SPECIES FACT SHEET
Scientific Name: Fisherola nuttalli (Haldeman, 1841)
Common Name: Shortface lanx, Giant Columbia River limpet
Phylum: Mollusca
Class: Gastropoda
Order: Basommatophora
Family: Lymnaeidae
Taxonomic notes:
1. This species was previously described as Lanx nuttalli, based on the
resemblance of its conical shell to described Lanx species (Clarke 1981, Neitzel
and Frest 1992). It has also been described as Ancylus crassus (family
Ancylidae) due to its limpet-like shell (ancylid species have shells that resemble
low flat cones), however subsequent studies have placed it in the family
Lymnaeidae.
2. Burch (1989) recognized three subspecies of the shortface lanx: F. nuttalli
nuttalli (Haldeman 1841), cited from the Snake River drainage in Idaho, the
Columbia River drainage in Oregon and Washington, and the Deschutes River
in Oregon; F. nuttalli kooteniensis (Baird 1863), cited from the Spokane River,
Washington, and the Kootenai River, British Columbia; and F. nuttalli lancides
(Hannibal 1912), cited from the Snake River basin in Oregon and Idaho. Neitzel
& Frest (1992) reject these subspecies and consider all known specimens of
Fisherola to be a single valid species, F. nuttalli, noting that subspecies
designations appear to have been based on young specimens and confused by
variable shell morphology.
Conservation Status:
Global Status (2008): G2 - Imperiled
National Statuses: United States (N2), Canada (N1)
State & Province Statuses: Idaho (S2), Montana (SH), Oregon (S1S2), Utah
(SNR), Washington (S2), Wyoming (SNR), Alberta (SNR), British Columbia (S1),
Saskatchewan (SNR)
(NatureServe 2013).
Technical Description:
Fisherola nuttalli is a member of the Lymnaeidae family, a diverse group of
small to large air-breathing pulmonate freshwater snails including 61 North
American species in nine genera (Johnson et al. 2013). Fisherola nuttalli is not
a “true limpet” (a term reserved for the gilled, marine Patellogastropoda) but the
common name “limpet” is applied based on the limpet-like appearance (having
a simple shell which is conical in shape rather than being spirally coiled).
1
The shell of F. nuttalli is broadly conical, having a wide oval base and a smooth
eccentric (off-center) apex (Neitzel and Frest 1989). The shells may grow up to
0.5 in. (12.7 mm) long, 0.4 in. (10.2 mm) wide, and 0.2 in (5.1 mm) high
(Neitzel and Frest 1989). Hannibal (1912) lists the shell dimensions as 8 mm
long, 6.25 mm wide, and 3 mm high. Frest (1999) notes that the adult size
varies considerably in different-sized streams, but is generally around 10 to 11
mm. The shell color of this species is described as opaque chesnut-brown
(Hannibal 1912), cinnamon-red (Frest 1999) and rich brown (Neitzel and Frest
1992). The shell shape is roundly ovate (elliptical in outline), slightly broader
posteriorly, high-arched, apex posterior; finely concentrically striate (appearing
striped due to fine concentric growth rings), and depressed conic (Hannibal
1912, Neitzel and Frest 1992). The shell is further described as “coarse,
somewhat ponderous, wide, ovate, elevated; lines of growth conspicuous; apex
eroded, placed far back: anterior and lateral slopes convex, posterior slope
steep and rectilinear” (Hannibal 1912). The collumellar muscle scar is
interrupted on the right side (Frest 1999).
Fisherola nuttalli is similar to and frequently confused with members of the
related Lanx genus, but may be distinguished by the central or subcentral apex
and incomplete mantle attachment scar of the latter. (Fisherola nuttalli has a
strongly anteriorly displaced apex and an incomplete attachment) (Neitzel
and Frest 1992). No F. nuttalli individuals have been seen with white spot or
lines, as is seen in some Lanx species (Frest 1999). See key in Frest (1999) for
further details on distinguishing F. nuttalli from related taxa (i.e., members of
the Lanx genus).
Life History:
Fisherola nuttalli is an air-breathing freshwater snail. Unlike marine “true
limpets”, which have gills, freshwater limpets have a mantle cavity that is
adapted to breathe air and functions as a lung. Generally, freshwater snails
require access to air for respiration, although integumental oxygen transfer
may also occur (Hyman 1967). Given the highly oxygenated habitat for the
shortface lanx, integumental respiration may be particularly important for this
species (NatureServe 2013).
While little is known about reproduction in this particular species, freshwater
pulmonates generally reproduce sexually by copulation and cross-fertilization.
Members of this genus are hermaphrodites but do not appear to be selffertilized, i.e. mating occurs between two individuals (comments by T. Frest in
USFWS 2006). In general, freshwater pulmonate snails lay their eggs from
spring to autumn in gelatinous capsules attached to plants, stones, or other
objects (Hyman 1967). More specifically, a study of F. nuttalli in the Columbia
River in Washington found that egg deposition by mature adults occurs in
April, May, and June, during the period of rising temperatures and maximum
river flows (Coutant & Becker 1970). Egg capsules of Fisherola seem to be laid
2
only on hard substrate, generally undersides or sides of cobbles in especially
protected areas where the adults occur (comments by T. Frest in USFWS
2006). In many areas, smooth cobbles, often of basalt, seem to be preferred.
There is little annual variation in site preferences (i.e., the same areas seem to
be selected repeatedly from year to year) (comments by T. Frest in USFWS
2006).
Members of this genus lack a free-swimming larval stage, and hatch as young
snails (Hyman 1967). Hatchlings are morphologically similar to adults, except
that they lack a functional reproductive system (Hyman 1967). Young snails
appear to grow rapidly and require only a few months to reach full size
(comments by T. Frest in USFWS 2006). In the Columbia River study by
Coutant & Becker (1970), growth of young F. nuttalli was most rapid from July
to October when the water temperatures were high. Growth rates stabilized
during the fall and winter when temperatures dropped and became minimum,
then increased with the warming temperatures of early spring. Adults collected
from down-stream areas and held in warmed water in the laboratory
reproduced successfully at this time (Coutant & Becker 1970).
Individual F. nuttalli breed once and die shortly afterwards (semelparous
breeding). The lifespan of this species seldom exceeds one year, except when
reproduction has not been achieved by an individual (Neitzel & Frest 1992;
Coutant & Becker 1970; comments by T. Frest in USFWS 2006). Highest
mortality of mature limpets has been found to occur during and following the
reproductive period (April through June) (Coutant & Becker 1970).
Fisherola nuttalli moves with a slow snail-like crawl, and is also subject to
transport by stream current. This species feeds by scraping algae and diatoms
from rock surfaces in the streams but may occasionally feed on other plant
surfaces (USDA 2008). Light intensity is considered important to this species
mainly in affecting the growth of its food sources (Hyman 1967).
Like other freshwater snails, this species is considered resistant to cold and
freezing (Hyman 1967). It is present all year, but is not active in winter
(NatureServe 2013). Like other freshwater mollusks, members of this species
are probably food items for fish, frogs, salamanders or birds (NatureServe
2013).
Range, Distribution, and Abundance:
Fisherola nuttalli was historically widespread, with populations scattered
throughout the lower Columbia and Snake Rivers as well as some of their
major tributaries. It has been documented from Washington (Asotin, Benton,
Clark, Cowlitz, Franklin, Grant, Klickitat, Okanogan, Skamania, Stevens, and
Spokane Counties); Oregon (Gilliam, Jefferson, Malheur,
Multnomah, Sherman, Wallowa, and Wasco Counties); Idaho
3
(Cassia, Elmore, Gooding, Idaho, Jerome, Minidoka, Nez Perce, Owyhee, Twin
Falls, and Snake Counties) and Montana (Clark Fork basin) (USNM 2013,
Neitzel & Frest 1992, NatureServe 2013, Montana.gov 2013, ORBIC 2013,
Deixis MolluskDB 2013). It has also been documented in the Columbia River
drainage in British Columbia, Canada, although its presence there was
assumed based on the discovery of a shell (Clarke 1981). Prior to 1987,
collections of F. nuttalli are reported from Columbia and Spokane Rivers in
Washington; the Snake and Salmon Rivers in Idaho; the Deschutes River in
Oregon; and the Kootenai River in British Columbia (Neitzel & Frest 1992). The
species appears to have been widespread historically in the mainstem
Columbia River and the Columbia River Basin prior to the installation of the
current dam system. Columbia River sites extended from Portland, Oregon, to
the Hanford Reach in Washington. All these sites, except the Hanford Reach,
were first surveyed before dam construction on the Columbia River, and are
now within impoundments that have eliminated most viable habitat for this
species (Neitzel & Frest 1992). This species is now presumed extirpated in
Montana and British Columbia, although it may persist in the Okanogan River
drainage in British Columbia (Stagliano et al. 2007).
Currently, large populations of F. nuttalli are known in only four streams: the
lower Deschutes River, Oregon; the Okanogan River and the Hanford Reach of
the Columbia River, Washington; and the Snake River in Oregon and Idaho
(Neitzel & Frest 1992). Additional small populations occur in the John Day and
Imnaha Rivers, Oregon; the lower Columbia River near Bonneville Dam,
Oregon; the Methow River, Washington; the Grande Ronde River, Washington
and Oregon; and the Salmon River, Idaho (Neitzel & Frest 1992; Frest &
Johannes 1995, 2000; Frest 1999; Richards et al. 2005; USNM 2013).
Forest Service/BLM lands: In Oregon, Fisherola nuttalli is Documented on
Wallowa-Whitman National Forest in Oregon and on BLM land in the Prineville
District. It is Suspected on the Columbia River Gorge National Scenic Area,
Malheur, Ochoco, and Umatilla National Forests. In Washington, this species is
Documented on Vale District BLM land. It is Suspected on the OkanoganWenatchee National Forest and on BLM land in the Spokane District based on
proximity to known records (see map in Appendix).
Abundance: Abundance estimates of this species have not been conducted.
Known collections range from one to “many” specimens, with reports of at least
15 specimens collected from a given site/date (Neitzel & Frest 1992, Deixis
MolluskDB 2013).
Habitat Associations:
Fisherola nuttalli occurs in relatively large perennial rivers and streams ranging
from 30-100 m (98-300 ft.) wide. Within such streams, it is most abundant in
4
highly oxygenated environments on gravel to boulder stable substrates. It may
occur in the main channels of fast-flowing streams and rivers, and on diatomcovered rocks or stable boulder or bedrock substrates, often in the vicinity of
rapids (Neitzel and Frest 1989). In an assessment of Hells Canyon Dam (Snake
River, Idaho), F. nuttalli was found on cobbles in higher velocity areas of the
stream much more frequently than any other mollusk species; this was
considered to reflect the species’ preference to attach themselves to hard
surfaces in high velocities to avoid competition with other species (Richards et
al. 2005). This species most commonly occurs in rapids' edges or immediately
downstream from sizable rapids in areas with suitable substrate (Neitzel and
Frest 1992).
Fisherola nuttalli becomes much less common or absent in major rapids, and
avoids the most violent white water areas (Neitzel & Frest 1992). In addition,
the species has not been found in areas with slow flow; silt or mud substrates;
warm water; massive seasonal discharges that destabilize the substrate; an
abundance of macrophytes (aquatic plants) or epiphytic algae; a bedrock
substrate; stream reaches with unstable substrate such as rivers with high
gradients (e.g., the Selway and Lochsa rivers, Idaho, and the Klickitat River,
Washington); streams with glacial flour (fine ground-up sand and stone, e.g.,
the Hood River, Oregon); the central deep areas in strongly channelized
streams; or places impacted by dredging or mining (Neitzel & Frest 1992, Frest
& Johannes 1995, Frest 1999, Richards et al. 2005). Reports of F. nuttalli from
even very large spring complexes, for example, Box Canyon, Idaho are
erroneous (the Box Canyon lanx is an undescribed species of Lanx) (Neitzel &
Frest 1992).
Threats:
Impaired water quality, habitat degradation and loss, and increasing
fragmentation and isolation of the few remaining populations are the main
threats to continued survival of F. nuttalli. This species has narrow habitat
tolerances and requires cold, unpolluted, fast-flowing, well oxygenated water in
moderately large perennial streams with cobble-boulder substrate. Most
historic populations of F. nuttalli have been extirpated due to stream
modifications resulting from dams, impoundments, agriculture, grazing,
development, and industry including pulp mills and mining (Frest & Johannes
1995; Neitzel & Frest 1992; Frest 1999). These modifications include increased
sedimentation, siltation, pollution and nutrient loading; and loss of rocky
substrate (Frest & Johannes 1995; Neitzel & Frest 1992; Frest 1999). Many of
these factors continue to threaten remaining habitat for this species (Stagliano
et al., 2007). In addition, changes in water quality and quantity due to
irrigation withdrawals pose threats to this species. A survey of the interior
Columbia River basin conducted by the US Forest Service (1996) found that
most streams in the region are fully or over-appropriated for water diversion,
with irrigation as the primary usage. Changes in riparian vegetation have been
5
noted basin-wide, including a significant decline in riparian-associated species
such as cottonwood and willow due to forest conversion, streamside
disturbance, roads, and dams (USDA 1996). Decreased riparian vegetation can
destabilize stream banks and increase sedimentation and siltation, filling in the
cobble substrate inhabited by F. nuttalli.
Since numerous F. nuttalli populations have been lost in recent years and
remaining sites are now separated by large areas of unsuitable habitat, this
species is further threatened by limited gene flow between populations (Neitzel
and Frest 1992). Small isolated populations are extremely vulnerable to
stochastic events, and are generally at greater risk of extirpation from normal
population fluctuations due to predation, disease, and changing food supply,
as well as from natural disasters such as floods or droughts. They may also
experience a loss of genetic variability and reduced fitness due to the
unavoidable inbreeding that occurs in such small populations.
Conservation Considerations:
Inventory: Although F. nuttalli has received a significant amount of survey
attention in Oregon and Washington, detections of the species have been very
low (Neitzel & Frest 1989, 1991, 1992). For example, Neitzel & Frest (1992)
conducted targeted surveys for this species at over 500 sites in more than 30
streams in the Columbia River Basin, and detected this species in just nine
streams. Since many of the known sites have not been visited in over two
decades (Neitzel & Frest 1989, 1991, 1992, Deixus MolluskDB 2013), surveys
designed to determine the current status of this species at known sites are
recommended. Additional surveys for this species at new sites may also be
useful. In Washington, surveys at new sites should focus on Okanogan
National Forest and Spokane District BLM land in the Methow River area, since
the species is currently considered Suspected on these lands based on
proximity to known sites.
Management: Minimize or eliminate conversion of this species’ habitat for other
uses. Avoid new construction of dams or other structures which slow water
flow and cause reduced oxygenation. In particular, habitat alteration or stream
modification at Hanford Reach, Washington (the only remaining undammed,
non-tidal stretch of the Columbia River) could be severely detrimental to the
survival of this species. Protect known habitat from further destruction and
restore it when opportunities are presented. Limit agricultural runoff into rivers
which may add nutrients and other pollutants to water. If insecticide or
herbicide use is planned for areas where the F. nuttalli occurs, utilize available
resources to assess alternatives to their use. Research effective habitat
management in the areas where the species still exists. Monitor management
activities and other habitat changes and assess for impacts on F. nuttalli.
6
Version 2:
Prepared by: Sarah Foltz Jordan & Celeste Mazzacano, Xerces Society
Date: 27 August 2013
Edited by: Sarina Jepsen, Xerces Society
Date: 10 September 2013
Final edits by: Rob Huff, FS/BLM ISSSSP
Date: 21 November 2014
Version 1:
Prepared by: Theresa Stone, Umpqua National Forest
Date: 02 September 2009
Edited by: Rob Huff, FS/BLM Conservation Planning Coordinator
Date: March, 2011
ATTACHMENTS:
(1)
References
(2)
List of pertinent or knowledgeable contacts
(3)
Map of species’ distribution
(4)
Photographs of this species
(5)
Aquatic Gastropod Survey Protocol, including specifics for this
species
7
ATTACHMENT 1: References:
Baird, W. 1863. Descriptions of some new species of shells collected at
Vancouver Island and in British Columbia by J.K. Lord esq. Naturalist to the
British North American Boundary Commission, in the Years 1858-1862.
Published Proceedings of the Zoological Society of London 31: 66-70.
Boler, P., and T. Frest. 1992. The non-native snail fauna of the Middle Snake
River. Southern Idaho Proceedings of the Desert Fishes Council. 23: 28-44.
Burch, J. B. 1989. North American Freshwater Snails. Malacological
Publications, Hamburg, Ml. 365 pp.
Clarke, A. H. 1981. The Freshwater Molluscs of Canada. National Museum of
Natural Sciences: Ottawa, Ontario, Canada. 446 pp.
Coutant, C. C. and C. D. Becker. 1970. Growth of the Columbia River limpet,
Fisherola nuttalli (Haldeman), in normal and reactor-warmed water. In:
Radionuclides in Ecosystems, 3rd National Symposium on Radioecology: 561568.
Deixis MolluscDB database. 2012. An unpublished collection of mollusk
records maintained by Ed Johannes.
Frest, T. J. 1999. A review of the land and freshwater mollusks of Idaho. Final
report prepared for Idaho Conservation Data Center, Idaho Department of Fish
and Game, Boise, Idaho. 281 pp. + appendices.
Frest, T. J. and E. J. Johannes. 1992. Distribution and Ecology of the Endemic
and Relict Mollusc Fauna of Idaho TNC's Thousand Springs Preserve. Prepared
for The Nature Conservancy of Idaho by Deixis Consultants, Seattle,
Washington.
Frest, T. J. and E. J. Johannes. 1995. Interior Columbia Basin mollusk species
of special concern. Final report to the Interior Columbia Basin Ecosystem
Management Project, Walla Walla, WA. Contract #43-0E00-4-9112. 274 pp.
plus appendices.
Frest, T. J. and Johannes, E. J. 2000. An annotated checklist of Idaho land
and freshwater mollusks. Journal of the Idaho Academy of Science 36(2): 1-51.
GeoBOB Database. GIS export provided to Sarah Foltz Jordan, Xerces, by
Diane Stutzman, GeoBob Coordinator, 30 Jan 2013.
Haldeman, S. S. 1841. Descriptions of two new freshwater snails. Proceedings
of the Academy of Natural Sciences of Philadelphia, 1: 78-79.
8
Hannibal, H. 1912. A synopsis of the recent and tertiary freshwater mollusca of
the Californian Province, based upon an ontogenetic classification. Proc. Malac.
Soc. Lond. X(II):112-165.
Hyman, L. L. 1967. The invertebrates. Vol VI. Mollusca I. McGraw-Hill, New
York. 792 pp.
Johnson, P. D., Bogan, A. E., Brown, K. M., Burkhead N. M., Cordeiro J. R., et
al. 2013. Conservation status of freshwater gastropods of Canada and the
United States. Fisheries 38(6): 247-282.
Montana.gov. 2013. Shortface lanx (Fisherola nuttalli). Field Guide. Available
at: http://fieldguide.mt.gov/detail_IMGASL6010.aspx (Accessed 25 June
2013).
NatureServe. 2013. “Fisherola nuttalli.” NatureServe Explorer: An online
encyclopedia of life [web application]. Feb. 2009. Version 7.1. NatureServe,
Arlington, Virginia. Available at: http://www.natureserve.org/explorer/
(Accessed 18 June 2013).
Neitzel, D. A. and T. J. Frest. 1989. Survey of Columbia River Basin streams for
giant Columbia River spire snail Flumincola columbiana and Great Columbia
River limpet Fisherola nuttalli. Tech. Rep. #PNL7103, Battelle Pacific Northwest
Labs. 59 pp.
Neitzel, D. A., and T. J. Frest. 1990. Survey of Columbia River Basin Streams
for Columbia Pebblesnail and Shortface Lanx, Fisheries. 15(2):2-3.
Neitzel, D., and T. Frest. 1992. Survey of Columbia River Basin Streams for
Columbia pebblesnail Fluminicola columbiana and shortface lanx Fisherola
nuttalli. PNL-8229, Pacific Northwest Laboratory, Richland, Washington.
Neitzel, D. A., and T. J. Frest. 1993. Survey of Columbia River Basin Streams
for Columbia Pebblesnail (Fluminicola columbiana) and Shortface Lanx
(Fisherola nuttalli). PNL-8229, Revision 1, Pacific Northwest Laboratory,
Richland, Washington.
Oregon Biodiversity Information Center. 2013. Data provided by Eleanor
Gaines, Portland State University, July 2013.
Richards, D. C., Falter, C. M., Lester, G. T., and Myers, R. 2005. Additional
Information Request Ar-2: Listed Mollusks. Final report to the Idaho Power
Company. Hells Canyon Project FERC #P-1971-079. 180 pp.
9
Stagliano, D.M., G.M. Stephens, and W.R. Bosworth. 2007. Aquatic
invertebrate species of concern on USFS Northern Region lands. Report
prepared for USDA Forest Service, Northern Region, Missoula, Montana.
Montana Natural Heritage Program, Helena, Montana and Idaho Conservation
Data Center, Boise, Idaho. Agreement number 05-CS-11015600-036. 95 pp. +
app.
Taylor, D. W. 1982. Status report on the Giant Columbia River Limpet in
southwestern Idaho. Unpublished report to the BLM. 7 pp.;
U.S. Department of Agriculture (USDA) Forest Service. 2008. Gifford Pinchot
National Forest Invasive Plant Treatment FEIS Columbia River Gorge National
Scenic Area, Washington side. Appendix C; Brief Life History Narratives for
Botanical, Wildlife, and Fish Species of Local Interest.
U.S. Department of Agriculture (USDA) Forest Service. 1996. Status of the
interior Columbia basin: summary of scientific findings. Gen. Tech. Rep. PNWGTR-385. Portland, OR: U.S. Department of Agriculture, Forest Service, Pacific
Northwest Research Station; U.S. Department of the Interior, Bureau of Land
Management. 144 p.
U.S. Fish and Wildlife Service (USFWS). 2006. Banbury Springs Lanx (Lanx n
sp.) (undescribed) 5-Year Review: Summary and Evaluation. Snake River Fish
and Wildlife Office, Boise, Idaho.
U.S. National Museum (USNM). 2013. Smithsonian National Museum of
Natural History: Invertebrate Zoology Collection. Online database
http://collections.nmnh.si.edu/search/iz/ (Accessed June 2013).
ATTACHMENT 2:
List of pertinent or knowledgeable contacts
Ed Johannes, Deixis Consultants, Seattle-Tacoma, Washington.
Robert Hershler. Smithsonian National Museum of Natural History,
Washington DC.
10
ATTACHMENT 3:
Map of species’ distribution
Known records of Fisherola nuttalli in Oregon and Washington, relative to BLM
and Forest Service land.
11
Known records of Fisherola nuttalli in the Methow River area, in proximity to
Okanogan National Forest and BLM land in the Spokane District.
12
ATTACHMENT 4:
Photographs of this species
Fisherola nuttalli, lateral and dorsal views. Note the anterior (vs. central)
position of the apex. Photographs copyright © 2006 Orma J. Smith Museum of
Natural History, used with permission. Available at:
http://www.stitchingnature.com/Snails/Mollusca/Gastropoda/Lymnaeidae/L
ymnaeidae008.htm
ATTACHMENT 5:
for this species:
Aquatic Gastropod Survey Protocol, including specifics
Survey Protocol
Taxonomic group:
Aquatic Gastropoda
How:
Please refer to the following documents for detailed mollusk survey
methodology:
1. General collection and monitoring methods for aquatic mollusks (pages 6471):
Frest, T.J. and E.J. Johannes. 1995. Interior Columbia Basin mollusk
species of special concern. Final report: Interior Columbia Basin
Ecosystem Management Project, Walla Walla, WA. Contract #43-0E00-49112. 274 pp. plus appendices.
13
2. Standard survey methodology that can be used by field personnel to
determine presence/absence of aquatic mollusk species in a given waterbody,
and to document species locations and habitats in a consistent format:
Duncan, N. 2008. Survey Protocol for Aquatic Mollusk Species:
Preliminary Inventory and Presence/Absence Sampling. Version 3.1.
Portland, OR. Interagency Special Status/Sensitive Species Program.
U.S. Department of Interior, Bureau of Land Management,
Oregon/Washington and U.S. Department of Agriculture, Forest Service,
Region 6. 52 pp. [Available at:
http://www.fs.fed.us/r6/sfpnw/issssp/species-index/faunainvertebrates.shtml].
Species-specific Survey Details:
Fisherola nuttalli
Where: Fisherola nuttalli was historically widespread, with populations
scattered throughout the lower Columbia and Snake Rivers as well as some of
their major tributaries. Currently, large populations of F. nuttalli are known in
only four streams: the lower Deschutes River, Oregon; the Okanogan River and
the Hanford Reach of the Columbia River, Washington; and the Snake River in
Oregon and Idaho (Neitzel & Frest 1992). Additional small populations are
found the John Day and Imnaha Rivers, Oregon; the lower Columbia River
near Bonneville Dam, Oregon; the Methow River, Washington; the Grande
Ronde River, Washington and Oregon; and the Salmon River, Idaho (Neitzel &
Frest 1992; Frest & Johannes 1995, 2000; Frest 1999; Richards et al. 2005;
USNM 2013).
Although F. nuttalli has received a significant amount of survey attention in
Oregon and Washington, detections of the species have been very low (Neitzel &
Frest 1989, 1991, 1992). For example, Neitzel & Frest (1992) conducted
targeted surveys for this species at over 500 sites in more than 30 streams in
the Columbia River Basin, and detected this species in just nine streams. Since
many of the known sites have not been visited in over two decades (Neitzel &
Frest 1989, 1991, 1992, Deixus MolluskDB 2013), surveys designed to
determine the current status of this species at known sites are recommended.
Additional surveys for this species at new sites may also be useful. In
Washington, surveys of new sites should focus on Okanogan National Forest
and Spokane District BLM land in the Methow River area, since the species is
currently considered Suspected on these lands based on proximity to known
sites.
Habitat: The known habitat for this species is described as relatively large
perennial rivers and streams ranging from 30-100 m (98-300 ft.) wide. Within
such streams, it is most abundant in highly oxygenated environments on
gravel to boulder stable substrates. It may occur in the main channels of fast14
flowing streams and rivers, and on diatom-covered rocks or stable boulder or
bedrock substrates, often in the vicinity of rapids (Neitzel and Frest 1989). In
an assessment of Hells Canyon Dam (Snake River, Idaho), F. nuttalli was found
on cobbles in higher velocity areas of the stream much more frequently than
any other mollusk species; this was considered to reflect the species’ preference
to attach themselves to hard surfaces in high velocities to avoid competition
with other species (Richards et al. 2005). The species occurs most commonly in
rapids' edges or immediately downstream from sizable rapids in areas with
suitable substrate (Neitzel and Frest 1992).
Fisherola nuttalli becomes much less common or absent in major rapids, and
avoids the most violent white water areas (Neitzel & Frest 1992). In addition,
the species has not been found in areas with slow flow; silt or mud substrates;
warm water; massive seasonal discharges that destabilize the substrate; an
abundance of macrophytes (aquatic plants) or epiphytic algae; a bedrock
substrate; stream reaches with unstable substrate such as rivers with high
gradients (e.g., the Selway and Lochsa rivers, Idaho, and the Klickitat River,
Washington); streams with glacial flour (fine ground-up sand and stone, e.g.,
the Hood River, Oregon); the central deep areas in strongly channelized
streams; or places impacted by dredging or mining occurs (Neitzel & Frest
1992, Frest & Johannes 1995, Frest 1999, Richards et al. 2005). Reports of F.
nuttalli from even very large spring complexes, for example, Box Canyon, Idaho
are erroneous (the Box Canyon lanx is an undescribed species of Lanx) (Neitzel
& Frest 1992).
When: This species is present year-round but is not active in winter. Surveys
are recommended from April to October, the time frame during which most of
the known specimens have been collected (Deixis MolluscDB 2013,
Smithsonian Database 2013, Neitzel & Frest 1992, GeoBOB 2013). In the
Columbia River Basin, Neitzel & Frest (1992) chose to conduct surveys for this
species during late summer and early fall, a schedule that coincided with the
more successful collections at Hanford Reach. In addition, water levels are
lowest and stream surveys are the safest at this time of year. Deixis surveys for
this species have been conducted in all months except January and February
(Neitzel & Frest 1992).
15