Adfluvial Bull Trout
Scientific Name: Salvelinus confluentus
Identifying Characteristics: Like all salmonids, bull trout have a fleshy adipose fin located between the dorsal fin and caudal fin (tail). The back and sides of bull trout are typically an olive-green/brown color with light cream to crimson colored spots that are similar in size to the pupil of the eye. The belly is often pale yellow or a whitish color. The pectoral, pelvic, and anal fins have a white leading edge and the dorsal fin lacks markings, appearing opaque. Bull trout have a slightly fork caudal fin.
Status: Native to the Pend Oreille Watershed. In 1998 Bull Trout were listed under ESA as a “threatened” species. The Pend Oreille Salmonid Recovery Team chose bull trout as the number 1 priority fish species for recovery in WRIA 62.
Distribution: Bull trout were historically abundant in the Pend Oreille River (Gilbert and Evermann 1895; WCC 2003). An adfluvial downstream migration pattern is believed to have occurred in the Pend Oreille/Priest River basin in Washington and Idaho. Adult bull trout would migrate out of Lake Pend Oreille, Idaho and then into tributary streams in WRIA 62 to spawn, with the progeny eventually returning to the lake (USFWS 2002). This migration pattern was, however, eliminated with the construction of Albeni Falls Dam in 1952 just upstream of the Idaho-Washington state-line (USFWS 2002). Currently, the abundance of bull trout is very low in the Pend Oreille watershed (USFWS 2002, WCC 2003). Bull trout observations in WRIA 62 in the mainstem Pend Oreille River and its tributaries are infrequent and little life history information is known. Bull trout productivity is not well understood, but is also believed to be low. Reproducing bull trout populations still exist in those WRIA 62 tributaries which are part of the Priest River drainage and in the South Fork of the Salmo River (WCC 2003) but are believed to be declining.
Species Notes: Bull trout are extremely sensitive to environmental disturbance (Fraley and Shepard 1989) which makes this an indicator species of environmental change. Several factors are significant to the decline of bull trout populations in the Pend Oreille River in WRIA 62: habitat degradation on the mainstem and within the tributaries; human-made fish passage barriers into tributaries to the Pend Oreille River; non-native fish species introductions and management (eastern brook trout, brown trout, rainbow trout); and, the construction and operation of three hydroelectric facilities (Boundary, Box Canyon, and Albeni Falls dams) on the mainstem Pend Oreille River (WCC 2003). Human-caused habitat degradation associated with forest management practices, fire, flood control, livestock grazing, road construction, and land use practices associated with agriculture and residential development have also impacted bull trout in the WRIA (WCC 2003).