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Trophic relationships of small nonnative fishes in a natural creek and several agricultural drains flowing into the Salton Sea, and their potential, effects on the endangered desert pupfish

This study was conducted to characterize trophic relationships of small nonnative fishes and to determine if predation by these fishes contributes to the decline of desert pupfish (Cyprinodon macularius), an endangered cyprinodont on the verge of extinction. We sampled 403 hybrid Mozambique tilapias (Oreochromis mossambica by O. urolepis), 107 redbelly tilapias (Tilapia zillii), 32 longjaw mudsuckers (Gillkhthys mirabilis), 182 western mosquitofish (Gambusia affinis), 222 sailfin mollies (Poecilia latipinna), 63 shortfin mollies (Poecilia mexicana), and 235 porthole livebearers (Poecilurpsis gracilis) from a natural creek and four agricultural drains during September 1999- December 2001. Evidence of piscivory was in gastrointestinal contents of 14 hybrid Mozambique tilapias, 3 redbelly tilapias, 10 longjaw mudsuckers, 8 western mosquitofish, 2 sailfin mollies, and 8 porthole livebearers. Although digestion often was too advanced for identification of fishes consumed by nonnative fishes, remains of desert pupfish were in gastrointestinal contents of a longjaw mudsucker. Our findings, along with Field evidence from other studies that inverse relationships exist between abundances of desert pupfish and nonnative species, are consistent with the hypothesis that predation by nonnative species is contributing to decline of desert pupfish. We suspect that competitive interactions with nonnative fishes might also adversely affect abundance of desert pupfish.

Southwestern Naturalist↗

Dietary exposure of mink (Mustela vison) to fish from the Housatonic River, Berkshire County, Massachusetts, USA: Effects on organ weights and histology and hepatic concentrations of polychlorinated biphenyls and 2,3,7,8-tetrachlorodibenzo-p-dioxin toxic equivalence

The effects of feeding ranch mink ( Mustela vison ) diets containing polychlorinated biphenyl (PCB)-contaminated fish (88 gold fish [ Carassius auratus ] weighing a total of 70.3 kg and 16 carp [ Cyprinus carpio ] weighing a total of 77.3 kg) collected from the Housatonic River (HR; Berkshire County, MA, USA) in October 1999 on organ weights and histology and hepatic concentrations of total PCBs (ΣPCBs) and 2,3,7,8-tetrachlorodibenzo- p -dioxin toxic equivalence (TEQ) were evaluated. Diets contained 0.22 to 3.54% HR fish, which provided 0.34 to 3.7 μg ΣPCBs/g feed (3.5-69 pg TEQ/g feed). Female mink were fed the diets eight weeks before breeding through weaning of kits at six weeks of age. Offspring were maintained on their respective diets for an additional 180 d. The dietary concentration of PCBs that caused a decrease in kit survival (3.7 μg ΣPCBs/g feed [69 pg TEQ/g]) resulted in a maternal hepatic concentration of 3.1 μg ΣPCBs/g wet weight (218 pg TEQ/g). Organ weights were not consistently affected. Mandibular and maxillary squamous cell proliferation was apparent in 31-week-old juveniles exposed to as low as 0.96 (xg ΣPCBs/g feed (9.2 pg TEQ/g). Juveniles in this treatment group had a liver concentration of 1.7 μg ΣPCBs/g wet weight (40 pg TEQ/g). Because inclusion of PCB-contaminated fish, which comprised approximately 1% of the diet, resulted in mandibular and maxillary squamous cell proliferation, it is possible that consumption of up to 30-fold that quantity of HR fish, as could be expected for wild mink, would result in more severe lesions characterized by loss of teeth, thus impacting survivability.

Environmental Toxicology and Chemistry↗

Use of the oligochaete, Lumbriculus variegatus, as a prey organism for toxicant exposure of fish through the diet

The oligochaete, Lumbriculus variegatus, has several characteristics that make it desirable as a prey organism for conducting dietary exposure studies with fish. We conducted 21- and 30-d experiments with young fathead minnows (Pimephales promelas) and rainbow trout (Oncorhynchus mykiss), respectively, to determine whether a diet consisting solely of L. variegatus would support normal growth and to compare performance with standard diets (Artemia nauplii, frozen brine shrimp, or trout chow). All diets were readily accepted, and fish survived and grew well. Food conversion in both fathead minnows and rainbow trout was as high as or higher for the oligochaete diet compared with others, although this comparison is influenced by differences in ration, ingestion rate, or both. The oligochaete diet had gross nutritional analysis similar to the other diets, and meets fish nutrition guidelines for protein and essential amino acids. Methodologies and practical considerations for successfully using oligochaetes as an experimental diet are discussed. Considering their ready acceptance by fish, their apparent nutritional sufficiency, the ease of culturing large numbers, and the ease with which they can be loaded with exogenous chemicals, we believe that L. variegatus represents an excellent choice of exposure vector for exposing fish to toxicants via the diet. ?? 2006 SETAC.

Environmental Toxicology and Chemistry↗

Organochlorine contaminants in fishes from coastal waters west of Amukta Pass, Aleutian Islands, Alaska, USA

Organochlorines were examined in liver and stable isotopes in muscle of fishes from the western Aleutian Islands, Alaska, in relation to islands or locations affected by military occupation. Pacific cod (Gadus macrocephalus) , Pacific halibut (Hippoglossus stenolepis) , and rock greenling (Hexagrammos lagocephalus) were collected from nearshore waters at contemporary (decommissioned) and historical (World War II) military locations, as well as at reference locations. Total (Σ) polychlorinated biphenyls (PCBs) dominated the suite of organochlorine groups (ΣDDTs, Σchlordane cyclodienes, Σother cyclodienes, and Σchlorinated benzenes and cyclohexanes) detected in fishes at all locations, followed by ΣDDTs and Σchlordanes; dichlorodiphenyldi-chloroethylene ( p , p ′DDE) composed 52 to 66% of ΣDDTs by species. Organochlorine concentrations were higher or similar in cod compared to halibut and lowest in greenling; they were among the highest for fishes in Arctic or near Arctic waters. Organochlorine group concentrations varied among species and locations, but ΣPCB concentrations in all species were consistently higher at military locations than at reference locations. Moreover, all organochlorine group concentrations were higher in halibut from military locations than those from reference locations. A wide range of molecular weight organochlorines was detected at all locations, which implied regional or long-range transport and deposition, as well as local point-source contamination. Furthermore, a preponderance of higher-chlorinated PCB congeners in fishes from contemporary military islands implied recent exposure. Concentrations in all organochlorine groups increased with δ 15 N enrichment in fishes, and analyses of residual variation provided further evidence of different sources of ΣPCBs and p , p ′DDE among species and locations.

Alaska↗

Fish habitat use and food web structure following pond and plug restoration of a Montane Meadow in the Sierra Nevada, California

Montane meadows are areas of high biodiversity and provide many important ecosystem services; however, degradation of 40–60% of these habitats in the Sierra Nevada region of California has left many of these areas impaired. The “pond-and-plug” meadow-restoration technique is 1 type of treatment implemented to restore montane meadows. The objectives of this technique are to re-water the meadow and promote downstream flow by increasing the water-table elevation and providing additional water storage that will promote the growth of mesic and hydric vegetation that maintains and stabilizes stream channels. However, aquatic habitat and the composition and functioning of aquatic communities in these systems post-treatment are poorly documented or understood. We evaluated: (1) fish habitat, community composition, and relative abundance among recently created ponds spanning the range of pond habitats; (2) seasonal movement and survival of fish within and among ponds; and (3) food web structure in ponds. We documented over-summer and winter survival in the fish community and short-distance movement by 1 species occupying the ponds. Mark-recapture data suggest that all fish species present are capable of surviving both summer and winter conditions when pond conditions could be most limiting. Food web structure among intensively sampled ponds was similar, with overlapping isotopic niche width for dominant taxa. However, basal resource diversity (BRD) varied among ponds, with those having higher macrophyte cover also showing greater BRD. Our findings suggest that pond-and-plug techniques can provide habitat for native fishes that are able to tolerate departures from the species thermal and dissolved oxygen optima. Future meadow treatments could benefit from short-term restoration techniques such as pond-and-plug to allow for longer-term processes to influence meadow condition over time.

California↗

Field evaluation of the Automated Barge Clearing Deterrent (ABCD): Hydrodynamic, navigation, and fish response effects

The escape and subsequent spread of invasive carp (notably, bighead carp [ Hypophthalmichthys nobilis ] and silver carp [ H. molitrix ]) from aquaculture ponds and sewage lagoons into the Mississippi and Illinois Rivers poses a significant risk to further spread of these fish into the Great Lakes. Prior research demonstrated that commercial tows can transport juvenile invasive carp through locks and other barriers to fish migration. A recent physical model study recommended a linear array of bubble diffusers, the Automated Barge Clearing Deterrent (ABCD), for further evaluation in mitigating the transport of small fish in commercial tows. The present field study evaluated the ABCD for navigation safety and barge junction flushing capacity. An instrumented commercial tow executed 119 lock approaches with the ABCD both operating and idle. Pilot interviews and tow trajectory analysis indicated no significant navigation safety issues. The measured velocity data, fish recapture data, and a simple fish displacement model indicated that the ABCD produced sufficient flow to expel all passive objects and many small juvenile invasive carp. However, the ABCD is less likely to expel large juvenile invasive carp due to their stronger swimming ability. The ABCD and two alternative configurations prove strong contenders for further development and application.

Illinois↗

Waterbird predation on fish in western Lake Erie: a bioenergetics model application

To better understand the role of piscivorous waterbirds in the food web of western Lake Erie, we applied a bioenergetics model to determine their total fish consumption, The important nesting species included the Herring Gull (Larus argentatus), Ring-billed Gull (L. delawarensis), Double-crested Cormorant (Phalacrocorax auritus), Great Blue Heron (Ardea herodias), Black-crowned Night-Heron (Nycticorax nycticorax), and Great Egret (Casmerodius albus). The impact of migrant waterbirds, including the Red-breasted Merganser (Mergus serrator), on western Lake Erie fish biomass was also considered in the analysis. According to the modeling results, during the early 1990s, piscivorous waterbirds consumed 13,368 tonnes of fish from western Lake Erie each year. This tonnage was equivalent to 15.2% of the prey fish biomass needed to support the walleye (Stizostedion vitreum) population in western Lake Erie during a single growing season. The model application was useful in quantifying energy flow between birds and fish in a large lake ecosystem.

Condor↗

Fish kill from underwater explosions

The U.S. Geological Survey has used 23 different shotpoints during two seasons of field work in our seismic study of crustal structure in western United States. Without exception, it has been found that under-water shotpoints result in a more efficient conversion of explosive energy into seismic energy than do drilled-hole shotpoints. This experience, together with elimination of drilling costs, has led to the use of underwater shotpoints wherever possible. Three of the 23 shotpoints were in the Pacific Ocean, and for these we have no detailed information on the fish kill. Another six shotpoints were located in inland bodies of water. These are: * Soda Lake near Fallon, Nevada * Mono Lake near Lee Vining, California * Lake Mead near Boulder City, Nevada * Shasta Lake near Redding, California * C.J. Strike Reservoir near Bruneau, Idaho * Lucky Peak Reservoir near Boise, Idaho The 22 high-explosive charges, weighing a total of 95,100 pounds, that were fired in lakes containing fish life resulted in the known death of 2,413 game fish with a total weight of 759 pounds. The average mortality was 110 game fish or 34.5 pounds of game fish killed per average shot of 4,325 pounds of high-explosives.

California;Nevada;Idaho↗

Status of pelagic prey fishes in Lake Michigan, 2013

Acoustic surveys were conducted in late summer/early fall during the years 1992-1996 and 2001-2013 to estimate pelagic prey fish biomass in Lake Michigan. Midwater trawling during the surveys as well as target strength provided a measure of species and size composition of the fish community for use in scaling acoustic data and providing species-specific abundance estimates. The 2013 survey consisted of 27 acoustic transects (546 km total) and 31 midwater trawl tows. Mean prey fish biomass was 6.1 kg/ha (relative standard error, RSE = 11%) or 29.6 kilotonnes (kt = 1,000 metric tons), which was similar to the estimate in 2012 (31.1 kt) and 23.5% of the long-term (18 years) mean. The numeric density of the 2013 alewife year class was 6% of the time series average and this year-class contributed 4% of total alewife biomass (5.2 kg/ha, RSE = 12%). Alewife ≥age-1 comprised 96% of alewife biomass. In 2013, alewife comprised 86% of total prey fish biomass, while rainbow smelt and bloater were 4 and 10% of total biomass, respectively. Rainbow smelt biomass in 2013 (0.24 kg/ha, RSE = 17%) was essentially identical to the rainbow smelt biomass in 2012 and was 6% of the long term mean. Bloater biomass in 2013 was 0.6 kg/ha, only half the 2012 biomass, and 6% of the long term mean. Mean density of small bloater in 2013 (29 fish/ha, RSE = 29%) was lower than peak values observed in 2007-2009 and was 23% of the time series mean. In 2013, pelagic prey fish biomass in Lake Michigan was similar to Lake Huron, but pelagic community composition differs in the two lakes, with Lake Huron dominated by bloater.

Lake Michigan↗

Summary of total mercury concentrations in fillets of selected sport fishes collected during 2000-2003 from Lake Natoma, Sacramento County, California

This report summarizes results of total mercury measurements in skinless fillets of sport fishes collected during August 2000, September?October 2002, and July 2003 from Lake Natoma, a small (8,760 acre-feet) afterbay for Folsom Dam on the lower American River. The primary objective of the study was to determine if mercury concentrations in fillets approached or exceeded guidelines for human consumption. The Food and Drug Administration (FDA) human-health action level for methylmercury in commercially caught fish is 1.0 ?g/g (microgram per gram); the U.S. Environmental Protection Agency (USEPA) human-health criterion for methylmercury residue in fish tissue is 0.30 ?g/g. Wet weight concentrations of total mercury in skinless fillets were as high as 0.19 ?g/g in bluegill (Lepomis macrochirus), 0.39 ?g/g in redear sunfish (L. microlophus), 1.02 ?g/g in largemouth bass (Micropterus salmoides), and 1.89 ?g/g in channel catfish (Ictalurus punctatus). Maximum concentrations of mercury in other fish species varied from 0.10 ?g/g in rainbow trout (Oncorhynchus mykiss) to 0.56 ?g/g in white catfish (A-meiurus catus). Altogether, 1 of 86 largemouth bass and 11 of 11 channel catfish exceeded the FDA human-health action level. In addition, 1 of 20 redear sunfish, 26 of 86 largemouth bass, 2 of 3 spotted bass (M. punctulatus), 1 of 1 brown bullhead (A. nebulosus), and 1 of 1 white catfish exceeded the USEPA human-health criterion. These results indicate that some fish species inhabiting Lake Natoma contain undesirably high concentrations of mercury in their skinless fillets.

Data Series↗

Fish assemblages in eelgrass beds of Bellingham Bay, Washington, Northern Puget Sound, 2019

Puget Sound is a critical part of the Pacific Northwest, both culturally and economically. Eelgrass beds are an important feature of Puget Sound and are known to influence fish assemblages. As part of a larger site-characterization effort, and to gain a better understanding of the fish assemblages in Bellingham Bay, Washington, four eelgrass beds ( Zostera marina ) along the shoreline were surveyed. Fish were captured from 24 through 26 September 2019 by using three beach-seine hauls per eelgrass bed. In total, 12 hauls yielded 2,135 fish that comprised 20 species from 14 families. Shiner perch ( Cymatogaster aggregata ) accounted for 52 percent of the total catch. The other common species included three-spine stickleback ( Gasterosteus aculeatus ), bay pipefish ( Syngnathus leptorhynchus ), saddleback gunnel ( Pholis ornata ), Pacific staghorn sculpin ( Leptocottus armatus ), and Pacific sand lance ( Ammodytes personatus ). Total catch and species richness were highest at the two locations closest to the urban center of Bellingham; however, species diversity and evenness were highest at the two eelgrass beds farthest from the city center. Descriptions of fish assemblages in eelgrass beds are expected to be useful in the development of future process-based investigations by study partners and will focus on the movements of sediments and contaminants and their influence on biota.

Washington↗

Data from in situ Observations of Fish Traps Set by Fishermen in St. John Waters, U.S. Virgin Islands, 1992-94

In order to estimate (1) the trapping pressure within Virgin Islands National Park (VINP) waters, (2) the effect of fish traps on park marine resources (both fishes and habitats), and (3) the effectiveness of park regulations in protecting marine resources, traps set by fishers were visually observed and contents censused in situ in 1992, 1993, and 1994, around St. John (U.S. Virgin Islands), within and outside of park waters. A total of 1,340 individual fish (56 species and 23 families) were identified and their lengths estimated for the 211 of 285 visually censused traps that contained fish. This dataset includes for each censused trap: location, depth, substrate/habitat, trap type and construction details, in or out of park waters, and species and estimated fork length (in centimeters) of each individual fish in a trap. Analysis and interpretation of this dataset are provided in previously published reports by the author.

St. John↗

The Western Fisheries Research Center studies: threatened and endangered fishes

Within historical time, western native fish communities have faced increasing threats from habitat loss, invasive species, and pollution. It should come as no surprise that human development has greatly altered fish habitat in the west because of the importance of water for domestic, agricultural, and industrial uses, power generation, waste disposal, flood protection, and transportation. Fish that were adapted to natural cycles of river flow, lake levels, and water temperatures have been unable to adapt to the changes to these cycles caused by development, leading to the listing as threatened or endangered of 68 species of western native fishes. Rapid expansion of non-native fishes, aquatic plants, and invertebrates has increased competition for food and space while pollutants from past and present degrade our lakes, streams, and rivers.

Fact Sheet↗

An online database for IHN virus in Pacific Salmonid fish: MEAP-IHNV

The MEAP-IHNV database provides access to detailed data for anyone interested in IHNV molecular epidemiology, such as fish health professionals, fish culture facility managers, and academic researchers. The flexible search capabilities enable the user to generate various output formats, including tables and maps, which should assist users in developing and testing hypotheses about how IHNV moves across landscapes and changes over time. The MEAP-IHNV database is available online at http://gis.nacse.org/ihnv/ (fig. 1). The database contains records that provide background information and genetic sequencing data for more than 1,000 individual field isolates of the fish virus Infectious hematopoietic necrosis virus (IHNV), and is updated approximately annually. It focuses on IHNV isolates collected throughout western North America from 1966 to the present. The database also includes a small number of IHNV isolates from Eastern Russia. By engaging the expertise of the broader community of colleagues interested in IHNV, our goal is to enhance the overall understanding of IHNV epidemiology, including defining sources of disease outbreaks and viral emergence events, identifying virus traffic patterns and potential reservoirs, and understanding how human management of salmonid fish culture affects disease. Ultimately, this knowledge can be used to develop new strategies to reduce the effect of IHN disease in cultured and wild fish.

Fact Sheet↗

Fish-community composition in Ouleout Creek, in the vicinity of East Sidney Lake, Delaware County, New York, 2000

The U.S. Army Corps of Engineers, Baltimore District, has been conducting biological surveys of the inflow and outflow streams of East Sidney Lake since the early 1980's. These surveys are made to identify possible detrimental effects as well as benefits of the lake and to better understand the aquatic communities in the vicinity of the lake at the present and over time. The U.S. Army Corps of Engineers and the U.S. Geological Survey jointly conducted a survey of the fish communities upstream and downstream of the reservoir in Ouleout Creek in September 2000. The fish communities upstream and downstream were compared and any differences or similarities seen in the fish communities were noted. This study found the fish communities upstream and downstream of East Sidney Lake to be in good condition, with Index of Biotic Integrity (IBI) scores 4.5 upstream and 4.3 downstream. The habitat conditions of both reaches were of optimal quality, with a score of 18 upstream and 17 downstream as determined by use of the U.S. Environmental Protection Agency's Rapid Bioassessment Protocols, and are capable of supporting fish communities. The Shannon Index was 2.95 upstream and 2.61 downstream of the lake, indicating that both reaches are slightly impacted by species richness and individual evenness among the species. Downstream, the dominant taxa was twice that of the co-dominant taxa. The Jaccards Coefficient and the Index of Similarity statistically shows these communities are similar, with scores of 0.76 and 0.86, respectively. Of the 19 species captured downstream, 16 of those also were captured upstream.

Open-File Report↗

Attitudinal survey component of the study Quantity, quality, and support for research in the U.S. Fish and Wildlife Service: An organizational assessment : Report of methods and frequencies

The U.S. Fish and Wildlife Service (FWS) is responsible for managing the Nation’s fish and wildlife resources so that these trust resources are preserved for the present and future use and enjoyment of the citizens of the United States. The FWS achieves this mission by managing many programs. These include the national system of refuges and fish hatcheries, Fish and Wildlife Management Assistance Offices, migratory birds program, law enforcement, and working with tribal, state, and other Federal agencies to ensure protection of threatened and endangered species. Another role of the FWS is consulting with tribal, state, and other Federal agencies and private sector interests on the best conservation management practices consistent with Federal law. Each of these activities requires a workforce that is recognized for its professionalism, dedication to public service, and command of expert knowledge. Recognition for expert knowledge in fish and wildlife conservation is demonstrated, in part, when FWS personnel direct, conduct, or report research that is well-designed to answer questions of importance for natural resource management. The data reported in this document are one part of a three-part study of the status of organizational support for research in FWS, which was commissioned by the Directorate of the FWS. Funding for this study was provided by the FWS, and the Science Support Program of the U.S. Geological Survey (USGS). In 1994, the biological research functions of the FWS were transferred to the National Biological Survey, and subsequently into the USGS. This transfer was principally accomplished by moving whole research units from one agency to another. The result was that some employees whose positions were involved with research were not transferred. In addition, some research, information, and management needs of the FWS have continued to be met by studies conducted within the FWS itself. Although the FWS relies on the USGS and others for most basic research investigations, the FWS also conducts its own studies to meet management needs. Because it is vital for FWS employees to be able to conduct such tactical and applied research tasks in a timely manner, the agency must promote the culture necessary to support and encourage these activities. Such research activities are spread widely across the various programs of the FWS, and there is presently no collective, formal, or systematic record of planned or existing research activities. In commissioning this organizational assessment research, the Directorate of the FWS recognized that it would be to the advantage of the agency to more fully understand its research capacity. To develop a clearer picture of the nature, extent, quality, and degree of administrative support available for conducting research within the FWS, investigations have been undertaken to: 1. identify positions in the FWS that may include, in whole or in part, a component of scientific research; 2. identify organizational units within the FWS that may conduct research as a significant portion of their mission; and 3. assess the attitudes of employees and managers about the obstacles and opportunities for scientific research existing within the FWS by using a scaled-response survey instrument. The findings presented in this report represent the basic results derived from the attitude assessment survey conducted in the last quarter of 2004. The findings set forth in this report are the frequency distributions for each question in the survey instrument for all respondents. The only statistics provided are descriptive in character - namely, means and associated standard deviations.

Open-File Report↗

Biological Evaluations of an Off-Stream Channel, Horizontal Flat-Plate Fish Screen-The Farmers Screen

Screens are commonly installed at water diversion sites to reduce entrainment of fish. Recently, the Farmers Irrigation District in Hood River, Oregon, developed a new flat-plate screen design that offers passive operation and may result in reduced operation and installation costs to irrigators. To evaluate the performance (its biological effect on fish) of this type of screen, two size classes of juvenile coho salmon (Oncorhynchus kistuch) were released over a small version of this screen in the field-the Herman Creek screen. The performance of the screen was evaluated over a range of inflow [0.02 to 0.42 m3/s (cubic meters per second)] and diversion flows (0.02 to 0.34 m3/s) at different weir wall heights. The mean approach velocities for the screen ranged from 0 to 5 cm/s (centimeters per second) and mean sweeping velocities ranged from 36 to 178 cm/s. Water depths over the screen surface ranged from 1 to 25 centimeters and were directly related to weir wall height and inflow. Passage of juvenile coho salmon over the screen under a variety of hydraulic conditions did not severely injure them or cause delayed mortality. For all fish, the mean percentage of body surface area that was injured after passage over the screen ranged from about 0.4 to 3.0%. This occurred even though many fish contacted the screen surface during passage. No fish were observed becoming impinged on the screen surface (greater than 1 second contact with the screen). When operated within its design criteria (diversion flows of about 0.28 m3/s), the screen provided safe and effective downstream passage of juvenile salmonids under a variety of hydraulic conditions. However, we do not recommend operating the screen at inflows less than 0.14 m3/s (5 ft3/s) because water depth can get quite shallow and the screen can completely dewater, particularly at very low flows.

Open-File Report↗

Relative abundance and distribution of fishes and crayfish at Ash Meadows National Wildlife Refuge, Nye County, Nevada, 2007-08

This study provides baseline data of native and non-native fish populations in Ash Meadows National Wildlife Refuge (NWR), Nye County, Nevada, that can serve as a gauge in native fish enhancement efforts. In support of Carson Slough restoration, comprehensive surveys of Ash Meadows NWR fishes were conducted seasonally from fall 2007 through summer 2008. A total of 853 sampling stations were created using Geographic Information Systems and National Agricultural Imagery Program. In four seasons of sampling, Amargosa pupfish (genus Cyprinodon) was captured at 388 of 659 stations. The number of captured Amargosa pupfish ranged from 5,815 (winter 2008) to 8,346 (summer 2008). The greatest success in capturing Amargosa pupfish was in warm water spring-pools with temperature greater than 25 degrees C, headwaters of warm water spring systems, and shallow (depths less than 10 centimeters) grassy marshes. In four seasons of sampling, Ash Meadows speckled dace (Rhinichthys osculus nevadesis) was captured at 96 of 659 stations. The number of captured Ash Meadows speckled dace ranged from 1,009 (summer 2008) to 1,552 (winter 2008). The greatest success in capturing Ash Meadows speckled dace was in cool water spring-pools with temperature less than 20 degrees C and in the high flowing water outflows. Among 659 sampling stations within the range of Amargosa pupfish, red swamp crayfish (Procambarus clarkii) was collected at 458 stations, western mosquitofish (Gambusia affinis) at 374 stations, and sailfin molly (Poecilia latipinna) at 128 stations. School Springs was restored during the course of this study. Prior to restoration of School Springs, maximum Warm Springs Amargosa pupfish (Cyprinodon nevadensis pectoralis) captured from the six springs of the Warm Springs Complex was 765 (fall 2007). In four seasons of sampling, Warm Springs Amargosa pupfish were captured at 85 of 177 stations. The greatest success in capturing Warm Springs Amargosa pupfish when co-occurring with red swamp crayfish and western mosquitofish was in water with temperature greater than 26 degrees C near the springhead, and in shallow (depths less than 10 centimeters) grassy marshes. Among 177 sampling stations within the range of Warm Springs Amargosa pupfish, red swamp crayfish were collected at 96 stations and western mosquitofish were collected at 49 stations. Removal of convict cichlid (Amatitlania nigrofasciata) from Fairbanks Spring was followed by a substantial increase in Ash Meadows Amargosa pupfish (Cyprinodon nevadensis mionectes) captures from 910 pre-removal to 3,056 post-removal. Red swamp crayfish was continually removed from Bradford 1 Spring, which seemed to cause an increase in the speckled dace population. Restoration of Kings Pool and Jackrabbit Springs promoted the success of native fishes with the greatest densities in restored reaches. Ongoing restoration of Carson Slough and its tributaries, as well as control and elimination of invasive species, is expected to increase abundance and distribution of Ash Meadows' native fish populations. Further analysis of data from this study will help determine the habitat characteristic(s) that promote native species and curtail non-native species.

Open-File Report↗