| Summary: | Fish sampling and habitat assessment were conducted at 24 sites in the lower 54 km of the Coeur d'Alene River, Idaho in 2005 and 2006 to I) characterize four shoreline habitat types-- failing banks (FB), riprap (RR), riprap with vegetation (RR V), and vegetation (V)--according to ranked and quantifiable habitat variables, 2) assess differences in relative fish abundance (catch-per-unit effort; CPUE), species diversity, and community composition associated with the four shoreline habitat types, two sections (upstream and downstream), and three seasons (summer, spring, fall), 3) assess the relationships between relative fish abundance and habitat variables, and 4) assess the relationship between relative fish abundance and a) depth of riprap structure and b) riprap rock diameter. The four habitat types differed significantly in habitat characteristics based on Rapid Bioassessment Protocols (RBP) scores (F=5.73, P<0.001). All four habitat types scored poor or marginal in substrate/available cover, pool variability, sediment deposition, and riparian zone width. Relative fish abundance as measured by CPUE at stabilized (RR and RR V) shorelines was consistently higher than at unstabilized (FB and V) shorelines among all seasons. Relative fish abundance was not significantly different between stabilized and unstabilized habitat types for gillnetting (F= 1. 9 5, P=0.167), but was significantly higher at stabilized than unstabilized habitats for electrofishing (F=5.66, P=0.020). Differences in species diversity were only evident between sections, not among habitat types or seasons. Fish community differences were apparent among habitat types as well as between sections and among seasons. Brown bullhead Ameirus nebulosus, northern pike Esox lucius, and pumpkinseed Lepomis gibbosus were captured in significantly higher numbers at stabilized than unstabilized sites and longnose suckers Catostomus catostomus were captured in greater numbers at unstabilized than stabilized sites. Water temperature and spawn timing ...
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