The Enigma of the South Fork Boise River
Northwest regional anglers have long held the highest regard for the South Fork Boise River’s blue ribbon trout fishery. Revered primarily for its hard-fighting, selective redband rainbows, local fly fishers often speak in hushed tones in “water cooler” conversations lest they reveal information that might draw more anglers to its already crowded banks.
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Tributary spawning survery
A number of small tributaries drain directly into the South Fork Boise River, but their contribution for spawning and rearing habitat is poorly understood. Potential tributary enhancement projects could be effective, but the first step is learning whether fish are presently using the tributaries and the water conditions, whether the culverts inhibit or prevent fish passage, and habitat present in those tributaries.
The Boise National Forest has identified the culverts on four South Fork tributaries as barriers to Aquatic Organism Passage, typically referring to fish but can be other biologically important species. Culverts installed typically prior to the 1990’s like those on the SFB tributaries, are not designed for fish passage since they typically move water faster than the stream itself. While fish swim against a current at higher speed in shallow water, their passage through the culvert when moving upstream from the river to the tributary can be restricted due to water velocity, length of the culvert and depth of water.
Tagged spawning, tributaries
Mainstem spawning survey
Tail water fisheries experience regular, consistent water flow and temperature compared to natural streams, allowing fish longer growing seasons and healthy habitat for invertebrates that the fish eat. At the same time dams prevent fish from migrating to headwater streams to spawn. These dams also trap gravels upstream that otherwise would move through a river during natural flooding and thus replenish in-stream spawning areas with new gravel that often gets silted over or scoured to other locations.
First post: South Fork Boise River rainbow trout population
First post: South Fork Boise River rainbow trout population. Lots of big fish. Indeed, more big fish than can be explained by the smaller and medium fish in the population.
South Fork Partners
