Nongame fish species distribution and habitat associations in the Snake River basin of southern Idaho

摘要

The distribution and abundance of game fish populations are commonly monitored closely, whereas sampling of nongame species is often neglected. We used a broad-scale salmonid sampling project both to simultaneously assess the distribution and relative abundance of nongame fish species in small streams (i.e., ≤15 m wetted width) in the Snake River basin of southern Idaho and to relate the distribution and abundance of nongame species to abiotic and biotic stream conditions in the study area. Of the 1738 reaches surveyed, 34% were dry or contained too little water to support fish, and an additional 21% had flowing water but were still absent of fish. At least one species of nongame fish was captured at 30% of the reaches surveyed, and all 18 native nongame fish species believed present in study area streams were captured. The most widely distributed species was speckled dace Rhinichthys osculus (present in 21% of surveyed reaches, excluding dry and nearly dry reaches), followed by bridgelip sucker Catostomus columbianus (19%), Paiute sculpin Cottus beldingi (15%), and redside shiner Richardsonius balteatus (13%). The species least often present (≤ 1%) were leopard dace Rhinichthys falcatus and peamouth Mylocheilus caurinus. Common carp Cyprinus carpio (captured at 3 locations) and oriental weatherfish Misgurnus anguillicaudatus (2 locations) were the only nonnative nongame species encountered. Catostomids and cyprinids generally formed a composite fish assemblage that was associated with higher stream order (i.e., farther from headwaters), lower elevation, and lower-gradient reaches where streams were wider and deeper. Stream order was the strongest loading factor for canonical correlations constructed for study reaches both above and below Shoshone Falls, suggesting that the increased abundance of catostomids and cyprinids generally occurred on a longitudinal downstream gradient. Biologists sampling game fish populations in streams should also record data on nongame species to more closely monitor their status through time.