SPECIES NAME AND GROUP DESIGNATION

Common Name and Scientific Name:

Santa Ana sucker (Catastomus santaanae) (Snyder, 1908b).

Status:

State: Species of Special Concern

Federal: Threatened (Federal Register 65: 19686-19698, April 12, 2000; Federal Register 64:3915, January 26, 1999)

GROUP DESIGNATION AND RATIONALE

Group 3

The Santa Ana sucker is narrowly distributed at few locations within the Plan Area. Although the preferred habitat, open water and emergent vegetation occurs in numerous areas within the Plan Area, suckers are concentrated within 5 to 10 miles of the Santa Ana River (between the Riverside/San Bernardino County line and Van Buren Boulevard) and disperse into more marginal habitats (between Van Buren and Prado Dam). There are suckers present below Prado Dam, however this area is probably a sink because the dam is a barrier to upstream migration. The Santa Ana sucker has specific habitat requirements and conditions within the larger riverine habitat within which it occurs. Because it requires specific habitat conditions, occurs in few locations within a larger habitat category, and occurs in low densities, the Santa Ana sucker will require conservation on a landscape level, with site specific considerations and management at the known locations and thus has been identified as a Group 3 species.

SPECIES CONSERVATION OBJECTIVES

The species-specific conservation objectives developed for this species are based upon the best available scientific information at the time of MSHCP preparation. Pursuant to Section 5.0, which includes Management, Monitoring and the Adaptive Management Program, the MSHCP's mitigation requirements will be monitored and analyzed to determine if they are producing the desired result. Based upon this information, the following species-specific conservation objectives will be adjusted if appropriate, as new information is gathered during Plan implementation. The Adaptive Management Program will be used to identify alternative strategies for meeting the MSHCP's general biological goals and objectives and, if necessary, adjusting future conservation strategies according to the information received.

Objective 1

Include within the MSHCP Conservation Area 3,480 acres of the suitable habitat for the Santa Ana sucker including the Santa Ana River within the natural river bottom and banks.

Objective 2

Include within the MSHCP Conservation Area the Core Areas upstream of River Road, between River Road and Prado Dam, and downstream of Prado Dam; the known spawning areas at Sunnyslope Creek and within the area just below Mission Boulevard upstream to the Rialto Drain; and refugia and dispersal areas including the Market Street Seep, Mount Rubidoux Creek, Anza Park Drain, Arroyo Tequesquite, Hidden Valley Drain, and Evans Lake Drain.

Objective 3

Include within the MSHCP Conservation Area the natural river bottom and banks of the Santa Ana River from the Orange County and Riverside County line to the upstream boundary of the Plan Area, including the adjacent upland habitat, where available, to provide shade and suitable microclimate conditions (e.g., alluvial terraces, riparian vegetation).

Objective 4

Within the MSHCP Conservation Area, the Reserve Managers responsible for the areas identified in Objectives 2 and 3 will assess barriers to sucker movement and the need for connectivity and identify measures to restore connectivity to be implemented as feasible.

Objective 5

Within the MSCHP Conservation Area, the Reserve Managers responsible for the areas identified in Objectives 2 and 3 will assess threats to the sucker from degraded habitat (e.g., reduced water quality, loss of habitat, presence of non-native predators and vegetation); identify areas of the watershed that are necessary to successful sucker spawning, identify areas for creation of stream meanders, pool riffle complexes and reestablishment of native riparian vegetation as appropriate and feasible and identify and implement management measures to address threats and protect critical areas.

SPECIES CONSERVATION ANALYSIS

Conservation Levels

For the purpose of the conservation analysis, potential habitat for the Santa Ana sucker includes the open water channels and emergent vegetation (freshwater marsh) areas in higher gradient stream sections for the entire length of the Santa Ana River within the Plan Area. A variety of wetland vegetation types adjacent to the streams essential to maintaining the ecological integrity of the freshwater systems were included as buffer habitat including riparian scrub, forest and woodland. Additional habitats that may be within the streambank or buffer adjacent to the Santa Ana River include Riversidean alluvial fan sage scrub, grassland, coastal sage scrub and agricultural lands. These habitats were included in the analysis for a width of approximately 1,300 feet centered on the channel of the Santa Ana River. Also included in the area conserved for the Santa Ana sucker are the main tributaries that are important for the species for a distance of at least 0.5 mile upstream from the confluence of the tributary with the Santa Ana River. These tributaries include Sunnyslope Creek, Mount Rubidoux Creek, Arroyo Tequesquite, Anza Park Drain, Evans Lake Drain, Temescal Creek and Aliso Creek. The elevation included in the analysis extends to 400 meters AMSL; elevations above this point were not present adjacent to stream sections within western Riverside County.

Based on these habitats, the Plan Area supports approximately 3,870 acres of potential habitat for the Santa Ana sucker. Table 1 shows the conservation and loss of potential habitat for the Santa Ana sucker. Overall, approximately 3,480 acres (90 percent) of potential habitat in the Plan Area will be conserved in Criteria Area or existing Public/Quasi-Public Lands. None of the land is within the rural/mountainous designation. The MSHCP Conservation Area includes a total of 190 acres (97 percent) of the preferred habitat of the Santa Ana Sucker: water and freshwater marsh. The MSHCP Conservation Area also includes the upland habitat adjacent to the channel, a total of 3,190 acres (89 percent), within an approximately 1,300-foot width centered on the channel of the Santa Ana River.

In addition, the wetland habitats policy described in Section 6.1.2 of the MSHCP, Volume I provides for conservation of wetlands which provide habitat for this species through avoidance and minimization. Mitigation for impacts to wetlands shall be incorporated in accordance with the "No Net Loss" policy of federal and state wetland regulations. The proposed mitigation shall be directly related to the functions and values of the wetland as related to this species and result in equivalent replacement.

TABLE 1
SUMMARY OF HABITAT CONSERVATION FOR SANTA ANA SUCKER

Vegetation Type	MSHCP Plan Area (Acres)	Within MSHCP conservation Area			Outside MSHCP conservation Area
		Criteria Area1 (Acres)	Public/ Quasi-Public (Acres)	Total Within MSHCP Conservation Area (Acres)	Rural/ Mountainous (Acres)	Outside MSHCP Conservation Area (Acres)	Total Outside MSHCP Conservation Area (Acres)
Santa Ana River Watershed
Water	200	20	170	190	0	10	10
Freshwater marsh	100	30	70	100	0	0	0
Riparian habitat, Riversidean alluvial fan sage scrub, and coastal sage scrub adjacent to the channel	3,570	360	2,830	3,190	0	380	380
TOTAL	3,870	410 (11%)	3,070 (79%)	3,480 (90%)	0 (0%)	390 (10%)	390 (10%)
1 Acres refer to Additional Reserve Lands to be assembled from within the Criteria Area.

Species location data for the Santa Ana sucker within the Santa Ana River was derived primarily from Swift (2001), Saiki (2000), and from the CNNDB. Only the most recent distributional information available for the species with the Santa Ana River in Western Riverside County was used to allow the MSHCP to incorporate those areas identified by recent focused surveys for the species in the plan. The Santa Ana sucker occurs within the Plan Area within the Santa Ana River between the San Bernardino/Riverside County lines and the Orange/Riverside County lines (Swift 2001). The greatest portion of the population exists between the San Bernardino/Riverside County line and the Metropolitan Water District (MWD) pipeline crossing, and then gradually decreases through the remainder of the Plan Area. Additionally, population concentrations are also high in the Sunnyslope Creek tributary during the spawning period (mid-March-mid-May). Equally important for the Santa Ana sucker is the conservation of the spawning areas which are located at Sunnyslope Creek and within the area just below Mission Boulevard upstream to the Rialto Drain. Other areas that will be conserved and restored if feasible include the Mount Rubidoux Creek, Anza Park Drain, Arroyo Tequesquite, Hidden Valley Drain, Evans Lake Drain, Temescal Creek, and Aliso Creek. The Market Street Seep may provide important refugia functions and will also be conserved. All of these areas identified above are included within the MSHCP Conservation Area. For the potential refugia and dispersal areas, a distance of at least 0.5 mile upstream from the confluence of each of these tributaries with the Santa Ana River will be conserved.

Species specific conservation measures for the Santa Ana sucker include an assessment of the barriers to Santa Ana sucker movement and identification of measures to restore connectivity if feasible. Species-specific conservation measures also will include an assessment of threats to the sucker, identification of areas that are necessary for spawning, identification of areas for the creation of stream meanders, pool and riffle complexes, and establishment of native vegetation. The MSHCP Conservation Area also includes reducing populations of non-native and exotic predatory fish species and bullfrogs where feasible.

Three major instream migration barriers are present on the Santa Ana River within the Plan Area: the Prado Dam outlet, which contains shallow, rapid flow over a laminar concrete surface; the diversion dam just downstream of River Road, which allows water to pass downstream through culverts with 40 to 70 centimeter falls at their downstream ends; and an area a few hundred meters downstream of Mission Boulevard that has an undefined thalweg which allows flows to spread out into a marsh area, reducing the ability of native stream adapted fish to migrate up- or downstream and increasing exposure to predatory exotic fish. In addition, all tributaries to the Santa Ana River between Riverside Avenue and the Prado Dam (excepting the seep under Market Street Bridge and Mt. Rubidoux Creek) are limited upstream by artificial barriers, primarily unpassable culverts or concrete-lined channels (Swift 2001). Flood control activity such as bank stabilization, channelization, vegetation removal, drop structures, and the construction of dams, dikes, and diversions also cause the decline of the quality of the habitat for the Santa Ana sucker. An estimated three to four miles of stream habitat have been directly removed in the last fifteen years due to intensive flood control projects within the Sunnyslope and Arroyo Tequesquite drainages, which contain optimal spawning and rearing habitat for the sucker. All of the barriers and in-stream causes of habitat decline listed above may be able to be improved for the sucker by modifying their current design.

Exotic predatory fish have caused population declines of the Santa Ana sucker and control of these populations is one of the methods of species specific conservation measures. Reduction of the populations of non-native and exotic predatory fish may need to be accomplished through active programs within areas that currently do not contain abundant sucker populations. Reductions of the non-native predatory fish populations may also be accomplished through restoration of habitat to benefit the sucker, manipulation of seasonal flow volumes at key points within the river to force populations of exotic fish downstream, and through direct pressure on non-native species such as fishing.

An additional habitat-based threat to the species within the Santa Ana River includes the spread of invasive giant reed (Arundo donax) and tamarisk (Tamarix sp.) throughout the watershed. These plants tend to create large monocultures of emergent vegetation and habitat areas more suitable to exotic predatory fish by gradually increasing water depth, lowering flow gradients, covering spawning gravels or cobbles with finer sediment particles, and out-competing shallow emergent vegetation beneficial to the sucker. Large areas dominated by these non-native plants occur between Riverside Avenue and Fremont Street, which contains the best spawning habitat available to the sucker within the Santa Ana River.

The Reserve Managers responsible for the areas identified in Objectives 2 and 3 will assess the threats to the sucker due to degraded habitat and implement management measures to address the threats and protect critical areas. Restoration of potential habitat areas through enhancement of existing habitats, removal of non-native vegetation, instream habitat modifications in tributaries that provide potential spawning and nursery habitat, and planting of stream side native riparian trees and shrubs may improve and restore the habitat for the Santa Ana sucker.

MSHCP Conservation Area Configuration Issues

The primary upstream source of water within the Santa Ana River in Western Riverside County is the RIX plant and the Rialto Drain, both located upstream in San Bernardino County. Unfortunately the control of either of these sources is outside the scope of the MSHCP. Inclusion of the tributaries listed above is essential to maintaining the ecological integrity of the entire existing sucker population. The tributaries flow at temperatures that often vary from the mainstem of the Santa Ana River throughout the year, creating habitat that is often warmer or cooler than the mainstem for suckers in various life stages. These tributaries also provide heterogeneity in habitat as they also vary in terms of canopy, substrate and depth from the mainstem.

The most favorable habitat for the sucker within the Plan Area exists between the Riverside/San Bernardino County line and Mission Boulevard. This habitat consists of cobble-gravel surfaces, erratic bank vegetation and clear water which provides optimum habitat for spawning, foraging and refugia.

Flood control activities likely decrease habitat quality by redirecting flow, reducing bank vegetation and increasing flow, thus encouraging the removal of larger-sized substrate. Highly variable flow from wastewater treatment plants may negatively affect the sucker by decreasing habitat availability and quality particularly during dry seasons. Additional activities that may adversely affect the sucker include the construction and operation of wetlands which create favorable habitat for predatory and competitive non-native fish species and development of uplands adjacent to the Santa Ana River may decrease habitat quality as runoff is directed away from the Santa Ana River.

Conservation Summary

In summary, conservation for this species will be achieved by inclusion of at least 3,480 acres of suitable Conserved Habitat including the occupied habitat (water and freshwater marsh) and adjacent buffer and streambank (includes a variety of habitats) within the MSHCP Conservation Area. All of the known and potential refugia and spawning areas are included within the MSHCP Conservation Area. In addition, Objectives 4 and 5 will provide assessment of barriers and threats to the Santa Ana sucker by the Reserve Managers and will identify measures to be implemented if feasible.

INCIDENTAL TAKE

The Take of the sucker is difficult to quantify because larva and adults are quite small in body sizes, finding a dead or impaired specimen is unlikely, the species occurs in habitat that make detection difficult and losses may be masked by fluctuations in abundance and distribution during the life of the permit.

About 390 acres of potential habitat for the Santa Ana sucker, including the preferred habitat and the habitat adjacent to the channel, will be outside the Criteria Area and Public/Quasi-Public designations, or about 10 percent of the total potential habitat. A total of 10 acres (3 percent) of the open water habitat that is potentially occupied by the Santa Ana sucker will be outside the Criteria Area and Public/Quasi-Public designations. These open water areas are currently unsuitable areas of isolated ponds that are not connected to the Santa Ana River but are located within the area analyzed for conservation of this species. Other upland and adjacent areas that are not conserved include adjacent habitat within the Green River Golf Club, an upland area within the Silver Lakes areas and upland area between Mission Boulevard and Rancho Jurupa Park where the adjacent habitat area narrows. None of the stream channel reaches of the Santa Ana River are outside of the MSHCP Conservation Area. None of the core population areas, spawning areas, dispersal, or refugia areas are outside of the MSHCP Conservation Area. It should be noted that wetland habitats located outside the MSHCP Conservation Area would be subject to the Protection of Species Associated with Riparian/Riverine Areas and Vernal Pools policy presented in Section 6.1.2 of the MSHCP, Volume I.

Data Characterization

Data reviewed includes the California Natural Diversity Database (CNDDB) and the University of California, Riverside GIS database, and available literature.

The location database for the Santa Ana sucker includes six records for the species all within the Santa Ana River. The records are dated from 1993 to 1997. Although there are few records, the Santa Ana River is the main location for the species recorded by UCR. Other locations documented by personal communications from experts include the tributaries of the Santa Ana River. Additionally, species location data for the Santa Ana sucker within the Santa Ana River was derived from Swift (2001), and Saiki (2000).

The literature available is moderate in scope and quantity, with the majority of locational information on the species derived from recent literature. The available literature describes current habitat conditions, distribution, and threats to the species within the Santa Ana and San Gabriel River watersheds, the general biology of the species, some historic locational information, as well as management recommendations.

Habitat and Habitat Associations

The Santa Ana sucker generally lives in small, shallow streams, less than 7 meters in width, with currents ranging from swift in the canyons to sluggish in the bottom lands. They are found in permanent streams in water ranging in depth from a few centimeters to a meter or more (Smith 1966). Preferred substrates are generally coarse and consist of gravel, rubble, and boulders with growths of filamentous algae (Smith 1966; Moyle 1976a), but occasionally they are found on sand/mud substrates (Moyle et al. 1995). They appear to be most abundant where the water is cool, clean, and clear, although the species can tolerate seasonally turbid water. Santa Ana suckers within the Santa Ana River use partially submersed emergent aquatic macrophytes and riparian vegetation as the predominant cover (Saiki 2000). Within the Santa Ana River, larvae and juveniles of the species are most abundant in near-shore edge habitats in long runs, with gradually tapering shallows and shallow backwaters, often with circular flow. Adult suckers concentrate in widely scattered deeper pools and wide areas of gravel and rock substrates in flowing sections of river (Swift 2001).

Streams in which the species is found are subject to periodic, severe flooding. The majority of recent literature suggests that these periodic high-flows and flooding events results in drastic decreases of predatory fish populations within suitable sucker habitat areas, and corresponding increases of sucker populations (Saiki 2000, Swift 2001). California streams have strong seasonal patterns of flow (i.e., low flows during rainless summers and high flows during winter and spring from rainfall and snow melt). Annual precipitation varies considerably, and extended droughts with very low stream flow are common. The species is adapted for living in unpredictable environments by having life history strategies that include a short generation time, high fecundity, and relatively prolonged spawning period. These characteristics enable Santa Ana suckers to rapidly recolonize rivers following a flood by producing more young over a longer time span. The species also has a greater dependence on detritus, algae, and diatoms by juveniles (Greenfield et al. 1970) which may be another adaptation for survival in highly variable environments. The species appears to persist only in river reaches that remain relatively unchannelized (USFWS 2000).

Biogeography

The native range of C. santaanae is southern California including the San Gabriel (east, north and west forks), Los Angeles, and Santa Ana River drainages (Smith 1966; Page and Burr 1991). Historically, it occurred from near the Pacific Ocean to its current locations. Although locational information for the species prior to 1990 is relatively sparse, the USFWS (2000) estimates that the Santa Ana Sucker has lost approximately 70 percent of its historical native range in the Santa Ana River, and remaining populations within the river occur over approximately 60 percent of its total remaining native range. The species is now restricted to the headwaters of the San Gabriel River System, Big Tujunga Creek in the Los Angeles River basin, and portions of the Santa Ana River.

Introduced populations include the Santa Clara River (Miller 1968; Bell 1978; Swift et al. 1993), St. Maria-St. Inez drainage (Moyle 1976b), and accidentally into River Springs in Mono County, although the River Springs population has since become extirpated (Miller 1968). Two populations occur partially on federal land within the Angeles National Forest (USFWS 1997). This taxa is the only native catostomid found in the coastal drainages of southern California (Greenfield et al. 1970).

Known Populations Within Western Riverside County

The Santa Ana sucker occurs within the entire portion of the Santa Ana River within western Riverside County (Swift 2001), from approximately Riverside Avenue downstream to the western Riverside/Orange County line. The species is now apparently absent from the upper reach of the Santa Ana River in the San Bernardino Mountains, and occurs downstream to approximately Imperial Highway (Saiki 2000). The portions of the Santa Ana River occupied by the Santa Ana sucker constitute approximately 60 percent of the remaining native range of the species (USFWS 2000). Length-frequency analysis indicates that the species is naturally reproducing in the Santa Ana River system (Saiki 2000). However, other investigators contend the large number of suckers reported in the tributaries are juveniles and may be the progeny of very few adults (USFWS 1999).

At least three distinct populations currently occur within this area of the river, each separated by instream migration barriers; fish upstream of River Road, between River Road and Prado Dam, and downstream of Prado Dam (Swift 2001). Recent work by Swift (2001) concludes that the species is common to abundant from approximately the MWD pipeline crossing upstream to the RIX tributary in San Bernardino County, and rare to absent downstream of this point. The Santa Ana sucker appears to spawn in the main river upstream of the MWD crossing, as well as within the RIX and Sunnyslope Creek tributaries (to a limited degree).

Biology

Genetics: Snyder (1908b), who collected the fish from the Santa Ana River, originally described Catostomus santaanae as Pantosteus santa-anae. Smith (1966) omitted the hyphen and reduced the genus to a subgenus of Catostomus. Variability in certain anatomical features is exhibited by the Santa Ana Sucker, whereas they are homogeneous among other members of the subgenus Pantosteus (Smith 1966). The increase in fragmentation of the remaining population causes a loss of genetic variability and results in higher vulnerability to random events, environmental factors, and inbreeding which may allow increased expression of deleterious genes. Small populations cannot respond successfully to environmental stressors when genetic variability is reduced. Several documented barriers to annual upstream migration of the Santa Ana sucker exist within the Santa Ana River, reducing gene flow between refugia populations within the watershed. Swift (2001) notes that the Prado Dam in the Santa Ana River may present a prominent genetic barrier if reproduction of the sucker does not occur below the dam, since several impassable upstream barriers prevent any fish below the dam from returning to reproducing populations upstream. Although the sucker may have several refugia populations within portions of the Santa Ana river, there may be annual gene flow between these populations, making the maintenance of the intermediate creek stretches important for long-term persistence of the species (Fisher and Swift 1998).

Diet and Foraging: Greenfield et al. (1970) conducted an extensive study of the species' life history. They found that detritus, algae and diatoms constituted 98 percent of the animal's diet; and the remaining 2 percent included aquatic insect larvae, fish scales and fish eggs. In addition, larger fish had a higher percentage of insect material in their diets. Young (age-group 0+) feed primarily on algae, diatoms, and detritus. As they reach the 1+ age-group, aquatic insects become a significant part of their diet (Greenfield et al. 1970). The Santa Ana sucker, typical of the sucker family, has large, thick lips and a small mouth used to "vacuum" algae and invertebrates from stream beds. A comparative analysis of sucker populations within the Santa Ana and San Gabriel Rivers revealed that the diet of the suckers collected in the Santa Ana River appears to consist of fewer aquatic insects by volume and species (Saiki 2000).

Growth Rate: Greenfield et al. (1970) concluded that at six months of age, suckers averaged 44 mm SL; they matured during their second summer and usually died at the end of their third summer at 75 to 110 mm SL; a few were found to reach their fourth summer, reaching 14 to 16 cm SL. Additionally, he found that females and males grew at the same rate.

Reproduction: By the first year, suckers become reproductively mature and begin spawning during the first and second years. They are explosive breeders, producing between 4,400 and 16,000 eggs at a time; more fecund than most other catostomids. There is a linear relationship between body size and number of eggs produced. Within 360 hours of fertilization, eggs hatch (at 13 degrees Celsius) and are demersal and adhesive (Greenfield et al. 1970). Spawning peaks between late May through early June, but can occur from March until early July (Moyle 1976a). In the Santa Ana River, spawning occurs from mid-March to mid-April, with larvae occurring from late March to early May (Swift 2001). In the Santa Clara River spawning primarily occurs between March and April as well (Greenfield et al. 1970). A comparative analysis of suckers within the Santa Ana and San Gabriel Rivers suggests that spawning occurs earlier in the year in the Santa Ana River, based on the appearance time of breeding tubercles (on reproducing fish) and on initial appearance time of juveniles (Saiki 2001). Greenfield et al. (1970) used three techniques to determine the time of spawning: increase in mean egg diameter throughout the season, the maturity index, and the first major appearance of young. Moyle (1976a) suggested that the combination of early maturity, protracted spawning period, and high fecundity allows Santa Ana suckers to quickly repopulate streams following periodic severe floods which can decimate populations.

Survival: Santa Ana suckers do not survive beyond the fourth year. They are adapted to living in unpredictable environments and their propensity for explosive breeding enables them to repopulate rivers and streams following population reducing flood events. Other aspects that contribute to this ability are short generation time and prolonged spawning period. Other survival mechanisms may include small size which allows them to utilize a greater range of instream refuges that would be unavailable to larger fish during high flows. Death usually occurs in the age-group 2+, with some fish carrying on into the 3+ age-group (Greenfield et al. 1970). A comparative analysis of the species within the Santa Ana and San Gabriel Rivers revealed that only two cohorts are generally present within the Santa Ana River, compared with three in the San Gabriel River, indicating that few individual suckers live beyond their second year of life in the Santa Ana River (Saiki 2000). The data show that spawning occurs during the first spring following hatching. Growth of river populations is slower than pond populations (Greenfield et al. 1970). Because the young feed primarily on algae, diatoms, and detritus, smaller individuals of the 0+ age-group can rapidly repopulate a flooded area (Greenfield et al. 1970).

Dispersal: Natural dispersal is typically up- or downstream as conditions and suitable habitat permit, and is typically facilitated by flooding events (Moyle 1976a). Dispersal within the Santa Ana River watershed is currently limited by the Prado Dam and several instream migration barriers both within the river mainstem and most tributaries containing suitable sucker habitat (Swift 2001). Sucker larvae tend to inhabit very shallow water (10-15 centimeters) over very soft sand or mud substrate. The juveniles tend to invade deeper water but remain in groups near shoreline features with predominantly sand or mud substrates until reaching approximately 30-40 millimeters in standard length (SL). Once the suckers grow beyond 30 to 40 millimeters SL, they are commonly associated with deeper pools and gravel or cobble substrates (Swift 2001). Within the Santa Ana River, the sucker larvae and juveniles were observed to migrate from the mainstem of the river to the mouths of tributaries, apparently dependant upon water temperature. The trend was for larvae and juveniles to prefer the warmer river water (15 to 25 degrees Celsius) in the April and May, with invasion of cooler, lower tributaries including the Market Street seep, Mt. Rubidoux Creek, Anza Park drain, and Evans Lake drain (17 to 24 degrees Celsius) occurring in June and July as river water warmed (22 to 30 degrees Celsius) (Swift 2001).

Socio-Spatial Behavior: Literature regarding socio-spatial behavior of the Santa Ana sucker is limited. Villa (1985) found that a related species, the Sacramento sucker (Catostomus occidentalis), begins migration in December and peaks during the first week of March. Within the migration, males outnumbered females 2:1, and 98 percent were repeat spawners (judging by spawning checks on scales). Four to five weeks after peak spawning, peak out-migration of juveniles occurred, lasting for three weeks (Villa 1985).

Community Relationships: No information.

Threats to Species

As the Los Angeles urban area has expanded, the Los Angeles, Santa Ana, and San Gabriel Rivers have been highly modified, channelized, or moved in an effort to either capture water runoff or protect property. The impacts associated with urbanization are likely the most significant cause of the extirpation of this species from lowland reaches of the Los Angeles and San Gabriel Rivers. In addition, all three rivers within the historic range of the Santa Ana sucker have dams that isolate and fragment fish populations. Dams likely have resulted in some populations being excluded from suitable spawning and rearing tributaries (USFWS 1999). Urban development also threatens the sucker in the Santa Ana River watershed. Intensive urban development of the watershed has resulted in water diversions, extreme alteration of stream channels, changes in the watershed that result in erosion and debris torrents, pollution, and the establishment of introduced non-native fishes. Threats to the Santa Ana sucker within the Santa Ana River in western Riverside County have been generalized into three categories for the purposes of this analysis; habitat based threats (e.g., degradation, fragmentation, destruction), biological threats ( e.g., predation, competition), and water quality threats (e.g., temperature, salinity, pollution).

Habitat-based threats to the Santa Ana sucker include extensive existing and proposed channelization and flood control projects that directly remove habitat for the sucker, modify it to a degree that the species can no longer utilize it, or fragment the existing areas of occupied habitat within the watershed. Flood control activity such as bank stabilization, channelization, vegetation removal, drop structures, and the construction of dams, dikes, and diversions has been implicated as a key factor responsible for the decline of not only the Santa Ana sucker but six other species of freshwater fishes native to the Los Angeles Basin (Swift et. al. 1993). The Santa Ana River is within several flood control districts, and contains all of the above mentioned flood control practices that have an adverse effect on sucker populations within the river.

The portion of the Santa Ana River within western Riverside County currently contains miles of rip-rap bank stabilization between Riverside Avenue and the Prado Dam. Swift (2001) documented a portion of Sunnyslope Creek that has been progressively migrating northward due to a capped landfill and associated rip-rap bank stabilization upstream at the present mouth of Arroyo Tequesquite; the river has been diverted to the north by this streambank armoring and is progressively eroding away an existing stream meander in lower Sunnyslope Creek, removing habitat occupied by suckers. An estimated three to four miles of stream habitat have been directly removed in the last fifteen years due to intensive flood control projects within the Sunnyslope and Arroyo Tequesquite drainages, which contain optimal spawning and rearing habitat for the sucker.

Bridges and diversions and their associated regular maintenance also negatively affect the species. The River Road bridge does not span the floodplain of the Santa Ana River and requires regular removal of sand to prevent drifting sand from overwhelming the bridge. Swift (2001) documented sand mining at River Road that restricted the downstream movement of suckers, and diversion practices downstream of River Road that reduce the amount of water in the river by half (Swift 2001), virtually eliminating portions of instream habitat within the river for native fish and creating a one-way flow of fish into the impounded habitat due to culverts and abundant predatory fish species.

Instream migration barriers in the form of culverts, drop-structures, and dams pose a serious habitat fragmentation threat to the Santa Ana River population of suckers. Swift (2001) documents three major instream migration barriers on the river within Western Riverside County alone; the Prado Dam outlet, which contains shallow, rapid flow over a laminar concrete surface; and the diversion dam just downstream of River Road, which allows water to pass downstream through culverts with 40 to 70 centimeter falls at their downstream ends. In addition, all tributaries to the Santa Ana River between Riverside Avenue and the Prado Dam (excepting the seep under Market Street Bridge and Mt. Rubidoux Creek) are limited upstream by artificial barriers, primarily unpassable culverts or concrete-lined channels (Swift 2001). These barriers restrict sucker distribution within the river and fragment the population into at least three distinct populations that are essentially reproductively isolated from one another.

An additional habitat-based threat to the species within the Santa Ana River include the spread of invasive giant reed (Arundo donax) and tamarisk (Tamarix sp.) throughout the watershed. These plants tend to create large monocultures of emergent vegetation and habitat areas more suitable to exotic predatory fish by gradually increasing water depth, lowering flow gradients, covering spawning gravels or cobbles with finer sediment particles, and out-competing shallow emergent vegetation beneficial to the sucker. Large areas dominated by these non-native plants occur between Riverside Avenue and Fremont Street, which contains the best spawning habitat available to the sucker within the Santa Ana River.

The primary water quality threat to the sucker in the Santa Ana River in western Riverside County is the long-term security of base flows within the river downstream of the RIX outlet. The flow within the river is subject to frequent drops downstream of the Rialto Drain and the RIX plant, which are the origination sources of flow for the river below the Seven Oaks Dam in San Bernardino County for much of the year. Swift (2001) indicates that every few weeks the flow drops by more than 50 percent for a few hours or more, dramatically reducing the shallow water habitats favored by native fishes downstream to Riverside Avenue and potentially limiting the number of fish that may inhabit the upstream areas of the river. A portion of these flows may be subject to sale in the future, potentially reducing the flow volume available to the sucker in the river.

In addition, increased levels of turbidity have been documented within the river south of Mission Boulevard, downstream to below Prado Dam. The Santa Ana sucker is intolerant of turbidity, probably because the suspended sediments interrupt light penetration into the water column and reduce algal growth and therefore the forage base for the sucker. Swift (2001) documents increased turbidity from Mission Boulevard downstream to River Road, where disturbances from sand mining elevate turbidity even more. Below Prado Dam, the turbidity increases again due to suspended sediments from lower Chino and Mill Creeks. Finally, water pollution from non-point sources including heavy metals, high-levels of bacteria, and low levels of protozoa and viruses has been identified as a potential threat to the species within western Riverside County (Egan et. al. 1992).

Biological threats to the species in the Santa Ana River include a combination of predation by exotic and introduced fish in warmer water habitats with lower flow gradients, as well as competition with non-native fish species within these habitats and higher gradient habitats more favored by all life stages of the Santa Ana sucker. The distribution and abundance of non-native fish and their affects on the sucker are difficult to quantify, and vary throughout the portion of the river within western Riverside County. Swift (2001) states that tributary lakes and ponds, the seasonal pool behind Prado Dam, and the diversion impoundment at River Road and downstream are the most likely sources of most of the exotic fish species that may limit the distribution and abundance of suckers in the Santa Ana River. These species include green sunfish, largemouth bass, mosquitofish, bullhead, and inland silversides, all of which are most common downstream of River Road and the best sucker habitat within the Santa Ana River, or in tributaries including Sunnyslope Creek and Evans Lake drains. Additional species such as channel catfish and carp are abundant below Prado Dam and likely contribute to increased predatory pressure and habitat degradation below Prado Dam. The predatory action of these species on the sucker has not been documented despite studies of stomach contents of exotic fish species conducted by several authors. Introduced carp and channel catfish are the primary threat to the sucker downstream of the Prado Dam, where the sucker appears to be restricted from upstream portion of the river by the dam. Several authors indicate that the reduction in numbers of suckers below the dam is probably influenced to a high degree by the presence of carp, which are extremely effective predators.

Competition with introduced tilapia is a potentially significant problem for the sucker in upstream portions of the river, including the Rialto and RIX drains where the species survives on warm effluent flows and may compete for forage on the abundant hard substrates.

An additional biological threat to the species may be the decline of aquatic invertebrate abundance and diversity within the Santa Ana River. Saiki (2000) relates low body condition of Santa Ana suckers in the Santa Ana River to an inadequate supply of high-energy animal forage, and indicated through a comparative analysis of the species in the Santa Ana and San Gabriel Rivers that suckers in the Santa Ana River had lower overall body condition and substrates within occupied habitats contained fewer species and numbers of aquatic invertebrates for the suckers to consume.

The high degree of fragmentation of the remaining populations make the Santa Ana sucker especially vulnerable to random events, environmental factors, and loss of genetic variability. Random events such as floods, variations of annual weather patterns, predation and associated demographic uncertainty, may lead to the demise of the remnant populations in the Santa Ana River.

Special Biological Considerations

During the 1970s, the Santa Ana sucker was described as common (Moyle 1976a). Since then, the species has experienced an approximately 75 percent reduction of its native range (Swift et. al. 1993; USFWS 2000). The four small river systems that comprise the entire native range of the Santa Ana sucker all flow through the expanding urban sprawl of Los Angeles, becoming subject to dams, pollution, channelization, poor watershed management and excessive flooding episodes. The Santa Ana sucker currently occupies only limited reaches of the Los Angeles, San Gabriel, and Santa Ana Rivers. The population of the Santa Ana sucker within the Santa Clara River is introduced, and a portion of population is hybridized. The preservation of refuges for this and other endemic species is a necessary step toward curbing present trends which, left unchanged, will inevitably lead to extinction.

The Santa Ana sucker evolved in habitats that were periodically destroyed by intense floods, and the species would recover to its former distribution within the watershed after harboring in natural refugia. No refugia are described by recent authors for the species within the Santa Ana River, reducing the ability of the current sucker populations to recover their distribution within the watershed after large-scale flooding disturbances.

A comparative analysis of the San Gabriel and Santa Ana Rivers conducted by Saiki (2000) indicted that few suckers live beyond their second year of life in the Santa Ana River, whereas a substantial number of third year suckers occur within the San Gabriel River. In addition, spawning occurs earlier in the year in the Santa Ana River than the San Gabriel River. These and other variables studied in the analysis lead Saiki to conclude that the San Gabriel River supports a healthy population of suckers whereas the Santa Ana River supports a marginal population of suckers.

Dams and reservoirs greatly reduce the natural variability in environmental conditions, resulting in the domination of nonnative fish faunas (Moyle 1976a; Herbold and Moyle 1986; Moyle and Light 1996). High disturbance systems support groups of species that would probably not coexist under natural conditions. For example, 3-4 species of predatory bass commonly live within reservoirs on California rivers, while rarely are more than two species are found together in natural systems (Moyle and Light 1996). Cornell and Lawton (1992) argue that ecological communities are rarely saturated with species, thus, even complex systems may be invaded relatively easily. Successful invasions are most likely to occur when native assemblages have been temporarily disrupted or depleted (Moyle and Light 1996). The match between an invader and the hydrologic regime seems to be the most important factor in determining the success of an invasion, rather than the biotic resistance (Moyle and Light 1996; Case 1991). However, most invasions do not result in direct extirpation, except in the case of Piscivores, or when invaders can hybridize with native species (Moyle and Light 1996). In relatively unmodified streams, such as Deer Creek (Tehama County), the natural hydrologic regime prevents repeated invasions of nonnative fish (Moyle and Light 1996).

Management considerations should include preservation and management of the main stem and upper tributaries of the Santa Ana River containing sucker spawning habitat, preservation and restoration of tributaries that provide seasonal habitat for all life stages of the sucker, including the implementation of sediment transport strategy and reduction or elimination of introduced predatory fishes including green sunfish and largemouth bass (Moyle 1976a). In addition, identification of the reasons for the reduced body condition of suckers within the Santa Ana River and appropriate responses to reduce or eliminate any contributing variables to poor body condition of suckers with the Santa Ana River is necessary to promote persistence of the species within the river. Finally, renovation of all possible instream migration barriers within the river should be considered to ensure the long-term genetic viability of those suckers present within the Santa Ana River.

LITERATURE CITED & ADDITIONAL REFERENCES

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Bell, M.A. 1978. Fishes of the Santa Clara River System, southern California. Nat. Hist. Mus. Los Angeles County, California, Contributions in Science Series. 295:1-20.

Case, T.J. 1991. Invasion resistance, species build up, and community collapse in metapopulation models with interspecies competition. Biological J. of the Linneaen Soc. 42:239-266.

Chadwick Ecological Consultants. 1996. Current Status of the Santa Ana sucker in the Santa Ana River, California. Prepared for the Santa Ana River Dischargers Association, CA.

Cornell, H.V. and J.H. Lawton. 1992. Species interactions, local and regional processes, and limits to the richness of ecological communities: a theoretical perspective. Journal of Animal Ecology. 61:1-12.

Egan, J.T., S.P. Canton, T.F. Moore, G.Y. Michael, M.M. Grimes, and A.P. Rochette. 1992. Tailoring Requirements to reality: The Santa Ana River Use Attainability Analysis. Water Environment Federation, Alexandria, VA. AC92-036-006.

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Saiki, M. 2000. Water quality and other environmental variables associated with variations in population densities of the Santa Ana sucker. Prepared for the National Fish and Wildlife Foundation, San Francisco, CA. 117 pp.

Smith, G. R. 1966. Distribution and evolution of the North American Catastomid fishes of the subgenus Pantosteus, genus Catostomus. University of Michigan Mus. Zool. Misc. Publ. 129: 1-33.

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U.S. Fish and Wildlife Service (USFWS). 1996. Endangered and threatened wildlife and plants; Notice of initiation of 12-month status review for petition to list the Santa Ana sucker as Endangered. Federal Register 61(229):60073.

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Villa, N.A. 1985. Life History of the Sacramento Sucker, Catostomus occidentalis, in Thomas Creek, Tehama County, California (USA). Cal Fish and Game, v. 71, n. 2, 1985:88-106.