The rainbow trout population in the Fall River has not been surveyed in over a decade. Idaho Fish and Game biologist John Heckel wants to change that. Heckel recently conducted population estimates on rainbow trout in two different sections of the river.
"Our intentions are to develop long term monitoring sites in upper and lower sections of the Fall River," says Heckel. "The upper site is upstream of all water diversions and begins near Sheep Falls and the lower site begins at Kirkham Bridge downstream of three diversions that lead to canals." Fish and Game last conducted population estimates on the Fall River in the early 2000s, which occurred at the lower site near Kirkham Bridge.
This year, rafts outfitted with electrofishing gear were used in late August to conduct mark/recapture population estimates on the two sections. The estimated number of rainbow trout calculated in the Fall River was 1,372 fish per mile in the upper section and 3,539 fish per mile in the lower section. A small number of brown trout and brook trout were also detected, but comprised less than 1% of all fish species captured.
Rainbow trout averaged 8.25 inches at the lower site with a slightly longer average of 8.59 inches at the upper site. The total length of the longest rainbow trout at the Kirkham Bridge site was 17.52 inches and 15.75 inches at the Sheep Falls site.