A Preliminary Checklist of the Aquatic and Terrestrial Mollusks of the Middle Snake River Sub- Basin / Un Listado Preliminar de los Moluscos Acuáticos y Terrestres de la Subcuenca en Medio del Río Snake

KEYWORDS: Mollusks; Middle Snake River; endangered snails; moluscos; caracoles; snails; clams; almejas

ABSTRACT

The freshwater mollusk fauna as presently understood comprises thirty native and two introduced snail species, and there are at least three additional taxa of non- native snails which inhabit thermal plumes in warmwater aquaculture outfalls. Seventeen native and a single introduced species of Bivalvia (clams) and nine living species of landsnails have been identified from the sub- basin. Several new regional and state records are presented. Mollusk species which are expected to occur but have not yet been verified from the Middle Snake River sub- basin are cited. Half of the eighteen native aquatic species which characteristically require cold, fastwater habitats or sediment sites in free- flowing reaches are presently either proposed for listing or are candidate endangered or threatened species and several others are declining. This is a working checklist to which there will undoubtedly be additions of both terrestrial and aquatic mollusks.

RESUMEN

La fauna malacológica de agua dulce actualmente conocida comprende treinta especies nativas de caracoles y dos introducidas. Además, existen al menos tres taxa de caracoles introducidos que viven en corrientes cálidas de las descargas de la acuacultura. Diecisiete especies nativas de bivalvos (almejas) y nueve especies de caracoles de tierra han sido identificadas para la subcuenca. Se presentan nuevos registros para la región y el estado. Las especies de moluscos que se esperaría encontrar pero que aún no se han verificado en la subcuenca del medio del Río Snake se citan. La mitad de las dieciocho especies acuáticas nativas que característicamente requieren habitats con aguas rápidas y frías o sitios con sedimentos sin flujo están actualmente propuestas para ser enlistadas, o ser candidatas a en peligro o amenazadas, y algunas otras están declinando. Este es un listado de trabajo para el cual habrá indudablemente adiciones de moluscos terrestres y acuáticos.

CONTRIBUTED PAPER

This checklist comprises a working list of the aquatic and terrestrial mollusks presently known from the Middle Snake River ecosystem. For the purposes of this study, the Middle Snake River is considered to include the reach between Milner Dam (River Mile 639.1) and C.J. Strike Reservoir (R.M. 517.6). Within this 121.5 mile reach the river gradient descends 1,680 feet, primarily in the first half of the stretch. There is no doubt that additional aquatic and landsnail species will be identified from the Middle Snake River, and this checklist will be updated as such new records arise. The freshwater mollusk fauna as presently understood comprises twenty seven native and two exotic snail species. There are at least three other exotic snail taxa which inhabit thermal plumes in warmwater aquaculture outfalls. There are fifteen native and a single introduced clam species. Nine living species of landsnails have been identified thus far (see Table 1).

The freshwater mollusc fauna of the mainstem Middle Snake River is now relatively well known, far more completely than that of the terrestrial molluscs. The aquatic fauna is rich in comparison to other drainages in western North America. The fauna is unusually diverse, composed of representatives which are: 1) relicts of the late Pliocene "Lake Idaho" (the Bliss Rapids snail and Pyrgulopsis idahoensis, among a few others), Pleistocene lakes and rivers (Physa natricina), or are endemics for which fossils have not been found (the Lanx n. sp., endemic to a few springs in the Snake River Plain Aquifer); 2) species which reflect the former connection of the present Snake River drainage with Oregon and California (Vorticifex effusus, for example); 3) species which are a part of the Columbia River fauna, such as Fisherola nuttalli, which ascended the Snake River after the draining of Lake Idaho, Snake River drainage capture by the Columbia River and the cutting of Hells Canyon; and 4) species with a broad distribution in the Northwest, more than two-thirds of the total number of species.

The mainstem fauna comprises 42 native mollusc species (27 snails in 7 families and 15 clams in 3 families). In the mainstem river there are three non-native taxa (two snails and the Asian clam Corbicula fluminea), and several other exotics exist in thermal plumes from warmwater hatcheries. Corbicula may have entered the area as a bait bucket release, since it is one of the most abundant molluscs in lower Snake River (eg. Frest and Johannes, 1992b). Radix auricularia was undoubtedly an aquarium escapee known from Idaho as early as 1931 (Bowler and Frest, 1992), and Potamopyrgus antipodarum could have reached the Middle Snake River in a variety of ways (Bowler, 1991). Frest and Johannes (1991) report concentrations up to 400 individuals per 6.25 sq. cm. in the mainstem river and up to 320 snails per 6.25 sq. cm. in The Nature Conservancy Preserve at Thousand Springs. This species is spreading in the sub-basin and is the dominant mollusc in the Middle Snake River. It appears to build larger populations in the polluted settings of the mainstem river or below fish hatcheries on tributaries, while it is less prolific in the springs above pollution sources. Several additional non-native species have been observed in warmwater aquaculture hatcheries, but have have not as yet been recorded as escapees into the natural environment.

Within the native fauna, the occurrence of the planorbid Promenetus exacuous is new to Idaho, and is reported here from the Snake River above Shoshone Falls. This species also occurs in Silver Creek, adjacent the Wood River drainage, and is another intriguing faunal link between the Wood River/Silver Creek sub-basins and the Snake River above Shoshone Falls. A similar local distribution was recorded for the leatherside chub, Gila copei, by Hubbs and Miller (1948). Lymnaea stagnalis appressa, the great pond snail, was also found in Silver Creek, and is a new record for the region.

In addition to the species inhabiting the maistem Snake River, there are at least eight other snails and five clam taxa known elsewhere in the system, in the headwaters of tributaries, or as thermal endemics (such as Pyrgulopsis bruneauensis). The faunas of the headwater settings of many of the more remote tributaries are incompletely known. At least one undescribed Pyrgulopsis is known from the tributaries.

Eight living landsnail species and two fossil taxa which have not yet been found living have been identified along the Middle Snake River. Most of the landsnails have regional distributions, and no endemics have been discovered. A few Pleistocene relicts could survive since fossils have been recovered in suitable modern habitat, and there are other landsnail species with regional distributions which likely occur in the area.

Table 1. The compilation of species presented below reflects reports by Taylor (1985), Bowler (1991), Bowler and Frest (1992), Neitzel and Frest (1989) and Frest and Johannes (1991; 1992a). Native species which characteristically require cold, fast water or sediments in free-flowing habitats are indicated in boldface, while many of the other species are more tolerant of eutrophic, warmer conditions (see Frest and Bowler, [1991] and Frest and Johannes [1991]). An asterix proceeds the name of non-native taxa. Candidate or Federal Threatened or Endangered Species are indicated by a + before the taxonomic name. Federally listed Endangered or Threatened Species are indicated by an E or a T in bold print.

Aquatic Snails

Class Gastropoda (Snails)

Ancylidae

Ferrissia parallelus (Haldeman, 1841)

Ferrissia rivularis (Say, 1817)

Hydrobiidae

+Fluminicola columbiana Hemphill(in Pilsbry)1899

Fluminicola hindsi (Baird,1863)

*Potamopyrgus antipodarum (Gray, 1843)

EPyrgulopsis (= Fontelicella) idahoensis (Pilsbry, 1933)

T Undescribed genus (Bliss Rapids snail)

Lancidae

+Fisherola nuttalli (Haldeman, 1841)

ELanx n. sp. (Banbury Springs lanx; Frest, in ed.) Lymnaeidae

Fossaria (Bakerilymnea) bulimoides (Lea, 1841)

Fossaria (B.) dalli (Baker, 1907)

Fossaria (F.) exigua Lea, 1841

Fossaria (F.) modicella Say, 1825

Fossaria (F.) parva(Lea, 1841)

Fossaria (F.) obrussa (Say ,1825) group

Stagnicola (Hinkleyia) caperata (Say, 1829)

Stagnicola (S.) catascopium (Say, 1817)

Stagnicola (S.) hinkleyi (F.C. Baker, 1906)

*Radix auricularia (Linnaeus, 1758)

Physidae

Physa mexicana (Phillippi, 1841)

EPhysa natricina Taylor, 1988

Physella (Physella) gyrina (Say, 1821)

Physella (Costatella) integra (Haldeman, 1841)

Planorbidae

Gyraulus (Torquis) parvus (Say, 1817)

Planorbella (Piersoma) subcrenatum (Carpenter, 1857)

Promenetus exacuous (Say, 1821)

Vorticifex effusus (Lea, 1856)

Valvatidae

Valvata humeralis Say, 1829

EValvata utahensis Call, 1884

Class Bivalvia (Clams)

Corbiculidae

*Corbicula fluminea (Muller, 1774)

Margaritiferidae

Margaritifera falcata (Gould, 1850)

Sphaeriidae

Musculium lacustre (Muller, 1774)

Musculium securis Prime, 1852)

Pisidium (Cyclocalyx) caesertanum (Poli, 1795)

Pisidium (C.) compressum Prime, 1852

Pisidium (Neopsidium) insigne Gabb, 1868

Pisidium (C.) nitidumJenyns, 1832

Pisidium (C.) pauperculum Sterki, 1896

Pisidium (N.) punctatum Sterki, 1895

Pisidium (C.) variabile Prime, 1852

Sphaerium nitidum Clessin, 1876

Sphaerium patella(Gould, 1850)

Sphaerium striatinum (Lamarck, 1818)

Unionidae

+Anodonta californiensis Lea, 1852

Gonidea angulata (Lea, 1839)

Landsnails

Cochlicopidae

Cochlicopa lubrica (Muller, 1774)

Deroceras laeve (Muller, 1774)

Discidae

Discus cronkhitei (Newcomb, 1865)

Oreohelicidae

Oreohelix strigosa depressa (Cockerell, 1890)

Pupillidae

Vertigo elatiorSterki, 1892 [fossil, not living] Succineidae

Catinella gelida (Baker, 1927) [fossil, not living]

Oxyloma haydeni (Binney, 1858)

Valloniidae

Vallonia cyclophorella(Sterki, 1892)

Zonitidae

Hawaiia minuscula (Binney, 1840)

Zonitoides arboreus (Say, 1816)

There are numerous other landsnail taxa which likely occur along the Middle Snake River and its spring tributaries. There is at least one additional species of Oxyloma which occurs in the Middle Snake River and its tributaries, and Vertigo idahoensis and V. concinnula are widespread species which could inhabit the area (see Frest and Johannes [1992a] for additional discussion of landsnails).

Table 2. Non-native aquatic taxa occurring in warm-water hatcheries and the thermal plumes at their outfalls into the Snake River (adapted from Bowler and Frest, 1992).

Thiaridae

*Tarebia granifera (Lamarck, 1822)

Physidae

*Physella sp. (not native)

Planorbidae

*Biomphalaria glabrata (Say, 1818)

*Biomphalaria havanensis (Pfeiffer, 1839)

*Marisa cornuarietis (Linne, 1758)

*Pomacea sp. (several color forms)

There are a number of additional exotic species yet to be identified which occur in warm-water hatcheries in the area.

Table 3. Additional aquatic mollusc species occurring outside the mainstem Middle Snake River in the sub-basin.

Gyraulus "vermicularis" Hot Creek, Bruneau River drainage (Bowler and Olmstead, 1991)

Lymnaea stagnalis appressa Say,1821 Silver Creek

Menetus callioglyptus (Vanatta, 1895) In the system elsewhere

Musculium transversum (Say, 1829) "

Pisidium (P.) idahoense Roper, 1890 "

Pisidium (C.) ferrugineum Prime, 1852 "

Pisidium (C.) lilleborgi Clessin, 1886 "

Pisidium (C.) rotundatum Prime, 1852 "

Pyrgulopsis bruneauensis Hershler, 1991 Thermal \endemic (Hot Creek)

Pyrgulopsis intermedia (Tryon, 1865) Owyhee River drainage

Pyrgulopsis hendersoni (Pilsbry, 1933) Harney and Malheur Lake drainages

Stagnicola (Hinkleyia) montanensis (F.C. Baker, 1913) Taylor, Walter, and Burch (1963)

The Middle Snake River has a suite of coldwater lotic species which is now in severe decline; some are endemics (such as the Bliss Rapids snail) and others are disjuncts. This group was formerly characteristic of the mainstem river. There is an apparent shift in the mollusc fauna in the Middle Snake River from a predominance of coldwater, lotic species to species which are characteristic of warm, shallow lakes. Within the native fauna at least eight are endangered, with one apparently locally extirpated, six are declining, 11 species appear to be increasing (a guild of lentic taxa), and there is inadequate data to understand trends in the remainder. Among the lotic species are three Candidate, four Endangered, and one Threatened species. In general, the area from Milner Dam to Shoshone Falls is species poor. The reach from Shoshone Falls to Upper Salmon impoundment has a depauperate, declining lotic fauna shifting to a lentic suite of species. The reach from Lower Salmon Falls Dam to the Bliss impoundment and from Bliss Dam to around Clover Creek still has a nearly complete remnant of the historic lotic fauna, though it is decreasing in both of these reaches. The impoundments are depauperate, with few species represented. Sub-fossil shells and early collections indicate that the lotic fauna was present until recently at least to Shoshone Falls. The diversion of the Snake River at Milner Dam for the past 80 years makes reconstructing the historic fauna difficult, though a few of the lotic taxa characteristic of the lower Middle Snake River were collected from the area by early collectors.

The shift in the mollusc fauna from a coldwater, lotic group to warmer water, lentic taxa mirrors a similar transformation in the aquatic environment. Many factors have contributed to present conditions, ranging from irrigation diversions and return flows, aquaculture developments on tributaries, hydroelectric projects, dairies and confined feedlots, to municipal sewage. Seasonal algal and macrophyte blooms, and anoxic bottom conditions also have an impact on mollusc survival. An organic-rich blanket of silt covers most of the river bottom from Upper Salmon Falls Dam to Shoshone Falls. In this reach species diversity is now low. In a study of fifteen sites Frest and Johannes (1991) found maximum species richness to range from 1 to 12 species, which is very poor considering a species pool of 42 taxa in the local fauna.

As Frest and Johannes (1991) noted in a study of three fastwater sites in this reach: "...The most notable mollusc faunal change from 1986 to the present is the tremendous expansion in numbers and distribution of the introduced Potamopyrgus antipodarum. The species was just becoming established in this stretch in 1986. It is now by far the most abundant species encountered in nearly all habitats....Areas of clear-water, cobble and boulder substrate habitat have decreased, while shallow water, soft-sediment habitats are now more widespread. Such areas often have reducing conditions, subsurface methane gas generation, and few live molluscs except for occasional sphaeriids....At best, present conditions are more like those of large, shallow lakes than of cold water rivers. As much of the endemic fauna of the Middle Snake River (including many of the candidates) is adapted to cold water river conditions, most cannot compete successfully under current conditions. Among the molluscs, large-scale faunal turnover appears to have begun."

Paste Table 4 from Frest and Bowler here

"It should be emphasized that this stretch of the Snake River is now becoming marginal mollusc habitat, particularly for cold water species, including the stream-dwelling candidates. Faunal changes have been described above, as has the general rarity of cold water taxa and relative abundance of eurytropic native taxa and one introduced taxon. In [our] opinion, water quality has deteriorated since 1986. This is noticeable in the mollusc fauna and also in the visually apparent massive increases in filamentous algae and in sediment influx in this stretch. With continued deterioration of water quality, the cold water fauna and all of the candidates and/or Snake River endemic taxa now present could soon be locally extirpated. If it is desirable to sustain the original river mollusc fauna, including candidate taxa, water quality should not be permitted to deteriorate further. Among other factors that could cause deterioration of water quality, decrease in flow, increase in nitrates, phosphates, or other forms of agricultural and piscicultural chemical pollution, and increases in siltation from any cause should be avoided."

Coldwater taxa formerly common and characteristic of the Middle Snake River which are now in rapid decline include species such as Fluminicola hindsi and Vorticifex effusus (see Table 4). The recently listed federal Endangered taxa are Valvata utahensis, Pyrgulopsis idahoensis, Lanx n. sp., and Physa natricina, and the Bliss Rapids snail was listed as Threatened. Fisherola nuttalli, Fluminicola columbiana, Anodonta californiensis are federal Candidate taxa. Valvata humeralis, historically known from much of the Middle Snake River, is now near local extinction. Stagnicola (S.) hinkleyi, a Snake River system endemic which our research indicates is endangered, had historic populations now apparently extirpated above Upper Salmon Falls, though a population still occurs in the reach below Lower Salmon Dam. Margaritifera falcata, a large clam found in abundance in Native American camps along the Middle Snake River, is now extirpated in this area of the river. Fluminicola columbiana has only been found living in the reach between Lower Salmon Dam and the Bliss impoundment, though it undoubtedly had an historic distribution up and down-gradient in the Middle Snake River.

In conclusion, the Middle Snake River has a remarkably diverse aquatic mollusc fauna of 42 species, among which those taxa requiring, cold, fast water settings are endangered or declining, with a concurrent increase in a group of more pollution-tolerant species characteristic of warm, shallow lakes. Eight living landsnail taxa have been identified from this area, and there are likely a number of additions which will be made to this preliminary list.

Literature Cited

Bowler, P.A. 1991. The Rapid Spread of Potamopyrgus antipodarum (Gray) in the Middle Snake River, Southern Idaho. Proc. Desert Fishes Council 21: 173- 182.

Bowler, P.A. and T.J. Frest. 1992. The Non-Native Snail Fauna of the Middle Snake River, Southern Idaho. Proc. Desert Fishes Council 23: 28- 44.

Bowler, P.A. and P. Olmstead. 1991. The Current Status of the Bruneau Hot Springs Snail, an Undescribed Monotypic Genus of Freshwater Hydrobiid Snail, and Its Declining Habitat. Proc. Desert Fishes Council 21: 195- 211.

Burch, J.B. 1989. North American Freshwater Snails. Malacological Publications, Hamburg, Michigan.

Frest, T.J. and P.A. Bowler. 1992. The Ecology, Distribution and Status of Relict Lake Idaho Mollusks and other Endemics in the Middle Snake River. Proc. Desert Fishes Council 23: 45- 48.

Frest, T.J. and E.J. Johannes. 1991. Mollusc Fauna in the Vicinity of Three Proposed Hydroelectric Projects on the Middle Snake River, Central Idaho. Report prepared for Don Chapman Associates, Inc. Boise, Idaho. Deixis Consultants, Seattle, Washington.

Frest, T.J. and E.J. Johannes. 1992a. Distribution and Ecology of the Endemic and Relict Mollusc Fauna of Idaho TNC's Thousand Springs Preserve. Final Report, Contract # IDFO 050291-A. Deixis Consultants, Seattle, Washington.

Frest, T.J. and E.J. Johannes. 1992b. Effects of the March, 1992 Drawdown on the Freshwater Molluscs of the Lower Granite Lake area, Snake River, SE Washington and W. Idaho. Deixis Consultants, Seattle, Washington.

Hubbs, C.L. and R.R. Miller. 1948. The zoological evidence: Correlation between fish distribution and hydrographic history in the desert basins of western United States. In The Great Basin with emphasis on glacial and postglacial times, Bull. University of Utah 38, Bio. Ser. 10: 17- 166.

Neitzel, D.A. and T.J. Frest. 1989. Survey of Columbia River Basin streams for Giant Columbia River Spire Snail Fluminicola columbiana and Great Columbia River Limpet Fisherola nuttalli. Battelle Pacific Northwest Laboratory, Pub. 7103, xi + 34 pp., appendix.

Taylor, D.W. 1985. Candidate Threatened or Endangered Molluscs in Box Canyon ACEC, Gooding County, Idaho. Unpublished report prepared for the Shoshone District Office of the Bureau of Land Management, Order No. ID- 050-PH5- 0093.

Taylor, D.W., H.J. Walter, and J.B. Burch. 1963. Freshwater snails of the subgenus Hinkleyia (Lymnaeidae: Stagnicola) from the western United States. Malacologia 1(2): 237- 281.

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