Oregonichthys crameri

Removed from the genus Hybopsis and placed in the genus Oregonichthys by Mayden (1989), Robins et al. (1991), and Coburn and Cavender (1992). Populations of Oregonichthys in the Umpqua River drainage were described as a new species, Oregonichthys kalawatseti, by Markle et al. (1991).

Small extent of occurrence in the Willamette River system in western Oregon; formerly eliminated from most of historical range, due to habitat alteration and the effects of introduced fishes; population has increased in number and distribution since listing, through reintroductions and management; populations continue to be threatened by fragmentation, non-native predators, and barriers to dispersal.

Range includes portions of the Willamette River system of the Columbia River drainage in western Oregon (see map in Scheerer 2002; Page and Burr 2011). In the early 1990s, populations were found predominantly in the Middle Fork Willamette River (Middle Fork), with a few, small populations found in the mid-Willamette River, Santiam River, and Coast Fork Willamette River (Coast Fork). The species is now well distributed throughout the Willamette Basin (in Polk, Marion, Linn, Lane, and Benton counties, Oregon), with populations in the Santiam River (9 sites), Mid-Willamette River (6 sites), McKenzie River (4 sites), Middle Fork (16 sites), and Coast Fork (3 sites) (see USFWS 2010).

Range extent = 12,341 sq km (includes historical records).

Currently there are 64 known extant populations (Bangs et al. 2012).

The decline possibly was due to the effects of dam construction, flood control structures, and/or introduced fishes (Markle et al. 1991, USFWS 1993). In the early 1990s, most remaining populations occurred near rail, highway, and power transmission corridors and within public park and campground facilities; these populations were threatened by (1) direct mortality from potential chemical spills and overflow from chemical toilets in campgrounds, (2) competition with and predation by non-native fishes (e.g., bass, crappie, mosquitofish) (Scheerer 2002), and (3) loss of habitat from siltation caused by logging and construction activities, unauthorized fill activities, and changes in water level or flow conditions from construction, diversions, or natural desiccation (USFWS 1993). This species does best in habitats isolated from non-native fishes; increased connectivity of floodplain habitats in a system where non-native fishes are widespread may be detrimental to the conservation and recovery of this species (Scheerer 2002).

Threats to existing habitats include manipulation of flows (can lead to desiccation), nutrient and pesticide runoff, and vegetative succession in shallow pond environments. The chief threat to existing populations is invasion by non-native fishes, which may occur as a result of flood events, intentional introductions, or through connections between isolated chub habitats and adjacent watercourses. However, the status of the species has improved since listing (i.e., more populations have been established and are being managed to minimize threats), so the relative effect of the threat of predatory nonnative fishes has declined. Monitoring for nonnative fish invasions and adaptively managing in response to such invasions is necessary for the long-term viability of this species. Source: USFWS (2010).