(DRAFT) - Taxonomy
Species DARTER, SNAIL
Species Id ESIS254004
Date 13 MAR 96
TAXONOMY
NAME - DARTER, SNAIL
OTHER COMMON NAMES - DARTER and SNAIL
ELEMENT CODE -
CATEGORY - Fish
PHYLUM AND SUBPHYLUM - CHORDATA,
CLASS AND SUBCLASS - OSTEICHTHYES,
ORDER AND SUBORDER - PERCIFORMES,
FAMILY AND SUBFAMILY - PERCIDAE,
GENUS AND SUBGENUS - PERCINA,
SPECIES AND SSP - TANASI,
SCIENTIFIC NAME - PERCINA TANASI
AUTHORITY -
TAXONOMY REFERENCES -
COMMENTS ON TAXONOMY -
Snail Darter
Percina tanasi Etnier, 1976
KINGDOM: Animal GROUP: Fish
FAMILY: Chordata CLASS: Osteichthyes
ORDER: Perciformes FAMILY: Percidae
The snail darter is a small, bottom-dwelling percid fish rarely
exceeding 3.4 inches in length (01). Percid, or perch-like, fish are
characterized by an elongate, cylindrical body, ctenoid (rough-edged)
scales, and spiny-rayed fins. The dorsal fin is divided into two
separate fins: an anterior spinous and posterior soft-rayed fin. The
general coloration of the snail darter is brown to brownish-gray with
a trace of green above and mostly white below. Four dorsal saddles
cross the back, with the most forward being centered under the
anterior end of the spinous dorsal fin and the rearmost contacting the
base of the caudal (tail) fin. These saddles fade down the sides. A
black bar extends vertically beneath the eye which has an
orange-yellow iris. The median fins are mostly clear with black
patterning and some yellow while the paired fins vary from mostly
clear to bright yellow-orange. For a far more detailed description
see Etnier (02).
Taxonomy - 1 (DRAFT) - Taxonomy
Species DARTER, SNAIL
Species Id ESIS254004
Date 13 MAR 96
To date no disagreement exists concerning Etnier's 1976
description and classification of Percina tanasi (02). Etnier (1976)
also includes an updated diagnosis and a key to the members of the
subgenus Imostoma (to which the snail darter belongs).
Type specimens of Percina tanasi are located at the University of
Tennessee, the Smithsonian Institution's National Museum of Natural
History, Cornell University, the Florida State Museum, the Illinois
Natural History Survey, Northeastern Louisiana State University, the
University of Alabama Ichthyological Collection, the Museum of Zoology
at the University of Michigan, and Oklahoma State University.
Additional specimens are located at the Tennessee Wildlife Resources
Agency in Nashville and the Tennessee Valley Authority Office of
Natural Resources in Norris, TN (02). The best written description of
this species is the original (02) which also includes photographs of
the fish. Additional photographs may be found in Starnes (03).
Deacon, et al. (04), Parker and Dixon (05), Page (06), and Kuehne and
Barbour (07), and there are illustrations in Hickman and Fitz (08).
Taxonomy - 2 (DRAFT) - Status
Species DARTER, SNAIL
Species Id ESIS254004
Date 13 MAR 96
STATUS
Coded Status
Alabama; Federal Threatened
Alabama; State Listed
Alabama; Unofficially Listed
Georgia; Federal Threatened
Georgia; State Recognized
Tennessee; State Listed
T: Federal Threatened
COMMENTS ON STATUS -
U.S. STATUSES AND LAWS:
The snail darter (Percina tanasi) has been designated a
Threatened species pursuant to the Endangered Species Act of 1973
(50 CFR 17.11; P.L. 93-205, 87 Stat. 884; 16 U.S.C. 1531-1540),
as amended. The species has this status wherever found including the
States of Alabama, Georgia, and Tennessee.
This species is protected by the Lacey Act (P.L. 97-79, as
amended; 16 U.S.C. 3371 et seq.) which makes it unlawful to import,
export, transport, sell, receive, acquire, or purchase any wild
animal (alive or dead including parts, products, eggs, or offspring):
(1) in interstate or foreign commerce if taken, possessed,
transported or sold in violation of any State law or
regulation; or
(2) if taken or possessed in violation of any U.S. law,
treaty, or regulation or in violation of Indian tribal law.
It is also unlawful to possess any wild animal (alive or dead
including parts, products, eggs, and offspring) within the U.S.
territorial or special maritime jurisdiction (as defined in
18 U.S.C. 7) that is taken, possessed, transported, or sold in
violation of any State law or regulation, foreign law, or Indian
tribal law.
RESPONSIBLE FEDERAL AGENCIES:
USFWS -Responsible for the management/recovery, listing, and
law enforcement/protection of this species.
All Federal agencies have responsibility to ensure that any
action authorized, funded, or carried out by that agency is not likely
to jeopardize the continued existence of the species or result in the
destruction or adverse modification of Critical Habitat (50 CFR 402),
and to utilize their authorities to carry out programs for the
conservation of the species.
STATE STATUSES AND LAWS:
STATE: Alabama
Status - 1 (DRAFT) - Status
Species DARTER, SNAIL
Species Id ESIS254004
Date 13 MAR 96
DESIGNATED STATUS: Nongame Wildlife Species
ADMINISTRATIVE AGENCY: Div. of Game and Fish
STATE STATUTES: Game and Fish Reg. 87-GF-7.
UNOFFICIAL LIST: Threatened; Mount, R.H. 1986. Vertebrate
Animals of Alabama in Need of Special
Attention. Ala. Agri. Expt. Sta., Auburn
Univ. 124 pp.
STATE: Georgia
DESIGNATED STATUS: Recognized Threatened
ADMINISTRATIVE AGENCY: Department of Natural Resources
STATE STATUTES: GA Game and Fish Code, GA Laws 1977, Page 396,
GA Code Ann., Sec. 45-101, et seq.
STATE: Tennessee
DESIGNATED STATUS: Endangered
ADMINISTRATIVE AGENCY: Wildlife Resources Agency
STATE STATUTES: TN Code Ann., Chapter 7, Sec. 11-1701 through
11-1715. Proclamations 75-15, 76-4 and
amendments.
INTERNATIONAL STATUSES, TREATIES, AND AGREEMENTS:
The snail darter is listed as Endangered in the IUCN Red Data
Book, Vol. 4, 1977.
ECONOMIC STATUSES:
This species has no cultural or commercial value. However, it
has some historic value in that it was the first fish species under
the Act to receive national recognition. The species also has
aesthetic and scientific value.
75/03/10:40 FR 11618/ - Notice of review
75/06/17:40 FR 25597/ - Proposed rule
75/10/09:40 FR 47506/ - Final rule, listed as Threatened
76/04/01:41 FR 13926/ - Final rule, Critical Habitat
81/01/27:46 FR 14652/ - Five year review
83/06/21:48 FR 33328/ - Notice of review
84/01/21:49 FR 06388/ - Prop. rule - reclass. as Thr./remove CH
84/06/05:49 FR 27510/ - Final rule - reclass. as Thr./remove CH
Status - 2 HABITAT ASSOCIATIONS
HABITAT - AQUATIC
INLAND AQUATIC
SOCIETY OF AMERICAN FORESTRY TYPES
SAF TYPE STAGE CLOSURE
Shortleaf Pine-Oak shrub--seedling
Shortleaf Pine-Oak young tree
Shortleaf Pine-Oak mature tree
Shortleaf Pine-Oak Old Growth
shrub--seedling
young tree
mature tree
Old Growth
LAND USE -
Industrial
Mixed Urban or Built-up Land
Cropland and Pasture
Deciduous Forest Land
Mixed Forest Land
Streams and Canals
Reservoirs
Strip Mines, Quarries, and Gravel Pits
Transitional Areas
NATIONAL WETLAND INVENTORY CODES
NWI NWICLS NWIMOD NWISPEC
2UB
Riverine, lower perennial UB3
Riverine, lower perennial UB2
Riverine, lower perennial UB1
Riverine, lower perennial RB2
Riverine, lower perennial RB1
Lacustrine, limnetic UB4
Lacustrine, limnetic UB3
Lacustrine, limnetic UB2
Lacustrine, limnetic UB1
Lacustrine, limnetic RB2
Lacustrine, limnetic RB1
COMMENTS ON HABITAT ASSOCIATIONS -
The snail darter's macrohabitat is several large streams and
rivers in the upper Tennessee River drainage in southeast Tennessee,
northwest Georgia, and northeast Alabama. These waters are associated
with a diverse assemblage of terrestrial habitats. Originally,
oak-pine and oak-hickory type forest systems predominated in most of
this area. Today, much of the original forests have been replaced by
agricultural land, ranging from pasture to intensive row-cropping, and
residential and urban land. Generally, alteration of few of these
habitat associations would have any impact on snail darters except
those which would directly affect the species' microhabitat discussed
below (See Reasons for Status narrative).
The limits on most environmental parameters, such as temperature,
pH, alkalinity, etc., required or preferred by the snail darter are
essentially unknown. What is apparently critical to the species'
Habitat Associations - 1 survival, however, are two types of microhabitat (03). Adults prefer
clean, gravel-sand shoals for feeding and almost certainly require
shoals that are relatively shallow or have a significant current for
successful reproduction. Survival of eggs and larval young is
dependent upon slackwater habitats such as deep pools or basins
downstream from the spawning sites. The existence of a few snail
darters in several Tennessee River reservoirs suggests that these
microhabitat requirements may be marginally met in those areas of the
reservoirs, but certainly the ideal occurrence of such habitat is
in relatively large, low-gradient, undisturbed rivers and streams with
alternating pools and riffles.
Habitat Associations - 2 (DRAFT) - Food Habits
Species DARTER, SNAIL
Species Id ESIS254004
Date 13 MAR 96
FOOD HABITS
TROPHIC LEVEL -
CARNIVORE
LIFESTAGE FOOD FOOD PART
General Arthropods
General Fish
General Zooplankton
General Crustaceans
General Molluscs
General Worms
Food Habits - 1 (DRAFT) - Environment Associations
Species DARTER, SNAIL
Species Id ESIS254004
Date 13 MAR 96
ENVIRONMENTAL ASSOCIATIONS
G = General A = Adult
LIM = Limiting RA = Resting Adult
J = Juvenile FA = Feeding Adult
RJ = Resting Juvenile BA = Breeding Adult
FJ = Feeding Juvenile P = Pupae
L = Larvae E = Egg
RL = Resting Larvae
FL = Feeding Larvae
LIFESTAGE ENVIRONMENTAL ASSOCIATIONS
G Aquatic Features: Pool areas
Environment Associations - 1 (DRAFT) - Life History
Species DARTER, SNAIL
Species Id ESIS254004
Date 13 MAR 96
LIFE HISTORY
FOOD HABITS:
The following is a general systhesis of two studies that have
been conducted to determine snail darter feeding habits (03,08) with
somewhat different results. By far the most important component of
the annual diet of adult snail darters is aquatic gastropods. These
are largely represented by Anculosa subglobosa and Physa spp. (snails)
as well as lesser numbers of such genera as Lithasia, Pleurocerca,
Menetus, and Ferrissia. One genus of clam, Sphaerium, is also eaten
in small numbers. All are swallowed whole and range in size up to
about 5 mm in diameter. Insects taken vary a great deal seasonally,
but are primarily represented by dipteran and trichopteran larvae
(chironomids, Simulium, Brachycentrus and Glossosoma predominate, but
including blepharicerids, tipulids, Hydropsyche, and Lepidostoma).
Ephemeropterans also contribute to a very small portion of the diet.
On a seasonal basis, the snail darter's diet is almost entirely
comprised of gastropods in fall and winter (80-90% of biomass
consumed), but is very diverse in the spring when Brachycentrus
etwoahensis (caddisfly) may be the primary food item (40% of biomass)
along with other insects and fish eggs (probably mostly cannibalized).
The summer diet is only slightly less varied with gastropods again
becoming predominant followed by large numbers of dipteran and
trichopteran larvae.
All juvenile snail darters examined have displayed a diet roughly
equivalent to adults with the only difference being size of prey items
due to gap size of the young. No larval snail darters have ever been
collected, but based on a study of Percina maculata (10) and benthic
samples of available prey taken in Starnes' study (03) it seems likely
that they feed on microcrustaceans such as copepods and cladocerans,
tardigrades, and small oligochaetes until large enough to feed on
small insects.
HOME RANGE/TERRITORY:
Non-territorial (03,08).
PERIODICITY:
Snail darters are apparently diurnal feeders at all life stages
(03) and have seasonal changes in diet (See Food Habits). They also
aggregate on the shallowest portions of gravel shoals in the swiftest
current during spawning season (February to April) with males doing so
shortly before females, then disperse in sometimes deeper waters the
rest of the year. Larvae that have drifted downstream following
spawning migrate back upstream during the late spring and summer as
juveniles.
MIGRATION PATTERNS:
Adult snail darters seasonally aggregate on the shallowest
portions of gravel shoals to spawn in the spring, moving probably not
more than a few tens of meters from deeper shoal areas. Following the
larval drift stage of early development, juvenile snail darters may
migrate upstream as much as several kilometers to the areas where
spawning occurred (03).
Life History - 1 (DRAFT) - Life History
Species DARTER, SNAIL
Species Id ESIS254004
Date 13 MAR 96
COVER/SHELTER REQUIREMENTS:
Two types of habitat are essential for strong snail darter
populations: relatively shallow gravel shoal areas with moderate to
swift current and deep slackwater pools in large stream and rivers.
Starnes (03) described such habitats in the Little Tennessee River
prior to inundation by the Tellico Reservoir. Shoals preferred by
Percina tanasi were typically in 0.3 to 0.7 meters of water with
currents of 0.25 to 0.7 or more meters per second, while pools
averaged 5 to 6 meters in depth with little or no current. Marginal
populations may be able to survive in somewhat less ideal habitats as
evidenced by the sightings of a few snail darters in Tennessee River
reservoirs.
REPRODUCTIVE SITE REQUIREMENTS:
Starnes (03) concluded that spawning of snail darters is "nearly
limited" to the swiftest portions of midchannel gravel shoals in
relatively shallow water (less than 0.5 m) while deeper shoals might
serve as marginal spawning habitat. Substrate in such areas consisted
of smooth gravel 4-10 cm in diameter impacted in sand. Water
temperature ranged from 5 to 16 degrees C during the spawning season,
but was near 11 degrees C near the peak of spawning in late February.
Evidence of apparent delayed spawning during periods of flooding and
visually cued aspects of spawning behavior (03) are indicators of the
probable necessity of good water clarity for successful spawning
activity.
REPRODUCTIVE CHARACTERISTICS:
Starnes (03) found that snail darters have a lifespan of one to
two years, spawning in both their first and second years if surviving.
TVA workers (08) also found a few three year old fish during spawning
seasons. Reproduction occurs once a year with the peak spawning
period in late February, though activity begins in early February and
continues through April. The average fecundity of the snail darter is
about 600 eggs (03). Spawning behavior may be characterized as
non-territorial (although in the past males may have maintained moving
territories under higher population densities) (03), with multiple,
promiscuous spawning and no parental care. Spawning is not entirely
random, however, in that snail darters tend to aggregate on swift
shallow shoals to reproduce. Details of spawning behavior are not
known with certainty, never having been observed in their entirety.
From what has been observed in Percina tanasi and other Percina, a
fairly elaborate courtship is involved with visual female solicitation
likely, followed by visual and tactile stimulation of the female by
the male (observed), culminating in the male mounting and clasping the
female and the pair quivering and spawning in synchrony (03).
PARENTAL CARE:
None.
POPULATION BIOLOGY:
The primary factor limiting snail darter population size and
numbers is the lack of suitable preferred habitats -- gravel shoal
Life History - 2 (DRAFT) - Life History
Species DARTER, SNAIL
Species Id ESIS254004
Date 13 MAR 96
areas with moderate to swift current where adults feed and reproduce
coupled with deep slackwater pools where semiplanktonic larvae
develop into juveniles. Survival and mortality rates have been
impossible to determine for young of the year snail darters, but
Starnes (03) estimated a mortality rate of greater than 85 pct.
and found mortality between the first and second years of life to be
75-80%. Few individuals survive to a third year and none older than 3
years have been taken. Thus turnover is nearly 100% every two years.
No one has attempted to estimate rate of increase or recovery
potential for the species due to lack of information. The overall sex
ratio for all collections made prior to and during Starnes' study (03)
was 1.1 males to 1 female and since snail darters are relatively
random and promiscuous spawners, he concluded an approximate 1.1 ratio
seemed likely. Density of populations on gravel shoals in the Little
Tennessee River varied seasonally and with depth from about 4
individuals/100 square meters in deeper waters and 8/100 square meters
in shallower areas with finer substrate (during a summer census) to
possibly as many as 40/100 square meters in spring spawning
aggregations(03).
SPECIES INTERRELATIONSHIPS:
Starnes (03) and TVA (08) noted several large potential predators
associated with snail darters, but concluded that none were probably
frequently preying upon the darter. Sculpins (Cottus carolinae), on
the other hand, appeared to be fairly significant predators of snail
darters on deeper shoals with coarser substrates. As mentioned in
the Food Habits section, very few prey species comprise the bulk of
the diet of Percina tanasi during different portions of the year.
These include the snails, Anculosa subglobosa and Physa, and the
caddisfly, Brachycentrus etowahensis.
OTHER LIFE HISTORY DESCRIPTORS:
Since it was not mentioned in any detail above, a brief summary
of early development and growth as described by Starnes (03) is
important. Following spawning, eggs drift freely for probably more
than 15 days before hatching. Larvae are essentially semiplanktonic,
likely feeding on microcrustaceans and possibly small benthic
microinvertebrates when near the bottom. These two stages are
extremely vulnerable and are subject to predation by many species
including adult snail darters prior to the transformation of the young
into benthic juveniles between 15-30 days after hatching. As
juveniles grow in size and strength they begin moving upstream,
appearing on shoal areas near where they were spawned begining in June
at an age of 3-4 months and 40 mm or less standard length (SL). By
spring one year old darters have attained 52-66 mm SL and by the
following spring are 67-74 mm SL. Those few surviving to 3 years of
age may reach a total length of 85 mm.
Life History - 3 (DRAFT) - Management Practices
Species DARTER, SNAIL
Species Id ESIS254004
Date 13 MAR 96
MANAGEMENT PRACTICES
RESULT MANAGEMENT PRACTICE
Beneficial Maintaining/Controlling Water Flow
Beneficial Controlling/Restricting Road Maintainance Actions
Beneficial Maintaining undisturbed/undeveloped areas
Beneficial Controlling pollution [thermal, chemical, physical]
Beneficial Controlling/Restricting Pesticide Use
Beneficial Controlling/Restricting Herbicide Use
Beneficial Controlling/Restricting Agricultural Practice
Beneficial Restricting Poaching
Adverse Harassment/Vandalism/Indiscriminate Killing
Existing Harassment/Vandalism/Indiscriminate Killing
Adverse Underground Mines
Existing Underground Mines
Adverse Surface Mines
Existing Surface Mines
Adverse Rural Residential/Industrial Areas
Existing Rural Residential/Industrial Areas
Adverse Siltation
Existing Siltation
Adverse Water Temperature Alteration
Existing Water Temperature Alteration
Adverse Reservoirs
Existing Reservoirs
Adverse Migration barriers
Existing Migration barriers
Adverse Dredging
Existing Dredging
Adverse Applying pesticides
Existing Applying pesticides
Adverse Environmental Contamination/Pollution
Existing Environmental Contamination/Pollution
Adverse
Existing
COMMENTS ON MANAGEMENT PRACTICES -
The primary reason for the present status of the snail darter is
simply habitat destruction. The fish is an inhabitant of relatively
silt free gravel shoals in the larger rivers and streams in the upper
Tennessee River drainage (01,03,09). This type of microhabitat has
now nearly been eliminated largely by impoundments throughout the
system in addition to other forms of alteration such as siltation,
channelization, dredging, etc. Remaining populations of snail darters
are susceptible to all of the above types of habitat destruction
(although additional impoundment throughout the species' range is
unlikely) in addition to more localized threats to relatively
restricted and isolated populations. Biggins (01) summarizes these on
a population-by-population basis: channelization, dredging and port
facility development in the Paint Rock and Tennessee Rivers, acid
spills from train wrecks in the Hiwassee River, pollution and
Management Practices - 1 (DRAFT) - Management Practices
Species DARTER, SNAIL
Species Id ESIS254004
Date 13 MAR 96
siltation from mining activities in the Sequatchie and Hiwassee
Rivers, industrial and urban waste-water pollution in the Chattanooga
area, and siltation and pesticides from agricultural practices in the
Paint Rock River. Additionally, due to the species' notoriety,
intentional kills are a threat.
Possible future threats include all those described above. In
addition, land uses potentially adversely affecting snail darter
habitats include agricultural, forestry and logging, mining and any
construction practices that might increase siltation and turbidity in
rivers, especially in the early spring during spawning. Pollution
from industry, urban wastes, or in the form of pesticides from
agriculture would also adversely affect snail darters. Finally, urban
and industrial development of floodplains encourages flood-control and
navigation enhancing measures such as channelization and impoundment
which destroy snail darter habitat.
APPROVED PLAN:
U.S. Fish and Wildlife Service. 1983. Snail Darter Recovery Plan.
U.S. Fish and Wildlife Service, Atlanta, GA. 46 pp.
Recovery actions for the snail darter include:
(1) Utilize existing regulations to protect the species and its
habitat. The protection of the five known Tennessee River tributary
populations is crucial to recovery, unless the main stem Tennessee
River is found to contain populations which can survive and
reproduce without tributary rivers or other tributary populations are
found.
(2) Determine the distribution and status of the species in the main
stem of the Tennessee River.
(3) Determine present and forseeable threats to the species. Impacts
which may need investigation include agricultural practices, herbicide
and pesticide use, pollutants, land development, road maintenance,
channelization, impoundments, and poaching.
(4) Assess the viability of known populations and monitor those
populations.
Except for enforcement of existing regulations, no recovery work
is presently being conducted for this species.
Management Practices - 2 (DRAFT) - References
Species DARTER, SNAIL
Species Id ESIS254004
Date 13 MAR 96
References
***** REFERENCES FOR ALL NARRATIVES EXCEPT N-OCCURRENCE *****
01 Biggins, R.G. 1984. Endangered and threatened wildlife and
plants: proposal to reclassify the snail darter (Percina tanasi)
from an endangered species to a threatened species and rescind
critical habitat designation. Fed. Reg. 49(35):6388-6389.
02 Etnier, D.A. 1976. Percina (Imostoma) tanasi, a new percid fish
from the Little Tennessee River, Tennessee. Proc. Wash. Biol. Soc.
88(44):469-645.
03 Starnes, W.C. 1977. The ecology and life history of the
endangered snail darter, Percina (Imostoma) tanasi Etnier. Ph.D.
Diss., Univ. Tenn., Knoxville. 143 pp.
04 Deacon, J.E., et al. 1979. Fishes of North America: endangered
threatened or of special concern. Fisheries 4(2):29-44.
05 Parker, W. and L. Dixon. 1980. Endangered and threatened wildlife
of Kentucky, North Carolina, South Carolina and Tennessee. N.C.
Agric. Extn. Serv., Raleigh. 166 pp.
06 Page, L.M. 1983. Handbook of Darters. T.F.H. Publications, Inc.
Ltd., Neptune City, NJ. 271 pp.
07 Kuehne, R.A. and R.W. Barbour. 1983. The American darters. Univ.
Press of Kent., Lexington. 177 pp.
08 Hickman, G.D. and R.B. Fitz. 1978. A report on the ecology and
conservation of the snail darter (Percina tanasi Etnier) 1875-1977.
TVA Tech. Note B28. 129 pp.
09 Etnier, D.A. 1984. Personal communication. Zoology Department,
Univ. Tenn., Knoxville, TN 37996.
10 Thomas, D.L. 1970. An ecological study of four darters of the
genus Percina (Percidae) in the Kaskaskia River, Illinois. Ill.
Nat. Hist. Surv. Biol. Note No. 70.
***** REFERENCES FOR N-OCCURRENCE NARRATIVE ONLY *****
01 Etnier, D.A. 1984. Personal communication. Zoology Department,
University of Tennessee, Knoxville, TN 37996.
02 Tennessee Valley Authority. 1984. TVA Regional Heritage Project.
Computer printout, TVA Office of Natural Resources, Norris, TN.
03 Hickman, G.D. and R.B. Fitz. 1978. A report on the ecology and
conservation of the snail darter (Percina tanasi Etnier) 1975 -
1977. TVA Tech. Note B28. 129 pp.
04 Biggins, R.G. 1984. Endangered and threatened wildlife and
plants; proposal to reclassify the snail darter (Percina tanasi)
from an endangered species to a threatened species and rescind
critical habitat designation. Fed. Reg. 49(35):6388-6392.
05 Starnes, W.C. 1977. The ecology and life history of the
endangered snail darter, Percina (Imostoma) tanasi Etnier. PhD.
Diss., Univ. Tenn., Knoxville, TN. 143 pp.
References - 1