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The Big Springs Fish

Most of the fish you see in Big Springs are either
rainbow trout or rainbow cutthroat hybrids. Although
rainbow trout, brook trout, and Kokanee salmon are
commonly found within the upper Henry's Fork
Watershed, the only native trout in this region is the
Yellowstone cutthroat trout. Yellowstone cutthroat
troute evolved in isolation from other trout, therefore,
they did not develop the mechanisms needed to
successfully compete with the introduced trout
species. This ?? led to the decline of the native
cutthroat throughout its range.

Big springs has long been a important spawning
environment for trout. In 1919, the State of Idaho closed the
Henry's Fork for fishing from Big Springs to the confluence
with Henry's Lake Outlet. The constant temperature of 32°F
enables the newly hatched trout to feed all winter long
during the optimal times of the day. Big Springs, however,
may not be an idea envornment for growing big fish. The
winter here is nutrient poor compared o Bor Canyon and
Island Park Reservoir. Low nutrients in a system can result in
aquatic insects, which often translates to slower growth, and
often, smaller fish.

The large fish often observed at Big Springs are
imigrants from Island park Reservoir. Therefore, the
management of the reservoir affects the fish
inhabiting its tributaries. The hatchery rainbow trout
that are stocked in the reservoir are electively bred
to spawn earlier to maximize their growing season in
the reservoi's nutrient rich water. These trout migrate
up the river in early winter. The number of spawning trout
at Big Springs peaks in February.

[picture captions]
Cutthroat trout
Oncorhynchus clarki

Rainbow trout
Oncorhynchus mykiss

Kokanee salmon
Oncorhynchus nerka

Brook trout
salvelinus fontinalis

Mountain whitefish
Prosopium williamsoni

Don't miss the rest of our virtual tour of Big Springs in 75 images.