Fish and Game Warning: Warm Water Will Affect Fish Survival

GREEN RIVER—Air and water temperatures are soaring and river flows are coming down and the Wyoming Game and Fish Department's Green River fish management staff is very concerned about the impacts to both fish and anglers in the Green River.

"Trout experience significant mortality at prolonged exposure to water temperatures greater than 75 degrees Fahrenheit and brief exposure to temperatures over 80 degrees are lethal," said Green River Fisheries Supervisor Robert Keith. "As water levels drop and water temperatures rise we are asking anglers fishing on the river to monitor water temperatures while fishing. Being caught and released is stressful on any fish, but especially trout and kokanee salmon. Anglers should give fish a break as water temperatures reach over 70 degrees Fahrenheit. The warmer water stresses fish and being caught and released stresses them even more. Fish handling mortality can be quite high when water temperatures get over 70 degrees Fahrenheit. Even if a fish swims away from an angler it does not mean it is going to survive."

Keith says anglers can reduce impacts to fish by fishing early in the morning, while water temperatures are cooler, and carry a thermometer to monitor water temperature. If the temperature is at or above 65 degrees, reconsider your plans to catch and release trout in local rivers and streams. It's a good idea to stop fishing for the day and give the fish a break.

Fish survival rates in Flaming Gorge Reservoir are also a concern, as the water temperature in local reservoirs is also warming up. Keith said many anglers are proud of the fact that they catch and release fish, however, the percentage of fish lost after release could be as high as 10%. For kokanee, the death rate is higher than other fish species because they are more fragile than other fish.

"Anglers are having a great year fishing for kokanee salmon," Keith said. "However, kokanee do not handle catch and release fishing very well and do even more poorly when water temperatures are warm. If you are fishing for kokanee, we recommend limiting the practice of catch and release, especially when surface temperatures are warm. Surface temperatures are reaching the low 70's on hot days. The kokanee are living at depths of 45 to 65 feet where the water temperature is around 45 degrees Fahrenheit. The more than 20 degree temperature change from depth to the surface is stressful to the fish. Add to that the stress of being caught, handled, and released. The result is some kokanee swimming away to die."

"If you are going to catch and release fish you should not bring the fish into the boat," Keith said. "The best strategy is to unhook the fish without lifting it from the water. If you net it, use a rubberized net and keep the fish in the water. As soon as you bring a kokanee into the boat the chances of it surviving decreases significantly."

Anglers planning to catch and keep their fish are encouraged to still do so. Be sure to bring plenty of ice and a cooler to keep the fish fresh after harvesting it and during transport. For more information about catch and releasing fish properly call the Green River Region Game and Fish Office at 307-875-3223. Anglers will find additional information at the Game and Fish website