Winter Flows and Impact to Trout on the Shoshone River
East Yellowstone TU members are concerned about a confluence of events that may result in harmful impacts to the wild trout population in the Shoshone River below Buffalo Bill Dam. The first event was the decision to reduce winter flows in the Shoshone River to 200 cubic feet per second (cfs). The decision is based on the 10 year Winter Release Operating Agreement approved in 2019. Under the criteria in the agreement, if the reservoir level is below 475,000 acre feet on October 1, and the Wyoming State Account is greater than 95,000 acre feet, the winter release is 200 cfs. As of October 1, reservoir levels were at 437,000 acre feet so the flows were reduced to 200 cfs.
The second event is population sampling conducted by Wyoming Game and Fish for the river reach above Belfry Bridge. The sampling estimates a population of over 8,000 fish per mile! So fish populations are at an all-time high while flows and habitat are reduced.
The third event relates to water temperature and impacts to trout metabolism. With the decreased flows, the impacts of DeMaris hot springs on water temperature is more pronounced. Water temperature data was collected at Belfry Bridge over the past several weeks: On Dec 8 the water temperature was 49.1 degrees F on Dec 12, 47.3, on Dec 20, 46.4 on Dec 27, 46.4 on Jan 6, 46.4 on Jan 14, 43.7 and on Jan 20, 44.6.
If you consider water temperature influence on trout metabolism, the current water temperatures are favorable for trout metabolism. However, with the reduced flows and loss of habitat due to exposed riffles and banks, food sources to support the high number of trout are likely to be inadequate, resulting in a loss of condition. EYTU members will continue to monitor temperatures and fish condition.
