Rhinichthys osculus subspecies

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General Information
Common Name: 
Santa Ana speckled dace

Conservation Status in California: Class 1, Endangered (Moyle et al. 2011). Santa Ana speckled dace are highly vulnerable to extinction in their native range within the next 50 years. Their distribution is largely restricted to the headwaters of the Los Angeles, Santa Ana, and San Gabriel rivers. These areas are, and will increasingly become, prone to catastrophic fire.

Life History: 

Life History: Little has been published on the life history of Santa Ana speckled dace so this account is largely based on information from other dace populations. The variability in body shape has allowed speckled dace to exploit a wide variety of habitats. The Santa Ana dace has a fairly streamlined body form (for a speckled dace) that indicates adaptation for living in flowing water (Moyle 2002). Although speckled dace are usually found in loose groups in appropriate habitats, such as rocky riffles, they avoid large shoals except while breeding. They can be active both day and night although, Moyle (unpubl. data) found that Lahontan speckled dace were more nocturnal in their habits when subjected to heavy bird predation in streams. Their activity is also mediated by stream temperatures, apparently staying active all year if stream temperatures remain above 4?C, which would be typical of streams inhabited by Santa Ana dace (Moyle 2002).
Speckled dace generally forage on small benthic invertebrates, especially taxa common in riffles including hydropsychid caddisflies, baetid mayflies, and chironomid and simuliid midges, but will also feed on filamentous algae on occasion (Li and Moyle 1976; Baltz et al. 1982; Hiss 1984, Moyle et al. 1991). Their subterminal mouth, pharyngeal tooth structure, and short intestine are characteristic of small invertebrate feeders. Not surprisingly, diet varies according with prey availability and speckled dace in general prey opportunistically on the most abundant small invertebrates in their habitat, which may change with season. Preference of forage items may also be influenced by the presence of other fishes that share similar habitats (e.g. sculpin, steelhead). Speckled dace in the Clearwater River, Idaho, shifted their diets to predominantly detritus in the presence on Paiute sculpin (Cottus beldingi) during the spring and early summer, perhaps as a mechanism of niche specialization to reduce competition (Johnson 1985).
Length frequency analyses have determined age and growth patterns. By the end of their first summer, dace grow to 20-30 mm SL (Moyle 2002), growing an average of 10-15 mm/yr in each subsequent year. Females tend to grow faster than males. However, growth rates can decrease in the presence of extreme environmental conditions, high population densities and limited food supply (Sada 1990). Slight changes in growth rates are also positively correlated with changes in temperature, as seen in the Colorado River (Robinson and Childs 2001). Life expectancy is approximately 3 years where maximum sizes do not exceed 80 mm FL, which is typical of Santa Ana speckled dace. Elsewhere, dace may reach 110 mm FL and live up to six years (Moyle 2002). Dace reach maturity by their second summer, with females producing 190-800 eggs depending on size and location (Moyle 2002). Presumably, Santa Ana speckled dace are at the low end of this range. Spawning is probably induced by rising water temperatures and/or high flow events, suggesting the Santa Ana speckled dace most likely spawn in March-May. Spawning in lakes occurs primarily over shallow areas of gravel within the lake or upstream in the edges of riffles of inlet streams. Groups of males will clear an area of algae and detritus and then surround a female when she enters the area. Females release eggs underneath rocks or near the gravel surface while males release sperm (John 1963). Eggs settle into interstices and adhere to the gravel. At temperatures of 18-19?C, eggs hatch in 6 days, but larvae remain in the gravel for another 7-8 days (John 1963). Fry in streams congregate in warm shallow areas, often in channels with rocks and emergent vegetation.
When extreme conditions such as floods, droughts or winter freezing eliminate local populations, speckled dace from nearby areas can readily recolonize or repopulate available habitats if there is access (Sada 1990, Pearsons et al. 1992, Gido et al. 1997). Densities of speckled dace in the Colorado River, Arizona, after a flood returned to pre-flood levels after eight months, as a function of reinvasion and reproduction from upstream and stream margin areas (Valdez et al. 2001).

Habitat Requirements: 

Habitat Requirements: Santa Ana speckled dace are found mainly in perennial streams fed by cool springs that maintain summer water temperatures below 20?C (CDFG 1995), although speckled dace in other regions of the west tolerate temperatures of 26-28°C. Surveys of trout streams in the Los Angeles basin indicate that the dace occupy shallow riffles dominated by gravel and cobble. Their habitat in the West Fork of the San Gabriel River was described as shallow (average depths of 15-30 cm) gravel-cobble dominated riffles with overhanging riparian vegetation (Deinstadt et al. 1990). Feeney and Swift (2008), however, characterized their preferred habitat as pools of low-gradient streams (0.5-2.5% slope) with sand to boulder substrates in slow-moving waters, noting that they were also found in the stream margins of fast-moving water.


Distribution: The ability of speckled dace to colonize new areas and adapt to different environments has resulted in their wide distribution. Speckled dace are the only native fish found in all major drainages in western North America. In California, their native range includes drainages in Death Valley (Amargosa River); Owens Valley; eastern Sierras (Walker River north to Eagle Lake); Surprise Valley; Klamath-Trinity basin; Pit River basin, including the Goose Lake watershed; Sacramento River basin, as far south as the Mokelumne River; San Lorenzo, Pajaro and Salinas River basins; San Luis Obispo, Pismo and Arroyo Grande Creek basins; Morro Bay; and San Gabriel and Los Angeles basins (Swift et al. 1993).
Santa Ana speckled dace historically inhabited streams in the upland areas of the Santa Ana, San Gabriel and Los Angeles rivers systems (CDFG 1995). They have since disappeared from many parts of their range, including the middle reaches of the Santa Ana River, Strawberry Creek (Santa Ana River), Mill Creek (Santa Ana River), and most of the Los Angeles River and San Jacinto River basins (Feeney and Swift 2008; G. Abbas, San Bernardino National Forest, pers. comm. 2008). Young of the year and 2 year old fish were found in City Creek (Santa Ana River) in 2008, a location from which speckled dace were thought to have gone extinct (G. Abbas, pers. comm. 2008). Their current distribution is thought to be restricted to only the headwaters of the Santa Ana and San Gabriel Rivers (CDFG 1995). A population was recently documented in Indian Creek, a headwater tributary of the San Jacinto River. Some fish were removed and held in captivity following the Esperanza Fire in 2006 to prevent total loss from flooding. They were reconfirmed as being present in 2007 and 2008 (G. Abbas, pers. comm. 2008). A few other populations of Santa Ana speckled dace were established through introductions into the Santa Clara and Cuyama Rivers, and River Springs, Mono County, although the introduction into the Santa Clara River is thought to have failed.

Abundance Trends: 

Trends in Abundance: Population estimates of Santa Ana speckled dace were not found. However, their abundance is likely a small fraction of what it was and populations have disappeared from two of five streams in which they were historically present (G. Abbas, pers. comm. 2008; Metcalf et al., unpubl.). Perhaps eight populations remain, mostly small and isolated from one another. The California Department of Fish and Game declared their numbers so diminished that they were in danger of extinction (CDFG 1995).
Swift et al. (1993), CDFG (1995) and Abbas (pers. comm. 2008) summarized the abundance of specific populations by location. Their findings are summarized below:
Big Tujunga Creek (Los Angeles River). Dace once inhabited the creek for 10-20 km below Big Tujunga Dam, and were thought to be extinct due to drought conditions and the establishment of red shiner (Cyprinella lutrensis) (CDFG 1995). Red shiners directly compete for food and space with dace and prey on dace eggs. Recent (2002-2005) surveys found only a few (10s) speckled dace at this and other locations in the Los Angeles River basin (Tujunga Wash, Haines Canyon; G. Abbas, pers. comm. 2008).
Fish Canyon (San Gabriel River). This population was thought to be extinct (CDFG 1995). Only 6-7 fish were seen in 1988. Optimal dace habitat has been infringed upon by a rock quarry operation. However, current quarry operations are focused on restoring the streambed in order to improve dace habitat (G. Abbas, pers. comm. 2008). Specimens were collected from this site in 2007 by ECORP. Morris dam isolates this population from other dace in the San Gabriel River, preventing genetic flow and recruitment between populations. Some recent (2002, 2006 and 2007) surveys established their presence in this location while others did not (2005; G. Abbas, pers. comm. 2008) The Forest Service was provided specimens by the rock quarry consultant and these are being analysed by Anthony Metcalf at Cal State San Bernardino to determine genetic relationships (G. Abbas, pers. comm. 2008).
West, North, and East Forks San Gabriel River. These areas constitute the best dace habitat (CDFG 1995). Populations in the West Fork in 1990 (Deinstadt et al. 1990) likely numbered less than 2000. Habitat in the West Fork is vulnerable to high water and sediment releases from the Cogswell Reservoir which is managed for flood control. As of 1995, the West Fork was still recovering from major sediment releases from 1981 and 1991. These sediments smothered most of the habitat used by dace until it was flushed out by rainfall and dam water releases in 1988. Surveys found 29 dace in a 68 m section of stream (3 pass electrofisher, Deinstadt pers. comm. in CDFG 1995), in 1993. Surveys in 2006 found dace only one of three locations sampled (G. Abbas, pers. comm. 2008). Dace were also abundant upstream of the reservoir in 2005. Surveys (2005) of the North Fork found dace in one of the two days of sampling. Suveys (2005) also documented the presence of 100s of speckled dace in Cattle Creek (G. Abbas, pers. comm. 2008).
Santa Ana River. Speckled dace are assumed to be extirpated from most of the Santa Ana River (CDFG 1995, Moyle 2002). They were last seen near Rialto in 2001 (G. Abbas, pers. comm., 2008). Only a few specimens (usually Lytle Creek Mainstem. (excerpt from Abbas 2008) “The stronghold area for Santa Ana speckled dace is currently in the mainstem reach from Miller’s Narrows downstream to Turk Point (approximately 1.4 river miles). The Forest Service has qualitatively monitored this reach since at least 1999. Santa Ana speckled dace have been there throughout this period with significant population fluctuations in response to drought induced low flows, major flooding (periods of declining population densities), and a couple years of sustained moderate flows (period of rapid population density increases). This reach is currently the species stronghold for this watershed, being the only place where they have persisted, and must be diligently protected from disturbance and enhanced at every opportunity. This stronghold reach is regularly threatened by encroachment into the wash by heavy equipment by a variety of forest users to protect infrastructure including public roads, public utilities and private access routes. There is perennial water above Miller’s Narrows in the mainstem up to the confluence with the Middle Fork, but dace were absent here between at least 1999 and 2005.
In 2005 the Forest Service, CDFG and Fontana Union Water Company Consultant Jonathan Baskin conducted a reintroduction of approximately 1000 Santa Ana speckled dace from the lower mainstem of Lytle Creek to the Applewhite Picnic Area on the North Fork of Lytle Creek. In 2007 Southern California Edison reported capture of Santa Ana speckled dace in their diversion works above Miller’s Narrows suggesting that some of the fish from the North Fork reintroduction had survived and migrated downstream (3.2 river miles) to this location. With this information we can now consider all of the mainstem above Turk Point occupied by Santa Ana speckled dace.
In 2007 the Forest Service and CDFG conducted a translocation of approximately 1300 Santa Ana speckled dace from the lower mainstem of Lytle Creek to the North Fork at Applewhite Picnic area.
In 2005 and 2006 sustained year-round flows from Turk point down to the Fontana Union Water Company (FUWC) diversion (1.8 river miles) resulted in an extreme expansion of speckled dace throughout the reach with yoy rearing in the settling pond at FUWCs intake structure (adults were also noted in the raceways of the intake structure). With this knowledge we can assume that in years when there are flows below Turk Point, that reach of the mainstem is occupied by Santa Ana speckled dace.”
North Fork Lytle Creek. The Middle Fork Lytle Creek is a high quality water source for this watershed, consistently producing perennial waters over a 2 mile reach which supports a popular rainbow trout fishery. Beginning near the National Forest boundary with the community of Scotland there is a reach of the South Fork mapped as intermittent for approximately 0.6 river miles. However this reach has rarely gone dry and also supports a popular trout fishery. In 2007 the Forest Service and CDFG conducted a reintroduction of approximately 500 Santa Ana speckled dace from the lower mainstem of Lytle Creek to the Middle Fork just a few hundred meters upstream of the Scotland boundary. Surveys by the Forest Service confirmed the persistence of these fish into 2008 but no assessment of their migration from the introduction point was conducted. There is high quality habitat available from the forest boundary with Scotland upstream at least 2.6 river miles. There are no significant fish passage barriers known within this reach so the full 2.6 mile reach above Scotland is now considered Santa Ana Speckled dace habitat.
Cajon Creek. (tributary to Lytle Creek) Dace appear to be abundant in this drainage, predominantly congregated upstream and downstream of Interstate 15 (CDFG 1995). Their presence was also documented by surveys in 2005 (G. Abbas, pers. comm. 2008). There have been several recent fires in the area. Hazardous waste spills from trucks and trains using the transportation corridor threaten aquatic habitat in this watershed. The San Bernardino National Forest, Fish and Game, and BNSF Railroad have been moving fish into headwater tributaries to protect them from highway or railway spills.
City Creek. Dace were seen in September of 2003, following the Bridge fire. No dace were found following the devastating Old Fire (October of 2003) and subsequent flooding. Several surveys were conducted 2005, 2006, and 2007 and no dace were found. However, in 2008 a small population was found in the West Fork and reconfirmed in 2009.
East Fork City Creek. Dace were observed immediately after the Bridge Fire in 2003 (G. Abbas, pers. comm. 2008). Fewer dace were seen after the Old Fire in October 2003, and none after subsequent flooding in December 2008. No dace were seen in 2004, 2005, 2006 and 2007.
Mill Creek. Dace were found in the 1980s but not in 1990 (CDFG 1995). Speckled dace were thought to be extirpated from Mill Creek (CDFG 1995), but a few were observed in a small pool created by a man-made grade control structure in 2007 (G. Abbas, pers. comm. 2008). However, dace were not seen in 2008 and are assumed to be extinct from Mill Creek (G. Abbas, pers. comm. 2008).
Plunge Creek. Speckled dace were observed in 2001 (9 individuals) and 2005 (G. Abbas, pers. comm. 2008). Dace were collected in 2004 to protect them from potential flooding. They were returned to the stream after the threat of flooding passed. (Abbas pers. comm. 2008)
Strawberry Creek. A small population was found in 1992 by the U.S. Forest Service (C. Swift pers. comm. in CDFG 1995). Surveys did not observe any in 2005 or 2006 (G. Abbas, pers. comm. 2008). Several surveys following the 2003 Old fire and Christmas Flood did not find dace. They are presumed extinct from Strawberry Creek.
Silverado Canyon. Although dace were found in 1987, none were found in the same or nearby areas in 1990 (CDFG 1995) or 2005 (G. Abbas, pers. comm. 2008).
San Jacinto River. Dace were recorded in 15-30 km of stream but not since the mid-1980s (T. Haglund, in CDFG 1995). Large portions of the river and the lower portion of its tributaries are now dry in the summer. Surveys in 2005 did not find speckled dace in the mainstem or in the North and South Forks (G. Abbas, pers. comm. 2008).
Indian Creek. (Headwater tributary of San Jacinto River) In 2006, some Santa Ana speckled dace found in Indian Creek were relocated to the Riverside-Corona RCD for captive breeding after the Esperanza Fire (G. Abbas, pers. comm. 2008). Fish survived the fire and the population is recovering. The population has been able to sustain itself following the fire due to the lack of big flooding events.
Santiago Creek. (Santa Ana River) Surveys in 2005 did not find speckled dace within the mainstem or tributaries (Harding Canyon Creek, Silverado Creek; G. Abbas, pers. comm. 2008).


Description: Speckled dace are small cyprinids, usually measuring 8-11 cm SL (Moyle 2002). Although physically variable, they are characterized by a wide caudal peduncle, small scales (47-89 along lateral line), and pointed snout with a small subterminal mouth. Larvae have deep bodies, small eyes, overhanging snout and are characterized by 35-41 myomeres, and distinctive coloration (Feeeney and Swift 2008). As larvae, they have large distinctive spots located on the sides of the bottom portion of the caudal peduncle and a wedge-shaped patch of spots on top of the head. Larvae have functioning eyes, mouth and gas bladder by the time the notochord flexes at about 7-9 mm TL. A noticeable band of pigment running just below the lateral midline is visible at about 9 mm. The terminal mouth of larvae becomes subterminal at about 9.7 mm. The pectoral fins remain unpigmented until the later stages of larval development. Later stages also develop a distinctive spot on the base of the caudal fin. Scales appear when dace reach 13 mm FL (Jhingran 1948). Once fully developed, the dorsal fin usually has 8 rays and originates well behind the origin of the pelvic fins (Moyle 2002). The anal fin has 6-8 rays. Pharyngeal teeth (1,4-4,1 or 2,4-4,2) are significantly curved with a minor grinding surface. The maxilla usually has a small barbel at each end. The snout is connected to the upper lip (premaxilla) by a small bridge of skin (frenum). Most fish larger than 3 cm have distinctive dark speckles on the upper and sides of the body, a dark lateral band that extends to the snout, and a spot on the caudal peduncle. The rest of the body is dusky yellow to olive, with the belly being a paler color. Breeding adults of both sexes have fins tipped by orange or red, while males also have red snouts and lips, and tubercles on the head and pectoral fins.