(DRAFT) - Taxonomy
Species TOPMINNOW, GILA
Species Id ESIS252015
Date 14 MAR 96
TAXONOMY
NAME - TOPMINNOW, GILA
OTHER COMMON NAMES - TOPMINNOW, GILA;TOPMINNOW, YAQUI; MINNOW, GILA; TOPMINNOW and SONORAN; TOPMINNOW
ELEMENT CODE -
CATEGORY - Fish
PHYLUM AND SUBPHYLUM - CHORDATA,
CLASS AND SUBCLASS - OSTEICHTHYES,
ORDER AND SUBORDER - ATHERINIFORMES,
FAMILY AND SUBFAMILY - POECILIIDAE,
GENUS AND SUBGENUS - POECILIOPSIS,
SPECIES AND SSP - OCCIDENTALIS,
SCIENTIFIC NAME - POECILIOPSIS OCCIDENTALIS
AUTHORITY -
TAXONOMY REFERENCES -
COMMENTS ON TAXONOMY -
Gila Topminnow
Poeciliopsis occidentalis (Baird & Girard, 1853)
KINGDOM: Animal GROUP: Fish
PHYLUM: Chordata CLASS: Osteichthyes
ORDER: Atheriniformes FAMILY: Poeciliidae
Poeciliopsis occidentalis is a small sexually-dimorphic fish with
males rarely exceeding 30 mm standard length (SL), and females rarely
exceeding 50 mm SL (27,35). In both sexes SL exceeds body depth by 3
(often 4) times, dorsal profile is slightly concave, the mouth is
small and superior, and dorsal and caudal fins are rounded to almost
square. Dorsal and anal fins originate about 2/3 of the SL posterior
from the head (27). Females' anal and dorsal fins are similar, but
the anal fin of males is modified to form a spike-like intromittent
organ or gonopodium (27,35). Fin rays are outlined with melanophores
with no dark spots between rays (27). Body scales are also outlined
with melanophores and a dark lateral line is usually present.
Although background coloration varies, most topminnows are cream to
light brown with tinges of greenish-blue iridescence (27,35,38).
Territorial males are entirely black except for yellowish dorsal,
anal, and caudal fins (27,35,38). The gonopodium may be blood red
Taxonomy - 1 (DRAFT) - Taxonomy
Species TOPMINNOW, GILA
Species Id ESIS252015
Date 14 MAR 96
(35). Teeth of P. occidentalis are spatulate (20).
The Gila and Yaqui topminnows have been separated or lumped
taxonomically by various authors since their original descriptions in
1853 and 1859 respectively. A chronological taxonomy for each
subspecies follows (11,27).
Poeciliopsis o. occidentalis
Heterandria occidentalis (1)
Girardinus occidentalis (9)
Girardinus sonoriensis (6)
Poecilia occidentalis (8)
Molliensia occidentalis (7)
Poeciliopsis occidentalis (12)
Arizonichthys psammophilus (30)
Poeciliopsis occidentalis occidentalis (26)
Poeciliopsis occidentalis sonoriensis (4)
Girardinus sonoriensis (9)
Girardinus occidentalis (17)
Poecilia occidentalis (8)
Heterandria occidentalis (16)
Poeciliopsis occidentalis (12)
Poeciliopsis sp. (25)
Poeciliopsis "F" (24)
Poeciliopsis sonoriensis (23)
Poeciliopsis occidentalis sonoriensis (26)
Although P. occidentalis is identified as the Gila topminnow in
the Federal Register (39), the Association of Systematic Collections
(43), the American Fisheries Society (33), and most ichthyologists
working with the fish use this common name to mean the Gila
subspecies (P. o. occidentalis) only. Yaqui topminnow commonly
refers to the other subspecies P. occidentalis sonoriensis. The
species as a whole, P. occidentalis, is usually referred to as the
Sonoran topminnow. Hendrickson (11) gives justification for these
names, which is based on distribution of the species and subspecies
relative to the areas identified by the modifiers: Sonoran, Gila,
and Yaqui. Most work subsequent to Hendrickson's (11), including
the Topminnow Recovery Plan (40), has adopted these conventions.
Often authors are not explicit in their taxonomic meaning,
however, or do not follow these guidelines. It is not uncommon
for P. occidentalis or one of it's subspecies to be called the
"Gila Minnow" or simply "Topminnow". Moreover, P. occidentalis is
often confused with Gambusia affinis (mosquitofish) which it resembles
very closely (20).
Distinguishing information and photographs are given for both
subspecies in Minckley (27). A color photograph of a female and
non-territorial male is given in Johnson (15). Photographs of a
female and territorial male P. occidentalis, and the easily confused
G. affinis are given in Meffe (20) (Figures 1), as are
photomicrographs of the teeth of each species (Figure 5). Tooth
Taxonomy - 2 (DRAFT) - Taxonomy
Species TOPMINNOW, GILA
Species Id ESIS252015
Date 14 MAR 96
morphology and position are two of the best characters for
distinguishing P. occidentalis from G. affinis (20,27,38).
Collections of P. occidentalis exist in the Collection of Fishes,
Department of Zoology, Arizona State University, and the Museum of
Zoology, University of Michigan.
Taxonomy - 3 (DRAFT) - Status
Species TOPMINNOW, GILA
Species Id ESIS252015
Date 14 MAR 96
STATUS
Coded Status
E: Federal Endangered
COMMENTS ON STATUS -
U.S. STATUSES AND LAWS:
The Gila topminnow (Poeciliopsis occidentalis) has been
designated an Endangered 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 Arizona and New Mexico, and Sonoran, Mexico.
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 foreign law; 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 (the San Carlos Apache Tribe to this date has no tribal
laws protecting this species).
RESPONSIBLE FEDERAL AGENCIES:
USFWS -Responsible for the management/recovery, listing, and
law enforcement/protection of this species.
BIA -Responsible for the law enforcement/protection of this
species with applicable State and Federal laws on
public lands under their control. Also responsible
for management/recovery on Bureau of Indian Affairs
lands.
BLM -Responsible for the law enforcement/protection of this
species with applicable State and Federal laws on
public land under their control (43 CFR 4140). Also
responsible for management/recovery on Bureau of Land
Status - 1 (DRAFT) - Status
Species TOPMINNOW, GILA
Species Id ESIS252015
Date 14 MAR 96
Management lands.
DOD -Responsible for the law enforcement/protection of this
species with applicable State and Federal laws on
public land under their control. Also responsible for
management/recovery on Department of Defense lands.
NPS -Responsible for the law enforcement/protection of this
species with applicable State and Federal laws on
public lands under their control. Also responsible
for conservation (Nat. Park System Organic Act - 16
U.S.C. 1, 2-3)/management/recovery on National Park
Service lands. Taking, possessing, or disturbing of
Federally listed species is prohibited on NPS lands
(36 CFR 2.1, 2.2, and 2.3).
USFS -Responsible for the law enforcement/protection of this
species with applicable State and Federal laws on
public lands under their control. Also responsible
for management/recovery on Forest Service lands. The
Forest Service is responsible for integrating
management, protection, and conservation of Federally
listed species into the Forest Planning process
(36 CFR 219.19 and 219.20). Management practices that
would cause detrimental changes in water temperature
or composition, water course blockage, or sediment
deposits within 100 feet of the edges of perennial
streams, lakes or other bodies of water are prohibited
(36 CFR 219.27(e)).
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: Arizona
DESIGNATED STATUS: Group 3; a species or subspecies whose
continued presence in Arizona could be in
jeopardy in the foreseeable future.
ADMINISTRATIVE AGENCY: Arizona Dept. of Game and Fish
STATE STATUTE: Arizona Revised Statutes, Sect. 17-231(B)7
STATE: New Mexico
DESIGNATED STATUS: Endangered, Group 2, those species or
subspecies whose prospects of survival or
recruitment in the State are likely to be in
jeopardy within the foreseeable future.
ADMINISTRATIVE AGENCY: New Mexico Dept. of Game and Fish
STATE STATUTE: New Mexico Statutes Annotated 17-2-37 to 17-2-46
STATE: Sonoran, Mexico
DESIGNATED STATUS: None.
Status - 2 (DRAFT) - Status
Species TOPMINNOW, GILA
Species Id ESIS252015
Date 14 MAR 96
INTERNATIONAL STATUSES, TREATIES, AND AGREEMENTS:
The Gila topminnow is listed as "vulnerable" in the 1986 IUCN Red
List of Threatened Animals, but was listed as "endangered" in the 1977
IUCN Red Book. It is also listed by the U.S. in the Convention of
Nature Protection and Wildlife Preservation in the Western Hemisphere
Annex, 1970.
ECONOMIC STATUSES:
The Gila topminnow has value as a component of Arizona's natural
heritage and biotic diversity.
67/03/11:32 FR 40001/ - Listed as Endangered
70/08/25:35 FR 13519/13520 - Proposed rule making
70/10/13:35 FR 16047/16048 - Notice of review
75/05/16:40 FR 21499/21500 - Notice of intent (Critical Habitat)
79/05/21:44 FR 29566/29577 - Notice of status review
85/07/22:50 FR 29901/29909 - Notice of review
87/07/07:52 FR 25522/ - Notice of 5-year review completion
Status - 3 HABITAT ASSOCIATIONS
HABITAT - AQUATIC
INLAND AQUATIC
LAND USE -
Herbaceous Rangeland
Shrub and Brush Rangeland
Mixed Rangeland
Deciduous Forest Land
Mixed Forest Land
Streams and Canals
Forested Wetland
Nonforested Wetland
NATIONAL WETLAND INVENTORY CODES
NWI NWICLS NWIMOD NWISPEC
Riverine, intermittent UB4
Riverine, intermittent UB3
Riverine, intermittent UB2
Riverine, intermittent UB1
Riverine, intermittent SB4
Riverine, intermittent SB3
Riverine, intermittent SB2
4SB
Riverine, intermittent RS2
Riverine, intermittent RS1
Riverine, intermittent RB2
Riverine, intermittent RB1
Riverine, intermittent OW0
Riverine, intermittent FL6
Riverine, intermittent FL5
Riverine, intermittent FL4
Riverine, intermittent FL3
Riverine, intermittent FL2
4FL
Riverine, intermittent AB5
Riverine, intermittent AB4
Riverine, intermittent AB3
Riverine, intermittent AB2
Riverine, intermittent AB1
Riverine, upper perennial UB4
Riverine, upper perennial UB3
Riverine, upper perennial UB2
Riverine, upper perennial UB1
Riverine, upper perennial SB4
3SB
Riverine, upper perennial SB2
Riverine, upper perennial SB1
Riverine, upper perennial RS2
Riverine, upper perennial RS1
Riverine, upper perennial RB2
Riverine, upper perennial RB1
Riverine, upper perennial OW0
Riverine, upper perennial FL6
Riverine, upper perennial FL5
Riverine, upper perennial FL4
Habitat Associations - 1
NWI NWICLS NWIMOD NWISPEC
3FL
Riverine, upper perennial FL2
Riverine, upper perennial FL1
Riverine, upper perennial AB5
Riverine, upper perennial AB4
Riverine, upper perennial AB3
Riverine, upper perennial AB2
Riverine, upper perennial AB1
Palustrine UB4
Palustrine UB3
Palustrine UB2
0UB
Palustrine SS6
Palustrine RB2
Palustrine RB1
Palustrine OW0
Palustrine FO1
Palustrine FL6
Palustrine FL5
Palustrine FL4
Palustrine FL3
Palustrine FL2
0FL
Palustrine EM6
Palustrine EM5
Palustrine EM4
Palustrine EM3
Palustrine EM2
Palustrine EM1
Palustrine AB5
Palustrine AB4
Palustrine AB3
Palustrine AB2
Palustrine AB1
COMMENTS ON HABITAT ASSOCIATIONS -
Poeciliopsis occidentalis (Gila topminnow) prefers the
sluggish, shallow margins of freshwater lotic habitats in southern
Arizona and Mexico below about 1500 meters elevation (11,27,40).
Once abundant in these habitats (13), today P. occidentalis exists in
very few, mostly isolated, sites (37). Populations persist in
isolated waters largely because these are least often contaminated by
exotic fishes (20, 29). Some populations have exotics anyway due to
movements by man or by the fish themselves during wet periods (20).
Although P. occidentalis is normally lost from a site after
contamination, coexistence may occur, at least temporarily, if floods
are frequent enough (18). Floods promote coexistence because exotics
are harmed more than natives during such events (18).
In the United States natural populations of P. occidentalis
persist in 7 spring systems and 5 intermittent streams (20,37). These
habitats include: 1) mature marshland (or "cienega") with rich organic
deposits, permanently saturated soils, and dense grass, hydrophytes,
debris, and canopy (20,28); 2) springheads and associated runs with
inorganic bottoms and well-oxygenated open flows bordered by dense
hydrophytes (20,37); and 3) isolated or intermittent streams with
sand, gravel, or bedrock bottoms, substantial subsurface flow, and
sparse to dense arid riparian vegetation (20,37). In any habitat
area cover such as downed logs is utilized by the Gila topminnow.
A summary of environmental regimes under which P. occidentalis
Habitat Associations - 2 exists naturally is given in Meffe (20). Ranges for various
parameters are: 6.0-36.7 C (temperature), 2.2-11 mgl-1
(dissolved O2), 300-5050 u ohms (conductivity), 1.1-5.9 meql-1
(alkalinity), 6.6-8.9 (pH), 2.2-15.2 mgl-1 (Cl), 0-563.0 mgl-1
(SO4-S), 1.3-11.1 mgl-1 (Si), 0-8.3 mgl-1 (NO3-N), 0-0.12 mgl-1
(solublereactive phosphate), and 0.001-0.017 mgl-1 (total dissolved
phosphate). In general, P. occidentalis tolerates a broad range of
environmental conditions and habitat types (20,35). In systems with
strong current, most P. occidentalis occur close to shore, among
debris, or in eddies, depressions, or other relatively quiet water
(27,38). In more lotic habitats, such as cienega pools,
P. occidentalis may occupy the entire water column (21,38). In at
least one stream P. occidentalis preferred the cover of algal mats
(32).
Man has also introduced P. occidentalis to at least 194 sites in
southern Arizona (02,03,37). Poeciliopsis occidentalis persisted at
38 of these sites in 1987 (37). These successful sites vary
tremendously and include earthen stockponds, artesian wells, isolated
springs, cement and metal watering troughs (in cattle feed
lots/holding pens), ditches/culvets, bedrock (plunge pool) drainages,
and cienega (37). Surrounding habitats include deciduous riparian,
desert, semi-desert grassland, rocky canyon, chaparral scrub,
pinyon-juniper forest, and mesquite bosque. Obviously, many of these
introduction sites differ substantially from natural habitats.
Multivariate classification analysis failed to identify habitat
characteristics which could predict reliably which sites would fail or
succeed (02). In a more subjective vein, common denominators for
success were permanence of water and lack of exotic fishes (02,03,37,
38). Probably as a result of flooding, several populations of
P. occidentalis were established up to 5 km downstream from
introduction sites. Nearly all P. occidentalis populations, both
natural and introduced, occur on livestock range -- though some sites
are fenced from cattle (02,03,37).
Habitat Associations - 3 (DRAFT) - Food Habits
Species TOPMINNOW, GILA
Species Id ESIS252015
Date 14 MAR 96
FOOD HABITS
TROPHIC LEVEL -
HERBIVORE
LIFESTAGE FOOD FOOD PART
General Bacteria
General Phytoplankton
General Diatoms
General Algae
General
General Zooplankton
General Arthropods
General Crustaceans
General Worms
General Carrion
Food Habits - 1 (DRAFT) - Environment Associations
Species TOPMINNOW, GILA
Species Id ESIS252015
Date 14 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
G
G Aquatic Features: Pool areas
G Aquatic Features: Springs [flowing]
G Inland Wetlands: Bogs
G Terrestrial Features: Depressions
G Terrestrial Features: Downed logs
G
G
Environment Associations - 1 (DRAFT) - Life History
Species TOPMINNOW, GILA
Species Id ESIS252015
Date 14 MAR 96
LIFE HISTORY
FOOD HABITS:
In present habitats, Poeciliopsis occidentalis (Gila topminnow)
feeds opportunistically on many items including organic detritus,
algae (Cyanophyta, Chlorophyta, and Chrysophyta), insects, and
crustaceans (27,31,35). Organic detritus is usually a major food
(31,35), but microfauna, especially amphipods, comprise nearly the
entire diet in some habitats (27,35). Poeciliopsis occidentalis
probably fed on a higher diversity of items when it occurred more
widely (27). Diets from four habitats are given below, first as
percent volume, and then as percent frequency (35).
LOCATION
(habitat type)
Monkey Spring Monkey Spring Page Springs Deer Valley
(artesian) (flume) (raceway) (pond)
SAMPLE
SIZE 174 178 34 64
FOOD TYPE:
(volume/frequency in percent)
Algae 87.8/87.8 trace/38.4 19.3/52.9 24.2/76.4
Diatoms 2.1/97.4 trace/48.2 trace/82.4 trace/trace
Amphipods trace/1.2 94.7/98.7 0/0 0/0
Chironomid trace/trace trace/trace 0/0 trace/trace
Heleidae trace/1.4 0/0 0/0 0/0
Culicidae trace/1.3 trace/trace 0/0 trace/trace
Organic 78.3/100.0 4.8/98.2 79.3/91.2 73.7/81.3
detritus
Inorganic 9.7/97.4 trace/96.5 2.4 trace/trace
detritus
Other items reportedly eaten by P. occidentalis include grass
seeds, Ostracodae, Hydropsychidae, Simuliidae, and Psephenidae (31,
35). Stomachs of P. occidentalis are never empty (35,31). Nematodes
reported in diets are probably parasites (31,35). P. occidentalis fed
vigorously on a dead cow in a natural habitat (14). Seasonal
variation in diets of P. occidentalis are not known, but probably
change with food availabilities. Choice experiments have for the most
part not been reported, but detritus seems to be a dietary mainstay if
not a preferred food (27,31,35). P. occidentalis teeth are spatulate
-- apparently well-adapted to a herbivorous rather than carnivorous
diet (20). Length of the intestine also suggests that P. occidentalis
is primarily herbivorous (35). Items observed in habitats with
P. occidentalis but not represented in diets include Naucoridae,
Planaria, copepods, snails, and rotifers (31,35).
Size influences diet in P. occidentalis (31). Juveniles and
males, which are smaller than females, are more inclined to eat
detritus (31). In both laboratory and nature the size of amphipods
Life History - 1 (DRAFT) - Life History
Species TOPMINNOW, GILA
Species Id ESIS252015
Date 14 MAR 96
eaten is positively correlated with size of female P. occidentalis
(31). In general, P. occidentalis eats the largest food items
available within size constraints of the fish's mouth (31).
Selectivity in P. occidentalis increases with time since the start of
a feeding bout (31). Intraspecific encounters cause both feeding
rates to increase and selectivity in smaller fish to decrease (31).
HOME RANGE/TERRITORY:
Quantitative information on territoriality and related parameters
is not available for P. occidentalis, and qualitative observations are
limited (27,35). Under favorable conditions, P. occidentalis exist in
dense numbers with a high frequency of intraspecific interactions.
Most interactions appear benign with juveniles, females, and some
males often feeding in close proximity to each other, usually without
obvious interaction (03). In both aquaria and nature, dark males
displace lighter males by chasing, and mate more frequently with
females (35,38). Females seem to swim and feed randomly without
regard to position of males. Since P. occidentalis is viviparous,
spawning sites are not used (20,35). Postpartum young are not
defended (35). Poeciliopsis occidentalis is often observed schooling
at the water surface, especially in response to disturbance such as
an approaching human (3). These schools may include all life stages
and both sexes (03). About 5 minutes after birth in aquaria,
P. occidentalis schooled in groups of 4 or 5 individuals (35).
PERIODICITY:
Densities of P. occidentalis peak during summer and decline, at
times precipitously, in winter (05,38,40). Reproduction is controlled
by temperature or photoperiod depending on habitat (05,35). In
habitats with variable temperatures, reproduction ceases in winter,
while in warm springs limited reproduction may occur in winter (05,27,
35). Brood size increases in summer (05). Topminnow appear fully
active at twilight (03), but information on nocturnal activity is
not available. Populational characteristics, such as length
frequency, vary with season and habitat in complex ways, and are
detailed by Constantz (05) and Schoenherr (35).
MIGRATION PATTERNS:
Migration by P. occidentalis is poorly understood, and has
limited possibilities in the isolated habitats presently occupied.
In once extensive and continuous habitats, such as along major rivers,
P. occidentalis may have migrated extensively. P. occidentalis has
moved up to 5 kilometers downstream -- possibly due to flooding (37).
Upstream migration occurs at least occasionally in P. occidentalis
(05), and frequently in some Poeciliopsis in Sonora, Mexico (42).
COVER/SHELTER REQUIREMENTS:
Two requirements are key: water, and escape from exotic
fishes -- especially Gambusia affinis (mosquitofish). Poeciliopsis
occidentalis can survive in the smallest of watered habitats with a
wide range of temperature and chemical conditions (02,20,35,37,38).
Poeciliopsis occidentalis cannot survive even temporarily without
water (27,37), nor in the presence of Gambusia affinis (20,27,29).
Life History - 2 (DRAFT) - Life History
Species TOPMINNOW, GILA
Species Id ESIS252015
Date 14 MAR 96
Flooding may ameliorate the presence of Gambusia affinis under rather
precise conditions, but even these situations are usually transitory
-- leading to a loss of P. occidentalis (18). Other habitat
characteristics which favor P. occidentalis include slow-moving
shallow water and algal mats or other forms of vegetative cover
(27,32,38).
REPRODUCTIVE SITE REQUIREMENTS:
Since P. occidentalis is viviparous and provides no postpartum
parental care, spawning, nesting, and nursery habitats are not
required. Special habitat is not necessary for growth of young
P. occidentalis (05,27). Large habitats and populations are
unnecessary, and minimum viable population size is low, based on the
long-term success of small founding populations in small habitats
(02,03,37,38,42).
REPRODUCTIVE CHARACTERISTICS:
P. occidentalis matures sexually at 4-12 months of age depending
on season of birth (05,35). Maximum breeding age is not known (05,
27). Breeding and reproduction may occur anytime (27), but peaks from
January to August, and shows strong site-specific tendencies (05,27).
Males chase females with a courtship display lasting several seconds
which terminates with internal fertilization by insertion of the
gonopodium into the female's genital aperture (35). Often females
flee these advances, but otherwise seem to swim and feed randomly with
respect to males (27,35,38). Mating relationships appear limited to
these ephemeral copulations. During active breeding nearly all
females are pregnant with two (occasionally three) simultaneous broods
of 1-22 young each in P. o. occidentalis, and 6-49 young in
P. o. sonoriensis (5,27,35). Interval between broods is about
24-28 days, and 12-15 days respectively (27). In P. o. occidentalis,
about 36 days are required for an individual ova to develop into a
free-living fry (35). Brood size increases with female size (35).
Individual fry are 4-5 mm Standard Length at birth (35).
PARENTAL CARE:
Poeciliopsis occidentalis does not exhibit parental care (35,05).
Discrepancies exist over whether P. occidentalis is cannibalistic
(05). If present at all, cannibalism is not pervasive (20,27,35).
POPULATION BIOLOGY:
P. occidentalis is limited in distribution by a scarcity of
suitable habitat (20,40). Currently, P. occidentalis exists naturally
only in isolated springs, in streams downstream from springs, or in
streams without exotic piscivorous fishes (18,27,29). Most other
historic habitats are now either impounded, dewatered, or infested
with exotic fishes (20). Poeciliopsis occidentalis is very
susceptible to fish predators -- possibly because it evolved in a
region historically depauperate of piscivorous fishes (27).
P. occidentalis exhibits a flexible life-history, capable of
adapting to a variety of conditions (05). In general, recruitment and
population fluctuations can be high (05,35,38). Within a single
population of P. o. occidentalis, generation time varied from 185 to
Life History - 3 (DRAFT) - Life History
Species TOPMINNOW, GILA
Species Id ESIS252015
Date 14 MAR 96
505 days, while fecundity (number of yolked eggs or embryos --
estimated by regression) varied from 3.6 to 19.7 (05). In an
experimental population at low density, females grew about 8 mm per
month. Although adult sex ratios reported from stabilized populations
ranged from 1.5 to 6.3 females per male, these estimates lumped small
unsexed fish as females, possibly biasing true sex ratios (35). Sex
ratio at birth is not known. Current management goals stress
establishment of additional introduced populations in suitable
habitat, especially populations which protect genetic diversity of
natural P. occidentalis populations (19,37).
SPECIES INTERRELATIONSHIPS:
Gambusia affinis undoubtably exerts the most significant
interspecific influence on P. occidentalis (20). G. affinis
eliminates P. occidentalis through predation and possibly competition
for space (20,27,29,35). Unless flooding purges G. affinis from a
habitat frequently, P. occidentalis is completely replaced, often
within one or two years (18,20,22). This relationship is directly,
though not wholly, responsible for P. occidentalis's endangered status
(20). Other exotic piscivorous fish also prey on P. occidentalis, but
normally are not small enough to displace P. occidentalis in its
preferred shallow habitats (20,27). Other predators include bullfrogs
(Rana catesbeiana; 36), and fishing spiders (Pisauridae), Naucoridae,
Odonate larvae, and Belostomatidae (05). Other likely predators
include snakes (especially Thamnophis), mud turtles (Kinosternon),
belted kingfisher (Megaceryle alcyon), herons, and leopard frogs (05,
35). Parasites of P. occidentalis include trematodes (Clinostomum)
and nematodes (35), although an exhaustive survey of parasites has not
been made for the species.
OTHER LIFE HISTORY DESCRIPTORS:
P. occidentalis and congeners are widely distributed and abundant
in Mexico and points southward (11,34). An all-female form of
Poeciliopsis occurs when P. monacha and P. occidentalis hybridize
(35). Genetic diversity in P. occidentalis was partitioned into
diversity: 1) within local colonies, 2) between colonies within
rivers, 3) between rivers within major geographic subdivisions, and
4) between major geographic subdivisions (41). Relative contribution
of these components to overall genetic diversity in the species was
21.3, 25.5, 0.4, and 52.8%, respectively (41).
Life History - 4 (DRAFT) - Management Practices
Species TOPMINNOW, GILA
Species Id ESIS252015
Date 14 MAR 96
MANAGEMENT PRACTICES
RESULT MANAGEMENT PRACTICE
Beneficial Restricting/regulating human disturbance of populations
Beneficial Maintaining/Controlling Water Flow
Beneficial Developing/maintaining/protecting wetlands
Beneficial Controlling water levels
Beneficial Land Acquisition
Beneficial Controlling pollution [thermal, chemical, physical]
Beneficial Controlling/Restricting Pesticide Use
Beneficial Controlling/Restricting Herbicide Use
Beneficial Controlling/Restricting Agricultural Practice
Beneficial Creating Artificial Habitat/Nesting Structure
Beneficial Reforestation
Beneficial Controlling/Removing Nonnative Vegetation
Beneficial Controlling/Removing Native Vegetation
Beneficial Stocking captive-reared wild-strain animals
Beneficial Transplanting wild animals
Beneficial Controlling/Removing Exotic Vertebrates
Adverse
Existing
Adverse Predation
Existing Predation
Adverse Surface Mines
Existing Surface Mines
Adverse Rural Residential/Industrial Areas
Existing Rural Residential/Industrial Areas
Adverse Recreational development
Existing Recreational development
Adverse Draining wetlands, marshes, ponds, lakes
Existing Draining wetlands, marshes, ponds, lakes
Adverse Flooding
Existing Flooding
Adverse Groundwater drawdown
Existing Groundwater drawdown
Adverse Irrigating
Existing Irrigating
Adverse Reservoirs
Existing Reservoirs
Adverse Migration barriers
Existing Migration barriers
Adverse Dredging
Existing Dredging
Adverse Developing/maintaining stream bank vegetation
Existing Developing/maintaining stream bank vegetation
Adverse Competition
Existing Competition
Adverse Exotic/Feral/Introducted Species
Existing Exotic/Feral/Introducted Species
Adverse Erosion
Existing Erosion
Adverse Grazing
Management Practices - 1 (DRAFT) - Management Practices
Species TOPMINNOW, GILA
Species Id ESIS252015
Date 14 MAR 96
RESULT MANAGEMENT PRACTICE
Existing Grazing
Adverse
Existing
Adverse Vegetation Composition Changes
Existing Vegetation Composition Changes
COMMENTS ON MANAGEMENT PRACTICES -
Poeciliopsis occidentalis is endangered for two reasons:
habitat destruction and modification (i.e., vegetation changes, water
drawdown and diversion, groundwater drawdown, wetland filling, passage
barriers, channel modification, bank modifaction and development,
agricultural development and practices, and erosion as a resultant
of any on/all of the above habitat destruction), and predation from
introduced exotic fishes (20,28,35). As Arizona was developed,
P. occidentalis's preferred habitat -- shallow waters -- was lost by
draining, channelization, arroyo-cutting, and impoundment (10,20,28,
35). P. occidentalis can survive in the smallest and simplest of
aquatic systems however (02,37), and probably could flourish in many
waters remaining today except for the presence of exotic piscivorous
fishes, especially Gambusia affinis (mosquitofish) (20,27,28).
Although any piscivorous fish might decimate P. occidentalis in
larger habitats (20), G. affinis is especially destructive since it
survives in the shallow habitats preferred by topminnows (27,35).
P. occidentalis has no refuge when G. affinis is present, and
replacement of the native by the exotic can occur within one year (20,
27,28,35). Gambusia affinis eats young P. occidentalis and the fins
of adults (27,35). These species may also compete for space (35).
These species coexists in mainstreams only when P. occidentalis has
sole access to headwater springs or other refugia (29), or if
flooding, which displaces G. affinis more than P. occidentalis, is
frequent enough (18). P. occidentalis also suffers from intense
flooding (04), and loss of habitat due to mine spoils (03,20), and
cattle (27).
The same threats remain today. Additional spread of exotic fish
(especially Gambusia affinis, the mosquito fish), or loss of remaining
habitat for P. occidentalis, should be avoided (40). Now that an
active reintroduction program for P. occidentalis is underway, one
new threat is genetic mixing, which could destroy differences between
natural lineages (19,38,41).
APPROVED PLAN:
U.S. Fish and Wildlife Service. 1984. Sonoran Topminnow (Gila and
Yaqui) Recovery Plan. U.S. Fish and Wildl. Serv., Albuquerque,
NM. 67 pp.
The prime objective of the recovery plan for the Gila topminnow
(Poeciliopsis occidentalis) is to improve its status to the point that
survival in the wild is secured. Maintenance, protection and
enhancement of existing Gila topminnow populations and their habitats
Management Practices - 2 (DRAFT) - Management Practices
Species TOPMINNOW, GILA
Species Id ESIS252015
Date 14 MAR 96
should include:
1. periodic (at least annually) standardized monitoring of Gila
topminnow populations (numbers, condition, and age structure of
fish) and those of its competitor Gambusia affinis, if present;
2. banning the introduction of non-native fishes;
3. stopping immigration of non-native fishes by building and
maintaining barriers into Gila topminnow habitat, where feasible;
4. petition the Arizona Game and Fish Department to remove Gambusia
affinis as a legal baitfish in the state,
5. remove Gambusia affinis (mosquitofish) and/or other undesirable
non-native fishes from topminnow habitats when detrimental, and;
6. improve occupied habitat and encourage sound land management within
each watershed. Management actions for this species includes:
a) controlling/removing native & exotic
vegetation (to improve marginal habitat),
b) revegetation/land rehabilitation,
c) creating artificial habitat/structure,
d) wetland management/modification,
e) maintain water table and stream flow,
f) limit human access/disturbance,
g) land acquistion,
h) controlling/restricting pollutants,
i) controlling/restrict pesticide and herbicide use, and
j) controlling/restricting impacts from agricultural
practices
Efforts should be made (agreements, management plans) to manage
existing Gila topminnow habitat cooperatively with private landowners.
There should be a continuing effort to survey waters in the Gila
River drainage for undiscovered populations of topminnow. It is
recommended that initial surveys be made from the air and that any new
population discovered be monitored and protected as outlined.
Efforts should be made to reestablish Gila topminnow within
portions of its former range. Such reintroductions should follow this
order:
1. develop evaluation criteria for site selection,
2. survey, evaluate, and select potential sites,
3. prepare selected sites (construct barriers, remove
non-native fishes, etc.),
4. transplant wild or use captively propagated Gila topminnows
to stock the new site, and
5. protect and monitor transplanted population.
Studies of Gila topminnow are needed, and should include: 1) the
mechanisms of topminnow-mosquitofish (Gambusia affinis) coexistence,
2) the effects of canabalism on juveniles noted in hatchery and
laboratory stocks, and 3) the relationships between topminnow
populations and multiple use management. Finally, public awareness
of the uniqueness of Gila topminnow should be increased through the
preparation of information pamplets, interpretive programs, and use
of the broadcast and print media.
Management Practices - 3 (DRAFT) - References
Species TOPMINNOW, GILA
Species Id ESIS252015
Date 14 MAR 96
References
***** REFERENCES FOR ALL NARRATIVES EXCEPT N-OCCURRENCE *****
01 Baird, S. F. and C. Girard. 1853. Descriptions of new species
of fish collected by Mr. John H. Clark, on the U.S. and Mexican
Boundary Survey, under Lt. Col. Jas. D. Graham. Proc. Acad. Nat.
Sci. Philadelphia 6:368-369.
02 Brooks, J. E. 1985. Factors affecting the success of Gila
topminnow introductions on four Arizona National Forests.
Report to: U.S. Fish and Wildl. Serv., Albuquerque, NM. AZ Game
and Fish Dept., Phoenix.
03 Brooks, J. E. 1986. Status of natural and introduced Sonoran
topminnow (Poeciliopsis o. occidentalis) populations in Arizona
through 1985. Rept. to: U.S. Fish and Wildl. Serv., Albuquerque,
NM. AZ Game and Fish Dept., Phoenix.
04 Collins, J. P., C. Young, J. Howell, and W. L. Minckley. 1981.
Elimination of a Gila topminnow (Poeciliopsis o. occidentalis,
Poeciliidae) population and other impacts of flooding in a Sonoran
desert stream. Southwestern Naturlist 26(4):415-423.
05 Constantz, G. D. 1976. Life history strategy of the Gila
topminnow, Poeciliopsis occidentalis: A field evaluation of theory
on the evolution of life histories. Ph.D. diss. AZ State Univ.,
89 pp.
06 Cope, E. D. and H. C. Yarrow. 1875. Report upon the collections
of fishes made in portions of Nevada, Utah, California, Colorado,
New Mexico, and Arizona, during the years 1871, 1872, 1873, and
1874. Rept. Geogr. Geol. Expl. Surv. W. 100th Meridian (Wheeler
Survey) 5:635-703.
07 Fowler, H. W. 1921. Descriptions of a new cyprinoid fish
(Notropis stonei) with notes on other fishes obtained in the United
States. Proc. Acad. Nat. Sci. Philadelphia 72:385-402.
08 Garman, S. 1895. The Cyprinodonts. Mem. Mus. Comp. Zool.
19:1-179.
09 Girard, C. 1859. Ichthyology of the Boundary. In, Report of the
United States and Mexican Boundary Survey, made under the direction
of the Secretary of the Interior, by W. H. Emory, Major, First
Cavalry, and United States Commissioner 3:1-85.
10 Hendrickson, D. A., and W. L. Minckley. 1984. Cienegas --
vanishing climax communities of the American Southwest. Desert
Plants. Special Issue 6(3):131-175 + 2 plates.
11 Hendrickson, D. A., W. L. Minckley, R. R. Miller, D. J. Siebert,
and P. H. Minckley. 1980. Fishes of the Rio Yaqui Basin, Mexico
and United States. Journ. of the AZ--NV. Acad. of Sci.
15(3):65-106.
12 Hubbs, C. L. 1926. Studies of the fishes of the order
Cyprinodontes. VI. Materials for a revision of the American genera
and species. Misc. Publ. Zool. Univ. Mich. 16:1-87.
13 Hubbs, C. L. and R. R. Miller. 1941. Studies of the fishes of
the order Cyprinodontes. XVII -- Genera and species of the
Colorado River system. Occ. Pap. Mus. Zoo., Univ. Mich. 433:1-9.
14 Johnson, J. E. 1987. Pers. comm., USFWS, Albuquerque, NM. 87103.
15 Johnson, J. E. and J. N. Rinne. 1982. The endangered species
References - 1 (DRAFT) - References
Species TOPMINNOW, GILA
Species Id ESIS252015
Date 14 MAR 96
act and southwest fishes. Fisheries 7(4):2-8 + 2 plates.
16 Jordan, D. S. and B. W. Evermann. 1896. The fishes of North and
Middle America. Bull. U.S. Nat. Mus. 47 (part I):i-ix, 1-1240.
17 Jordan, D. S. and C. H. Gilbert. 1883. Synopsis of the fishes
of North America. Bull. U.S. Nat. Mus. 16:i-lvi, 1-1018.
18 Meffe, G. K. 1984. Effects of abiotic disturbance on coexistence
of predator-prey fish species. Ecology 65(5):1525-1534.
19 Meffe, G. K. 1986. Conservation genetics and the management of
endangered fishes. Fisheries 11(1):14-23.
20 Meffe, G. K., D. A. Hendrickson, and W. L. Minckley. 1983.
Factors resulting in decline of the endangered Sonoran topminnow
Poeciliopsis occidentalis (Atheriniformes: Poeciliidae) in the
United States. Bio. Conser. 25(1983):135-159.
21 Meffe, G. K., D. A. Hendrickson, and J. N. Rinne. 1982.
Description of a new topminnow population in Arizona, with
observations on topminnow/mosquitofish co-occurrence. The
Southwestern Naturalist 27(2):226-228.
22 Miller, R. R. 1961. Man and the changing fish fauna of the
American southwest. Papers of the Michigan Acad. of Sci., Arts,
and Letters.
23 Miller, R. R. and C. H. Lowe. 1964. An annotated check list of
the fishes of Arizona. In: The Vertebrates of Arizona. C. H. Lowe
(ed.). Univ. AZ Press, Tucson. Pp. 133-151.
24 Miller, R. R. and R. J. Schultz. 1959. All female strains of
the teleost fishes of the genus Poeciliopsis. Sci. 130:1656-1657.
25 Miller, R. R. and J. R. Simon. 1943. Notropis mearnsi from
Arizona, an addition to the known fish fauna of the United States.
Copeia 1943:253.
26 Minckley, W. L. 1969. Native Arizona Fishes, Part 1 --
Livebearers. Wildlife Views 16:6-8.
27 Minckley, W. L. 1973. Fishes of Arizona. AZ Game and Fish Dept.
Phoenix.
28 Minckley, W. L. and J. E. Deacon. 1968. Southwestern fishes and
the enigma of 'endangered species'. Science (New York)
159:1424-1432.
29 Minckley, W. L., J. N. Rinne, and J. E. Johnson. 1977. Status
of the Gila topminnow and its co-occurrence with mosquitofish.
USDA Forest Serv. Res. Paper RM-198:1-8.
30 Nichols, J. T. 1940. Results of the Archibald expeditions, No.
28. A new toothcarp from Arizona. Amer. Mus. Novitates, 1084:1-2.
31 Plantz, D. V., Jr. 1976. Size-selective predation by Poeciliopsis
occidentalis (Baird and Girard). Ph.D. thesis, AZ State Univ.
32 Rinne, J. N., B. Rickel, and D. Hendrickson. 1980. A New Gila
Topminnow Locality in Southern Arizona. USDA For. Serv. Rocky Mt.
For. and Range Exper. Stat. Research Note RM-382.
33 Robins, C. R., R. M. Bailey, C. E. Bond, J. R. Brooker, E. A.
Lachner, R. N. Lea and W. B. Scott. 1980. A list of common and
scientific names of fishes from the U.S. and Canada. Fourth
Edition. Spec. Publ. 12 of the Amer. Fish. Society. 174 pp.
34 Rosen, D. E., and R. M. Bailey. 1963. The poeciliid fishes
(Cyprinodontiformes), their structure, zoogeography, and
systematics. Bull. of the Amer. Mus. of Nat. Hist. 126:1-176.
35 Schoenherr, A. A. 1974. Life history of the topminnow
References - 2 (DRAFT) - References
Species TOPMINNOW, GILA
Species Id ESIS252015
Date 14 MAR 96
Poeciliopsis occidentalis (Baird and Girard) in Arizona and an
analysis of its interaction with the mosquitofish Gambusia affinis
(Baird and Girard). Unpub. Ph.D. diss., AZ State Univ., Tempe.
36 Schwalbe, C. 1987. Pers. comm. Nongame Branch, AZ Game Fish
Dept., Phoenix.
37 Simons, L. H. 1987. Status of the Gila topminnow (Poeciliopsis
occidentalis occidentalis) in the United States. A Spec. rept. on:
Proj. E-1 Title VI of The End. Spec. Act of 1973, As Amended.
AZ Game and Fish Dept., Phoenix.
38 Simons, Lee H. 1987. Pers. observ. Nongame Branch, AZ Game and
Fish Dept., Phoenix.
39 U.S. Fish and Wildlife Service. 1986. Endangered and threatened
wildlife and plants (republication of list of species). Fed.
Reg. 48:34182.
40 U.S. Fish and Wildlife Service. 1983. Gila and Yaqui Topminnow
Recovery Plan. U.S. Fish and Wildl. Serv., Albuquerque, NM 56 pp.
41 Vrijenhoek, R. C., M. E. Douglas, and G. K. Meffe. 1985.
Conservation genetics of endangered fish populations in Arizona.
Science 229:400-402.
42 Vrijenhoek, R. C. 1986. Pers. comm. Bureau of Bio. Res.,
Rutgers Univ., New Brunswick, NJ 08903.
43 Association of Systematic Collections. 19??. Checklist of Fishes
of the United States and the U.S. Territories. Coop. Agree. No.
14-16-0009-1038 for: U.S. Fish and Wildl. Serv., Kearneysville, WV.
72 pp.
***** REFERENCES FOR N-OCCURRENCE NARRATIVE ONLY *****
01 Brooks, J.E. 1985. Factors affecting the success of Gila
topminnow introductions on four National Forests. Rept. to: U.S.
Fish and Wildl. Serv., Off. of End. Species, Albuquerque, NM.
Arizona Game and Fish Dept., Phoenix, AZ.
02 Brooks, J.E. 1986. Status of natural and introduced Sonoran
topminnow (Poeciliopsis o. occidentalis) populations in Arizona
through 1985. Rept. to: U.S. Fish and Wildl. Serv., Off. of End.
Spec., Albuquerque, NM. Arizona Game and Fish Dept., Phoenix, AZ.
03 Collins, J.P., C. Young, J. Howell, and W.L. Minkley. 1981.
Impact of flooding in a Sonoran Desert stream, including
elimination of an endangered fish population (Poeciliopsis o.
occidentalis, Poeciliidae). The Southwestern Naturalist 26(4):
415-423.
04 Hendrickson, D.A., W.L. Minkley, R.R. Miller, D.J. Siebert, and
P.H. Minkley. 1980. Fishes of the Rio Yaquai BAsin, Mexico and
United States. Journ. of the Ariz.--Nevada Academy of Sci. 15(3):
65-106.
05 Hubbs, C.L. and R.R. Miller. 1941. Studies of the order
Cyprinodontes, XVII. Genera and species of the Colorado River
System. Occ. papers of: Mus. of Zool., Univ. of Mich. 433:1-9.
06 Koster, W.J. 1957. Fishes of New Mexico. Univ. of New Mexico
Press, Albuquerque.
07 Meffe, G.K., D.A. Hendrickson, and W.L. Minckley. 1983. Factors
resulting in decline of the endangered Sonoran topminnow,
References - 3 (DRAFT) - References
Species TOPMINNOW, GILA
Species Id ESIS252015
Date 14 MAR 96
Poeciliopsis occidentalis (Antheriniformes: Poeciliidae) in the
United States. Biol. Conserv. 25:135-159.
08 Minckley, W.L. 1969. Attempted re-establishment of the Gila
topminnow within its former range. Copeia 1969 1:193-194.
09 Minckley, W.L. 1973. Fishes of Arizona. Ariz. Game and Fish
Dept., Phoenix, AZ.
10 Minckley, W.L. and J.E. Brooks. 1985. Transplantations of native
Arizona fishes; records through 1980. Jour. of the Ariz.-Nev.
Academy of Sci. 20(2):73-89.
11 Minckley, W.L. and J.E. Deacon. 1968. Southwestern fishes and the
enigma of `endangered species'. Science, New York, 159,
pp. 1424-1432
12 Simons, Lee H. 1987. Status of the Gila topminnow (Poeciliopsis
occidentalis occidentalis) in the United States. A special rept.
on Proj. E-1 Title VI of the Endangered Species Act. Ariz. Game
and Fish Dept., Phoenix. 85023-4339.
13 U.S. Fish and Wildlife Service. 1982. Gila and Yaqui Topminnow
Recovery Plan. U.S. Fish and Wildl. Serv., Albuerque, NM. 56 pp.
14 Vrijenhoek, Robert C., Dr. 1987. Pers. comm. Bureau of Biol.
Res., Rutgers Univ., New Brunswick, NJ. 08903.
References - 4