Three Yellowstone rivers closed to fishing
July 21, 2003
The rivers _ as well as their tributaries _ will remain closed until their daily maximum temperatures fall below 73 degrees for three consecutive days and the seven-day forecast calls for lower maximum daily temperatures, park officials announced Monday.
Water temperatures have been unusually high due to warm weather and runoff from the park's thermal features. Warm water can be life-threatening to trout, especially after they are caught and released.
At the U.S. Geological Survey gauging station on the Firehole River, for example, temperatures have been above 79 degrees since July 10. And the Gibbon River's temperature has been above 73 degrees over the same period.
Temperatures above 77 degrees can be lethal to trout.
Research has shown that fish in the three rivers have adapted to higher temperatures. A study of fish in the Firehole River revealed that rainbow and brown trout migrated to tributaries or colder parts of the river when temperatures rose above 75 degrees.
Researchers observed that tagged fish often migrated through warmer
parts of the stream to reach cooler areas.
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