Gary P. Garrett

An Annotated Checklist of the Freshwater Fishes of Texas, With Keys to Identification of Species

University of Texas at Austin, University of Texas - Pan American, Texas Parks and Wildlife Department

Fishes in North American deserts

Surveys the biology and ecology of desert fishes. Detailed articles cover the fishes physiological, evolutionary, and ecological characteristics, as well as the nature and management and conservation problems of their habitats.

Modular Experimental Riffle–Pool Stream System

Abstract We describe a modular method for building a large, outdoor experimental stream system that has great flexibility for research projects in fish ecology, behavior, conservation, or management. The system has been in use for more than a decade at the University of Oklahoma Biological Station (Kingston, Oklahoma) and has been used with modification at four other research facilities in the Midwest. Here, we document the system in detail, including specifications for construction of the original system and modifications or improvements at other sites. The system uses commercially available, customized fiberglass round tank and trough units that can be configured in many different ways to create flowing pool and riffle habitats. The system appears to be a good mimic of small natural streams based on system flow rates, establishment of natural substrates and cover, stream chemistry relative to that of a natural creek, and fish behaviors. At least 39 fish species have been used successfully in 1–14-month ...

Conservation and status of the fish communities inhabiting the Río Conchos basin and middle Rio Grande, México and U.S.A.

The Chihuahuan Desert region contains a numberof unique aquatic environments, but with fewexceptions, these have been little studied. Because of the dearth of information aboutthese environments and because many of the fishin the region are threatened with extinction orhave gone extinct, we sampled the RíoConchos basin and adjoining aquatic habitats inthe Rio Grande to assess the status of the fishof this region. Most sites showed some degreeof human-induced impacts. A number ofpotentially threatened fish were eitherabundant at only a few sites or rare or absentthroughout the localities sampled. Withoutconcerted binational efforts to conserve thefish of the region, further deletions to thenative fish fauna will likely occur.

Hormonal Sex Control of Largemouth Bass

Abstract Experiments were conducted to determine the potential for controlling sex of largemouth bass (Micropterus salmoides) by administration of steroid hormones (17β-estradiol, estrone, 17∝-methyltestosterone, and androsterone) in food to larvae. In one experiment, a commercial pelleted feed was soaked in hormone (50 or 100 mg/kg). In a second experiment, fish were fed live brine shrimp (Artemia gracilis) reared in culture media containing hormone (5 mg/L). Both methods were successful in masculinizing females, but only the live brine shrimp method was 100% successful in changing sex in either direction.

DISCOVERY OF A NEW POPULATION OF DEVILS RIVER MINNOW (DIONDA DIABOLI), WITH IMPLICATIONS FOR CONSERVATION OF THE SPECIES

Abstract The Devils River minnow (Dionda diaboli) has a limited distribution in Texas and Mexico. It is listed as threatened in the United States and endangered in Mexico. Recent collections in previously inaccessible locations in the headwaters of Pinto Creek, Kinney County, Texas, revealed a large population of D. diaboli. This species was found in habitats of flowing, spring-fed waters over gravel-cobble substrates, usually associated with aquatic macrophytes, but was confined to the upper segment of the creek. The confined distribution of Devils River minnow can offer valuable insight into its habitat and conservation. The future of this population might be threatened by reduced spring flows resulting from excessive pumping from the associated aquifer.

Habitat and Substrate Use in Reproduction of Captive Devils River Minnows

Abstract The Devils River minnow Dionda diaboli is a threatened species once endemic to a portion of the Rio Grande drainage in western Texas and northern Mexico but now found only in the Devils River and San Felipe and Pinto creeks. Because little is known about the biology of this species, it is difficult to establish protocols for maintaining captive populations. We monitored the production of Devils River minnows in two laboratory culture systems containing four substrate types (rocks, gravel, sand, and Spawntex) within each of two habitat types (riffle and pool) that had two subhabitat types each (upper and lower riffle, covered and uncovered pool). A total of 38 adult fish (mean weight = 1.38 g; mean total length = 54 mm) were introduced into the two culture systems (19 fish each, approximately equal sex ratio) on 5 September 2001. From 18 September to 6 December, 2,269 young were removed. A significantly greater number (1,922; three-factor nested analysis of variance [ANOVA], Fishers least-signifi...

Results of an Eradication Program on the Ecological Relationships of Fishes in Leon Creek, Texas

The fishes of Leon Creek are an assemblage of opportunists with a wide spectrum of feeding habits. The relative abundance of various taxa changed following a rotenone treatment designed to reduce genetic contamination of an endemic (Cyprinodon bovinus) by an introduced exotic (C. variegatus). Except for green sunfish, each fish (and a Gambusia hybrid swarm) was reestablished and is predicted to resume its role in the ecosystem in the near future. The introduction of Cyprinodon variegatus (sheepshead minnow) into Leon Creek and its subsequent hybridization with and extensive genetic contamination of Cyprinodon bovinus (Leon Springs pupfish) resulted in the recommendation for efforts to eradicate the exotic genetic material by rotenone treatment (Kennedy 1977; Echelle et al., ms). Our participation emphasized a study of the impact of the program on the other fishes inhabiting Leon Creek. Much of the literature on this creek has been devoted to Cyprinodon bovinus, a fish with its range restricted to Leon Creek. The first report on fishes in Leon Creek (actually Leon Springs approximately 22 kilometers northwest of the extant population) was of the 1851 samples by J. H. Clark, who obtained Cyprinodon bovinus and Gambusia nobilis (Girard 1859). Subsequent collections at Leon Springs contain other fishes that are likely to have been stocked. Minckley and Arnold (1969) alluded to a bovinus-like Cyprinodon that had been collected from downstream Leon Creek, but the first published reports of other fishes were by Hubbs and Echelle (1972), Echelle and Miller (1974), and Kennedy (1977), who report Cyprinus carpio (carp), Gambusia geiseri (largespring gambusia), Gambusia nobilis (Pecos gambusia), Gambusia affinis (mosquitofish), Lucania parva (rainwater killifish), Fundulus kansae (plains killifish), and Lepomis cyanellus (green sunfish) as

Threatened fishes of the world: Dionda diaboli Hubbs & Brown, 1956 (Cyprinidae)

Common name: Devils River minnow. Conservation status: Listed as threatened by the U.S. Fish and Wildlife Service 1999. Identification: Darkly outlined scales above the lateral stripe give a cross-hatched appearance. Also with a black spot on the caudal fin base that is often wedgeshaped, a black lateral stripe through the eye and onto the snout, and double dashes along the lateral line. Adults typically 30–40 mm SL. Drawing by Robert G. Howells. Distribution: Type locality is Baker’s Crossing on the Devils River, Val Verde County, Texas (Hubbs & Brown 1956). It is known to occur in Texas in the Devils River, San Felipe Creek and Sycamore Creek, Val Verde County. Extirpated from Las Moras Creek, Kinney County (Garrett et al. 1992). There are also historic records of occurrence in two small streams in Coahuila, Mexico, the Rio San Carlos and Rio Sabinas. Because no collections have been made there since the early 1970s, their current status in Mexico is unknown but, at best they are thought to be rare (Miller 1978). Abundance: The Devils River minnow has a spotty distribution within its range. At various times it has been relatively abundant (Hubbs & Brown 1956, Harrell 1978), yet at other times exceedingly rare (Garrett et al. 1992). Habitat and ecology: Little is known of the life history of the species and habitat specificity is not known. Often found in association with spring outflows and adjacent to aquatic macrophytes and may inhabit a microhabitat associated with the interface between spring runs and the river (Hubbs & Garrett 1990). Reproduction: Likely to spawn in the spring with non-adhesive and demersal eggs, similar to traits reported for D. serena (Hubbs 1951). Threats: Populations appear to have become reduced in number and size in recent history (Garrett et al. 1992). Reasons for this decline are not known, although remaining populations are potentially threatened by loss of habitat through reduced spring flows, reduction in water quality and predation and competition with exotic species. However, since little is known of the life history requirements or the ecological interactions of the Devils River minnow, it is difficult to properly assess threats or fully implement recovery actions. Conservation action: A Conservation Agreement was developed in 1998 among the Texas Parks and Wildlife Department, the City of Del Rio and the U.S. Fish and Wildlife Service and is designed to foster research to ‘eliminate or significantly reduce the probability that potential threats to the minnow will actually harm this species and to recover populations of the minnow to viable levels’. A critical subset of the range of D. diaboli is now owned by the Texas Parks and Wildlife Department and the Nature Conservancy of Texas. Conservation recommendation: The conservation actions and recommendations listed in the Conservation Agreement should be fully implemented in order to ensure survival of the species. Further research on the ecological requirements of this species is especially warranted.

Threatened Fishes of the World: Gambusia nobilis Baird & Girard, 1853 (Poeciliidae)

Common name: Pecos gambusia. Conservation status: Gambusia nobilis is listed as federally endangered by the United States (U.S. Fish and Wildlife Service 1970) and endangered by the states of New Mexico and Texas. Identification: The Pecos gambusia is a relatively robust Gambusia, with a caudal peduncle depth that is approximately two-thirds of the head length. The margins of the scale pockets are outlined in black and the dorsal fin has a subbasal row of spots. Females have a prominent black area on the abdomen that surrounds the anus and anal fin (Hubbs & Springer 1957). Drawing by Robert G. Howells. Distribution: Gambusia nobilis was described by Baird & Girard (1853) from Leon and Comanche springs, Pecos County, Texas. Leon Springs was later designated the type locality (Hubbs & Springer 1957). The species is endemic to the Pecos River basin in southeastern New Mexico and western Texas. At present, the species is restricted to four main areas, two in New Mexico and two in Texas. Abundance: Where suitable habitats exist, Pecos gambusia populations can be dense, ranging from 27 000 to 900 000 individuals in the isolated environments in which they occur (Bednarz 1979, U.S. Fish and Wildlife Service 1983). Habitat and ecology: Pecos gambusia usually inhabit stenothermal springs, runs, spring-influenced marshes (ciénegas), and irrigation canals carrying spring waters (Echelle & Echelle 1980). One or two other Gambusia may also be found in association with G. nobilis but these segregate by habitat (Hubbs et al. 1995). Pecos gambusia feed relatively non-selectively, consuming a diversity of food types (Hubbs et al. 1978). Reproduction: Gambusia nobilis produce live young. Bednarz (1979) reported an average of 38 embryos in the Blue Spring females and Hubbs (1996) found that newborns from Texas populations ranged between 35 and 50 mg with interbrood intervals of 52 days. Hybrids between G. nobilis and G. affinis or introduced G. geiseri are occasionally found, especially in habitats where one of the species is rare (Hubbs & Springer 1957). Threats: Pecos gambusia face severe threats from spring flow declines and habitat modifications throughout their range and from competition with G. geiseri. Conservation action: A recovery plan for G. nobilis has been developed (U.S. Fish and Wildlife Service 1983). Efforts have been made to improve habitat in the Balmorhea area including constructing a small refugium canal and an artificial ciénega in Balmorhea State Park, and a 110-m refugium canal at Phantom Spring. A renovation of the Diamond-Y Draw in 1998 removed G. geiseri from that system. Conservation recommendation: The recommendations in the Pecos gambusia recovery plan should be implemented and additional efforts need to be directed to the recently failing Phantom Spring system.