Westslope Cutthroat Trout

 

 

 

 

 

 

 

Scientific Name: Oncorhynchus clarki lewisi

Identifying Characteristics: Like all salmonids, westslope cutthroat trout have a fleshy adipose fin located between the dorsal fin and caudal fin (tail). Westslope cutthroat trout also vary in color but have red slashes on the underside of the jaw. The spots are small and irregular and are more concentrated near the caudal fin with few, sparsely distributed spots on the underside of the belly. In fish longer than 4 inches, the maxillary or upper jaw extends beyond the eye. The key characteristic however is the presence of basibranchial (hyoid) teeth behind the tongue; rainbow trout lack this feature.

Status: Native to the Pend Oreille Watershed. Westslope cutthroat trout were petitioned in 1998 for listing under ESA as a threatened species. To date, the USFWS has determined that the listing is not warranted. Westslope cutthroat trout are currently designated as a “species of concern” in both Idaho and Washington. The Pend Oreille Salmonid Recovery Team chose westslope cutthroat trout as the number two priority fish species recovery in WRIA 62.

Distribution: Historically, westslope cutthroat trout were abundant in the Pend Oreille River basin (Wydoski and Whitney 2003) and both fluvial and resident forms were believed to be present (USFWS 1999).  Westslope cutthroat trout historically occupied greater than 99% of the streams in the Pend Oreille River Basin, which encompasses areas of the Idaho Panhandle and the corner of northeast Washington. Based on surveys, it is believed that westslope cutthroat trout are present in only 35% of their historically occupied stream reaches (KNRD).

Currently, resident westslope cutthroat trout are found in many WRIA 62 tributary streams and adfluvial populations are found in the Sullivan subbasin (Sullivan Lake/Harvey Creek) and those subbasins which drain to Priest Lake (i.e. Hughes Fork, Kalispell, Granite).  Abundance is largely unknown (C. Vail, WDFW, pers. comm. 2004), but appears to be dependent upon quality and quantity of habitat and competition from other species (T. Shuhda, USFS, pers. comm. 2004; M. Fairchild, USFS, pers. comm. 2004).    Diversity has been reduced from historic levels due to the loss of the fluvial form of cutthroat trout, which are no longer believed to be present in the watershed (C. Vail, WDFW, pers. comm. 2004).  Fluvial stocks apparently could not adapt to an adfluvial life history upon construction of dams on the mainstem Pend Oreille River (Scholz 2000 in Wydoski and Whitney 2003). 

Species Notes: Factors which have contributed to the decline of westslope cutthroat trout include conversion of the Pend Oreille River from a riverine to a reservoir environment (Wydoski and Whitney 2003) through the construction and operation of three hydroelectric facilities (T. Shuhda, USFS, pers. comm. 2004), displacement from streams by non-native salmonids (T. Andersen, KNRD, pers. comm. 2004), human-made fish passage barriers, and habitat degradation (Wydoski and Whitney 2003) associated with forest management practices, fire, flood control, livestock grazing, road construction, and agriculture (T. Shuhda, USFS, pers. comm. 2004).

Genetic analysis of resident cutthroat trout populations in WRIA 62 has shown that several tributaries support genetically distinct populations of westslope cutthroat trout (Shaklee and Young 2000).  However diversity is limited in some subbasins due to introgression with non-native rainbow trout (M. Fairchild, USFS, pers. comm. 2004).

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