Torrent Sculpin - Cottus rhotheus
State Rank Reason (see State Rank above)
The torrent sculpin is currently listed as an "S3" species of special concern by the state of Montana (Montana Natural Heritage Program 2004), and is also designated as a sensitive species by the U.S. Forest Service in Region 1 (Lee et al. 1997). A "S3" designation means that the species in Montana is potentially at risk because of limited and potentially declining numbers, extent and-or habitat, even though it may be abundant in some areas.
In Montana, the Torrent Sculpin is found only in the fast headwater streams of the Kootenai River drainage in the northwest portion of the state. As with all sculpins, it presents a somewhat grotesque appearance with its large head, huge pectoral fins, and bulging eyes. Sculpins have a very flattened hydrodynamic shape, which serves them well as they dart along the bottom between the cracks and crevices of rocks (Montana AFS Species Status Account
For a comprehensive review of the ecology, conservation status, threats, and management of this and other Montana fish species of concern, please see Montana Chapter of the American Fisheries Society Species of Concern Status Reviews.
This species is gray-brown with black speckling. The underside is light and the chin strongly mottled. The first dorsal fin is fringed with orange on spawning males. Palatine teeth are usually present. The body is robust. They usually have coarse prickles on the back, sides, and sometimes on the caudal peduncle.
Western Hemisphere Range
The torrent sculpin is native to the Pacific Northwest and is found in Washington, Oregon, British Columbia, Idaho, and Montana. It occurs primarily in tributary systems of the Columbia River basin, but also occurs in the Fraser River System in British Columbia, and in coastal streams from Oregon to British Columbia.
Observations in Montana Natural Heritage Program Database
Number of Observations:
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Map Help and Descriptions
(Observations spanning multiple months or years are excluded from time charts)
Movements of torrent sculpin are poorly understood. In Washington, torrent sculpin have been documented moving upstream to spawn from late-January to mid-April, then moving back downstream, presumably to pre-spawning nodal habitats, after completion of spawning in May and June (Thomas 1973).
These fish are typically found in the riffles of cold, clear streams, but are also reported in the rocky shores of lakes. They hide among the boulders and cobbles on the bottom.
The torrent sculpin feeds predominately on zooplankton and aquatic insect larvae as a sub-adult; adult diets also include small fish and fish eggs (Northcote 1954; Brown 1971). The fry eat mostly plankton. Adults feed mainly on aquatic insects and a variety of invertebrates, but also include plankton. Larger individuals often eat small fish.
They are sexually mature in 2 years and spawn in late spring. The eggs hatch in 30 to 50 degrees F. The male remains close to the nest until after the eggs hatch.
A primary focus of managing the torrent sculpin in Montana should be to more accurately determine the status of the species. Efforts should be made to describe its complete range, as well as to estimate abundance at locations where its presence is currently known. Populations should be routinely monitored to describe population trends over time.
Threats or Limiting Factors
In Montana, the torrent sculpin is likely most threatened by land use practices that could diminish habitat quality. Lee et al. (1997) considered sedimentation, increased water temperature, and pollution as the major potential negative impacts to the torrent sculpin.
- Literature Cited AboveLegend: View Online Publication
- Montana Chapter of the American Fisheries Society species status accounts.
- Additional ReferencesLegend: View Online Publication
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- Brusven, M.A., and S.T. Rose. 1981. Influence of substrate composition and suspended sediment on insect predation by the torrent sculpin, Cottus rhotheus. Canadian Journal of Fish and Aquatic Sciences 38:1444-1448.
- Edson, S.A. 1992. Sculpin (Cottus) distribution in the Kootenai National Forest and northwestern portions of the Flathead National Forest, Montana. Montana Natural Heritage Program, Helena. 37 pp. including appendices.
- Gangemi, J.T. 1992. Sculpin (Cottus) distribution in the Kootenai National Forest and western portions of the Lolo National Forest, Montana. Montana Natural Heritage Program, Helena, MT 59620. 54 pp.
- Northcote, T. G. 1954. Observations on the comparative ecology of two species of fish, Cottus asper and Cottus rhotheus, in British Columbia. Copeia 1954:25-28.
- Patten, B. 1971. Increased predation by the torrent sculpin, Cottus rhotheus, on coho salmon fry, Oncorhynchus kisutch, during moonlight nights. J. Fish. Res. Board Can. 28:1352-1354.
- Thomas, A. E. 1973. Spawning migration and intragravel movement of the torrent sculpin, Cottus rhotheus. Trans. Am. Fish. Soc. 102:620-622.
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