CPR for Fish!

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Published on: May. 2, 2006

Last revision: Nov. 29, 2010


Never stringer a fish that you plan to release. Stringers damage a fish’s gills.

When you release a fish do it carefully. Don’t just toss it. It might be stunned by the impact with the water, or it could land on rocks or sticks.

When releasing an exhausted fish, hold it upright by its tail and move the fish very slowly forward and back until it recovers enough to swim away on its own.

Water temperature dramatically affects the survival rate of released fish. In spring and fall, when water temperatures are less than 80 degrees, properly handled bass often have survival rates over 90 percent, if immediately released, or even under delayed-release situations, such as bass tournaments.

However, as water temperatures climb above 80 degrees the chances of bass survival decrease sharply. Missouri Department of Conservation fisheries biologists cooperated with Mississippi State University to assess survival of bass that were caught, weighed in and released by anglers during summer tournaments. Release survival was less than 50 percent, even when anglers did all they could to pamper the bass.

The high mortality rate seems to be due to the combined effects of handling, confinement and high water temperatures, and the presence of largemouth bass virus. Warm water in livewells provides an environment under which this and other fish pathogens can thrive and rapidly infect healthy fish. Nearly all of Missouri’s large lakes have tested positive for largemouth bass virus.

Water temperature is also a key factor in catch-and-release survival of cool- and cold-water fish such as trout, muskies or walleye. Walleye studies have shown that release survival rates decrease at temperatures above 70 degrees.

During warm-water periods, all tournament organizers should consider alternatives to the standard weigh-in format. Several muskie tournaments in Missouri have combined digital photography and on-the-water witnesses to verify catches so fish can be released immediately. Fish also require oxygen, which they get from the water. A fish out of water is like a person with his or her head underwater.

Try holding your breath while you are unhooking, photographing or transporting a fish, and you’ll understand the oxygen deprivation a fish might be experiencing. Make every effort to release fish quickly. Keep the camera ready so you can take pictures quickly.

Fish kept in overcrowded or poorly aerated livewells also suffer from oxygen deprivation.

A constant flow of fresh, cool, aerated water through the livewell will help maintain a healthy environment for the fish. Because cooler water holds more oxygen, and fish in cooler water consume less oxygen, some anglers and researchers recommend adding ice to the livewell. However, it is important not to cool the livewell water more than 10 degrees below the surface temperature of the lake to avoid creating a temperature shock for the fish.

A livewell additive that can reduce stress is common, uniodized table salt. Add one-third of a cup of salt per 5 gallons of water in the livewell. This is similar to the concentrations used in many hatchery transport vehicles.

The best way to pamper a fish that you’re not going to keep is to reduce the length of time between catching and releasing it. Any confinement, whether the fish are held in a livewell, a weigh-in bag or a pickle bucket, can reduce survival rates, especially when the water is warm.

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