|Scientific Name:||Chasmistes brevirostris|
|Species Authority:||Cope, 1879|
|Taxonomic Notes:||Genetic introgression with Catostomus snyderi has occurred in the Lost River system and with C. rimiculus in Copco Reservoir (but gene pool relatively intact). Hybrids with Deltistes luxatus or Catostomus snyderi are common in Upper Klamath Lake (Scoppettone and Vinyard 1991).|
|Red List Category & Criteria:||Endangered A2bc; B1ab(iii,v)+2ab(iii,v) ver 3.1|
|Reviewer/s:||Smith, K. & Darwall, W.R.T.|
|Facilitator/s:||Hammerson, G.A. & Ormes, M.|
Listed as Endangered because the extent of occurrence is less than 5,000 sq km, area of occupancy may be less than 500 sq km, the species is represented by not more than five locations, and the population has experienced a decline in the number of mature individuals over the past three generations (probably at least 25 years). Habitat is subject to extreme fluctuations in water availability. Also, adult population size may have declined by at least 50% over the past three generations.
|Range Description:||Historical range included the upper Klamath River and Lost River basins in Oregon and California (Moyle 2002; USFWS 1994, 2007). Current range in the Lost River drainage includes Clear Lake Reservoir, the main river below the reservoir, the Boles Creek and Willow Creek drainage above the reservoir, Gerber Reservoir, and small reservoirs scattered along the creeks, plus a small population in Tule Lake at the terminus of the Lost River (USFWS 1993, Moyle 2002). Genetic data suggest that the populations in Gerber Reservoir and Clear Lake may not be Chasmistes brevirostris (see USFWS 2007); further study is needed. Current range in the Klamath River basin includes Upper Klamath Lake (Oregon) and its major tributaries, (Williamson, Sprague, and Wood rivers) and possibly the lower reaches of smaller tributaries as well (Moyle 2002). Small populations occur in Iron Gate and Copco reservoirs on the Klamath River (USFWS 1993, Moyle 2002).|
|Range Map:||Click here to open the map viewer and explore range.|
This species is represented by only two primary populations. Other populations, such as those in the Klamath River reservoirs, are apparently sustaining themselves with the input of larvae or older suckers from other areas (i.e., those in Upper Klamath Lake and Clear Lake) (USFWS 2007).
Total adult population size is unknown but likely exceeds 10,000.
Formerly the species was very abundant in Upper Klamath Lake, Oregon. Population size and habitat quality clearly have declined greatly over the long term; degree of decline is uncertain but probably quite large.
Available information for the 1980s indicates that the population was declining as a result of little or no recruitment coupled with mortality from the sport fishery and fish die-offs (USFWS 2007).
Spawning migrations have declined significantly in recent years. Recent data indicate that the population has not recovered from the substantial declines in the 1990s (USFWS 2007). A major decline in an abundance index for the Williamson River occurred in the mid to late 1990s, and the index remained low through at least 2003 (USFWS 2007). Survivorship in Upper Klamath Lake appears to have been relatively low in the early 2000s (see USFWS 2007). Recruitment in Upper Klamath Lake was essentially nil from 1997-2004 (Janney and Shively 2007). Populations in Gerber Reservoir and Clear Lake show evidence of frequent recent recruitment and declines in the number of large adults (Barry et al. 2007a, USFWS 2007). The small population in the Tule Lake sumps appears to be isolated from suitable spawning habitat and likely is not self-sustaining (USFWS 2007).
The time frame for short-term trend (10 years or three generations, whichever is longer) is probably at least 25 years.
|Habitat and Ecology:||
Adults and juveniles prefer shallow, turbid, and highly productive lakes that are cool, but not cold, in summer (generally 15 to 25°C), have adequate dissolved oxygen, (above 4 mg/l), and are moderately alkaline (Moyle 2002).
Spawning occurs in lake tributaries, in riffles or runs with gravel or cobble substrate, moderate flows, and depths of 11-130 cm (USFWS 2007). Historically, spawning occurred also along the margins of Upper Klamath Lake, but that now appears to be rare (Barry et al. 2007b). Fry move into lakes soon after hatching. Shoreline river and lake habitats are important for larvae and young (especially emergent vegetation for larvae) (USFWS 2007).
Spawning migrations have declined significantly in recent years, due in part to alteration of habitat (especially damming). Chiloquin Dam, constructed in 1928 on the Sprague River, Oregon, cut off 85% of spawning range; recruitment has been essentially nonexistent in recent decades (Scoppettone and Vinyard 1991).
Human-caused increases in nutrient inputs to Upper Klamath Lake have resulted in massive summer and fall blooms of cyanobacteria and elevated lake pH levels of 9.5-10.5, which in turn have led to mass mortalities and curtailed reproduction of the Shortnose and Lost River Suckers (Falter and Cech 1991, G. Scoppettone pers. comm. 1995). Fish kills also may result from low dissolved oxygen levels (G. Scoppettone pers. comm. 1995).
Extensive modification of the watersheds and wetlands of the Lost River - Tule Lake system, the Lower Klamath Lake system, and the Upper Klamath Lake system resulted in substantial loss of habitat. The rate of habitat change has slowed markedly, but only a small fraction of the original habitat remains, and much of the remaining habitat is in a degraded condition. Restoration efforts are beginning to reverse the trend, but will probably require many years to produce a substantially increased and stable habitat base. Adverse water quality is the most critical threat, and substantial improvement is not expected in the near future. Based on the record of the past two decades and the expected future summer water quality of Upper Klamath Lake, it is reasonable to conclude that within the foreseeable future, there is a high probability of multiple mortality events that would greatly reduce population sizes. It is possible that infrequent recruitment would be unable to offset declines from such die-offs. [Source: USFWS 2007]
Fish entrainment and restricted passage are threats. Entrainment at Link River Dam and associated hydropower diversions probably poses a high risk to the species. The threat there could be reduced if the hydropower diversions are screened or eliminated, and if discharges at the dam could be modified to reduce entrainment. Passage to spawning habitat in the Sprague River is still impeded by Chiloquin Dam, but that structure is planned for removal in the near future. Elsewhere in the upper basin, some entrainment of suckers is occurring, but mostly larvae are entrained, and we do not consider this a substantial threat at the population level. [Source: USFWS 2007]
Disease, parasites, and predation/competition by exotic fishes pose some risk, although the degree to which they affect the shortnose sucker is not quantified. Disease and parasites alone may not pose a significant risk, but paired with the impacts of adverse water quality, they can substantially affect sucker survival (USFWS 2007).
Low water levels continue to affect sucker habitats, especially in drought years (USFWS 2007). Drought is a threat because of its potential to cut off spawning habitat, to reduce rearing habitat and to increase disease, parasitism, and predation. However, historically the species has endured periods of prolonged drought and persisted, indicating that drought is not a major threat to the species (USFWS 2007).
Since the listing, protections under the Endangered Species Act have limited take of suckers and stimulated restoration actions. Water quality regulations have begun to lead toward improved water quality, but have not yet resulted in substantial improvement, and significant questions remain regarding the potential for improvement in Upper Klamath Lake. With the exception of management of water quantity under the Act, regulation of water quantity is not focused on improvement of sucker habitat, and relationships between water quantity and sucker performance remain incompletely demonstrated. Thus, while application of federal and state regulations has apparently helped stabilize sucker habitat and has initiated progress toward improvement of water quality, existing regulations cannot be expected to substantially reduce the primary threat to the species for many years. [Source: USFWS 2007]
Hybridization with other sucker species has resulted in part from the high degree of habitat alteration that has occurred in recent decades (Moyle 2002). The impact of hybridization on species' conservation is currently unclear (USFWS 2007).
|Conservation Actions:||A number of landowners and agencies are directly or indirectly focused on sucker recovery. The high rates of participation in federal and state conservation programs by ranchers and farmers in the Sprague and Wood river valleys suggests that essential elements of habitat recovery on private land (i.e., voluntary participation and funding) are now in place. This should make it more efficient to conduct restoration in the future. Furthermore, the USFWS and its partners are committed to developing and implementing a rigorous monitoring program to evaluate the effectiveness of recovery actions and to providing a feedback loop for adaptive-management. These efforts, if successful and sustained, should help recover the Shortnose Sucker. [Source: USFWS 2007, which see for further information on restoration efforts]|
|Citation:||NatureServe 2013. Chasmistes brevirostris. In: IUCN 2013. IUCN Red List of Threatened Species. Version 2013.2. <www.iucnredlist.org>. Downloaded on 16 April 2014.|
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