Umpqua River Cutthroat Trout
Umpqua River Cutthroat Trout
Oncorhynchus clarki clarki
|Listed||August 9, 1996, Endangered|
|Delisted||April 26, 2000|
|Description||Profusion of small to medium-sized spots of irregular shape; not brilliantly colored.|
|Habitat||Two to five months in saltwater.|
|Reproduction||Ideal spawning in cool streams with moderate flows and little change in water temperature.|
|Threats||Degradation of habitat due to logging, recreational fishing, drought.|
The Umpqua River cutthroat trout, Oncorhynchus clarki clarki, is a distinct population segment of the coastal cutthroat trout. Coastal cutthroat trout differ from all other trout by their profusion of small to medium-sized spots of irregular shape. In addition, they do not develop the brilliant colors associated with inland cutthroat trout, which are a separate species. In the sea-run populations, spots and colors are further obscured by the silvery skin deposit common to sea-run trout. Non-anadromous (resident) fish tend to be darker, with a copper or brass sheen.
Coastal cutthroat trout have the most complex and flexible life history of the Pacific salmonids, one characterized by three patterns of migratory behavior. These behaviors are termed anadromy, potamodromy, and residency, and examples of each are presently found in the Umpqua River. Anadromy is a common life-history trait of Pacific salmonids, and is exemplified by a species that migrates from freshwater to the ocean and then returns to freshwater as an adult to spawn. Potamodromy, a relatively uncommon life-history trait, is exemplified by a species that undertakes freshwater migrations of varying length without entering the ocean. Residency, a relatively common life-history trait, is exemplified by a species that remains within a relatively small freshwater range throughout its entire life cycle.
Coastal cutthroat trout that sea-run, unlike other anadromous salmonids, do not overwinter in the ocean, and they only rarely make extended migrations across large bodies of water. They migrate in the near-shore marine habitat, rarely going farther than 6 mi (9 km) from land. Most anadromous cutthroat trout enter seawater as two-or three-year olds, although some may remain in freshwater up to five years before entering the sea. Other cutthroat trout may never out-migrate at all, remaining residents of small headwater tributaries. Still other cutthroat trout may migrate only into rivers and lakes, even when they have access to the ocean.
The Umpqua River cutthroat trout spends two to five months in salt water, usually close to shore near estuaries and beaches. Because they spend less time in a marine environment, ocean conditions have a lesser impact on the cutthroat than on other salmon species, and during periods of poor ocean conditions, such as rises in water temperature as a result of El Nino, the cutthroat will return to a freshwater habitat.
For adequate spawning conditions to occur, streams must be cool with moderate flows and little change in water temperature. The lowest cutthroat populations occur in streams whose forest canopy has been removed by silviculture (clearing of forest), which caused fluctuation of water temperatures leading to outbreaks of disease, altered timing of migration, and accelerated maturation. The removal of streamside vegetation decreases woody debris that provides cover for the cutthroat and interrupts the food chain for other species that comprise the cutthroat's diet. Cutthroats require a fairly clean gravel substrate, and siltation will hinder the emergence of fry, as well as limit the production of invertebrates that are a part of the cutthroat's diet. Logging also alters the oxygen content of the water, and changes the velocity and depth.
Each salmonid species has had a unique evolutionary history and utilizes ecological niches different from all other species. The coastal cutthroat trout subspecies, native to western North America, is found in the coastal temperate rainforests from southeast Alaska to northern California.
The Umpqua River cutthroat trout, a distinct population segment of the coastal cutthroat trout, inhabits a large coastal basin draining in the southwestern Oregon coast. The Umpqua River cutthroat trout lives and spawns in the main-stem Umpqua River, the North Umpqua River, the South Umpqua River, and their respective tributaries—the chief of which are the Smith River and Calapooya, Elk, and Scholfield Creeks. The estuary of the Umpqua River is one of the largest on the Oregon coast, and any factors that degrade its productivity and quality are likely to decrease the Umpqua River cutthroat trout population.
The historical range of anadromous cutthroat trout may have extended up to Toketee Falls on the North Umpqua River, with populations most likely inhabiting areas above both Soda Springs and Galesville Dams. Natural barriers form gene flow barriers, resulting in a distinction between resident cutthroat trout populations above natural barriers and migrating populations below such barriers. However, the isolated cutthroat trout populations created several decades ago by these impassable barriers are believed to be still genetically similar to those cutthroat trout residing below the artificial barriers, so the populations residing above Galesville and Soda Springs Dams are listed as Umpqua River cutthroat trout.
The North Umpqua River has larger and healthier populations of cutthroat trout than the South Umpqua River, as determined by Winchester Dam counts, although ladder counts at the Winchester Dam indicate that the sea-run population of the cutthroat trout has declined to precipitously low levels. Although no long-term surveys of cutthroat trout were conducted in the South Umpqua River before 1993, a very small, wild cutthroat trout population probably exists in the South Umpqua River system. The South Umpqua River appears to have always been less conducive to cold-water dependent species like the cutthroat trout than the North Umpqua River. The North Umpqua River begins farther inland and flows for a substantial distance at a higher elevation than most other Oregon coastal rivers; as a result, the North Umpqua River has historically had cooler water temperatures and larger summer water flows than other local rivers. The South Umpqua River also begins at a relatively high altitude but stays there only for a short time. Its rapid drop in elevation leads to higher water temperatures and lower summer flows than the North Umpqua River. Present conditions in the North Umpqua River continue to be more favorable for cutthroat trout production than those found in the South Umpqua River.
The extremely low numbers of adult cutthroat trout counted at Winchester Dam on the North Umpqua River signal a high risk of extinction for the species. The primary threats to the survival of the Umpqua River cutthroat trout are recreational fishing, and loss or degradation of habitat due to logging. Drought, which leads to decreased stream-flows and increased water temperatures, is the principal natural condition that may have contributed to reduced numbers of cutthroat trout, especially in the seven dry years prior to 1996.
There are other conditions and factors that may have affected cutthroat trout populations, although they are less well-established as active agents than the ones cited above. These include the following: predation by marine competitors and birds; adverse environmental conditions resulting from natural factors such as floods and poor ocean conditions; pollution caused by agriculture and urban development; disease outbreaks caused by hatchery introductions and warm water temperatures; mortality resulting from unscreened irrigation inlets; and competition in estuaries between native and hatch-ery cutthroat trout; and loss of habitat caused by the construction of dams. Non-native fish and pinnipeds are known to prey on or compete with salmonids but there is no specific information regarding the impact of predation on Umpqua River cutthroat trout. Disease is not believed to be a critical factor in the decline of cutthroat trout.
The documentary evidence available suggests that land-use practices in Oregon have generally contributed to the curtailment, modification, and destruction of habitat diversity and complexity there. This habitat attrition has reduced salmonid production and accelerated the frequency and magnitude of both flooding and drought. Estuarine habitats, highly productive environments vital to the life cycle of the Umpqua River cutthroat trout, have been especially affected. There, degradation and loss through dredging, filling, and diking for agricultural, commercial, and municipal uses have substantially contributed to the decline in cutthroat trout.
At least 60% of the Oregon streams used by anadromous salmonids are rated as having low or very low habitat quality. These poorly rated streams are all found in watersheds that have been moderately to heavily harvested for lumber, while those streams rated good are found almost exclusively in drainages that have had little or no history of timber harvest and road construction. This strongly suggests that silviculture has degraded water quality and contributed heavily to the decline of the Umpqua River cutthroat trout. Silviculture is practiced on approximately 70% of the federal, state, and private timberland within the Umpqua River basin area, and more than 80 of the basin's river reaches are designated as being of limited water quality.
Commercial logging and other forest and rangeland management practices often have multiple adverse effects on the habitats that support the cutthroat trout. The removal of forest canopy can cause an increase in both the maximum and the diurnal fluctuation of water temperatures, leading to disease outbreaks, altered timing of migration, and accelerated maturation. The removal of streamside vegetation can deplete the bank area of potential new woody debris that provides cover for cutthroat trout. Loss of riparian areas can also result in decreased invertebrate production and detritus sources, both of which are key components of the species' food chain. Siltation, another result of some logging practices, is known to hinder fry emergence from the gravel, and may limit production of benthic invertebrates. Logging can also decrease the dissolved oxygen content of both surface and intra-gravel water while changing stream flow regimes, adversely affecting water velocity and depth characteristics.
The riparian habitat loss attributed to logging can also affect river temperature and acidity in ways that are harmful for cutthroat trout. Summer water temperatures and the frequency of winter flooding have increased in the Umpqua River watershed since the mid-1950s, presumably as a result of poor logging practices. Summer water temperatures are often above the preferred range for cutthroat trout and other salmonid populations (about 44-61°F [6-16°C]) in portions of the river. The riparian forest canopy has begun to recover recently in the North Umpqua River watershed, but maximum water temperatures are still higher than those preferred by cutthroat trout. This recovery has been slower in the South Umpqua River watershed and conditions for cutthroat trout have remained poorer than in the North Umpqua River. Data indicates that pH levels in various tributaries of the Umpqua River basin exceed the state of Oregon's water quality standards, and these pH levels can be attributed to the effects of logging.
Recent increased timber harvest on federal land could increase the chance of further damage to aquatic resources in the Umpqua River basin. The emergency salvage timber sale provisions of a 1995 appropriations act have resulted in harvest of at least seven timber sales in the Umpqua River basin. The impacts of such sales are especially great in the South Umpqua River basin since existing habitat and water quality conditions are recognized as poor in this area.
Cutthroat trout are not harvested commercially—though they are believed to be the victims of undocumented illegal harvest—but they are a popular gamefish throughout the Pacific Northwest. Recreational fishing has likely contributed to the general decline in Umpqua River cutthroat trout populations. Current fish hatchery practices may also play a role in the decline of native cutthroat trout. A long-standing fishery in the lower main-stem Umpqua River aimed at hatchery-reared cutthroat trout probably promoted an incidental harvest of native Umpqua River cutthroat trout. Extensive releases of Alsea River hatchery-reared cutthroat trout have occurred near the Umpqua River estuary in the Smith River from 1975 to 1994 and in Scholfield Creek from 1983 to the present time. Until recently, approximately 12,000 hatchery-reared cutthroat trout per year have been released into the Smith River. Releases of approximately 4,000 hatchery-reared cutthroat trout per year continue to occur into Scholfield Creek. Given the life history of cutthroat trout, their extensive use of estuaries, their susceptibility to angling, and the potential impact of recreational fishing to native fish stocks, it is likely that these releases have had a substantial impact on native populations.
Cutthroat trout upstream migrations historically extended from June through January. It has been observed that currently migration may only be possible during late July and August, the period of highest water temperatures in the Umpqua River. This may be detrimental to the cutthroat trout because the adults experience delays during the spawning migration from the lower Umpqua River estuary to the North and South Umpqua Rivers. The high water temperatures on the main-stem Umpqua River in late July and August may have had a significant impact on the survival and time of arrival of cutthroat trout at Winchester Dam. Ongoing Oregon Department of Fish and Wildlife radio-tagging studies are expected to provide more insight into this issue.
Conservation and Recovery
Several recovery efforts are underway that may slow or reverse the decline of Umpqua River cutthroat trout. These include the Northwest Forest Plan, Coastal Salmon Restoration Initiative, and Umpqua River Basin Fisheries Restoration Initiative. There are several current trapping efforts underway in the Umpqua River basin to trap juvenile cutthroat trout for population inventory. There may be other ongoing research to determine population presence and abundance.
In August 1996, the U. S. Fish and Wildlife Service (FWS) added the species to the List of Endangered and Threatened Wildlife. The National Marine Fisheries Service, which has jurisdiction for this population, has determined that the Umpqua River cutthroat trout, which was identified as an ESU (Evolutionarily Significant Unit) of the species, is part of a larger population segment that is not endangered or threatened. The Umpqua River cutthroat trout was removed from the list effective April 26, 2000, and the FWS has removed the protections given to this species by the Endangered Species Act.
Regional Office of Endangered Species
U. S. Fish and Wildlife Service
Eastside Federal Center
911 N. E. 11th Ave.
Portland, Oregon 97232-4181
Telephone: (503) 231-6121
National Marine Fisheries Service
Environmental and Technical Services Division
525 NE Oregon St.—Suite 500
Portland, Oregon 97232-2737
Telephone: (503) 231-2005
Office of Protected Resources
1315 East-West Highway
Silver Spring, Maryland 20910
Telephone: (301) 713-1401
National Marine Fisheries Service. 9 August 1996."Endangered Status for Umpqua River Cutthroat Trout in Oregon." Federal Register 61 (155):41514-41522.
"Umpqua River Cutthroat Trout." Beacham's Guide to the Endangered Species of North America. . Encyclopedia.com. (November 16, 2018). https://www.encyclopedia.com/environment/science-magazines/umpqua-river-cutthroat-trout
"Umpqua River Cutthroat Trout." Beacham's Guide to the Endangered Species of North America. . Retrieved November 16, 2018 from Encyclopedia.com: https://www.encyclopedia.com/environment/science-magazines/umpqua-river-cutthroat-trout
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