Overview

Comprehensive Description

Biology

Inhabits vegetated springs and effluents.
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Distribution

Range Description

Range includes the Pecos River basin, Texas and New Mexico (Page and Burr 2011).

In New Mexico, the species occurred historically as far north as the Pecos River near Fort Sumner; now it is restricted to sinkholes or springs and their outflow on the west side of the Pecos River in Chaves and Eddy counties. Twelve populations are extant in the vicinity of Roswell; of these, natural populations are in two isolated gypsum sinkholes along with Sago and Dragonfly springs and their outflows, which combine to form the perennial portion of the Lost River (Bitter Creek drainage), all in Bitter Lake National Wildlife Refuge; other populations in the refuge are the result (in whole or in part) of introductions. An additional natural population occurs in Blue Spring, Eddy County, New Mexico. The species has been introduced in various areas of Salt Creek Wilderness Area and in artificial ponds at Living Desert State Park near Carlsbad, New Mexico. See Sublette et al. (1990).

In Texas, this species inhabits the headwaters of Phantom Lake (Jeff Davis County); San Solomon, Giffin, and East Sandia springs (Reeves County); and Diamond Y Draw and Diamond Y Springs (Pecos County) (Hubbs et al. 2008). Originally, it also inhabited Leon Springs (the type locality, approximately 16 km upstream from Diamond Y Springs) and also Comanche Springs (within the city of Fort Stockton) prior to their desiccation (Hubbs et al. 2008).
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Global Range: (250-5000 square km (about 100-2000 square miles)) Range includes the Pecos River basin, Texas and New Mexico (Page and Burr 2011).

In New Mexico, the species occurred historically as far north as the Pecos River near Fort Sumner; now it is restricted to sinkholes or springs and their outflow on the west side of the Pecos River in Chaves and Eddy counties. Twelve populations are extant in the vicinity of Roswell; of these, natural populations are in two isolated gypsum sinkholes along with Sago and Dragonfly springs and their outflows, which combine to form the perennial portion of the Lost River (Bitter Creek drainage), all in Bitter Lake National Wildlife Refuge; other populations in the refuge are the result (in whole or in part) of introductions. An additional natural population occurs in Blue Spring, Eddy County, New Mexico. The species has been introduced in various areas of Salt Creek Wilderness Area and in artificial ponds at Living Desert State Park near Carlsbad, New Mexico. See Sublette et al. (1990).

In Texas, this species inhabits the headwaters of Phantom Lake (Jeff Davis County); San Solomon, Giffin, and East Sandia springs (Reeves County); and Diamond Y Draw and Diamond Y Springs (Pecos County) (Hubbs et al. 2008). Originally, it also inhabited Leon Springs (the type locality, approximately 16 km upstream from Diamond Y Springs) and also Comanche Springs (within the city of Fort Stockton) prior to their desiccation (Hubbs et al. 2008).

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North America: found only in Pecos River system in New Mexico and Texas, USA.
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endemic to a single nation

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National Distribution

United States

Origin: Native

Regularity: Regularly occurring

Currently: Present

Confidence: Confident

Type of Residency: Year-round

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Historic Range:
U.S.A. (NM, TX)

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New Mexico and Texas, U.S.A.
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Physical Description

Size

Maximum size: 48 mm TL
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Max. size

4.8 cm TL (male/unsexed; (Ref. 5723))
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Length: 4 cm

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Ecology

Habitat

Habitat and Ecology

Habitat and Ecology
Habitat includes shallow margins of clear vegetated spring waters (pools and outflows) high in calcium carbonate, as well as more adverse gypsum sinkhole habitats (Lee et al. 1980, Page and Burr 2011). High salinities in gypsum sinkholes have precluded the success of most stockings in those habitats (Hendrickson and Brooks 1991). This fish is not tolerant of total hardness above 5000 mg/l CaCO3 (Bednarz 1979). Consistent habitat factors seem to be clear, clean water, stable flows, and fairly constant temperatures (Matthews and Moseley 1990). Abundance tends to be highest near spring sources (Minckley et al. 1991). Submerged cliffs and debris and aquatic vegetation are used for cover (Bednarz 1979).

Systems
  • Freshwater
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Habitat Type: Freshwater

Comments: Habitat includes shallow margins of clear vegetated spring waters (pools and outflows) high in calcium carbonate, as well as more adverse gypsum sinkhole habitats (Lee et al. 1980, Page and Burr 2011). High salinities in gypsum sinkholes have precluded the success of most stockings in those habitats (Hendrickson and Brooks 1991). This fish is not tolerant of total hardness above 5000 mg/l CaCO3 (Bednarz 1979). Consistent habitat factors seem to be clear, clean water, stable flows, and fairly constant temperatures (Matthews and Moseley 1990). Abundance tends to be highest near spring sources (Minckley et al. 1991). Submerged cliffs and debris and aquatic vegetation are used for cover (Bednarz 1979).

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Environment

benthopelagic; non-migratory; freshwater; pH range: 7.5 - 8.0; dH range: 30
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Depth range based on 1 specimen in 1 taxon.

Environmental ranges
  Depth range (m): 0.5 - 0.5
 
Note: this information has not been validated. Check this *note*. Your feedback is most welcome.

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Migration

Non-Migrant: Yes. At least some populations of this species do not make significant seasonal migrations. Juvenile dispersal is not considered a migration.

Locally Migrant: No. No populations of this species make local extended movements (generally less than 200 km) at particular times of the year (e.g., to breeding or wintering grounds, to hibernation sites).

Locally Migrant: No. No populations of this species make annual migrations of over 200 km.

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Trophic Strategy

Comments: Feeding occurs at the surface and in mid-water; diet includes insects (e.g., corixids and culicids) and amphipods, also some filamentous algae. Feeding occurs throughout the day, but primary feeding time correlates with insect activity at night.

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Population Biology

Number of Occurrences

Note: For many non-migratory species, occurrences are roughly equivalent to populations.

Estimated Number of Occurrences: 6 - 20

Comments: This species is represented by a small number of occurrences. It occurs in four main areas, two in New Mexico and two in Texas (Hubbs et al. 2002). These could be interpreted as four locations with respect to threats related to water availability.

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Global Abundance

>1,000,000 individuals

Comments: Total adult population size is very large. New Mexico population was estimated to total about 933,500 in 1979 (Bednarz 1979). Texas populations: 113,000 adults in vicinity of Balmorhea, 1 million adults in Leon Creek, Pecos County (Echelle and Echelle 1980). Yet Page and Burr (2011) stated that this species is "uncommon and localized."

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General Ecology

Introductions in sinkhole lakes failed when either Gambusia affinis (competitor) or Lepomis cyanellus (predator) were present; however, G. nobilis can coexist with G. affinis in sites with sufficient habitat diversity (Bednarz 1979).

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Life History and Behavior

Reproduction

Mean litter size was 38 in a sample of 20 (Bednarz 1979).

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Conservation

Conservation Status

IUCN Red List Assessment


Red List Category
EN
Endangered

Red List Criteria
B1ab(iii)+2ab(iii)

Version
3.1

Year Assessed
2013

Assessor/s
NatureServe

Reviewer/s
Smith, K. & Darwall, W.R.T.

Contributor/s

Justification
This species is listed as Endangered because extent of occurrence is less than 5,000 sq km, area of occupancy is less than 100 sq km and possibly less than 20 sq km, number of locations may not exceed five, and habitat is vulnerable to ongoing declines in quality/quantity due to reductions in water availability and impacts of non-native species.

History
  • 1996
    Vulnerable
  • 1994
    Vulnerable
    (Groombridge 1994)
  • 1990
    Vulnerable
    (IUCN 1990)
  • 1988
    Endangered
    (IUCN Conservation Monitoring Centre 1988)
  • 1986
    Endangered
    (IUCN Conservation Monitoring Centre 1986)
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Current Listing Status Summary

Status: Endangered
Date Listed: 10/13/1970
Lead Region:   Southwest Region (Region 2) 
Where Listed: Entire


Population detail:

Population location: Entire
Listing status: E

For most current information and documents related to the conservation status and management of Gambusia nobilis , see its USFWS Species Profile

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National NatureServe Conservation Status

United States

Rounded National Status Rank: N2 - Imperiled

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NatureServe Conservation Status

Rounded Global Status Rank: G2 - Imperiled

Reasons: Abundant in small range in the Pecos River basin, New Mexico and Texas; potentially threatened by dewatering of habitat, exotic species, and hybridization.

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Population

Population
This species is represented by a small number of occurrences. It occurs in four main areas, two in New Mexico and two in Texas (Hubbs et al. 2002). These could be interpreted as four locations with respect to threats related to water availability.

Total adult population size is very large. New Mexico population was estimated to total about 933,500 in 1979 (Bednarz 1979). Texas populations: 113,000 adults in vicinity of Balmorhea, 1 million adults in Leon Creek, Pecos County (Echelle and Echelle 1980). Yet Page and Burr (2011) stated that this species is "uncommon and localized."

This species is less abundant now than in the past.

USFWS (1990) categorized the status as "stable". Recent trend has not been reported, but range extent, area of occupancy, and number of subpopulations probably have been relatively stable or declining at a rate of less than 30 percent over 10 years or three generations.

Population Trend
Unknown
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Global Short Term Trend: Relatively stable to decline of 30%

Comments: USFWS (1990) categorized the status as "stable." Recent trend has not been reported, but range extent, area of occupancy, and number of subpopulations probably have been relatively stable or declining at a rate of less than 30 percent over 10 years or three generations.

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Threats

Major Threats
The most pervasive threat is drying of springs due to lowering water tables (e.g., via groundwater pumping, which eliminated populations at Comanche and Tunis springs in western Texas, and which probably will occur at other sites in the near future) (Echelle et al. 1989). Other threats include predation by introduced fishes (especially in sites lacking aquatic vegetation or shallow water), and competition and possibly hybridization with other Gambusia species. A renovation of Diamond Y Draw in 1998 removed Gambusia geiseri from that system (Hubbs et al. 2002). So far, hybridization has not had a significant impact. Introduced fishes (Green Sunfish) eliminated one transplanted population in Lake St. Francis and perhaps elsewhere on the Bitter Lakes NWR (Minckley et al. 1991). Alterations in the natural flow and physical conditions of the Pecos River have interfered with or eliminated movements of Gambusia among now isolated suitable habitats, which as a result cannot be naturally recolonized should local extinctions occur during drought years.

Jelks et al. (2008) categorized this species as Endangered due to (1) present or threatened destruction, modification, or reduction of habitat or range and (2) other natural or anthropogenic factors that affect existence, including impacts of nonindigenous organisms, hybridization, competition, and/or predation.
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Degree of Threat: Medium

Comments: The most pervasive threat is drying of springs due to lowering water tables (e.g., via groundwater pumping, which eliminated populations at Comanche and Tunis springs in western Texas, and which probably will occur at other sites in the near future) (Echelle et al. 1989). Other threats include predation by introduced fishes (especially in sites lacking aquatic vegetation or shallow water), and competition and possibly hybridization with other Gambusia species. A renovation of Diamond Y Draw in 1998 removed G. geiseri from that system (Hubbs et al. 2002). So far, hybridization has not had a significant impact. Introduced fishes (green sunfish) eliminated one transplanted population in Lake St. Francis and perhaps elsewhere on the Bitter Lakes NWR (Minckley et al. 1991). Alterations in the natural flow and physical conditions of the Pecos River have interfered with or eliminated movements of gambusia among now isolated suitable habitats, which as a result cannot be naturally recolonized should local extinctions occur during drought years.

Jelks et al. (2008) categorized this species as Endangered due to (1) present or threatened destruction, modification, or reduction of habitat or range and (2) other natural or anthropogenic factors that affect existence, including impacts of nonindigenous organisms, hybridization, competition, and/or predation.

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Vulnerable (VU) (D2)
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Management

Conservation Actions

Conservation Actions
Efforts have been made to improve habitat and provide refugia in the Balmorhea area (Hubbs et al. 2002).

Minckley et al. (1991) recommended that annual or more frequent monitoring should be continued throughout the native range and that the search for new sites for possible introduction be continued and intensified (though previous attempts have not been especially productive).

Minckley et al. (1991) recommended that major efforts be made to maintain each of the existing natural populations. Populations most critical to maintaining present morphological variation are those in three springs in Toyah Creek drainage, Texas, and one in Blue Spring, New Mexico (Echelle and Echelle 1986). See also Echelle et al. (1989) for recommendations regarding preservation of species' genetic diversity (about half of genetic diversity due to differences between samples at different localities, and half due to variability within samples). Echelle and Echelle (1986) recommended that the genome of the Balmorhea area, Texas, be preserved at sites within the historic range but outside the Balmorhea area, where springs are declining in flow. See recovery plan.
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Management Requirements: Efforts have been made to improve habitat and provide refugia in the Balmorhea area (Hubbs et al. 2002).

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Global Protection: Few to several (1-12) occurrences appropriately protected and managed

Comments: Several occurrences are on Bitter Lake NWR.

Needs: Minckley et al. (1991) recommended that major efforts be made to maintain each of the existing natural populations. Populations most critical to maintaining present morphological variation are those in three springs in Toyah Creek drainage, Texas, and one in Blue Spring, New Mexico (Echelle and Echelle 1986). See also Echelle et al. (1989) for recommendations regarding preservation of species' genetic diversity (about half of genetic diversity due to differences between samples at different localities, and half due to variability within samples). Echelle and Echelle (1986) recommended that the genome of the Balmorhea area, Texas, be preserved at sites within the historic range but outside the Balmorhea area, where springs are declining in flow. See recovery plan.

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Wikipedia

Pecos gambusia

The Pecos gambusia (Gambusia nobilis) is a species of fish in the Poeciliidae family. It is endemic to the Pecos River in Texas and New Mexico in the United States. This two-inch species, as most of the family, is a live bearer. Females produce broods of up to 40 fry every four to five days. The fish are omnivorous, eating algae and small invertebrates, and are endangered due to loss of their spring-fed desert habitat.[2]

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Names and Taxonomy

Taxonomy

Comments: Both morphological and genetic analyses indicate relatively strong differentiation among populations. For example, Balmorhea (Texas) populations include a unique male color morph not present elsewhere (Minckley et al. 1991). See Echelle (1991) for information on the geographical distribution of genetic diversity. Has hybridized with G. affinis at Blue Spring and Bitter Lakes National Wildlife Refuge, New Mexico (Sublette et al. 1990). Has hybridized also with introduced Gambusia geiseri (Minckley et al. 1991). See Rauchenberger (1989) for a study of the interrelationships of the subgenera and species groups within the genus Gambusia.

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