White River Springfish; Hiko White River Springfish

Crenichthys baileyi baileyi Crenichthys baileyi grandis

Description

The White River springfish reaches a maximum length of about 2.5 in (6.3 cm). It has a large, steeply sloping head, which is very broad in older individuals. Its mouth is small and straight with bicuspid teeth. Dorsal and anal fins are set far back from the caudal base, and no pelvic fins are present. The caudal fins are straight in terminal outline. Coloring ranges from olivaceous above to silvery on lower sides and bottom. These fish usually have two lengthwise series of coarse black spots, one along the middle line of the body, the other on a level with the caudal peduncle. The White River springfish is a thermal endemic fish, i.e., it originates in warm, isolated water and is adapted to the living conditions there. Cold water acts as a barrier that prevents these fish from moving away from the warm water springs where they originated.

Crenichthys baileyi is one of two species within the genus Crenichthys. Distinctive characteristics of the genus include a lack of pelvic fins and bicuspid teeth, a long, coiled intestine, and restricted range. Fishes in this genus have been of particular scientific interest because of their adaptation to extremely high temperatures and low dissolved oxygen. White River springfish and Hiko White River springfish are uniquely adapted for surviving in environments of extreme temperatures and low dissolved oxygen content.

The White River springfish and Hiko White River springfish were described in 1981 as two of five sub-species of C. baileyi. These two subspecies are visually similar. Greenish above and silvery below, both have a dark lateral stripe, comprised of double rows of spots on the sides that may be connected, that runs from behind the gills to the tail fin. Breeding males exhibit more intense coloration than females, with mid-dorsal markings becoming very dark (al-most black) in contrast to the light, sometimes yellow, sides above the fused spots.

Behavior

Individual female springfish will spawn at different times of the year. Most females average two spawning periods a year, while the spawning season of the entire population extends over a long period of time each year. Moapa White River spring-fish spawn year-round with peak spawning activity from April through August. The period of spawning activity may be regulated by the production of food in the spring system. During the spawning season the males are more brightly colored than the females; courting behavior and breeding occur in and around dense vegetation, which provides cover for the attached eggs; copulation occurs in an S-shaped clasp and the male's anal fin is folded under the female's ovipositor to enhance sperm transfer; one egg at a time is laid and fertilized; 10-17 eggs are produced by each spawning; and the incubation period is five to seven days. Males aggressively defend territories in order to monopolize reproductive females. Springfish forage along the substrate and in plants, as evidenced by the ingestion of bottom-dwelling invertebrates, plant fragments, and detritus.

Because simple, short food chains in the desert springs do not permit diet specialization, C. baileyi is probably an opportunistic feeder whose diet consists of half plant matter, primarily filamentous algae, supplemented by detritus, midges, caddisfly larvae, and animal matter, including gastropoda, amphipoda, trichoptera, and lepidoptera. During the winter when invertebrates are not available, the diet becomes herbivores. Smaller fish need to consume a large percentage of their body weight in food every day to meet their metabolic demands, which vary directly with water temperature. White River springfish inhabiting warm water have respiratory rates four times greater than springfish in cool waters.

The White River springfish appears to exhibit a pronounced daily activity cycle with a peak in activity occurring in mid-afternoon and reduced activity levels at night. It is possible that stress caused by interaction with exotic fish may be responsible for the observed reduction in activity levels in C. b. baileyi compared to other C. baileyisubspecies. C. baileyi grandis is most active at sunrise and sunset.

Habitat

Both subspecies are known from single populations in springs in the Pahranagat Valley in Lincoln County, Nevada. The White River spinefish occurs in the headwater pool of Ash Spring whose predominant substrate is sand and silt with some areas of gravel. Pastureland adjacent to the out-flow stream has been planted with saltgrass for cattle grazing; the upper end of the outflow stream consist of ash trees, cottonwoods, willows, and wild grape. Mats of filamentous algae become abundant in the spring pool during spring and summer, which provides an important source of cover.

Hiko and Crystal Springs, habitat for the Hiko White River spinefish, have relatively deep source pools and associated effluent streams. Aquatic vegetation, especially filamentous algae, is abundant during spring and summer. Shoreline vegetation includes spikerush and cattails, ash trees, cottonwoods, and willows.

Distribution

The species is endemic to the remnant waters of the White River system in eastern Nevada; these two subspecies are restricted to the Pahranagat Valley. During pluvial times, 10,000-40,000 years ago, a far larger White River flowed into the Colorado River by way of the Virgin River. When the White River dried up, the springfishes were restricted to the remaining permanent springs and outflows.

The White River springfish is presently found only in Ash Springs, which is used for public swimming and is principally inhabited by non-native fishes. Recent surveys indicate a severe reduction in numbers. The Hiko White River spring-fish was extirpated from Hiko Spring when game fishes were introduced in 1967, and it now survives as a single population of less than 100 individuals in Crystal Springs. The springs and most of the surrounding lands are privately owned, but a small portion is managed by the Bureau of Land Management. The Hiko White River springfish occurs in Hiko and Crystal Springs located in the Pahranagat Valley in the northern Mohave Desert.At the time of its listing, this subspecies existed only as a single, small population restricted to Crystal Springs. Predation by largemouth bass had caused its extirpation from Hiko Spring in the 1960s. In 1985 C. b. grandis was re-introduced into Hiko Spring and is apparently now well established while the population in Crystal Springs is quite small.

A program sponsored by the University of Nevada introduced Crenichthys baileyi baileyi into Blue Link Spring in Mineral County to establish a refuge population, which is now well established. When last surveyed in 1995 less than 125 individuals were observed in Crystal Spring but the population in Hiko Spring was approximately 5,500 and in Blue Link Springs 12,000.

Threats

White River springfish and Hiko White River springfish were listed as endangered species with critical habitat in 1985. At that time, the one known population of the White River springfish and the single remaining population of the Hiko White River springfish were threatened by habitat alteration and the presence of non-native species, which compete and prey upon the springfishes. Populations of both subspecies of springfish continue to face threats to their existence from continued presence of non-native species, diseases not previously found in native fish populations, habitat manipulation, and loss of genetic material exchange between populations.

The greatest spatial overlap between native and introduced fishes is between springfish (both sub-species) and shortfin molly, followed by springfish and convict cichlids. Both springfish species larvae overlapped most with adult mollies. Mollies and cichlids are thermophilic (warm temperature loving), like the springfish, and are abundant in the areas occupied by springfish. In laboratory experiments, both the convict cichlid and shortfin molly were found to be extremely adept at larval predation. Competition for food between springfish and short-fin molly is minimal, although both forage at or near the bottom, because of the molly's tendency towards herbivory. The greatest competition for food resources occurs between cichlids and springfish as they are both omnivorous and thermophilic.

Recent experiments, using the Moapa White River springfish as a substitute for the two listed species, clarified behavioral relationships between the springfish, the shortfin molly, and the convict cichlid. Springfish are more aggressive amongst themselves in the presence of shortfin molly, which increased mortality among springfish. Mollies were also observed preying upon newly laid springfish eggs. Springfish were most often the target of aggressive cichlid attacks, resulting in significant springfish mortality. When springfish were confined with both non-native species, the aforementioned practices became more intense. Experimental reproductive data confirmed severely reduced larval production and recruitment for springfish cohabiting with convict cichlids and shortfin mollies.

The desert springs inhabited by these spring-fishes are extremely localized and vulnerable to alteration by diversion of water or introduction of non-native fishes. Efforts to restock the Hiko White River springfish in Hiko Spring have been made in recent years but the long-term viability of this re-stocking effort is questionable. Most of the re-stocked springfish have fallen prey to the numerous exotic fishes that inhabit the spring, such as the convict cichlid and mosquitofish. The introduced fish also carry parasites, most notably the copepod Lernea, which infects the springfish.

Conservation and Recovery

Critical Habitat was designated for both sub-species to include Ash Springs for the White River springfish, and Crystal and Hiko Springs for the Hiko White River springfish. The Desert Fishes Council opposed designation of Critical Habitat because it feared that the action would attract undue animosity from local landowners.

Specific conservation measures should include removing feral and exotic animals from the lands around the springs, controlling and restricting agricultural practices, restricting construction and development in areas near the habitat that could affect water quality, prohibiting stream bank and stream channel modification, and limiting human access to the area.

The White River springfish may be considered for delisting when: a self-sustaining White River springfish population (comprising three or more age-classes, a stable or increasing population size, and documented reproduction and recruitment) is present in the spring pools of Ash Spring for three complete generations (or a minimum of six consecutive years); and impacts to the species and its habitat have been reduced or modifed to a point where they no longer represent a threat of extinction or irreversible population decline.

The Hiko White River springfish may be considered for delisting when: a self-sustaining Hiko White River springfish population (comprising three or more age-classes, a stable or increasing population size, and documented reproduction and recruitment) is present in the spring pools of Hiko and Crystal Springs for three complete generations (six consecutive years).

Contact

U. S. Fish and Wildlife Service
Regional Office, Division of Endangered Species
Eastside Federal Building
911 N. E. 11th Ave.
Portland, Oregon 97232-4181
Telephone: (503) 231-6121
http://pacific.fws.gov/

References

Constantz, G. D. 1981. " Life History and Patterns of Desert Fishes." In: Fishes of the American Desert. New York: John Wiley: 137-290.

Deacon, J. E., C. Hubbs, and B. J. Zahuranec. 1964."Some Effects of Introduced Fishes on the Native Fish Fauna of Southern Nevada." Southwestern Naturalist 12:31-44.

La Rivers, I. 1994. Fishes and Fisheries of Nevada. University of Nevada Press, Reno, Nevada.

U.S. Fish and Wildlife Service. 1985. "Determination of Endangered Status for Two White River Springfish." Federal Register 50:37194-37197.

U. S. Fish and Wildlife Service. 1998. "Recovery Plan for the Aquatic and Riparian Species of Pahranagat Valley." U.S. Fish and Wildlife Service, Portland.

Williams, J. E., and G. R. Wilde. 1981. "Taxonomic Status and Morphology of Isolated Populations of the White River Springfish, Crenichthys baileyi(Cyprinodontidae)." Southwestern Naturalist 25: 485-503.

Williams, J. E., and G. R. Wilde. 1985. "Endangered Aquatic Ecosystems in North American Deserts with a List of Vanishing Species in the Region." Journal of the Arizona-Nevada Academy of Sciences 20(1): 1-61.