Trout populations are strong in the Henrys Fork near St. Anthony
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The following is a news release and data from the Idaho Department of Fish and Game.
ST. ANTHONY – In October 2020, Fish and Game biologists conducted the sixth population estimate on the St. Anthony reach of the Henrys Fork Snake River. Based on sampling data since 2010, there’s an increasing trend in brown trout abundance in this reach. This estimate is conducted in the fall every three years and extends from the Railroad Bridge downstream to the Red Road Bridge. Based on our sampling data since 2010, we can see an increasing trend in Brown Trout abundance in this reach.
We can see in the figure above that the number of brown trout per mile has been increasing since we started surveying the reach in 2004 while Rainbow Trout abundance has remained low and relatively constant. Currently, brown trout make up 96 percent of the trout in this reach where we caught 1,468 trout in total. As can be seen in the images, there are some very large brown trout with fish up to 25 inches in this reach!
The trout population in this portion of the Henrys Fork is managed as a wild trout fishery, so these large trout captured in this reach are in fact wild fish. Therefore, referring to the length distribution of fish captured here, this section of the river grows some very large trout.
Although water temperature in this section of the Henrys Fork can become warmer than 70°F during portions of the summer, trout can find thermal refuge from groundwater and spring inputs that help coldwater fish remain cool. In addition to brown and rainbow trout, we also estimated mountain whitefish abundance in the reach. There were 685 whitefish per mile. Based on our length-frequency data from whitefish we observed several age classes present, which is evident by the multiple peaks in different length groups.
Survey results indicate sport fish populations in the St. Anthony reach are healthy and in good numbers. Managing this section of the river as a wild trout fishery with a two trout limit appears to be conducive for growing large fish and allowing population numbers to increase.