endemic to a single nation
Regularity: Regularly occurring
Type of Residency: Year-round
Global Range: (5000-20,000 square km (about 2000-8000 square miles)) Range of subspecies gilae: Upper Gila and San Francisco River drainages (USFWS 2009), New Mexico and Arizona, at elevations of 1,660-2,810 meters (Propst and Stefferud 1997).
Range of subspecies apache: Historically occurred in Arizona in the upper Salt River division of the Gila River basin (Black and White rivers), in the headwaters of Little Colorado River drainage, and in the Blue River (specimen from KP Creek) in the San Francisco River drainage; these streams all are close to each other in the White Mountains (Behnke 1992). Introduced in several streams and lakes in Arizona. Mainly in small headwater streams at elevations above 1,800 meters in the White Mountains (Behnke 1992).
A now extinct trout population in the upper tributaries of the Verde River in Arizona exhibited characteristics of both Gila and Apache trouts (Behnke 2002).
U.S.A. (AZ, NM)
Length: 26 cm
Habitat and Ecology
Habitat Type: Freshwater
Comments: Subspecies gilae: Habitat includes clear, cold mountain streams in arid regions; streams largely intermittent (not flowing in summer and fall) (Behnke 1979); clear runs in mountain streams that typically are narrow and shallow; trout may be confined to pools during prolonged drought (Sublette et al. 1990). Usually these fishes congregate in deeper pools and in shallow water only where there is protective debris or plant beds (Matthews and Moseley 1990).
Subspecies apache: Habitat is presently restricted to clear, cool, high-elevation mountain streams that flow through cienegas (marshes) and coniferous forests, upstream from natural barriers. This subspecies also has been introduced into several streams and lakes.
Spawning occurs in flowing water in saucer-like depression excavated by female. Eggs are covered with gravel after fertilization takes place (Minckley 1973).
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: Yes. At least some 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.
Subspecies apache: Migrates between spawning and nonspawning areas.
Comments: Subspecies GILAE: Feeds opportunistically on insects and insect larvae (e.g.: Trichoptera, Ephemeroptera, Diptera, Coleoptera, simuliid larvae, terrestrial organisms). Subspecies APACHE: Feeds on aquatic and terrestrial insects (e.g., Ephemeroptera, Trichoptera, and Diptera).
Number of Occurrences
Note: For many non-migratory species, occurrences are roughly equivalent to populations.
Estimated Number of Occurrences: 21 - 80
Comments: This species is represented by a moderate number of occurrences (subpopulations) and locations (as defined by IUCN). Subspecies gilae: currently, 12 viable populations of Gila trout exist in the absence of non-native salmonids (USFWS 2006). Subspecies apache: 28 populations now exist within historical range (USFWS 2009).
10,000 - 1,000,000 individuals
Comments: Total adult population size is unknown but certainly exceeds 10,00 and may exceed 100,000.
See Turner (1989) for information on seasonal and annual population changes in subspecies GILAE in headwater streams in New Mexico. Populations of subspecies APACHE become depleted during severe winters.
Life History and Behavior
Comments: Subspecies GILAE: Peak feeding period is 0900-1300 h (Sublette et al. 1990).
Subspecies GILAE: Spawns apparently in spring and summer in New Mexico (March-June when water temperature is 8 C or greater). Egg production is considered low (usually a few hundred or fewer). Fry emerge in 45-60 days at 20-25 TL (Lee et al. 1980), or in 8-10 weeks at 15-20 mm TL (Sublette et al. 1990). Females sexually mature at 3-5 years, depending on conditions; males mature usually 1-2 years sooner than do females in the same stream (Sublette et al. 1990). Maximum lifespan is 5-9 years in different streams.
Subspecies APACHE: Reaches maturity in three years. Spawning occurs March-mid June, when water temperature about 8 C. Egg production is variable, (70-4000+ per female), usually listed as 200-600. Hatches at 30 days, young emerge at 20-25 mm SL in 60 days (Lee et al. 1980).
See Stearley (1992) for a discussion of the historical ecology and life history evolution of Pacific salmons and trouts (ONCORHYNCHUS).
IUCN Red List Assessment
Red List Category
Red List Criteria
- Needs updating
- 1994Vulnerable (V)
- 1990Vulnerable (V)
- 1988Endangered (E)
- 1986Endangered (E)
National NatureServe Conservation Status
Rounded National Status Rank: N3 - Vulnerable
NatureServe Conservation Status
Rounded Global Status Rank: G3 - Vulnerable
Reasons: Small range in New Mexico and Arizona; negatively impacted by habitat isolation and fragmentation, non-native species, wildfire, and climate change; significant management has occurred; may be conspecific with rainbow trout.
Date Listed: 03/11/1967
Lead Region: Southwest Region (Region 2)
Where Listed: Entire
Population location: Entire
Listing status: T
For most current information and documents related to the conservation status and management of Oncorhynchus gilae , see its USFWS Species Profile
Global Short Term Trend: Relatively stable (=10% change)
Comments: Trend over the past 10 years or three generations has been relatively stable. Three generations span probably about 12 years
Global Long Term Trend: Decline of 50-70%
Comments: Subspecies apache: The estimated historic distribution of 965-1,320 kilometers of stream habitat (USFWS 2009) was reduced to about 50 km before restoration efforts began (Behnke 1992). Occupied habitat has increased greatly through intensive management in recent decades.
Degree of Threat: A : Very threatened throughout its range communities directly exploited or their composition and structure irreversibly threatened by man-made forces, including exotic species
Comments: Subspecies gilae: Declined mainly due to hybridization and competitive/predatory interactions with introduced trout species (rainbow, cutthroat, brown) and to habitat degradation through overgrazing, fires, lumbering, and mining (Sublette et al. 1990). Natural catastrophes such as drought, fires, and flooding can decimate populations (Propst et al. 1992, Brown et al. 2001). During the 1800s and 1900s, habitat degradation and loss through livestock grazing and timber harvest practices, overfishing, and the introduction of non-native trout reduced Gila trout to a few isolated populations. Current threats to Gila trout are habitat isolation and fragmentation, non-native species, wildfire, and climate change (USFWS 2009).
The short length of the occupied stream fragments and resulting small population sizes is also of concern; stream length is important to ensure adequate complexity and suitable habitat for life history requirements (see USFWS 2009). Restoration of Gila trout populations has not been successful in Raspberry, Dude, or Sheep Corral Creeks, most likely because of poor quality and/or limited habitat; failure of the Dude Creek restoration was likely a consequence of continued post-wildfire disturbances to the stream (USFWS 2009). Stocking and naturalization of nonnative trout and ensuing hybridization, predation, and competition are major causes for the imperiled status of the Gila trout (USFWS 2009).
Wildfires capable of eliminating or decimating fish populations are relatively recent phenomena resulting from the cumulative effects of historical or ongoing grazing practices (removes fine fuels needed to carry low-intensity, natural ground fire), fire suppression, and climate change. The absence of ground fires allowed a buildup of woody fuels that promotes infrequent, yet intense, crown fires. Since the mid-1990s, wildfire has occurred within or near all drainages containing Gila trout populations. High-severity wildfires, and subsequent floods and ash/debris flows have caused the extirpation of six populations of Gila trout since 1989. Widespread and intense wildfires remain a threat to Gila, especially in light of the projected effects of climate change. An emergency evacuation plan is in place, and has been used to help offset the immediate loss of populations from wildfire and subsequent channel degradation. Source: USFWS (2009, which see for supporting documentation).
Climate change is predicted to have four major effects on the cold-water stream habitat: 1) increased water temperature; 2) decreased stream flow; 3) a change in the hydrograph; and 4) an increased occurrence of extreme events (fire, drought, and floods) (USFWS 2009). It is anticipated that any of these outcomes, alone or in combination would reduce that amount of suitable habitat available to Gila trout. Kennedy et al. (2008) predicted a 20 percent decrease in summer precipitation and a 2° C increase in average summertime air temperature by mid-century in watersheds occupied by Gila trout. Because of the warmer air temperatures and corresponding increase in water temperature, a 70 percent loss of suitable habitat in existing Gila trout streams was predicted (Kennedy et al. 2008).
Subspecies apache: Suffered 95 percent reduction in range due to hybridization with rainbow trout and competition with brook and brown trouts (Lee et al. 1980). Much more vulnerable to angling exploitation than is the brown trout when the two live together in the same stream (see Behnke 1992). Release of hatchery-produced fishes into waters in which pure wild populations exist probably would be detrimental. Small populations of Apache trout have persisted throughout history in several small headwater streams where they are isolated from non-native trout, but those populations may be subject extirpation from stochastic events such as drought, fire, and periodic flooding (USFWS 2009).
Global Protection: Few (1-3) occurrences appropriately protected and managed
Comments: Apache tribe has limited fishing and created Christmas Tree Lake to preserve trout of subspecies apache.
Needs: Protect existing EOs from habitat degradation and hybridization with other trout.
Relevance to Humans and Ecosystems
Comments: Regulations have been proposed that would allow sport fishing of subspecies gilae in New Mexico (USFWS 1987); this is not expected to interfere with recovery.
The gila trout (Oncorhynchus gilae) is a species of salmonid, related to the rainbow and cutthroat trouts native to the Southwest United States. Prior to 2006 the Gila trout was federally listed as endangered. In July 2006, after much work by the Game and Fish departments in New Mexico and Arizona, the US Forest Service and the US Fish and Wildlife Service, the Gila trout was down-listed to threatened, with a special provision called a "4d rule" that will allow limited sport fishing – for the first time in nearly half a century. This possibility is distinct: there may be no one alive today that has legally angled a pure Gila trout from its native waters. By the time the Gila trout was closed to fishing in the 1950s, its numbers and range were so depleted and so reduced this copper-colored trout simply wasn’t all that accessible to anglers. As of 2011 there is fishing in both states for this beautiful fish.
The gila trout is native to tributaries of the Gila River in Arizona and New Mexico. The gila trout is found historically in the Verde and Agua Fria drainages in Arizona. Gila trout have persisted in five streams within the Gila National Forest, New Mexico, including: Iron, McKenna, and Spruce creeks in the Gila Wilderness Area, along with Main and South Diamond creeks in the Aldo Leopold Wilderness Area.
Gila trout has yellow head, with black spots. The average total length is about 300.0 mm (11.8 in.); with maximum total length approximately 550.0 mm (21.7 in.). Gila trout is closely related to Apache trout. However, Apache trout have a spot behind the eye, another on the head, and big noticeable spots on the body whereas Gila trout lacks the spot and is characterized by numerous small dark spots on the upper half of the body.
Gila trout can be found in small mountain water streams, and in confined pools. They are opportunistic feeders that feed on aquatic insects such as trichopterans, ephemeropterans, chironomids, and coleopterans, as well as small fishes.
Depending on the water temperature, spawning season occurs in late spring and summer. The number of eggs produced from females held in hatcheries averaged about 150. The maximum fecundity observed was 686 eggs.
The Gila trout has been threatened by competition and hybridization with introduced game fish such as the rainbow trout. However, the primary cause of reduced Gila trout populations is habitat loss caused by loss of water flow and shade-giving trees, caused in turn by fires, human destruction of riparian vegetation, livestock overgrazing, agricultural irrigation and water diversion, and channelization of streams in the Gila trout's native range. By the time the Gila trout was listed by the U.S. Fish and Wildlife Service in 1967 its range had reduced from several hundred miles of stream to just 20 in the Gila Wilderness and Aldo Leopold Wilderness. After listing USFWS began an aggressive program of stream restoration, removing the introduced trout, restoring and repairing riparian vegetation (to maintain cooler water temperatures), and restocking restored streams with young Gila trout. The Mora National Fish Hatchery and Technology Center in northern New Mexico keeps brood stocks of the Gila trout and supplies the fish for restocking. The species is now more secure than it was in the 1970s, having been moved to 10 new streams, though populations and habitat are still far below those originally established. Conservationists hope to eventually delist the species and allow fishing, thus forming alliances with fishermen in order to help preserve the species.
- Loudeslager, E.J., J.N. Rinne, G.A.E. Gall, and R.E. David. 1986. "Biochemical genetic studies of native Arizona and New Mexico trout," The Southwestern Naturalist. 31(2): 221-234.
- Behnke, R.J. and M. Zarn. 1976. Biology and management of threatened and endangered western trouts. Technical Report RM-28, Rocky Mountain Forest and Range Experiment Station, Fort Collins, Colorado. pp. 45
- Sublette, J.E., M.D. Hatch and M. Sublette. 1990. The fishes of New Mexico. University of New Mexico Press, Albuquerque. pp. 57-60.
- Van Eimeren, P.A. 1988. Comparative food habits of Gila trout and speckled dace in a southwestern headwater stream. Unpublished M.S. Thesis, New Mexico State University, Las Cruces. pp. 59.
- Regan, D.M. 1964. Ecology of Gila trout, Salmo gilae, in Main Diamond Creek, New Mexico. Unpublished M.S. Thesis, Colorado State University, Fort Collins. pp. 57.
- Sublette, J.E., M.D. Hatch and M. Sublette. 1990. The fishes of New Mexico. University of New Mexico Press, Albuquerque. pp. 57-60.
- Gila Trout at Center for Biological Diversity.
- Springer, Craig (27 September 2006) "Gila trout down-listed to threatened status," Fishing World
- Gimenez Dixon (1996). Oncorhynchus gilae. 2006. IUCN Red List of Threatened Species. IUCN 2006. www.iucnredlist.org. Retrieved on 9 May 2006. Listed as Endangered (EN B2ad+3c v2.3)
- "Oncorhynchus gilae". Integrated Taxonomic Information System. Retrieved 24 January 2006.
- Froese, Rainer and Pauly, Daniel, eds. (2005). "Oncorhynchus gilae" in FishBase. 10 2005 version.
Names and Taxonomy
Comments: Subspecies gilae: Hybridizes with rainbow trout (e.g., in Gila National Forest in Black Canyon, Langstroth, Lipsey, upper Mogollon, White, and Sycamore Canyon creeks; see Sublette et al. 1990). Chitty, Sycamore, Lipsey, and W. F. Mogollon creek populations are rainbow trout, apparently with introgressed gilae genes (Loudenslager et al. 1986).
Subspecies apache: Hybridizes with O. mykiss. Populations in Ft. Apache Indian Reservation are more genetically pure than those in Apache-Sitgreaves National Forest (Rinne and Minckley 1985). Paddy Creek population apparently comprises apache-mykiss hybrids (Loudenslager et al. 1986). Allozyme and mtDNA data may yield different conclusions regarding gene exchange between Apache trout and rainbow trout; exteme care must be exercised when considering elimination of any population that is presumed to be genetically contaminated based on allozyme data alone (Dowling and Childs 1992).
MtDNA data indicate that the nominal species O. apache and O. gilae are very similar to each other, and more similar to rainbow trout (O. mykiss) than to cutthroat trout (O. CLARKI) (Dowling and Childs 1992). Data from karyotyping, electrophoresis, and mtDNA comparisons indicate a close genetic relationship between Gila and Apache trout, much closer than among the four major subspecies of cutthroat trout (Behnke 1992). For this reason, Behnke (1992) recognized the Gila and Apache trouts as two subspecies of a single species, O. gilae. He stated that further taxonomic revisions, based on quantitative genetic data and the lack of reproductive isolation, might classify Gila and Apache trout as subspecies of rainbow trout. Behnke (2002) retained gilae and apache as subspecies of O. gilae, noting that recognition of O. gilae is a compromise between taxonomic splitting (treating gilae and apache as different species) and lumping (including gilae and apache as subspecies of O. mykiss). The latest AFS checklist (Nelson et al. 2004) also regarded apache as a subspecies of O. gilae.
MtDNA data indicate the presence of a diagnosable Gila trout (narrow sense) lineage in four relictual populations from the Gila River and San Francisco River drainages, New Mexico; results suported recognition of a O. gilae/apache ESU (evolutionarily significant unit); also, mtDNA data indicated that the population in the Gila River drainage should be treated as a separate management unit relative to the San Francisco drainage (Riddle et al. 1998).
Formerly included in the genus Salmo (see Smith and Stearley 1989, Robins et al. 1991).