Bliss Rapids Snail

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Bliss Rapids Snail

Taylorconcha serpenticola

ListedDecember 14, 1992
FamilyHydrobidae (Aquatic Snail)
DescriptionColorless or orange-red snail with smaller rounded whorls.
HabitatFree-flowing cool spring alcoves.
FoodPlant debris or diatoms.
ReproductionEgg laying occurs with two months of reproduction.
ThreatsDeteriorating water quality from hydroelectric development, competition with other snails.


The Bliss Rapids snail is an example of a "living fossil." This is due to the fact that it is a relict from an ancient lakethe late Pliocene (Blancan) Lake Idaho. This snail is 0.08-0.1 in (2-2.5 mm) long with three whorls and is roughly ovoid in shape. There are two color variants, or morphs, of the Bliss River Rapids snail. One is the colorless or "pale form" and the other is the orange-red or "orange form." The pale morph is slightly smaller with rounded whorls with more melanin pigment on the body.


Reproduction in the Bliss Rapids snail varies according to habitat. Reproduction occurs October to February in mainstem Snake River colonies and February to May in large-spring colonies. Egg laying occurs within two months of reproduction and eggs appear to hatch within one month. Adult snails exhibit a strong seasonal die-off after reproduction.This species is known to migrate only to food sources.


The Bliss Rapids snail is restricted to a few isolated free-flowing reaches or spring alcove habitats of the Snake River. This aquatic system is characterized by cold, well-oxygenated, unpolluted water. The Bliss Rapids snail occurs on stable, cobble-boulder substratum only in flowing waters in the Snake River and also in a few spring alcove habitats in the Hagerman Valley. The species does not burrow in sediments and normally avoids surfaces with attached plants. Known river colonies of the Bliss Rapids snail occur only in areas associated with spring influences or rapids edge environments and tend to flank shorelines. Generally, the species requires cold, clean, well-oxygenated flowing water of low turbidity. The species is found at varying depths if dissolved oxygen and temperature requirements persist and is found in shallow, (less than 0.4 in, or 1 cm) permanent cold springs. This snail is thought to be somewhat photophobic and resides on the lateral sides and undersides of rocks during daylight. The species will migrate to graze on perilithon on the uppermost surfaces of rocks nocturnally. The Bliss Rapids snail can be locally quite abundant, and is especially abundant on smooth rock surfaces with common encrusting red algae.


Prior to 1987, the Bliss Rapids snail was known primarily from the mainstem Snake River boulder bars above King Hill and upstream in Box Canyon Springs. Prior to dam construction there was probably a single population throughout the historic range and possibly upstream as well. Based on live collections, the species currently exists as fragmented populations primarily concentrated in the Hagerman reach in tailwaters of Bliss and Lower Salmon Dams and Thousand Springs, Minnie Miller Springs, Banbury Springs, Niagara Springs, and Box Canyon Springs.


The free-flowing, cool water environments required by this species have been impacted by and are vulnerable to continued adverse habitat modification and deteriorating water quality from hydroelectric development, peak-loading effects from existing hydroelectric project operations, water withdrawal and diversions, water pollution, and inadequate regulatory mechanisms. The Bliss River Rapids snail may also be adversely affected by competition with an exotic snail (Potamopyrgus antipodarum ). With the exception of segments of land owned by The Nature Conservancy (Thousand Springs), the aquatic habitats occupied by this species are virtually unprotected from the aforementioned threats.

Ground water mining or withdrawal may also impact spring stream habitats of the Bliss Rapids snail population above American Falls Reservoir. Biologists of the Shoshone Bannock Tribal Reservation have observed water fluctuations and seasonal declines in spring flows along this stretch of the Snake River concurrent with the irrigation season. Winter cattle grazing and recreational access may also be impacting spring habitats of the Bliss Rapids snail on the Shoshone Bannock Reservation. Although access is controlled, waterfowl hunters, and fishermen to some extent, utilize these spring areas throughout the fall and early winter.

Changes in the use of stored water in the Snake River basin to assist recovery efforts for other threatened and endangered species may also impact this species and its habitat. The Bonneville Power Administration, State of Idaho, and Idaho Power Company are exploring alternatives to assist outmigrating endangered Snake River Sockeye salmon and threatened Spring and Summer Chinook from utilizing water from the upper Snake River Basin. The Idaho Department of Health and Welfare, Division of Environmental Quality, under authority of the State Nutrient Management Act, is coordinating efforts to identify and implement preventative actions which will reduce nutrient loading to the middle Snake River. These efforts will address pollution control strategies.

Conservation and Recovery

The U. S. Fish and Wildlife Service published a Recovery Plan for the Bliss Rapids snail and other endangered mollusks in the Snake River Basin in 1992. Critical habitat of this species occurs on Federally owned lands (Shoshone Bannock Tribal Reservation and lands owned by the Bureau of Land Management). This publicly owned habitat must be protected from impoundment, diversion, pollution, and other threatening activities within the rivers or in their watersheds. Some of its habitat is protected in the Thousand Springs Preserve owned by The Nature Conservancy, a private conservation organization. Other habitats (including critical water-shed lands) are on private land and are at risk from various human activities. These areas should be protected by acquiring the habitat and designating ecological reserves, or by negotiating conservation easements with the landowners. The populations of the Bliss Rapids snail should be monitored, and research undertaken into its biology and habitat needs.


U. S. Fish and Wildlife Service
Eastside Federal Complex
911 N. E. 11th Avenue
Portland, Oregon 97232-4181
Phone: (503) 231-6121

Snake River Basin Fish and Wildlife Office
1387 South Vinnell Way, Suite 368
Boise, Idaho 83709-1657
Telephone: (208) 378-5243
Fax: (208) 378-5262


U. S. Fish and Wildlife Service. 14 December 1992. "Endangered and Threatened Wildlife and Plants: Determination of Endangered or Threatened Status for Five Aquatic Snails in South Central Idaho." Federal Register 57 (240): 59244-59257.

U. S. Fish and Wildlife Service. 1995. "Snake River Aquatic Species Recovery Plan." Snake River Basin Office, Ecological Services, Boise, Idaho.