Extent of occurrence is roughly 20,000 square kilometres.
endemic to a single state or province
Regularity: Regularly occurring
Type of Residency: Year-round
Global Range: (5000-200,000 square km (about 2000-80,000 square miles)) Range includes southern California coastal drainages; this species is native to the Los Angeles, San Gabriel, San Luis Rey, Santa Ana, and Santa Margarita rivers and Malibu and San Juan creeks; successfully introduced in the Santa Ynez, Santa Maria, Cuyama, and other small coastal streams (e.g., Arroyo Grande Creek), and in the Mohave River drainage (Death Valley basin), California (Moyle et al. 1989, Moyle 2002, Page and Burr 2011). This species is now absent from much of the native range, it is abundant only in the upper Santa Margarita River and its tributary De Luz Creek; Trabuco Creek below O'Neill Park; and San Juan creek (San Juan Creek drainage), Malibu Creek, and West Fork of the upper San Gabriel River below Cogswell Reservoir (Moyle 2002). The species also occurs in (but is scarce) in several additional drainages (Moyle 2002).
Extent of occurrence is roughly 20,000 square kilometers.
Length: 30 cm
Habitat and Ecology
Habitat Type: Freshwater
Comments: Habitat includes headwaters, creeks, and small to medium rivers, often intermittent streams (Page and Burr 2011); permanent, small to moderate-sized, moderate to high gradient streams with more than 50% of the habitat as runs and pools < 10 cm deep and reaches of permanent water more than 2 km long; requires some flow. In natural habitat prefers slow moving sections of streams with sand or mud substrate. Midwater and benthic, becomes increasingly secretive with age. Physiologically adapted to hypoxic conditions and wide temperature fluctuations (Castleberry and Cech 1986). Spawns usually in stream pools.
Non-Migrant: No. All populations of this species make significant seasonal migrations.
Locally Migrant: No. No populations of this species make local extended movements (generally less than 200 km) at particular times of the year (e.g., to breeding or wintering grounds, to hibernation sites).
Locally Migrant: No. No populations of this species make annual migrations of over 200 km.
Comments: Aquatic insects, snails, and (mostly) algae. Feeds most abundantly on invertebrates in spring, least in winter (Moyle 1976). Diet includes physids, pelecypods, Euparypus, Heliopsyche; apparently seeks mollusks associated with the bottom (Richards and Soltz 1986); also knwon to feed extensively on the roots of a floating water fern infested with nematodes (Moyle 1976).
Number of Occurrences
Note: For many non-migratory species, occurrences are roughly equivalent to populations.
Estimated Number of Occurrences: 6 - 20
Comments: This species is represented by at least 7 native populations and several additional populations outside the native range (Moyle 2002).
2500 - 10,000 individuals
Comments: Total adult population size is unknown but may not exceed 10,000. Within the native range, the species is common at only four locations.
Life History and Behavior
Spawns March-May (Moyle 1976, Lee et al. 1980), March-April according to Moyle et al. (1989). Lives 3-4 years.
Molecular Biology and Genetics
Barcode data: Gila orcuttii
Below is a sequence of the barcode region Cytochrome oxidase subunit 1 (COI or COX1) from a member of the species.
See the BOLD taxonomy browser for more complete information about this specimen and other sequences.
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Download FASTA File
Statistics of barcoding coverage: Gila orcuttii
Public Records: 10
Specimens with Barcodes: 10
Species With Barcodes: 1
IUCN Red List Assessment
Red List Category
Red List Criteria
National NatureServe Conservation Status
Rounded National Status Rank: N2 - Imperiled
NatureServe Conservation Status
Rounded Global Status Rank: G2 - Imperiled
Reasons: Small range in southern California coastal drainages; range and abundance have been reduced by habitat degradation associated with urbanization and impacts of non-native fish species (ogoing threats) introductions outside the native range have improved the status somewhat, but some introduced populations have been negatively impacted by hybridization.
Total adult population size is unknown but may not exceed 10,000. Within the native range, the species is common at only four locations.
If not for introductions outside the native range, this species would probably be listed as endangered or threatened (Moyle 2002).
Trend over the past 10 years or three generations is uncertain, but distribution and abundance probably are declining. Three generations does not exceed 10 years. Continued habitat degradation and hybridization with other species is only accelerating the decline of this species.
Global Short Term Trend: Decline of 10-30%
Comments: Trend over the past 10 years or three generations is uncertain, but distribution and abundance probably are declining. Three generations does not exceed 10 years. Continued habitat degradation and hybridization with other species is only accelerating the decline of this species.
Degree of Threat: B : Moderately threatened throughout its range, communities provide natural resources that when exploited alter the composition and structure of the community over the long-term, but are apparently recoverable
Comments: Most streams in the native range are degraded as a result of their location in the Los Angeles metropolitan area, and chub populations are fragmented and reduced, especially in the low-gradient reaches that were optimal habitat (see Moyle 2002). Some introduced populations (e.g., those in the Cuyama and Mohave rivers) have been negatively impacted by hybridization with other cyprinids and cannot be regarded as secure or genetically pure (Moyle 2002). Introduced red shiner may competitively exclude the arroyo chub from many areas (Moyle et al. 1989). Arroyo shiner dramatically increased in abundance in the Santa Margarita River following extreme high flows in 1997-1998, which reduced the abundance of several non-native fish species. Negative impacts of non-native species, combined with continued degradation of urbanized streams, mean that this species is not secure (Moyle 2002).
Biological Research Needs: Determine extent of hybridization in Mohave and other rivers.
Global Protection: None. No occurrences appropriately protected and managed
Needs: At least three streams in L.A. basin with this and other native fish need to be preserved for native fishes; the West Fork of the San Gabriel River is the strongest candidate for a native fish refuge (Moyle et al. 1989).
The shape of the arroyo chub is somewhat chunky, with a deep body and thick caudal peduncle. The eyes are larger than average for cyprinids. Coloration ranges from silver to gray to olive green above, shading to white below, usually with a dull gray band along each side. The dorsal fin has 8 rays, while the rounded anal fin has 7. Males have larger fins than females, and, during the breeding season, patches of breeding tubercles on the upper surfaces of the pectoral fins. This is a small fish, with most adults in the 7–10 cm length range, and a maximum of 12 cm.
Omnivorous, their diet includes algae, insects, and crustaceans. Studies of fish from warmwater streams shows a preponderance of algae in the stomach (60-80%), and they are also known to feed on the roots of Azolla (floating water ferns). In cooler streams, molluscs and caddisfly larvae predominate in the diet.
Arroyo chub habitat is primarily the warm streams of the Los Angeles Plain, which are typically muddy torrents during the winter, and clear quiet brooks in the summer, possibly drying up in places. They are found both in slow-moving and fast-moving sections, but generally deeper than 40 cm.
They are native to Los Angeles, Santa Margarita, San Gabriel, San Luis Rey, and Santa Ana Rivers, as well as to Rainbow, Temecula, Malibu and San Juan Creeks. Many of the original populations have been extirpated, but it has recently been reestablished in the Arroyo Seco (Los Angeles County), a tributary of the Los Angeles River. It has been found in the Los Angeles River (Sepulveda Dam Basin) as recently as 1978. The species also has been successfully introduced in a number of other rivers in the area, and can be found as far north as Chorro Creek in San Luis Obispo County, and as far east as the Mojave River. The Mojave and Cuyama River populations extend into the ranges of related fishes, and hybridize with Mojave chub and California roach, respectively.
The species epithet was chosen in honor of C. R. Orcutt, who in 1889 made the first collection of this fish, improvising by using a blanket as a seine. It is often misspelled as orcutti, although this is still considered a valid synonym, and is for instance used by Moyle in his book.
- "Gila orcuttii". Integrated Taxonomic Information System. Retrieved 18 April 2006.
- Peter B. Moyle, Inland Fishes of California (University of California Press, 2002), pp. 130–131
- Froese, Rainer and Pauly, Daniel, eds. (2006). "Gila orcuttii" in FishBase. April 2006 version.
- Central Arroyo Stream Restoration Program cf: Chub in the Arroyo Seco
Names and Taxonomy
Comments: Hybridizes with G. bicolor mohavensis and with Lavinia symmetricus under stressed conditions (Lee et al. 1980). Placed with the closely related G. purpurea in the subgenus Temeculina.
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