Rhinichthys osculus
Rhinichthys osculus
(Speckled Dace)
Native Transplant
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Rhinichthys osculus (Girard, 1856)

Common name: Speckled Dace

Synonyms and Other Names: western dace, spring dace, dusky dace, Pacific dace

Taxonomy: available through www.itis.govITIS logo

Identification: Moyle (1976a); Wydoski and Whitney (1979); Sublette et al. (1990); Page and Burr (1991); Bond (1994). It is considered a species complex; some subspecies are protected as endangered (Page and Burr 1991). Gilbert (1998) recognized 15 subspecies. One subspecies is R. o. nubilis from Washington and closely adjacent areas, sometimes reported as Rhinichthys nubilus (Miller 1952).

Size: 11 cm.

Native Range: Western drainages (Pacific and endorheic) from Columbia River, British Columbia, to Colorado River, Arizona and New Mexico, and south into Sonora, Mexico (Page and Burr 1991).

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Native range data for this species provided in part by NatureServe NS logo
Interactive maps: Point Distribution Maps

Nonindigenous Occurrences: This species was recorded from the Santa Clara River basin just north of Los Angeles, and from tributaries of the Cuyama River in southern San Luis Obispo County, California (Miller and Alcorn 1946; Miller 1968). The presence of this species in San Luis Obispo Creek in San Luis Obispo County, California, also may have been the result of an introduction (Moyle 1976a; but see Bell 1978). The subspecies, R. o. robustus, was recorded from Lake Webber, Sierra County, California, a high-altitude water body in the Truckee-Lahontan drainage system (La Rivers 1962). Also in California, small numbers of this species were introduced into Willow Creek, east of Independence, Inyo County, in 1939; into River Springs, Mono County, in 1940; and to the Old (Eagle) Borax Works on the west side of Death Valley in 1940 (Miller 1968). Specimens have been reported in Cuyama River, Sisquoc River, Davy Brown Creek, Tepusquet Creek, Saline Valley, and River Springs on the east side of Adobe Valley (Swift 1993).  The species is known from the Mimbres River in southwestern New Mexico (Sublette et al. 1990). The Lahontan Speckled Dace, R. o. robustus, was introduced into Ruby Marsh and Ruby Marsh complex in northeastern Nevada twice during the early 1950s (La Rivers 1962; Hubbs et al. 1974) and is now established in Ruby Lake National Wildlife Refuge (USFWS 2005).  It has been collected in Rogers Spring (Overton Arm of Lake Mead) (Courtenay et al 1983).  The subspecies R. o. klamathensis has been introduced to the Rogue River drainage in Oregon (Bond 1994). This species has also been collected near Huntington, Emery County, Utah (Miller 1952).

Means of Introduction: Several transplants into parts of California during 1939 and 1940 were considered experiments to test the effects of changed environment on meristic and morphometric characters (Miller 1968). This species was intentionally stocked by Nevada Fish and Game officials in Ruby Marsh-Ruby Lake complex as forage for introduced largemouth bass Micropterus salmoides; the first introduction, in 1950, involved R. osculus robustus from a headwater of the Humboldt River, and the second, in 1951, from nearby Diamond Valley, Eureka County (La Rivers 1962; Hubbs et al. 1974). Although La Rivers (1962) recognized that R. osculus robustus was native to the Truckee River system, he concluded that the high-altitude lake had no native fishes and that small fishes present in the lake had likely arrived as a result of being stocked along with trout. Introductions of this species in other areas were probably the result of bait bucket releases (e.g., Miller 1952; La Rivers 1962). For instance, Miller (1946) indicated that the presence of Rhinichthys osculus in the Santa Clara River system (California) was possibly the result of its introduction as bait by trout fishermen.

Status: Established in San Luis Obispo Creek and Webber Lake, California (Moyle 1976a), and in Ruby Marsh, Nevada (La Rivers 1962). Reported from New Mexico (Sublette et al. 1990). Fishes introduced into Willow Creek and the Old Borax Works of California failed to survive; however, the species was common at River Springs, California, in 1967, more than 25 years after its initial introduction (Miller 1968). Although Miller (1968) reported on its occurrence in the Santa Clara River system, California, Bell (1978) did not collect the species there.

Impact of Introduction: Unknown in introduced areas. Speckled Dace are known to hybridize with least chubs Iotichthys phlegethontis (Sigler and Sigler 1987), a species under review for federal listing, and therefore present a threat to this rare species.

Remarks: Widely used as a baitfish in certain parts of the western United States (Miller 1952; La Rivers 1962; Baxter and Simon 1970). Contrary to Moyle (1976a), Miller (1968) and Bell (1978) believed that R. osculus is native to San Luis Obispo Creek. They based that conclusion on Jordan (1894), who included this species under the name Agosia nubila in his early list of fishes found in San Luis Creek.

References: (click for full references)

Miller, R.R. 1952. Bait fishes of the lower Colorado River, from Lake Mead, Nevada, to Yuma, Arizona, with a key for identification. California Fish and Game. 38: 7-42.

Miller, R.R. and J.R. Alcorn. 1946. The introduced fishes of Nevada, with a history of their introduction. Transactions of the American Fisheries Society. 73: 173-193.

Sigler, W.F., and J.W. Sigler. 1987. Fishes of the Great Basin: a natural history. University of Nevada Press, Reno, NV.

Other Resources:
FishBase Fact Sheet

Author: Leo Nico, and Pam Fuller

Revision Date: 4/21/2006

Citation Information:
Leo Nico, and Pam Fuller, 2017, Rhinichthys osculus (Girard, 1856): U.S. Geological Survey, Nonindigenous Aquatic Species Database, Gainesville, FL, https://nas.er.usgs.gov/queries/factsheet.aspx?SpeciesID=640, Revision Date: 4/21/2006, Access Date: 11/21/2017

This information is preliminary or provisional and is subject to revision. It is being provided to meet the need for timely best science. The information has not received final approval by the U.S. Geological Survey (USGS) and is provided on the condition that neither the USGS nor the U.S. Government shall be held liable for any damages resulting from the authorized or unauthorized use of the information.

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Citation information: U.S. Geological Survey. [2017]. Nonindigenous Aquatic Species Database. Gainesville, Florida. Accessed [11/21/2017].

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