2010 Preliminary Boise River Population Survey Results

In October 2010, the IDFG conducted its electroshock fish population survey on the Boise River in town. The final report from the fishery biologists is still in progress, but Art Butts in Nampa was kind enough to share some preliminary highlights.

The biologists are primarily interested in wild rainbow and brown trout, mountain whitefish, and hatchery rainbows. While pikeminnows and suckers were present, data representing those two species was not recorded.

• 2010 was not a good recruitment year for wild trout or whitefish. In other rivers such as the South Fork of the Boise, fingerlings are found in many types of holding water. This has never been the case in the Boise River, however. Art is tentatively planning to check each year for young fish going forward to better understand recruitment and holding patterns of yearling fish.
• Brown trout populations are predominantly down from 2007 for all age classes.
• Until 2009, brown trout had not been stocked in the river since 1998. In July 2009, 15,010 fingerling browns were stocked, and in July 2010, another 18,713. To distinguish these trout from wild browns, many were lacking adipose fins when released. The overall survival rate of these browns appears to be quite low.
• On the bright side, catchable wild rainbows are doing well, with higher numbers in the middle section of the river. The number of rainbows in the 6-12" range is up from 2007.
• Mountain whitefish numbers are relatively unchanged from 2004, and they are the dominant species in the river in terms of quantity.

Releasing a Wild Boise River Rainbow