Why Is Pettingell Lake in Rocky Mountain National Park Closed to Fishing This Week? Removing Nonnative Fish

The following Fun Fact was published on September 9, 2002.

Past fishery management activities in Rocky Mountain National Park and in most national parks focused on recreation and paid less attention to issues of biodiversity and native species. Many nonnative fish species or subspecies (especially trout) were previously stocked in park waters. In some cases, interbreeding has occurred resulting in hybrid fish populations. In others, native species have been out-competed by exotics. This might not cause problems in many areas, but in national parks the mission is to maintain and protect native species in natural habitats. This has become especially important in Rocky Mountain National Park as one "Federally Listed Threatened" fish - the greenback cutthroat trout and one state designated "Rare" fish - the Colorado cutthroat trout are native. Fishery management plans involve restoring these rare or threatened species to their native waters in the park.

The first step in this process is to remove any nonnative or hybrid fish from park waters. This is done after careful planning and discussion, and is done one lake at a time. First, a lake is closed to prevent fishing, and a fish toxicant is introduced to the system to remove all the fish. After an appropriate period of time, the fish toxicant is chemically removed from the lake. Biologists monitor the lake to assure the treatment was successful. This often takes more than one year to be sure no nonnatives or hybrids remain. Once biologists are sure no fish remain in the lake, it will be restocked with pure strains of trout.

In the case of Pettingell Lake, historic records show that it is located in the known habitat for Colorado cutthroat trout. During the week of September 9, 2002, US Fish and Wildlife Service and National Park Service biologists will close the lake and treat it to remove the hybrid fish that currently inhabit it. Next summer they will restock it with the native fish. Within a few years park visitors will have the thrill of fishing for a rare species and know that biologists are protecting the native biodiversity of the park.

Last updated: March 31, 2012

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