endemic to a single state or province
Regularity: Regularly occurring
Type of Residency: Year-round
Global Range: Historic range included portions of the Los Angeles, San Gabriel, and Santa Ana rivers (Los Angeles County); headwaters of the Santa Clara River (northern Los Angeles County); and the Santa Maria River and San Antonio Creek (Santa Barbara County), all in southern California. Now extirpated from most of this range. Current distribution: a small tributary in the San Francisquito Canyon in the upper Santa Clara River drainage in Los Angeles County; the Santa Clara River at Soledad Canyon, and the Del Valle area further downstream; potential remnant population in Shay Creek, San Bernardino County [apparently this pertains to subspecies SANTAANNAE, which some authors have regarded as consubspecific with WILLIAMSONI]; isolated, introduced population outside historic range in San Felipe Creek, San Diego County (California Department of Fish and Game 1990). Matthews and Moseley (1990) mentioned an extant population also in San Antonio Creek near Lompoc and a transplanted population possibly surviving in Honda Creek on the Vandenburg Air Force Base Reservation.
Differs from other nominal subspecies in lacking bony plates (occasionally has tiny ones) and having shorter, weaker spines and more rounded pectoral and caudal fins (Moyle 1976).
Catalog Number: USNM 340
Collection: Smithsonian Institution, National Museum of Natural History, Department of Vertebrate Zoology, Division of Fishes
Collector(s): L. Williamson
Locality: Williamson'S Bay California., California, United States, Pacific
Habitat Type: Freshwater
Comments: Clear, slow-flowing streams with sand or mud substrate, water temperature less than 24 C, and abundant aquatic vegetation; occurs in deeper pools with slow current or, in stronger currents, behind obstructions. Lack of turbidity is a requirement. Juveniles congregate in backwaters among aquatic plants (Matthews and Moseley 1990).
Eggs are laid in nests constructed on stream bottoms in shallow water by males; nest consists of aquatic vegetation.
Non-Migrant: Yes. At least some populations of this species do not make significant seasonal migrations. Juvenile dispersal is not considered a migration.
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: Opportunistic; diet includes mainly insects and snails.
Number of Occurrences
Note: For many non-migratory species, occurrences are roughly equivalent to populations.
Estimated Number of Occurrences: 1 - 5
Comments: Occurs in no more than a half dozen areas.
Life History and Behavior
Breeds throughout the year, with a peak in March; male guards eggs in nest; lives usually only about one year at the most (Matthews and Moseley 1990).
National NatureServe Conservation Status
Rounded National Status Rank: N1 - Critically Imperiled
NatureServe Conservation Status
Rounded Global Status Rank: T1 - Critically Imperiled
Reasons: Small, remnant range in southern California streams; large decrease in range due to increasing urban encroachment; only a few remaining populations, all of which are in trouble.
Date Listed: 10/13/1970
Lead Region: California/Nevada Region (Region 8)
Where Listed: Entire
Population location: Entire
Listing status: E
For most current information and documents related to the conservation status and management of Gasterosteus aculeatus williamsoni , see its USFWS Species Profile
Global Short Term Trend: Relatively stable (=10% change)
Comments: USFWS (1990) categorized the status as "stable."
Degree of Threat: A : Very threatened throughout its range communities directly exploited or their composition and structure irreversibly threatened by man-made forces, including exotic species
Comments: Major threats include stream channelization, urbanization (cause of extirpation in Los Angeles Basin), agricultural development, groundwater pumping, introduction of predators (e.g., Afican clawed frog) and competitors (mosquitofish), ORV use, and chemical spills (CDF&G 1990). These factors have permanently eliminated this species from most of its historic habitat. Survives in areas that are relatively undeveloped and where natural barriers have prevented hybridization (in San Antonio Creek, threatened by hybridization with the accidently introduced subspecies microcephalus). Most stockings into wild habitats have failed, apparently due to exotic fishes and marginal habitat conditions (Hendrickson and Brooks 1991). Urbanization of remaining stream areas threatens the water supply and may increase siltation and decrease water quality. Many areas have heavy recreational use. The San Antonio Creek population is threatened by increasing pesticide runoff and development of the area as a missile base.
Global Protection: Few (1-3) occurrences appropriately protected and managed
Comments: Based on administrative reasons, USFWS (Federal Register 17 September 2002) recently decided not to make final an old (1980) proposal to designate critical habitat along 51 km of streams in Los Angeles and Santa Barbara counties.
Needs: Protect at least 3 populations.
Names and Taxonomy
Comments: Systematics of sticklebacks is complicated. Recent studies may lead to taxonomic changes in one or more of the extant populations (CDF&G 1990). Some authors have regarded subspecies SANTAANNAE to be consubspecific with subspecies WILLIAMSONI, but Moyle et al. (1989) regarded them as separate subspecies, citing unpublished electrophoretic evidence suggesting that SANTAANNAE might warrant even full species status.
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