Federal Register: December 14, 2010 (Volume 75, Number 239)
DOCID: fr14de10-8 FR Doc 2010-30447
DEPARTMENT OF THE INTERIOR
Veterans Affairs Department
CFR Citation: 50 CFR Part 17
Docket ID: [Docket No. FWS-R8-ES-2009-0072; 92210-1117-0000-B4]
RIN ID: RIN 1018-AW23
NOTICE: Part II
DOCUMENT ACTION: Final rule.
Endangered and Threatened Wildlife and Plants; Revised Critical Habitat for Santa Ana Sucker
DATES: This rule becomes effective on January 13, 2011.
We, the U.S. Fish and Wildlife Service (Service), designate critical habitat for Santa Ana sucker (Catostomus santaanae) under the Endangered Species Act of 1973, as amended. In total, approximately 9,331 acres (3,776 hectares) of habitat in the Santa Ana River in San Bernardino, Riverside, and Orange Counties and the San Gabriel River and Big Tujunga Creek in Los Angeles County in southern California fall within the boundaries of the critical habitat designation. This final revised designation constitutes an overall increase of approximately 1,026 acres (415 hectares) from the 2005 designation of critical habitat for Santa Ana sucker.
Interior Department, Fish and Wildlife Service
It is our intent to discuss only those topics directly relevant to the development and designation of revised critical habitat for Santa Ana sucker in this final rule. In the proposed rule (74 FR 65056; December 9, 2009) and the document that made available the draft economic analysis (DEA) (75 FR 38441; July 2, 2010), we stated that there was new information on the distribution of Santa Ana sucker and its habitat within the Santa Ana River that we did not discuss in the 2005 final critical habitat designation for this species (70 FR 425; January 4, 2005). As a result of public comments on this new information, we are providing clarification of this information in the Habitat and Geographic Range and Status sections of this final rule. Additionally, we incorporated information from recent surveys in the Santa Ana River (see Geographic Range and Status section) and new information on the hydrology and flow regime of the Santa Ana River (see Sites for Breeding, Reproduction, and Rearing (or Development) of Offspring section). No new information pertaining to the species' description, life history, or ecology was received following the 2009 proposed revised rule and the document that made available the DEA. For more information on Santa Ana sucker, refer to the final listing rule published in the Federal Register on April 12, 2000 (65 FR 19686); the designation and revision of critical habitat published in the Federal Register on February 26, 2004 (69 FR 8839), and on January 4, 2005 (70 FR 425), respectively; the proposed revised critical habitat published in the Federal Register on December 9, 2009 (74 FR 65056); and the document that made available the DEA published in the Federal Register on July 2, 2010 (75 FR 38441).
As discussed in detail in the Habitat section of the proposed revised critical habitat rule (74 FR 65056; December 9, 2009), Santa Ana sucker requires various substrate types throughout different stages of its life. The presence of coarse substrates, including gravel, cobble, and a mixture of gravel or cobble with sand, and a combination of shallow riffle areas and deeper runs and pools provide optimal stream conditions (Haglund et al. 2001, p. 60; Haglund and Baskin 2003, p. 55). Areas of shifting sandy substrates are less suitable for development of algae, an important food source for suckers (Saiki et al. 2007, p. 98). Therefore, an integrated water system that contains and provides the appropriate quantity of coarse substrates such as gravel, larger cobbles, or boulders that provide the space for reproductive development and growth of algae as a primary food source is important for a viable population of Santa Ana suckers.
Saiki et al. (2007, p. 98) indicates that the San Gabriel River supports higher body condition Santa Ana suckers (as described by their higher lengthweight relationship) and greater availability of various habitat types than the Santa Ana River. They state that the San Gabriel River generally contains a higher abundance of Santa Ana suckers and larger individuals, which may be attributed to more suitable habitat characters such as cooler water temperature, intermediate water velocities, and commonality of pools and riffles with coarser bottom substrates, all of which may contribute to a better functioning system and more suitable habitat for Santa Ana suckers (Saiki et al. 2007, pp. 99100).
In the San Gabriel River, there are some distinct differences
between the three forks of the river (north, west, and east), which
seem to correlate with both fish abundance and life stage occupancy
(Tennant 2006, pp. 45, 9). Overall, the water condition (i.e., lower
temperature, lower specific conductance, and lower turbidity) and
habitat available in the San Gabriel River system appear to be primary
reasons that Santa Ana suckers are in higher abundance and better
condition compared to those in the Santa Ana River, although other
variables (i.e., stream width or depth) may also influence the species'
abundance and condition. For example, in the Santa Ana River, the
predominate riparian vegetation is the nonnative species Arundo donax
(giant reed). In Big Tujunga Creek, A. donax can be common in the lower
reaches (Baskin and Haglund 1999, p. 11; Saiki 2000, pp. 6280). In the
San Gabriel River, this nonnative plant is rarely found, and the
riparian vegetation consists of primarily native vegetation or may be
bare due to the steeper, mountainous terrain (Saiki 2000, pp. 1819;
Saiki et al. 2007, p. 90). Native riparian vegetation provides cover
and shelter from predators, which is essential for juvenile and adult
Santa Ana suckers (see Primary Constituent ElementsCover and Shelter
and Primary Constituent Elements for Santa Ana Sucker below). Arundo
donax is an aquatic plant in the genus of perennial reedlike grasses
(Poaceae) and is often found growing along lakes, streams, and other
wetted areas. Compared to other riparian vegetation, it is known to use
excessive amounts of water to supply its exceptionally high growth
rates (Bell 1997, p. 104) and could crowd out native riparian
vegetation or possibly lower the water table (Zembal and Hoffman 2000, p. 66). In areas where A.
donax is common, flows may become diminished and sandy pools may form. Slowmoving flows and formation of pools are preferred habitat for nonnative predators such as largemouth bass (Micropterus salmoides) and green sunfish (Lepomis cyanellus), which have been suggested to prey heavily on Santa Ana suckers. The effects of A. donax presence may negatively affect Santa Ana sucker by altering the instream habitat and, may also provide habitat for nonnative predators. However, these types of impacts would need to be evaluated within the context of potential threats to the Santa Ana sucker.
The unmodified and unpolluted habitat in the San Gabriel River supports what appears to be a healthier and more viable population of Santa Ana sucker. Habitat assessments conducted throughout the Big Tujunga Creek indicate that the habitat suitability is variable throughout the system; however, the river does contain areas that are suitable for all Santa Ana sucker life stages (LACDPW 2009, Google Earth kmz file). It is likely that because of the variability in habitat suitability, the density of Santa Ana suckers in the Big Tujunga Creek is patchy and often low (Ecorp Consulting 2010a, p. 5; Haglund and Baskin 2010, pp. 56).
Santa Ana sucker habitat may be impacted as a result of wildfires. Impacts associated with wildfires may occur immediately or may not become apparent until much later. Immediate impacts may include the loss of upland and riparian vegetation and creation of roads for fire fighting, which may allow greater access to streambeds and facilitate increased Off Highway Vehicle (OHV) use, resulting in further habitat degradation (USGS 2009, p. 7). Excessive debris flows and changes to water quality are anticipated to occur during seasonal rains over the next several years in the Big Tujunga Creek and surrounding San Gabriel Mountains (USGS 2009, p. 7). Anticipated postfire impacts to streams within the critical habitat designation for Santa Ana sucker include ash and debris deposition that may physically alter streambeds and pools, increased scouring of riparian and aquatic vegetation, and increased water temperature from the shortterm loss of canopy shading (USFS 2009, p. 5). Postfire impacts to water quality (such as increased turbidity) are also anticipated along with release and mobilization of toxic chemicals such as gas, oil, and building materials from burned structures and their contents (USFS 2009, p. 6). The impacts associated with postfire winter flows include but are not limited to changes in sediment composition, high flows that flush Santa Ana suckers into unsuitable habitats, and changes in water quality (such as increased turbidity and the introduction of chemicals from debris and fire retardant).
Recreational uses of streams may pose significant impacts to Santa Ana sucker habitat. Throughout the drainage systems where Santa Ana suckers persist, there are varying levels of recreational use. On U.S. Forest Service lands, recreational pressures may be considerable. Permanent or intermittent dams are frequently created for recreational purposes, such as those used for suction dredging or bathing. These dams may degrade instream and bank habitat, decrease water quality by increasing turbidity (affect PCE 4), disrupt sediment transport (affect PCEs 1 and 2), impede upstream movement, degrade habitat by slowing water velocities (affect PCE 3), increase water temperatures (affect PCE 5), and encourage excessive growth of algae (Ally 2003, p. 3). In addition, presumably, since water depths increase and velocities decrease, these areas may harbor nonnative predators (Ally 2003, p. 1; Chambers Group 2004, p. 64). Recreational residences located within the riparian area of the San Gabriel River and Big Tujunga Creek may impact Santa Ana sucker because of the improperly functioning septic systems at these residences which can degrade water quality conditions by increasing water turbidity (PCE 4) as a result of the increased nutrient loads in the water (USFS 2007, p. 18), which lead to excessive algal growth.
Geographic Range and Status
As discussed in detail in the Geographic Range and Status section of the proposed revised rule (74 FR 65056; December 9, 2009), genetic introgression (when a hybrid breeds with one of the parent species) has been detected in both Santa Ana sucker and Owens sucker (Catostomus fumeiventris) within the Santa Clara River (Ferguson 2009, p. 1; Chabot et al. 2009, p. 24), indicating that hybridization between these two species has occurred. Moyle (2002, p. 184) and Chabot et al. (2009, p. 1) recently described hybridization of Santa Ana sucker with Owens sucker in the lower Santa Clara River in the vicinity of Fillmore and Sespe Creek. As stated in the proposed revised critical habitat rule (74 FR 65056; December 9, 2009), a genetic analysis of the populations in all four watersheds would provide information on the status of the fish throughout the range, including whether the Santa Clara population is native, introduced, or hybridized. However, this analysis has not been completed to date. Researcher and species' expert opinions on the status of the population in the Santa Clara River vary widely. Additional research is needed to determine the impact and extent of hybridization on genetically pure Santa Ana sucker in the Santa Clara River. Given the lack of new genetic information to help us determine whether Santa Ana suckers in the Santa Clara River are native or introduced, as well as a lack of information on the impact and extent of hybridization on genetically pure Santa Ana sucker, we continue to adhere to our 2000 decision not to include the Santa Clara River population of the Santa Ana sucker as part of the listed entity. Therefore, the Santa Clara River area was not included in the proposed revision to critical habitat or this final rule.
The Santa Ana sucker is considered a listed species in the Los Angeles, San Gabriel, and Santa Ana River drainages (Service 2000, pp. 1968619687). Additionally, the listing rule states that Arroyo Tesquesquite, Sunnyslope Creek, Anza Park Drain, and the lower outlet of Hidden Valley Drain are used for spawning and nurseries (Service 2000, p. 19687), and therefore Santa Ana sucker in those areas are considered part of the listed entity. The historical survey records for this species are not considered complete, and the precise areas occupied by the species are difficult to determine with certainty because not all areas were surveyed exhaustively and distribution literature states that the Los Angeles, San Gabriel, and Santa Ana River drainages as a whole were occupied (Moyle 2002, p. 183; Greenfield et al. 1970, p. 166; Smith 1966, pp. 5356). In particular, the upper limit of habitat occupied by the Santa Ana sucker within each of the Los Angeles, San Gabriel, and Santa Ana River drainages is difficult to determine. However, as we note in our analysis of criteria used to define critical habitat (see Criteria Used To Identify Critical Habitat section below), Santa Ana suckers have not been observed in streams or rivers where the instream gradient exceeds 7 degrees. Even in areas where the stream gradient is less than 7 degrees, the upper limits of occupied habitat within the drainages likely have varied through time because of the dynamic nature of these drainage systems. Portions of streams may dry out in some years while the same area may become occupied by Santa Ana suckers in subsequent years due to the [[Page 77964]]
presence of water (Baskin et al. 2005, pp. 12).
The current status of Santa Ana sucker in the Santa Ana River appears to be declining. In 2009, the lowest Santa Ana sucker density since sampling began in 2001was reported by the Santa Ana Sucker Conservation Program Team (Team). Although densities of Santa Ana sucker have been variable from year to year, the overall density trend in the Santa Ana River is decreasing (SMEA 2009, p. 2). Recent research conducted by Thompson et al. (2010, pp. 321332) indicates that the areas in the Santa Ana River with the highest quality habitat (gravel and cobbles) available for adult, juvenile, and larval stages of Santa Ana sucker occur just downstream of Riverside Avenue near the RiversideSan Bernardino County line. Further, they believe Santa Ana sucker abundance is directly related to the abundance of cobbles and gravel and that the lower portion of the survey area contains little to no suitable substrates (Thompson et al. 2010, pp. 328331). Monitoring and research results from both the Team (SMEA 2009, pp. 15) and Thompson et al. (2010, pp. 328330) show that low abundance of suitable habitat is correlated with low Santa Ana sucker abundance, indicating that altered fluvial processes (i.e., diminished transport of water and coarse sediments), lack of suitable substrate, and impediments to movement continue to fragment much of the current distribution of Santa Ana sucker in the Santa Ana River watershed.
Recent survey reports from the West Fork of the San Gabriel River indicate that there may be a decreasing trend in Santa Ana sucker population (Ecorp Inc. 2007, p. 9; Ecorp Inc. 2010b, p. 9). Monitoring of the West Fork of the San Gabriel River within and outside of the offhighway vehicle (OHV) area has indicated that Santa Ana sucker is generally more abundant at the control sites than in the OHV area (Haglund and Baskin 2002, pp. 915; Ecorp Inc. 2007, p. 9; Ecorp Inc. 2010b, p. 9). However, during the 2009 monitoring period, very low numbers of Santa Ana suckers and hundreds of nonnative predators were captured at all sites within the study area (Ecorp Inc. 2010b, p. 9). The report postulates that the flood basin of the San Gabriel Dam was full and flooded into areas where Santa Ana suckers are normally present; however, water quality measurements do not indicate any measureable change (Ecorp Inc. 2010b, p. 7). It is possible that the operations of the Cogswell and San Gabriel Dams have impacted the habitat suitability for Santa Ana sucker, and, in turn, abundance has decreased in the West Fork of the San Gabriel River. More information is needed to evaluate the status of Santa Ana sucker in the West Fork of the San Gabriel River.
Previous Federal Actions
Santa Ana sucker was listed as a threatened species under the Endangered Species Act of 1973, as amended (Act; 16 U.S.C. 1531 et seq.) on April 12, 2000 (65 FR 19686), in the Los Angeles River basin, San Gabriel River basin, and Santa Ana River basin. A fourth population in the Santa Clara River was not listed because it was presumed to be introduced into that watershed. Critical habitat was designated on January 4, 2005 (70 FR 425).
On November 15, 2007, California Trout, Inc., the CaliforniaNevada Chapter of the American Fisheries Society, the Center for Biological Diversity, and the Friends of the River filed suit against the Service alleging the 2005 final designation of critical habitat violated provisions of the Act and Administrative Procedure Act [(California Trout, Inc., et al., v. United States Fish and Wildlife, et al., Case No. 07CV05798 (N.D. Cal.) transferred Case No. CV 084811 (C.D. Cal.)]. We entered into a stipulated settlement agreement with plaintiffs that was approved by the district court on January 21, 2009.
The stipulated agreement required that we submit a proposed revised
critical habitat for the Santa Ana sucker to the Federal Register by
December 1, 2009, and a final revised critical habitat by December 1,
2010. On December 9, 2009, we published in the Federal Register a
proposed revised critical habitat for the Santa Ana sucker (74 FR
65056). On July 2, 2010, we published a notice in the Federal Register
reopening the comment period on the proposed rule and making available
the DEA (75 FR 38441). With this final rule, we are submitting a final
revised critical habitat designation to the Federal Register by
December 1, 2010, in accordance with the stipulated agreement. For
additional information, please see the Previous Federal Actions section of the proposed rule (74 FR 65056; December 9, 2009).
Critical habitat is defined in section 3 of the Act as:
(i) The specific areas within the geographical area occupied by a
species, at the time it is listed in accordance with the Act, on which are found those physical or biological features
(I) Essential to the conservation of the species and
(II) That may require special management considerations or protection; and
(ii) Specific areas outside the geographical area occupied by a species at the time it is listed, upon a determination that such areas are essential for the conservation of the species.
Conservation, as defined under section 3 of the Act, means the use of all methods and procedures that are necessary to bring any endangered or threatened species to the point at which the measures provided under the Act are no longer necessary. Such methods and procedures include, but are not limited to, all activities associated with scientific resources management such as research, census, law enforcement, habitat acquisition and maintenance, propagation, live trapping, transplantation, and in the extraordinary case where population pressures within a given ecosystem cannot otherwise be relieved, may include regulated taking.
Critical habitat receives protection under section 7(a)(2) of the Act through the prohibition against Federal agencies carrying out, funding, or authorizing the destruction or adverse modification of critical habitat. Section 7(a)(2) of the Act requires consultation on Federal actions that may affect critical habitat. The designation of critical habitat does not affect land ownership or establish a refuge, wilderness, reserve, preserve, or other conservation area. Such designation does not allow the government or public to access private lands. Such designation does not require implementation of restoration, recovery, or enhancement measures by private landowners. Where a landowner requests Federal agency funding or authorization for an action that may affect a listed species or critical habitat, the consultation requirements of section 7(a)(2) of the Act would apply, but even in the event of a destruction or adverse modification finding, the landowner's obligation is not to restore or recover the species, but to implement reasonable and prudent alternatives to avoid destruction or adverse modification of critical habitat.
For inclusion in a critical habitat designation, the habitat within
the geographical area occupied by the species at the time it was listed
must contain the physical and biological features essential to the
conservation of the species, and be included if those features may require special
management considerations or protection. Critical habitat designations identify, to the extent known using the best scientific and commercial data available, habitat areas that provide essential life cycle needs of the species (areas on which are found the physical and biological features laid out in the appropriate quantity and spatial arrangement essential to the conservation of the species). Under the Act and regulations at 50 CFR 424.12, we can designate critical habitat in areas outside the geographical area occupied by the species at the time it is listed only when we determine that those areas are essential for the conservation of the species and that designation limited to those areas occupied at the time of listing would be inadequate to ensure the conservation of the species.
Section 4 of the Act requires that we designate critical habitat on the basis of the best scientific and commercial data available. Further, our Policy on Information Standards Under the Endangered Species Act (published in the Federal Register on July 1, 1994 (59 FR 34271), the Information Quality Act (section 515 of the Treasury and General Government Appropriations Act for Fiscal Year 2001 (Pub. L. 106554; H.R. 5658), and our associated Information Quality Guidelines provide criteria, establish procedures, and provide guidance to ensure that our decisions are based on the best scientific data available. They require our biologists, to the extent consistent with the Act and with the use of the best scientific data available, to use primary and original sources of information as the basis for recommendations to designate critical habitat.
When we are determining which areas should be designated as critical habitat, our primary source of information is generally the information developed during the listing process for the species. Additional information sources may include the recovery plan for the species, articles in peerreviewed journals, conservation plans developed by States and counties, scientific status surveys and studies, biological assessments, or other unpublished materials and expert opinion or personal knowledge.
Habitat is often dynamic, and species may move from one area to another over time. Furthermore, we recognize that critical habitat designated at a particular point in time may not include all habitat areas that we may later determine are necessary for the recovery of the species. For these reasons, a critical habitat designation does not signal that habitat outside the designated area is unimportant or may not be required for recovery of the species.
Areas that are important to the conservation of the species, but are outside the critical habitat designation, will continue to be subject to conservation actions we implement under section 7(a)(1) of the Act. Areas that support populations are also subject to the regulatory protections afforded by the section 7(a)(2) jeopardy standard, as determined on the basis of the best available scientific information at the time of the agency action. Federally funded or permitted projects affecting listed species outside their designated critical habitat areas may still result in jeopardy findings in some cases. Similarly, critical habitat designations made on the basis of the best available information at the time of designation will not control the direction and substance of future recovery plans, habitat conservation plans (HCPs), or other species conservation planning efforts if information available at the time of these planning efforts calls for a different outcome.
Physical and Biological Features
In accordance with section 3(5)(A)(i) and 4(b)(1)(A) of the Act and the regulations at 50 CFR 424.12, in determining which areas within the geographical area occupied by the species at the time of listing to designate as critical habitat, we consider the physical and biological features essential to the conservation of the species which may require special management considerations or protection. These include, but are not limited to:
1. Space for individual and population growth and for normal behavior;
2. Food, water, air, light, minerals, or other nutritional or physiological requirements;
3. Cover or shelter;
4. Sites for breeding, reproduction, and rearing (or development) of offspring; and
5. Habitats that are protected from disturbance or are representative of the historic, geographical, and ecological distributions of a species.
We consider the specific physical and biological features essential to the conservation of the species laid out in the appropriate quantity and spatial arrangement for the conservation of the species. We derive the specific physical and biological features for Santa Ana sucker from the biological needs of this species as described in the Critical Habitat section of the proposed rule to designate critical habitat for Santa Ana sucker, which published in the Federal Register on December 9, 2009 (74 FR 65056).
Based on the needs and our current knowledge of the lifehistory,
biology, and ecology of the species and the habitat requirements for
sustaining the essential life history functions of the species, we
determined that Santa Ana sucker's physical and biological features
consist of flowing stream habitat (see Primary Constituent Elements
section for further discussion). However, some portions of this habitat
may experience significant reductions in, or an absence of, surface
flows during certain portions of the year (such as during summer
months) or under certain conditions (such as during severe droughts or
when artificial sources of water are temporarily suspended). Some areas
that we consider essential to the conservation of Santa Ana sucker may
not experience flows except during major storms events. However, these
areas are critically important components of naturally occurring
hydrologic and geologic processes because they provide a connected
hydrologic system within the historical range of this species. We have
attempted to capture the dynamic nature and importance of these
processes in identifying the habitat upon which Santa Ana sucker depends.
Habitats That Are Representative of the Historic Geographical and Ecological Distribution of the Species
Santa Ana sucker inhabits flowing streams, and has not been collected from reservoirs (Swift 2001, p. 15; Moyle 2002, p. 184). Water depths and velocities, as well as bed substrates, vary over the reaches of these streams creating various habitat features including:
1. Moderate currents over a uniform, unbroken stream bottom (i.e., runs);
2. Water flowing over gravel and cobble substrates that causes ripples to form on the surface of the water (i.e., riffles); and
3. Deep water areas created by submerged boulders where water is cool and relatively still (i.e., pools).
Streams in southern California are subject to periodic, severe
flooding that alters channel configuration, instream habitat
conditions, and vegetation structure (Moyle 2002, p. 183). Hence, as
stream conditions change, the characteristics of stream and bank
habitats and their suitability for Santa Ana sucker change, influencing
the distribution of the fish over time. Therefore, even stream reaches
where flows may periodically be interrupted or dewatered become essential during periods of high flows to allow Santa
Ana suckers to move between other habitat areas necessary for breeding, feeding, and sheltering.
Gravel beds in shallow, but clear, flowing stream reaches are needed for spawning. Shallow areas with sandy substrates and overhanging vegetation are needed to support larvae and fry. Juvenile and adult Santa Ana suckers require deeper pools of water for foraging, shelter during storms, and cover.
Santa Ana sucker prefers cool water temperatures but has been found
in waters between 59 and 82 [deg]Fahrenheit (F) (15 and 28 [deg]Celsius
(C)) in the Santa Ana River (Swift 2001, p. 18). Cooler water
temperatures are only maintained in some areas by the upwelling of
cooler groundwater, tributary flows, or shade from overhanging
vegetation. Overhanging and instream vegetation are also needed for the
development of an aquatic invertebrate community to supply food for
adult suckers as well as for protective cover, and shade, which reduces
water temperature during summer and fall months. Therefore, a complex
and integrated stream system is needed that: (1) Encompasses sand,
gravel, cobble, and rock substrates; (2) harbors diverse bed
morphologies found in deep canyons and alluvial floodplains; (3)
provides varying water depths and velocities; (4) contains tributaries
that provide fish with areas of refuge (refugia) from predators and
during floods and that can also provide suitable breeding habitat; and
(5) harbors sources of coarse sediment for renewal of substrate in
occupied areas. The primary constituent elements (PCEs; see Primary
Constituent Elements for Santa Ana Sucker section for detailed
discussion) and the resulting physical and biological features
essential to the conservation of Santa Ana sucker are derived from
studies of this species' habitat, ecology, and life history as
described below, in the Background section of the proposed revised rule
published in the Federal Register on December 9, 2009 (74 FR 65056), in
the final listing rule published in the Federal Register on April 12,
2000 (65 FR 19686), in the final critical habitat designation published
in the Federal Register on February 26, 2004 (69 FR 8839), and in the
final revised critical habitat designation published in the Federal Register on January 4, 2005 (70 FR 425).
Space for Individual and Population Growth and for Normal Behavior
Santa Ana suckers use various water depths, depending on their lifehistory stage and activity, and do not occupy all reaches of their habitat at any one time (Saiki 2000, p. 19; Haglund and Baskin 2003, p. 53). Larval and earlystage juvenile Santa Ana suckers prefer the shallow margins of streams in water of 2 to 4 inches (in) (5 to 10 centimeters (cm) in depth; as fish mature, they move into deeper water. Adults prefer deep pools for feeding and seeking refuge, riffles of varying depths for spawning, and riffles and runs of varying depths for movement between pools (Haglund et al. 2003, p. 102). For example, in the Santa Ana River, adult Santa Ana suckers have been found in diverse habitat areas, including shallow runs of less than 4 in (10 cm) in depth, in flowing water up to 5 feet (ft) (150 cm) deep (Saiki 2000, p. 19; Swift 2001, p. 66), and in pools 6 to 10 ft (200 to 300 cm) deep (Allen 2004). They have been found in similarly varying water depths in the San Gabriel River (Saiki 2000, p. 48), and Saiki speculates that their capture in these various depths is reflective of their ability to take advantage of a variety of habitat conditions (2000, p. 25). Flows within occupied habitat areas may occasionally become very shallow due to seasonal reductions in flow volumes or be interrupted as a result of dam operations or releases from wastewater treatment plants (such as in the Santa Ana River) in some portions of a stream reach. When stream depth is significantly reduced, deep pools become a critically important refuge for fish.
Surface water flows must be present within the stream, but water velocities where Santa Ana suckers occur can vary from slight to swift (Haglund and Baskin 2003, p. 2). Larvae and fry congregate exclusively in almoststill waters, not moving into swifter currents until they have matured into later juvenile stages (Swift 2001, pp. 1718). Swift (2001, p. 61) suggests that juvenile fish prefer areas with less water velocity than do adults because they can expend less energy maintaining their position in the stream. Adult and juvenile Santa Ana suckers in the San Gabriel River have been found in waters with bottom velocities ranging from 0.17 to 0.51 ft per second (0.05 and 0.15 m per second) and midcolumn velocities reaching 1.95 ft per second (0.6 m per second) (Haglund and Baskin 2002, pp. 3839). Haglund and Baskin (2003, pp. 39 and 53) concluded that there was no evident pattern in the locations Santa Ana suckers selected relative to water velocity and suggested that they preferentially seek out locations that provide the best combination of habitat parameters. In the Santa Ana River, Santa Ana suckers have been found in areas with water velocities of up to 2.4 ft per second (0.74 m per second) where wastewater discharges and channelization of the river bed increase water velocity (Saiki 2000, pp. 1819).
Stream beds containing the mosaic of rock, cobble, and gravel preferred by Santa Ana suckers are most prevalent in the San Gabriel River (Saiki 2000, pp. 1819). Within the Santa Ana River, shifting sands are the primary substrate constituent upstream of the Prado Basin. In the Santa Ana River bed, substrates containing at least 10 percent gravel, cobble, and rock were documented for a distance of 7 mi (12.3 km) downstream from the Rialto Drain in 1999 and 2000 (Swift 2001, pp. 4, 6875). Habitat assessments conducted between 2006 and 2008 indicated that these substrates fluctuated from 2.6 to 6.0 mi (4.2 to 9.6 km) downstream of the Rialto Drain (Thompson et al. 2010, p. 328).
The distribution of Santa Ana suckers across streams varies depending upon bed conditions and stream depth. Santa Ana suckers within the San Gabriel River are often found midchannel adjacent to submerged cobble, boulders, or manmade structures such as culverts. In the Santa Ana River where the streambed is sandier, they are rarely found midchannel, but rather adjacent to shoreline areas near rooted vegetation (Saiki 2000, pp. 25, 27). Where preferred habitat conditions are absent, Santa Ana suckers make use of available habitats that provide some of the same functions provided by preferred habitats (Saiki 2000, p. 19).
The distribution of Santa Ana suckers is also likely dependent on
instream gradient. While several authors have acknowledged that this
species cannot access high gradient areas, we are not aware of any
research quantifying the maximum slope passable by Santa Ana suckers.
In an attempt to estimate the maximum slope passable by the species, we
used GIS to analyze the slopes associated with Santa Ana sucker
occurrence polygons and points in our database for the Santa Ana River,
San Gabriel River, and Big Tujunga Creek. Based on our analysis, Santa
Ana suckers have not been found in areas where the instream slope
exceeds 7 degrees. This could be due to the species' inability to swim
up these higher gradients or due to the lack of suitable habitat in
these areas as a result of higher water velocity and a subsequent lack
of suitable spawning and feeding substrates or both. Also, the
probability of encountering vertical barriers (such as waterfalls)
increases as the overall slope across a given distance increases;
therefore, even if habitat is suitable upstream, it may be inaccessible to the species. However,
more extensive analysis is needed to determine the gradient limitations of the species.
A comparative analysis of suckers 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, p. 13). No investigations have occurred to determine the relative lifespan or fecundity of Santa Ana suckers as they relate to habitat conditions. However, overall habitat conditions for Santa Ana suckers are generally better in the San Gabriel River than in the Santa Ana River, which is reflected in the overall greater abundance of fish and their better body condition in the San Gabriel River (Saiki 2000, pp. 1828). Food, Water, Air, Light, Minerals, or Other Nutritional or Physiological Requirements
Suckers (Family Catostomidae) are primarily bottom feeders, sucking up algae, small invertebrates, and organic detritus from gravel, cobble, rock, and other hard surfaces (Moyle 2002, p. 179). Forage for adult Santa Ana suckers is also found in pools (Allen 2003, p. 6). Riparian vegetation and emergent aquatic vegetation provide additional sources of detritus and aquatic invertebrates such as insects (Leidy et al. 2001, p. 52). Insects may provide a high energy source of food for adult Santa Ana suckers (Saiki 2000, p. 23). In a comparative analysis of Santa Ana suckers in the Santa Ana and San Gabriel Rivers, Saiki (2000, pp. 27, 98) found that body condition (lengthweight relationship) of Santa Ana suckers in the San Gabriel River was better than that of fish in the Santa Ana River, possibly due to a greater abundance of food resources (including algae and insects) found on the rocky substrate in the San Gabriel River relative to the sandy substrate in the Santa Ana River.
Although the specific tolerances to water quality variables have not been evaluated for Santa Ana sucker, water temperature, dissolved oxygen content, and turbidity (such as excessive detritus in the water column or protracted suspension of finegrained sediments) are all important aspects of water quality that affect the physiology of fish (California Regional Water Quality Control Board (CRWQCB) 1995, pp. 4 1415). This species has been found in waters between 59 and 82 [deg]F (15 and 28 [deg]C) in the Santa Ana River (Swift 2001, p. 18). Swift (2001, p. 34) states that although a lethal limit for water temperature is unknown, water temperatures much above 86 [deg]F (30 [deg]C) likely limit distribution and movement of this species. Santa Ana suckers are generally more abundant in the cooler waters of the San Gabriel River than they are in the warmer waters of the Santa Ana River (Saiki 2000, pp. 2728). Researchers conclude that in addition to having poor habitat conditions such as sandy substrate and lack of instream cover, areas of the Santa Ana River may be devoid of Santa Ana suckers due to higher water temperatures (Chadwick and Associates, Inc. 1992, p. 37).
Adequate dissolved oxygen is necessary for aquatic life and as water warms, its concentration of dissolved oxygen drops, stressing fish (CRWQCB 1995, p. 43). In general, waters occupied by Santa Ana suckers are high in dissolved oxygen (Saiki 2000, pp. 1819).
Santa Ana suckers are more abundant in clear rather than in turbid (cloudy or hazy) water conditions (Saiki 2000, pp. 28, 52; 2007, p. 95). This is most likely because suspended sediments interrupt light penetration through the water column, causing a reduction in algal growth and thus limiting the primary food source of Santa Ana sucker. However, while Santa Ana suckers likely avoid turbid waters when possible, they have been documented in turbid conditions on occasion (Haglund et al. 2002, p. 11). One measurement of turbidity is Nephelometric Turbidity Units (NTU), where turbidity level of 1.0 NTU equals 1 milligram of particulate per liter of water. Saiki et al. (2007, pp. 9596) found that Santa Ana suckers were more abundant in the San Gabriel River where turbidity averaged 5.9 NTUs (ranging from 4.3 to 8.2 NTUs), and less abundant but not absent in more turbid areas of the Santa Ana River where turbidity averaged 29 NTUs (ranging from 10.1 to 83.4 NTUs). However, Santa Ana suckers have been found in the Santa Ana River in an area where turbidity was measured between 85 and 112 NTUs (Baskin and Haglund 2001, p. 6). Saiki (2000, p. 25) speculates that fish occur under lessthanoptimal ambient conditions because they are using whatever habitat is available to them and cites these conditions as a possible reason for reduced abundance of Santa Ana suckers in the Santa Ana River relative to their abundance in the San Gabriel River.
Multiple wastewater treatment plants discharge into the Santa Ana River and its tributaries and account for most of the dryseason flows within the river (CRWQCB 1995, pp. 17). The City of San Bernardino Municipal Water District's Rapid Infiltration and Extraction Facility, Rialto Treatment Plant, and the City of Riverside Regional Water Quality Control Plant all discharge into the Santa Ana River. As a result of rising groundwater, nonpoint source urban runoff, and these wastewater discharges, perennial flows are maintained from the vicinity of the Rialto Drain and downstream. Although these discharges contain contaminants not found in natural runoff, there is no evidence that the concentrations of regulated compounds found in Santa Ana suckers in this river exceed mean concentrations found in freshwater fish in other areas of the United States (Saiki 2000, p. 24). However, research has indicated that anthropogenic chemicals introduced into riverine systems may have lasting negative impacts on fish reproductive success (Service 2008, p. 3). The specific impacts of residual chemicals in discharged treated wastewater (such as inorganic compounds, hydrocarbons, solvents, steroids, and hormones) are the subject of investigation for Santa Ana suckers (Service 2008, p. 2).
Cover or Shelter
Instream emergent and overhanging riparian vegetation along the banks of stream courses provide shade, shelter, and cover for fry, juvenile, and adult Santa Ana suckers. Shading is very important to Santa Ana suckers that inhabit shallow waters because it reduces water temperatures during periods of high summer ambient temperatures. A complex stream system including tributaries that contain submerged boulders, deep pools, and undercut banks provides cover and shelter for juvenile and adult Santa Ana suckers (Saiki et al. 2007, p. 99; Moyle et al. 1995, p. 202). Tributaries may provide important shallowwater refugia for larvae and fry from larger, predatory fish and act as refugia for juvenile and adult Santa Ana suckers during storms. Sites for Breeding, Reproduction, and Rearing (or Development) of Offspring
Adult Santa Ana suckers spawn over gravel beds in flowing water
(riffles) where the female deposits the eggs in fine gravel substrate.
Substrate collected from two spawning locations in tributaries to the
Santa Ana River consisted of gravelsized particles ranging in diameter
from 0.04 to 1.6 in (1.0 to 41.5 mm) (Haglund et al. 2001, p. 47). The
presence of appropriately sized substrate allows for water flow around
eggs to prevent sediment from depositing on and smothering the eggs. Eggs deposited on sand or silt are likely
to be washed downstream or be smothered. In addition to appropriate substrate, adequate water velocities are necessary to oxygenate eggs. Observations of Santa Ana sucker spawning have been reported in streams with bottom velocities of 0.65 and 0.77 ft per second (0.20 and 0.23 m per second) (Haglund et al. 2003, p. 63).
Once emerged from the eggs, Santa Ana sucker larvae congregate in shallow, slowmoving waters from 1 to 5.5 in (3 to 14 cm) deep over very soft sand or mud substrate (Swift 2001, p. 17; Haglund et al. 2002, pp. 6971; Haglund et al. 2003, p. 11). This type of habitat is usually found along the margins of streams in proximity to emergent vegetation. Fry are found almost exclusively found in edgewater habitats over silt or sand in water depths of less than 7 in (17 cm) where there is little measurable flow; Haglund and Baskin (2003, p. 47) speculate this reduces access by larger predatory fish and, because shallow waters are warmer, may increase the growth rates of developing suckers. Juvenile fish move away from edgewater habitats and congregate at the interface of the almoststill waters at the adjacent bankedge and the main stream flows (Swift 2001, pp. 1718). By the end of their first summer, juvenile Santa Ana suckers move into deeper water habitats with adults, presumably because they are large enough to compete with adult suckers for forage (Swift 2001, p. 18).
Tributaries may provide essential spawning habitat for the Santa Ana sucker, particularly in the Santa Ana River (Chadwick and Associates, Inc. 1992, p. 49; Chadwick Ecological Consultants, Inc. 1996, p. 16; Haglund et al. 2002, pp. 5460). An abundance of juvenile fish has been recorded in multiple tributaries in the Santa Ana River (such as the Tequesquite Arroyo and the Evans and Anza drains), and, hence, these have been considered possible spawning sites (Chadwick and Associates, Inc. 1992, p. 49). However, Swift (2001, p. 26) concluded that the species may be attracted to tributaries due to the relatively colder water temperatures found there. He stated that most tributaries to the Santa Ana River lack either suitable substrates or water velocities to support successful spawning. Swift (2001, p. 26) considered that only the Rialto Drain and Sunnyslope Creek provided habitat conditions suitable to support spawning. These sites are two of the few remaining areas containing gravel beds, and management may be required to maintain substrate conditions over time (Orange County Water District (OCWD) 2009, pp. 6465).
In the hydrologically altered systems in which Santa Ana suckers exist, tributaries provide another essential function through contribution of water and coarse sediments into the mainstem of rivers. In typical unaltered stream systems periodic high flow events not only remove fine sand and silt that have covered up coarse sediments that are essential for breeding and foraging of Santa Ana sucker, they also deliver and replenish coarse sediments (i.e., gravel and cobble) to occupied areas from upstream sources. Historical records indicate that the upper Santa Ana River above Seven Oaks Dam was a principle contributor of sediment to the lower reaches of the Santa Ana River (Humphrey et al. 2004, p. 3). However, much of the input of gravel and cobble substrate to the lower reaches of the river has decreased since the construction and operation of the Seven Oaks Dam in the upper Santa Ana River. Therefore, tributaries are of even greater importance to ensure flow velocities that clear out silt and other fine sediments from occupied areas, and to replenish essential coarse sediment to the lower reaches of the Santa Ana River. A sediment transport study of the Santa Ana River (Humphrey et al. 2004, p. 2) indicates that historically the upper Santa Ana River (above Seven Oaks Dam), City Creek, Plunge Creek, and Mill Creek were significant contributors of coarse sediment to the occupied reaches of the Santa Ana River. However, currently City Creek and Mill Creek are the remaining contributors of coarse sediment into the occupied reaches of the Santa Ana River since the coarse sediment that was historically delivered by the upper Santa Ana River has been trapped behind Seven Oaks Dam and Plunge Creek now contains a settling basin that has been modified for mining. Therefore, these two tributaries are the only remaining significant sources of essential coarse sediment into the mainstem of the Santa Ana River below the Seven Oaks Dam, which supplies coarse sediment downstream to the occupied reaches of the river.
Presumably there has been a reduction in transported cobble and gravel from the upper Santa Ana River because periodic high flow events have been controlled by Seven Oaks Dam, which has also trapped coarse sediment behind it. However, there has not been a similar reduction in fine sediments, such as silt and sand, to the lower reaches of the Santa Ana River (Humphrey et al. 2004, p. 5; Warrick and Rubin 2007, p. 3). Gravel and cobbles are essential coarse sediments for Santa Ana sucker spawning habitat (Moyle 2002, pp. 182185). Fine sand and silt may be deposited on top of suitable coarse spawning sediment because flows have declined due to the altered fluvial process in the Santa Ana River. Tributaries and lower order streams (upstream areas) provide a source of water and coarse sediments that are transported downstream (to higher order streams) where the presence of water and coarse sediments are essential to the conservation of the species. Therefore, flows to clear out fine sand and silt from suitable spawning substrate (i.e., gravel and cobble) and flows to transport suitable materials from upstream sources for maintenance of spawning substrate are essential to the conservation of Santa Ana sucker.
In the Santa Ana River, Humphrey et al. (2004, p. 7) states a
critical flow of water of 4,000 cubic feet per second (cfs) or more is
necessary to transport gravel and cobbles downstream and lower velocity
flows (5004,000 cfs) have the ability to move silt and other fine
sediment that accumulates on top of suitable spawning substrates. The
critical velocity necessary to move gravel and cobbles is variable
depending on the conditions and location within the system. For
example, during a test release of water from behind Seven Oaks Dam of
approximately 2,500 cfs, bouldersized rocks were observed moving
within several hundred feet of the plunge pool (Wood 2010, pers.
comm.). United States Geological Survey gauging stations along the
Santa Ana River and City Creek indicate that there are flows sufficient
to clear out fine sand and silt, and also flows that reach
approximately 4,000 cfs and above that would deliver essential gravel
and cobble substrates from upstream sources to downstream to occupied
areas. These coarse sediments are a component of the physical and
biological features essential to the conservation of the species (see
Primary Constituent Elements for the Santa Ana Sucker below). In all
three of the watersheds where Santa Ana sucker persists, the existence
of dams has regulated flows and trapped sediments from being
transported downstream. Therefore, sources of water and coarse
sediments and the transport of these materials to occupied areas to
create and maintain habitat conditions suitable for Santa Ana sucker
breeding and foraging within these tributaries and lower order streams is essential to the conservation of the species.
Primary Constituent Elements (PCEs) for Santa Ana Sucker
Under the Act and its implementing regulations, we are required to identify the physical and biological features within the geographical area occupied by Santa Ana sucker at the time of listing that are essential to the conservation of the species and which may require special management considerations or protection. The physical and biological features are those PCEs laid out in a specific spatial arrangement and quantity determined to be essential to the conservation of the species. We are designating critical habitat in areas within the geographical area that were occupied by the species at the time of listing that continue to be occupied, and that contain the PCEs in the quantity and spatial arrangement to support lifehistory functions essential to the conservation of the species. We are also designating areas outside the geographical area occupied by the species at the time of listing that are not occupied but are essential for the conservation of the species. See Criteria Used To Identify Critical Habitat section below for a discussion of the species' geographic range.
We believe conservation of Santa Ana sucker is dependent upon multiple factors, including the conservation and management of areas to maintain suitable ecological functions where existing populations survive and reproduce. The areas we are designating as critical habitat provide some or all of the physical or biological features essential for the conservation of this species. Based on the best available information, the PCEs essential to the conservation of Santa Ana sucker are the following:
1. A functioning hydrological system within the historical geographic range of Santa Ana sucker that experiences peaks and ebbs in the water volume (either naturally or regulated) that encompasses areas that provide or contain sources of water and coarse sediment necessary to maintain all life stages of the species, including adults, juveniles, larvae, and eggs, in the riverine environment;
2. Stream channel substrate consisting of a mosaic of loose sand, gravel, cobble, and boulder substrates in a series of riffles, runs, pools, and shallow sandy stream margins necessary to maintain various life stages of the species, including adults, juveniles, larvae, and eggs, in the riverine environment;
3. Water depths greater than 1.2 in (3 cm) and bottom water velocities greater than 0.01 ft per second (0.03 m per second);
4. Clear or only occasionally turbid water;
5. Water temperatures less than 86 [deg]F (30 [deg]C);
6. Instream habitat that includes food sources (such as zooplankton, phytoplankton, and aquatic invertebrates), and associated vegetation such as aquatic emergent vegetation and adjacent riparian vegetation to provide: (a) Shading to reduce water temperature when ambient temperatures are high, (b) shelter during periods of high water velocity, and (c) protective cover from predators; and
7. Areas within perennial stream courses that may be periodically dewatered, but that serve as connective corridors between occupied or seasonally occupied habitat and through which the species may move when the habitat is wetted.
All occupied units designated as critical habitat contain the PCEs in the appropriate quantity and spatial arrangement essential to the conservation of this species and support multiple life processes for Santa Ana sucker.
Special Management Considerations or Protection
When designating critical habitat, we assess whether the specific areas within the geographical area occupied by the species at the time of listing contain the physical and biological features that are essential to the conservation of the species and may require special management considerations or protection.
All areas included in this final critical habitat designation will require some level of management to address the current and future threats to the physical and biological features essential to the conservation of Santa Ana sucker. Special management considerations or protection may be required to minimize habitat destruction, degradation, and fragmentation associated with the following threats, among others: Water diversion; alteration of stream channels and watersheds; reduction of water quantity associated with urban development and human recreational activities, including swimming, and construction and operation of golf courses; and OHV use. For discussion of the threats to Santa Ana sucker and its habitat, please see the Summary of Comments and Recommendations and Summary of Factors Affecting the Species sections of the final listing rule (65 FR 19686; April 12, 2000) and the Public Comments and Critical Habitat Unit Descriptions sections of the 2005 final critical habitat rule (70 FR 425; January 4, 2005). Please also see Critical Habitat Units section below for a discussion of the threats in each critical habitat unit.
In addition to the threats to Santa Ana sucker and its habitat described in the final listing and previous critical habitat rules, the physical and biological features essential to the conservation of Santa Ana sucker may require special management considerations or protection to minimize habitat destruction, degradation, and fragmentation associated with the construction of dams, the operation of recreational residences, the construction of road crossings and bridges across waterways, nonnative vegetation and predators, the impacts of wildfires to riparian and instream conditions, and the degradation of water quality.
Artificial manmade dams are often constructed from boulders, logs, and trash to create pools within these rivers for fishing, swimming, wading, and bathing (Ally 2003, p. 1; Chambers Group 2004, p. 64). The construction of these ``recreational'' dams degrades instream and possibly bank habitat, increases turbidity (PCE 4), disrupts sediment transport, and impedes upstream movement of Santa Ana suckers, especially during droughts (Ally 2003, pp. 13), thereby fragmenting habitat connectivity within occupied habitat. During the spawning season, these dams cause instream disruptions that can bury gravel beds (PCE 2) used for spawning (Ally 2003, p. 1). Recreational dams can also further degrade habitat by slowing water velocities (PCE 3), increasing water temperatures (PCE 5), and encouraging excessive growth of algae (Ally 2003, p. 3). In addition, presumably, because water depths increase and velocities decrease, these areas may harbor nonnative predators. Management activities that could ameliorate these threats include patrolling by enforcement officers or rangers throughout the accessible recreational areas within the critical habitat designation. Prevention of recreational dams will help protect the PCEs by ensuring the hydrologic system continues to function (PCE 1) by delivering cool, clear water with sufficient food sources (PCEs 2 through 6) that are essential to the conservation of Santa Ana sucker.
The U.S. Forest Service (USFS) issues special use permits for the
operation and maintenance of private recreational residences within the boundaries of the
Angeles National Forest along Big Tujunga Creek and the North and West Forks of the San Gabriel River. Improperly functioning septic systems at these residences can degrade water quality conditions by increasing water turbidity (PCE 4) as a result of the increased nutrient loads in the water (USFS 2007, p. 18), which lead to excessive algal growth. Management activities that could ameliorate these threats include limiting the number of allowable recreational residences and requiring that septic systems are properly functioning within areas that are hydrologically connected to areas designated as critical habitat. Limiting the number of residences and ensuring the proper function of their septic systems will help protect PCE 4 by preventing additional nutrient loads from entering the water and increasing water turbidity (PCE 4) to the detriment of Santa Ana sucker.
Road Crossings and Bridges
Road crossings and bridges constructed across waterways can impact Santa Ana sucker by creating permanent or intermittent barriers to upstream movement and fragmenting connective corridors between areas of occupied habitat (PCE 7). Bridge footings and pier protections (such as concrete aprons that span the waterway) accelerate water velocities (PCE 3) and, in the absence of sediment in the water (PCE 2), scour sediments from the streambed immediately downstream. With sufficient scouring, the elevation of the downstream bed of the stream may become so low that Santa Ana suckers cannot swim upstream from that point; scouring can also create pools that favor predatory nonnative fish. Culverts constructed under road crossings can act as barriers to movement when a culvert becomes filled in with sediment, reducing the amount of water (PCE 1) and sediment (PCE 2) that could be transported downstream. Drop structures that function as a support for road crossings or bridges as a result of gradient changes within the river may also create a temporary barrier to water and sediment transport and Santa Ana sucker movement. The extent, however, to which these structures constitute barriers depends on the quantity of water flowing and sediment transport in a given year and over time. For example, sedimentfilled culverts that create a barrier to movement one year may be passable in another year if high water flows remove trapped sediments. Road crossings and bridges can also impact the species by altering the hydrology of the system (PCE 1), rerouting water flow into less suitable habitat. Management activities that could ameliorate these threats include modifying culverts or drop structures to ensure the connective corridor is maintained through a gradient that is passable by water and sediment and Santa Ana suckers (i.e., 7 degrees as described in the Criteria Used To Identify Critical Habitat section) within the critical habitat designation. Maintenance of these corridors (PCE 7) and ensuring a passable gradient (PCE 1) will help protect the PCEs (2 through 5) that are essential to the conservation of Santa Ana sucker.
Water and Sediment Transport or Removal
The transport of both water and sediment are essential components to the conservation of Santa Ana sucker (PCEs 1 through 5). The presence of sufficient water and appropriate sediment may be impacted by operations attributed, but not limited to, dams operation of hydroelectric power facilities, water diversion, sediment removal, or flood control activities. Natural flow regimes have inevitably been impacted in the Santa Ana River, Los Angeles River, and San Gabriel River basins as a result of alterations such as dams, diversions, channelization, or other flood control activities. The impacts to Santa Ana sucker and its habitat attributable to these activities have yet to be fully described or understood. However, as these activities continue, there appear to be impacts to Santa Ana sucker and its habitat through alteration of the hydrologic system and the function of the watershed as a whole. Recent research indicates that the presence of preferred substrates such as gravel and cobble in the Santa Ana River are less common at sites farther downstream compared to sites that are closer the Seven Oaks Dam (Thompson et al. 2010, p. 328). This is likely due to the presence of flowing water from the Rialto/RIX sewage treatment plant immediately upstream that clears out silt and fine sand and exposes gravel and cobbles; however, the flow diminishes downstream due to percolation. Therefore, in the occupied areas of the Santa Ana River, downstream areas contain less suitable habitat for Santa Ana sucker (Thompson et al. 2010, pp. 327328).
The extant populations of Santa Ana suckers throughout the species' range are currently isolated from one another as a result of water diversions or dams that have likely resulted in their exclusion from suitable spawning and rearing habitat (Service 2000, p. 19693). Management activities that could ameliorate these threats throughout the species' range include removing or preventing channelization and restoring the river with its natural substrates and riparian vegetation, increasing flows into occupied areas by decreasing the amount of water contained by dams or removed from the hydrologic system, preventing mining activities that remove coarse sediments, and preventing further instream modifications from flood control activities throughout the critical habitat designation. Maintenance of the natural flow (PCEs 3, 4, and 5) and sediment transport (PCE 2) will help protect the PCEs that are essential to the conservation of Santa Ana sucker.
OffHighway or OffRoad Vehicles (OHVs)
Throughout the designated critical habitat, OHV use occurs in authorized and unauthorized areas. We are aware of authorized OHV activity in the USFS's San Gabriel Canyon OHV Area at the junction of the East, North, and West Forks of the San Gabriel River. There have been reports of unauthorized OHV activity in the Santa Ana River, although the level of impact and frequency of use have not been quantified. However, the reach where the unauthorized OHV activities have been reported occurs just upstream of one of the remaining Santa Ana sucker populations (near Rialto/RIX; SAWPA 2010, p. 110). This area has recently been cleared of the nonnative plant, Arundo donax, which may have facilitated access for OHVs. The use of the river as an OHV recreational area may result in adverse effects to Santa Ana sucker by increasing turbidity (PCE 4); disrupting the physical structure of habitat for spawning, resting, and feeding (PCE 2); and introducing pollutants (such as oil and gas) into streams (PCE 4) (65 FR 19686; April 12, 2000). Management activities that could ameliorate these threats include patrolling by enforcement officers or rangers throughout the accessible recreational areas, providing signage to discourage access, or installing fencing where access is unauthorized within the critical habitat designation. Minimizing the impacts to the hydrologic system (PCE 1) and reducing the instream impacts (i.e., increased turbidity (PCEs 2 and 4)) and impacts to instream and riparian vegetation (PCE 6
FOR FURTHER INFORMATION CONTACT
Jim Bartel, Field Supervisor, U.S. Fish and Wildlife Service, Carlsbad Fish and Wildlife Office, 6010 Hidden Valley Road, Suite 101, Carlsbad, CA 92011; telephone 760431 9440; facsimile (760) 760 4315901. If you use a telecommunications device for the deaf (TDD), call the Federal Information Relay Service (FIRS) at 8008778339.