.8˚F).

The authors then concluded that preventative treatments used to reduce fish stress in live wells may do more harm than good if anglers use the treatments without circulating water in live wells. For example, attempts to cool live wells may not only be unnecessary, but could also be harmful. Largemouth bass can show signs of stress due to cold shock if temperature is rapidly reduced by 9˚F.

Michigan Sea Grant helps to foster economic growth and protect Michigan’s coastal, Great Lakes resources through education, research and outreach. A collaborative effort of the University of Michigan and Michigan State University and its MSU Extension, Michigan Sea Grant is part of the NOAA-National Sea Grant network of 33 university-based programs.

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