ATTACHMENT A
CONSERVATION STRATEGY
Virgin spinedace
Lepidomeda mollispinis mollispinis
PURPOSE
The purpose of the present document is to describe specific procedures and strategies required for conservation of Virgin spinedace. The general conservation approach focuses on two main objectives. The first objective is to eliminate threats where possible, and reduce threats to the greatest extent possible that cannot be eliminated entirely. The second is to enhance and/or stabilize instrearm flows in specific reaches of occupied and unoccupied habitat. Though the primary focus of this strategy is conservation and enhancement of the virgin spinedace, it cotild also reduce or eliminate threats and improve habitat for many other species, which could preclude their need for federal listing pursuant to the Endangered Species Act of 1973 as amended
(ESA) .
Definitions
For the purposes of the Agreement and Strategy, the following terms are defined as:
occupied Habitat - Occupied habitat consists of stream reaches containing self-sustaining Virgin spinedace populations.
Historic Habitat - Historic habitat consists of stream reaches that have been shown, can be shown, and/or can logically be deduced as historically being occupied by Virgin spinedace. This area is approximately 226 km (141 mi) . The exact extent of historic habitat is unknown. Historically, spinedace habitat probably fluctuated with changing environmental conditions.
Population Maintenance Flows - Population maintenance flows are flows of sufficient magnitude to maintain self-sustaining Virgin spinedace populations during low-flow periods. These flows are dependent on flow events of sufficient magnitude, timing, and duration to maintain channel characteristics and provide environmental cues .
self-sustaining Population - self-sustaining populations are those with sufficient numbers, age class structure, and natural reproductive success to provide for their long-term survival.
Non-indigenous - An organism that is not native, or occurs naturally in a specific area or environment.
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BACKGROUND
The Virgin River basin is characterized by a diverse landscape with unique communities of fauna and flora. The basin encompasses approximately 15,600 km2 (6000 mi2) . Virgin River headwaters are in washington and Kane County, Utah, and the stream flows in a general southwesterly direction to empty into Lake Mead on the Colorado River in Nevada. Elevations range from 3300 m (10,000 ft) above mean sea level (msl) near the headwaters to less than 700 m (2000 ft) at Littlefield, Arizona. The river varies from reaches with narrow, steep-walled canyons and steep gradients to low desertland with broad open canyons and low gradients. Mean annual precipitation ranges front about 20 cm (8 in) at low elevations to about 100 cm (40 In) at higher elevations -
Due to the diverse topography, this river and its associated riparian area and floodplain provides habitat for over 366 species of wildlife (Appendix A) . of these, 81 species have been identified as sensitive. There are six fish species indigenous to the basin: woundfin (Plagopterus argentissimus), virgin River chub (Gila seminuda), flannelmouth sucker (Catostomus latipinnis), desert sucker (Catostomus clarki), speckled dace (Rhinichthys osculus), and Virgin spinedace Lepidomeda in mollispinis . Except for the speckled dace, all of these have been listed or are candidates for federal listing under the ESA.
The virgin spinedace was recognized in 1979 as a threatened species by the scientific community. The Endangered species Committee of the American Fisheries society added it to their list of threatened and endangered fish after assessing criteria consistent with the ESA (Deacon et al., 1979). Their determination of the species' status was based on review of original data and discussions with pertinent agencies and knowledgeable scientists. On May 18, 1994, the United States Fish and wildlife Service (FWS) proposed the species for listing as a threatened species pursuant to the ESA (59 FR 25875).
Systematics and Descript ion
The Virgin spinedace, Lepidomeda mollispinis mollispinis is a member of an endemic tribe of western cyprinids, the Plagopterini (Miller and Hubbs, 1960). The group is comprised of three genera: Meda, Plagopterus and Lepidomeda The first two are monotypic, represented by the spikedace (M. fulgida) and woundfin (. argentissimus) . Lepidomeda is a polytypic genus containing four species: the White River spinedace (L. albivallis), the pahranagat spinedace (L. altivelis), the Little Colorado spinedace (L. vittata), and the virgin spinedace (L. mollispinis) . L. mollispinis is further classified into two subspecies; L. m. pratensis (Big Springs spinedace) and L. m.
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mollispinis (Virgin spinedace. The pahranagat spinedace is considered extinct (Miller and Hubbs, 1960; Valdez et al.,1991). Extant members of the tribe piagopterini are rare. The woundfin and white River spinedace are listed as endangered (35 CFR 16047 and 50 FR 37198 respectively) . The spikedace (51 FR 23781), Big springs spinedace (50 FR 12302) and the Little Colorado kiver spinedace (52 FR 35040) are listed as threatened.
spinedace get their name from the fusion of two anterior, hardened spiny rays of the dorsal fin and a similar structure located in the pelvic fin. The Virgin spinedace derives its specific name from the latin words mollis, meaning soft, and spinis, meaning spine, both referring to the soft-tipped second dorsal spine (Miller and Hubbs, 1960).
The body of the Virgin spinedace is silvery with a brassy sheen and occasionally with light sooty blotches on the dorso-lateral half. During breeding, bases of the paired fins are reddish orange. The Virgin spinedace is characterized by a terminal mouth, rounded head and belly, and a body size typically ranging from 60 mm to 120 mm (2.4 to 4.7 in SL) (Rinne, 1971; Addley and Hardy, 1993). The species has a well-scaled body, with 77-91 scales on the lateral line and two rows of pharyngeai teeth which typically number 2, 5-4, 2 (Addley and Hardy, 1993; sigler and Miller, 1963; Valdez et al., 1991). The dorsal fin has eight rays and the anal fin usually includes nine rays, but may vary from eight to ten rays.
Life History
The life history of the Virgin spinedace was described by Rinne (1971). Having a life-span of about three years, the fish reaches sexual maturity at about one year. Populations typically are comprised mostly of young-of-the-year (YOY) and one-year-old fish. Because of the mild climate of Virgin spinedace habitat, age determination after one year can be difficult. However, Rinne (1971) indicated that fairly accurate estimates could be made using SL: young-of-the-year <55 mm, age 1 55-76 mm, age 2 77-85 mm, age 3 >85 mm.
Although sexual dimorphism is not apparent most of the year, sexes can be distinguished during peak breeding season. Females tend to be more robust and plump, while males remain streamlined. Furthermore, the vent of the female becomes swollen and the ovipositor becomes a reddish color (Rinne, 1971). Both sexes exhibit the reddish-orange coloration at the bases of the paired fins .
Annual spawning of the Virgin spinedace has been observed from April through June at mean daily water temperatures of 13-17 C and day lengths of about 13 hrs. Rinne (1971) found that one- year-old females had the lowest mean relative fecundity averaging
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459 eggs, while two and three-year~old females averaged a 42% and
34% increase in mean relative fecundity over one-year-olds
respectively. Since populations are comprised primarily of one
year olds, they often comprise 90% of the spawning population
(Addley and Hardy, 1993).
virgin spinedace are typically found in clear, cool, swift streams that have interspersed pools, runs, and riffles (Deacon et al., 1979; valdez et al., 19.91). Upper thermal preferences have been reported as 23.1oc (Deacon et.al, 1987). Rinne (1971) found virgin spinedace most frequently in pools with some type of protection such as undercut banks, boulders or debris; however, variations in habitat preferences have been noted. For example, in Beaver Dam Wash, virgin spinedace utilize narrow, shallow runs with large amounts of emergent vegetation, while in North Fork of the virgin River, they most often occupy quiet pools (Rinne, 1971). virgin spinedace have also been documented to prefer shear zones between high (100 cm/sec) and low (10 cm/sec) velocities containing cover (Deacon et al., 1979; Deacon et al., 1991; Hardy et al, 1989). Nursery habitat preferences, however, remain unclear.
virgin spinedace are primarily insectivorous, feeding on a wide range of insects and occasionally plant material and organic debris (Angradi et al., 1991; Gregor and Deacon, 1988; Rinne, 1971). virgin spinedace feed on drifting prey in midwater and at the surface. Usually they maintain equilibrium in the midwater column darting to the surface to capture prey in a manner similar to drift-feeding salmonids (Addley and Hardy, 1993; Rinne, 1971).
Historic Distribution
The historic distribution of the virgin spinedace is not well documented. Holden (1977) speculated that historic occurrence was in most of the clearwater tributaries and several mainstem reaches of southwestern Utah, northwestern Arizona, and southeastern Nevada (Figure 1) . Museum records from the University of Nevada at Las Vegas, Brigham Young University, University of Michigan Museum of Zoology, and the United States National Museum support Holden (Addley and Hardy, 1993; Cross 1975; Rinne, 1971; Valdez et al., 1991). The earliest survey records indicated this species was common in the Santa Clara River and North Fork of the Virgin River, but probably less common in the Virgin (Tanner (1932, 1936). C.L. Hubbs (unpub. data) collected Virgin spinedace near Bunkerville, Nevada, in 1938, but surveys in 1942 in the same area lacked virgin spinedace (Cross, 1975). Furthermore, the species was absent from surveys below Littlefield, Arizona between 1942 and 1975 (Cross 1975).
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PROBLEMS FACING THE SPECIES
populations of Virgin spinedace currently exist in the mainstem virgin River and eleven of its tributaries including East Fork Virgin River, Shunes Creek, North Fork virgin River, North Creek, La Verkin Creek, Ash Creek, Santa Clara River, Beaver Dam Wash, Coal Pits Wash, Moody Wash and Magotsu Creek (Table 1). According to Addley and Hardy (1993), the largest populations are in the upper mainstem above Quail Creek diversion and in drainages of the Santa Clara River and Beaver Dam Wash. Small populations exist in Ash Creek, La Verkin Creek, and the lower mainstem below Pah Tempe Springs. The remaining areas contain interntediate sized populations.
The present distribution of Virgin spinedace is significantly smaller than historically, with approximately 37-4C% (84 km/52 mi) now unoccupied (Table 1). In addition, 24% of currently occupied habitat has experienced some degree of adverse modification (Table 1). Dewatered streams, water depletions, introductions of non-indigenous fish, and habitat degradation through agricultural and recreational uses have been identified as the primary factors involved in the reduction of range of the species (Valdez et al., 1921; Addley and Hardy, 1993).
In 1994, the FWS described pertinent problems and threats they perceived as facing the Virgin spinedace based on criteria for federal listing as required by Section 4(a) (1) of the ESA (59 FR 25875). The threats they listed do not necessarily reflect the view of all signatories to this Agreement. The following discussion summarizes the significant threats to Virgin Spinedace that will be addressed by conservation actions identified in this Strategy .
Present or threatened destruction, modification. or curtailment of its habitat or range.
virgin spinedace habitat modification and/or elimination has occurred primarily through human activities such as dam and diversion construction, water depletion or diversion, and agricultural practices (Table 1). Approximately 7 km (4 mi) of Virgin spinedace historical habitat has been inundated by reservoirs including Quail Creek Reservoir on Quail Creek, Gunlock on the Santa Clara River, and Schroeder Reservoir on Beaver Dam Wash (Figure 1). Approximately 60 km (37 mi) of historic habitat has been dewatered by diversions. Furthermore, diversions have depleted water in approximately 31 km (19 mi) of currently occupied habitat. Lack of stable instream flows and low water levels as a result of diversions cause changes in water temperature, affect aquatic vegetation, and alter water chemistry and dissolved oxygen levels. Darns and diversions also act as barriers to fish movement within the system and fragment Virgin
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spinedace habitat and populations. In areas of extensive habitat fragmentation, migration becomes virtually non-existent.
Agricultural practices have also modified several areas of Virgin spinedace habitat through alteration of the riparian zone. Riparian alterations often cause stream bank erosion, siltation, and devegetation. A recent evaluation of the Virgin River basin riparian zone (Fridell, Hansen, Leany, and Douglas, pers. comm., 1994) indicated that some alterations front crop production are occurring along lower La Verkin creek, lower Ash Creek, and middle Virgin River reaches. Several reaches are impacted by livestock, including the Santa Clara River below Gunlock Reservoir, lower Santa Clara River, lower North Creek, lower La Verkin Creek, lower Ash Creek, and portions of the Virgin River mainstem. The remaining riparian zones appear to be relatively intact .
Predation. Competition, and Disease
Aquatic species introduced into the Virgin River system have been identified as contributing to reductions of native fish populations (Addley and Hardy, 1993; USEWS, 1993). several non- indigenous fish species have been identified as occupying the same habitat as Virgin spinedace (Table 2). Several of these prey on the Virgin spinedace. Other non-indigenous species (Table 2), such as crayfish (i.e., Astacidac), may be preying on larval and young-of-year life stages in lower reaches of several tributaries (Addley and Hardy, 1993). some non-indigenous species may also affect virgin spinedace habitat by competing for limited resources such as food and space. Disease and parasites do not appear to have had significant roles in the declining status of the Virgin spinedace; however, they may have adverse effects when coupled with other threat and stress factors (Addley and Hardy, 1993).
Other natural cr manmade factors affecting the species' continued existence.
Several other natural and manmade factors play a role in the declining status of the Virgin spinedace. Natural limiting factors include drought, flood and in some instances, natural barriers and native species interactions. The extent that natural factors affect Virgin spinedace is unclear.
pollution from return flows, municipal drains and agriculture is a potential problem for all native species within the basin. Return flows from municipal drains and agriculture can make up a significant portion of a stream's total flow. Water from these return flows can be polluted with pesticides as well as other wastes. Mining along Beaver Dam Wash may contribute to habitat degradation. Low flows, caused naturally or by diversions, increase the impacts of pollution, erosion, siltation and mineral
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springs have on the chemical composition of the water.
Recreational use (e.g. off-road vehicles) has been documented (Fridell et al., pers comm.) as significantly impacting several reaches including the Santa Clara below Gunlock Reservoir, the lower Santa Clara, and the lower mainstem virgin River
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