Independence Valley Speckled Dace

Rhinichthys osculus lethoporus

Description

The Independence Valley speckled dace, Rhinichthys osculus lethoporus, is distinguished from other speckled dace by a more laterally compressed body. It differs from the Clover Valley speckled dace, found in nearby springs, by a less developed lateral line, fewer number of pectoral fin rays, and a straighter, more oblique mouth.

Behavior

The speckled dace is an adaptable species, able to occupy a variety of habitats, from cold streams and rivers with rocky bottoms to thermal springs with silt bottoms. This adaptability has enabled it to survive in environments too harsh for other species. The isolation of populations has led to a large number of forms that are recognized as sub-species. They feed primarily on insects, and are presumed to spawn in mid-summer.

Habitat

Independence Valley speckled dace are found in a temperate, permanent desert stream/marsh fed by numerous springs. Although known as Independence Valley Warm Springs, these springs are not cited as thermal waters. The speckled dace are found primarily in the shallow water of the marsh of this spring system among the sedges and grasses. It is believed that they also occupied the stream, but were forced out due to predation by non-native fish species such as rainbow trout, largemouth bass, and bluegill. No data exist on the flow velocities or temperatures of habitat currently occupied by Independence Valley speckled dace, but preliminary data show the speckled dace inhabit a large portion of the marsh as well as two seep areas northeast of the marsh.

The flows from Independence Valley Warm Springs are impounded into two reservoirs. The upper, and shallower of the two, is roughly 5 ft (1.5 m) deep and 98 ft (30 m) wide. The lower reservoir is approximately 10 ft (3 m) deep with a diameter of approximately 148 ft (45 m). A dense mat of vegetation consisting mostly of stonewort with some water milfoil and hornwort covered the bottom of the large reservoir. The edges of the pond are lined with pondweed. When flows are high, all flows from the upper reservoir enter the lower one. Water flows from the lower impoundment through a looping channel for 200 ft (70 m) before entering a marsh. Once entering the marsh, the channel disappears, becoming eroded and shallow. Water depth in the channel ranges from 4 to 18 in (10 to 46 cm), with a shallower water depth in the marsh. Several small ponds occurred in the marsh area, one approximately 500 ft (152 m) northeast of the lower reservoir and one approximately 1,000 ft (305 m) to the southeast. Approximately 25 speckled dace were observed in October 1994. Several springheads located further south of this system have not been extensively mapped.

Distribution

Independence Valley warm springs was surveyed in 1983, and only 33 Independence Valley speckled dace were minnow trapped from the lower marsh. The Nevada Division of Wildlife surveyed the area in 1992 and captured only one speckled dace in the shallowest area of the marsh. In October 1994, Nevada Division of Wildlife and U. S. Fish and Wildlife Service personnel collected and released five individuals and observed approximately 20 more in the extensive marsh area.

Based on general habitat characteristics of other closely related dace species, the Independence Valley speckled dace should have been found throughout the Independence Valley Warm Springs system, not just the marshy area below the springs. It is believed that the historical range of the Independence Valley speckled dace was throughout the spring system and its associated marsh. The vast marsh area has not been intensively surveyed in the past 11 years so the current distribution is unknown. It is unclear whether the distribution of the Independence Valley speckled dace has expanded or diminished since the sub-species was listed.

Threats

The building and manipulation of reservoirs for irrigation was thought to be a serious threat to both speckled dace due to the reduction of available stream/outflow habitat and pond/reservoir habitat when water levels were regulated. At the turn of the twenty-first century, in Independence Valley no lands were being irrigated for crop production and no land had been used for crop production for over 10 years. The reservoirs and stream outflows had not been used for irrigation for approximately the same amount of time. The landowner stated that no plans exist for irrigation to occur on the property the fish presently occupy.

Conservation and Recovery

The reservoirs at Independence Valley Warm Springs continue to be a popular fishing area. Bluegill were established years ago and are still found in the reservoir. Despite the largemouth bass and bluegill in the reservoir and outflow, speckled dace persist in the marsh, but determining how the population is affected remains to be resolved. Removal of the normative fish and establishment of an alternative fishery at another location remains the most viable option for both speckled dace recovery and meeting anglers needs. Essential to the recovery of the Independence Valley speckled dace is the removal and relocation of the largemouth bass and bluegill that inhabit the stream, segments of the marsh, and the reservoir at Independence Valley Warm Springs. Since the ranch is a fairly popular fishing area, the bass could be relocated nearby to protect the Independence Valley speckled dace and still provide a sport fishery.

Contacts

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

U. S. Fish and Wildlife Service
4600 Kietzke Lane, Building C
Reno, Nevada 89502

References

Hubbs, C. L., R. R. Miller, and L. C. Hubbs. 1974.Hydrographic History and Relict Fishes of the North Central Great Basin. Memoirs of the California Academy of Sciences. Volume 7.

McNatt, R. M. 1988. "Field Trip Report on Investigation of Three Speckled Dace Sites in Clover Valley, Nevada." U. S. Fish and Wildlife Service, Great Basin Complex, Reno, Nevada.

Vinyard, G. L. 1984. "A Status Report about the Independence Valley Speckled Dace (Rhinichthysosculus lethoporus ), Independence Valley Tui Chub (Gila bicolor isolata ), and Clover Valley Speckled Dace (Rhinichthys osculus oligoporus );Three Fishes Restricted to the Northeastern Portion of Nevada." U. S. Fish and Wildlife Service, Reno, Nevada.