Condition status of the endangered desert pupfish,Cyprinodon macularius Baird and Girard, 1853, in the Lower Colorado River Basin (Mexico)

The length‐weight relationship (LWR) was used to test differences in the fish somatic condition factor among four populations of the endangered desert pupfish, Cyprinodon macularius, from the Lower Colorado River Basin, Mexico. Bimonthly fish sampling and habitat assessments were carried out from September 1996 to August 1997 for four sites in Baja California and Sonora. Slope b of the WLR varied from 3.238 (Cerro Prieto population) to 3.613 (Welton‐Mohawk population), showing in all populations a positive allometric growth. Male b values were higher than those of females for Cerro Prieto (3.303 vs 3.071), Welton‐Mohawk (3.866 vs 3.579), and Flor del Desierto (3.357 vs 3.169) populations. The Cerro Prieto population showed the highest somatic condition (y‐intercept, a = ?11.759). Water depth and salinity were the ecological variables that better accounted for most of the variation in the somatic condition of this pupfish, with a negative and a positive effect, respectively.     

Relation of desert pupfish abundance to selected environmental variables in natural and manmade habitats in the Salton Sea basin

Synopsis We assessed the relation between abundance of desert pupfish, Cyprinodon macularius, and selected biological and physicochemical variables in natural and manmade habitats within the Salton Sea Basin. Field sampling in a natural tributary, Salt Creek, and three agricultural drains captured eight species including pupfish (1.1% of the total catch), the only native species encountered. According to Bray–Curtis resemblance functions, fish species assemblages differed mostly between Salt Creek and the drains (i.e., the three drains had relatively similar species assemblages). Pupfish numbers and environmental variables varied among sites and sample periods. Canonical correlation showed that pupfish abundance was positively correlated with abundance of western mosquitofish, Gambusia affinis, and negatively correlated with abundance of porthole livebearers, Poeciliopsis gracilis, tilapias (Sarotherodon mossambica and Tilapia zillii), longjaw mudsuckers, Gillichthys mirabilis, and mollies (Poecilia latipinnaandPoecilia mexicana). In addition, pupfish abundance was positively correlated with cover, pH, and salinity, and negatively correlated with sediment factor (a measure of sediment grain size) and dissolved oxygen. Pupfish abundance was generally highest in habitats where water quality extremes (especially high pH and salinity, and low dissolved oxygen) seemingly limited the occurrence of nonnative fishes. This study also documented evidence of predation by mudsuckers on pupfish. These findings support the contention of many resource managers that pupfish populations are adversely influenced by ecological interactions with nonnative fishes.     

Summer movements of desert pupfish among habitats at the Salton Sea

Summer movement behavior of native desert pupfish (Cyprinodon macularius Baird and Girard) was evaluated among various habitats around the Salton Sea, located in southern California. Agricultural drains, shoreline pools, and Salt Creek were sampled six times between June 28 and September 16, 1999. Collected pupfish were marked using fluorescent elastomer implants. Unique marks were used at each site. Movements were detected from locations of recaptured pupfish. Desert pupfish were found in 10 of 12 sites sampled. Of 3239 pupfish captured during the study, 278 were recaptures, including 27 recaptures at areas different from where they were initially marked. The best evidence of pupfish movements was in the southwestern area of the Salton Sea between a drain and a connected shoreline pool. Movements were also observed from lower Salt Creek into a shoreline pool at the mouth of the creek as the water level dropped. The use of the Salton Sea as a migration corridor between habitats was not documented during this short study. The marking technique was successful and showed promise for future mark and recapture studies of desert pupfish.     

Genetic structure of wild populations of the endangered Desert Pupfish complex (Cyprinodontidae: Cyprinodon)

Data from 10 microsatellite DNA loci were used to describe the genetic structure of the two extant species (Cyprinodon macularius and C. eremus) of the endangered Desert Pupfish complex of southwestern United States and northwestern Mexico. Variation at microsatellite loci was significantly correlated (Mantel test) with that of previous mtDNA results, both for the complex and for the relatively wide-ranging C. macularius alone. Both species showed unusually high levels of microsatellite diversity for non-marine fish (H _e = 0.84–0.93; A_R = 11.9–17.0). There was evidence (R _ST > F _ST) that the two extant populations of C. eremus have been isolated sufficiently long for mutation to contribute significantly to genetic divergence, whereas divergence among the nine assayed populations of C. macularius could be attributed to genetic drift alone. Correspondingly, 10% of the diversity in C. eremus was attributable to differences between the two populations, whereas, for C. macularius, only 2.7% was attributable to among-population variation. Within C. macularius, a small (0.8%), but statistically significant, portion was attributable to differences between populations in the Salton Sea area and those on the lower Colorado River delta. The two populations of C. eremus and five groups of populations of C. macularius are recommended as management units for conservation genetics management of the two species.     

MITOCHONDRIAL DNA VARIATION AND EVOLUTION OF THE DEATH VALLEY PUPFISHES (CYPRINODON,CYPRINODONTIDAE)

A phylogenetic analysis of mitochondrial DNA (mtDNA) restriction sites was used to examine the geographic history of the Cyprinodon nevadensis complex of pupfishes, a group of four species (seven extant subspp.) in two endorheic (closed) basins of the Death Valley System in California and Nevada (Owens River Valley and Ash Meadows-Death Valley). The mtDNA results suggest that the group contains mtDNAs from two divergent clades. One such clade is represented by the mtDNAs of the Owens Valley pupfish (C. radiosus) and the existing species in the Colorado River (C. macularius), while the other includes the mtDNAs of the Ash Meadows-Death Valley species (C. nevadensis, C. salinus, and C. diabolis) and a species located much farther to the east (C. fontinalis from the Guzman Basin, Chihuahua, Mexico). These results, together with evidence from other studies, suggest two separate invasions of the Death Valley System by pupfishes carrying phylogenetically divergent mtDNAs. The C. nevadensis complex apparently is either an artificial group or else it is monophyletic and its genetic history includes loss of the original mtDNA in either Owens Valley or Ash Meadows-Death Valley following genetic introgression after an invasion by a pupfish carrying a divergent mtDNA.     

Predation by the desert pupfish,Cyprinodon macularius onCulex mosquitoes and benthic chironomid midges

Predation ofCulex mosquitoes and chironomid midges was demonstrated byCyprinodon macularius Baird & Girard in two types of shallow ponds. In large ponds (5.5×2.6 m) with fish, all mosquito breeding ceased 4 weeks after introduction ofC. macularius. A significant, density-dependent reduction of several chironomid biotypes was sustained, although an increase was evident for other chironomid biotypes. Fish biomass increased 2.43 fold in 76 days in m² ponds and 23.22 fold in 70 days in larger ponds. Behavioral studies showedC. macularius capable of feeding effectively on mosquitoes in floating algal mats. The desert pupfish deserves serious attention in the biological-integrated control of medically important aquatic arthropods, and may possess attributes making it a preferred, ecologically adapted substitute forGambusia affinis (Baird & Girard) in certain habitats.     

Parasites and salinity: costly tradeoffs in a threatened species

Parasites and environmental conditions can have direct and indirect effects on individuals. We explore the relationship between salinity and parasites in an endemic New Mexico State threatened fish, the White Sands pupfish (Cyprinodon tularosa). Spatial variation in salinity limits the distribution of the endemic springsnail (Juturnia tularosae) within Salt Creek, a small desert stream. The springsnail is the presumed intermediate host for trematodes that infect the White Sands pupfish, and trematode prevalence and intensity in pupfish are positively associated with the springsnail. Salinity and parasites both have negative impacts on pupfish, but in areas of high salinity, pupfish can effectively escape parasites. Pupfish trematodes were absent from sites lacking snails. At the upstream site, the absence of parasites and lower variance in salinity were correlated with larger pupfish that were in better condition than pupfish at either the middle or lower sites. Springsnails were present in the middle section, an area with moderate salinity, and all pupfish had trematodes (median abundance 847 trematodes/fish). Lipid levels and condition were lowest in fish from the middle site. Additionally, fewer older fish indicated an increased mortality rate. At the lower site, springsnails were absent due to high salinity; pupfish trematode abundance was much lower (six trematodes/fish), and fish condition was intermediate. An additional experiment revealed that snail activity and survival were significantly reduced at high salinities commonly present at the lower site. Although both high salinity and parasites significantly affect pupfish, parasites might be more detrimental.     

Fish habitat associations in a spatially variable desert stream

White sands pupfish Cyprinodon tularosa were sampled with minnow traps along the length of Lost River, a highly variable desert stream in New Mexico, to evaluate if their abundance, median standard length ( L _S) and sex ratio values differed by microhabitat variables. Habitat measurements were made in a 4 m² area around the minnow trap. White Sands pupfish populations were primarily structured by L _S. As specific conductance and surface area increased, median size of fish decreased. Shallow areas with higher specific conductance were correlated with an increased number of fish.     

Comparative ecology of prickly sculpin,Cottus asper,and coastrange sculpin,C. aleuticus,in the Eel River,California

Synopsis We documented species' distributions, size structure of populations, abundance in mainstem and tributary streams, habitat use, and diets of prickly sculpin, Cottus asper, and coastrange sculpin, C. aleuticus, in the Eel River drainage of California, to determine the processes allowing coexistence of these very similar fishes. We observed prickly sculpins at 43 sites and coastrange sculpins at 34. The species co-occurred at 26 sites. Young-of-year coastrange sculpins were only observed within 42 km of the ocean, but young-of-year prickly sculpins were present throughout the species range. Mean, maximum, and minimum lengths of coastrange sculpins were positively correlated with distance from the ocean but no significant relationships were found for prickly sculpins. Absolute abundance of both species was highest in mainstem habitat (prickly sculpins = 0.6 sculpins m^–2 and coastrange sculpins = 0.4 sculpins m^–2) . Tributary densities of both species tended to be less than 0.1 sculpins m^–2. The species inhabited very similar habitats and had very similar diets. Coastrange sculpin populations in upstream areas were maintained by immigration from downstream areas in contrast with prickly sculpin populations that produced young-of-year fish throughout their range. Densities were probably not high enough for interspecific interactions to be important. The factors limiting the upstream distribution of the species may include high water temperatures, stability of the stream bed, and behavior of the fish. In the past, the range of sculpins within the Eel River drainage probably fluctuated with changing physical conditions. Recent introductions of exotic species that compete with and prey upon sculpins, and ongoing human activities in the drainage could result in major reductions in the distribution and abundance of one or both species.     

The significance of meandering channel to habitat diversity and fish assemblage: a case study in the Shibetsu River,northern Japan

This study examined the structure and function of habitats for fish, the contribution to fish populations, and the effects of channel modification on habitats and fish populations in the lowland meandering Shibetsu River, northern Japan. Electrofishing and environmental measurements were conducted in bank areas of habitats constituting natural meandering and modified reaches. All types of habitats in a meandering reach highly contributed to the fish population(s). In particular, the contributions of lateral and wood habitats to fish populations were generally high, despite the low spatial extent of these habitats. The modified reach was simplified and had fewer types of habitats with uniform currents, and there was a low abundance of most fish within these habitats. Abundance of each fish group (taxa) was negatively affected by the changes in the habitats and/or channel shortening (i.e., decrease in the absolute abundance of habitat) due to river modification, which was implemented during 1950–1978. This study suggests that the recovery of all the habitat types is important in meander restoration and that the changes in habitat types and abundance should be examined in monitoring meander restoration and channel shortening.     

Habitat Restoration as a Means of Controlling Non-Native Fish in a Mojave Desert Oasis

Non‐native fish generally cause native fish decline, and once non‐natives are established, control or elimination is usually problematic. Because non‐native fish colonization has been greatest in anthropogenically altered habitats, restoring habitat similar to predisturbance conditions may offer a viable means of non‐native fish control. In this investigation we identified habitats favoring native over non‐native fish in a Mojave Desert oasis (Ash Meadows) and used this information to restore one of its major warm water spring systems (Kings Pool Spring). Prior to restoration, native fishes predominated in warm water (25–32°C) stream and spring‐pool habitat, whereas non‐natives predominated in cool water (≤23°C) spring‐pool and marsh/slack water habitat. Native Amargosa pupfish (Cyprinodon nevadensis) and Ash Meadows speckled dace (Rhinichthys osculus nevadensis) inhabited significantly faster mean water column velocities (MWCV) and greater total depth (TD) than non‐native Sailfin molly (Poecilia latipinna) and Mosquitofish (Gambusia affinis) in warm water stream habitat, and Ash Meadows speckled dace inhabited significantly faster water than non‐natives in cool water stream habitat. Modification of the outflow of Kings Pool Spring from marsh to warm water stream, with MWCV, TD, and temperature favoring native fish, changed the fish composition from predominantly non‐native Sailfin molly and Mosquitofish to predominantly Ash Meadows pupfish. This result supports the hypothesis that restoring spring systems to a semblance of predisturbance conditions would promote recolonization of native fishes and deter non‐native fish invasion and proliferation.     

Influence of riffle characteristics,surficial geology,and natural barriers on the distribution of the channel darter, <Emphasis Type="Italic">Percina copelandi,</Emphasis> in the Lake Ontario basin

Synopsis The channel darter, Percina copelandi, is a small benthic fish with a wide but disjunct distribution across central North America. The development of conservation and recovery strategies for Canadian populations is limited by a lack of knowledge regarding ecology, population size and other factors that affect its distribution and abundance. We sampled five rivers in the Lake Ontario basin to test whether the distribution of P. copelandi reflected riffle habitat characteristics or landscape-scale factors such as surficial geology and natural barriers (waterfalls). At most sites yielding P. copelandi, riffles flowed into deep sand bottomed run or pool habitats. Despite a lack of association with local surficial geology or riffle habitat characteristics, both the upstream limits of P. copelandi occurrence and distribution of suitable habitats reflected the distribution of waterfalls, chutes and bedrock outcroppings. In contrast to P. copelandi, distributions of Etheostoma flabellare, P. caprodes and Rhinichthys cataractae reflected among site differences in riffle habitat.     

Australian lungfish, <Emphasis Type="Italic">Neoceratodus forsteri</Emphasis>, threatened by a new dam

The Australian lungfish, Neoceratodus forsteri, exists as remnant natural populations in two rivers of south-east Queensland, Australia, and several translocated populations. Lungfish habitats have been impacted by agriculture and forestry, alien plants and fish and by river impoundment and regulation of flows. The species has been listed as vulnerable under Australian Commonwealth legislation. A proposal to construct Traveston Crossing Dam on the free-flowing main channel of the upper Mary River could seriously threaten the lungfish. The dam can be stopped by Commonwealth legislation if important populations of lungfish in the Mary River are likely to be significantly impacted by the new dam. This paper assembles evidence that impoundment of the Mary River and regulation of river flows are likely to decrease and fragment important lungfish populations, disrupt the breeding cycle, reduce juvenile recruitment, and isolate and decrease habitat availability/quality to such an extent that the species is likely to decline. Proposed mitigation strategies include fish transfer facilities, provision of flow releases from the dam (environmental flows) to sustain lungfish habitat and breeding downstream, and translocation of hatchery-reared juvenile lungfish into suitable natural habitats. These mitigation efforts may not be sufficient to secure the genetic diversity and long-term viability of lungfish populations in the Mary River.     

锡林河流域潜在不产氧光合细菌陆向分异特征及影响因素

【目的】为探明锡林河流域潜在不产氧光合细菌（anoxygenic photosynthetic bacteria,AnPB）的陆向分异特征及影响因素。【方法】本研究沿着陆向梯度依次采集水生湍流带、缓流带、滞流带、水偏湿生样带、湿偏旱生样带、旱生样带土壤样品。基于文献建立AnPB在科水平的数据库,运用16S rRNA基因高通量测序筛选科水平潜在AnPB类群及其组成丰度的陆向分异,运用皮尔逊相关性及冗余分析等研究土壤理化因子对潜在AnPB陆向分异的影响。【结果】紫色硫细菌（外硫红螺菌科）和紫色非硫细菌（红杆菌科、红环菌科、醋酸杆菌科、丛毛单胞菌科、全噬菌科）主要分布在水生及水偏湿生生境,其相对丰度与湿度呈显著（P<0.05）或极显著（P<0.01）正相关关系;紫色非硫细菌（红螺菌科、慢生根瘤菌科、生丝微菌科、红菌科）、芽单胞菌科、酸杆菌科、绿色非硫细菌（蔷薇菌科）等主要分布在湿偏旱生和旱生环境中,其相对丰度与盐度和全氮含量呈显著（P<0.05）或极显著（P<0.01）正相关关系;多元回归树分析显示,盐度、湿度、全氮对潜在AnPB陆向分异的总解释度分别为62.39%、...     

Influence of habitat heterogeneity on the distribution of larval Pacific lamprey (Lampetra tridentata) at two spatial scales

1. Spatial patterns in channel morphology and substratum composition at small (1–10 metres) and large scales (1–10 kilometres) were analysed to determine the influence of habitat heterogeneity on the distribution and abundance of larval lamprey. 2. We used a nested sampling design and multiple logistic regression to evaluate spatial heterogeneity in the abundance of larval Pacific lamprey, Lampetra tridentata, and habitat in 30 sites (each composed of twelve 1‐m² quadrat samples) distributed throughout a 55‐km section of the Middle Fork John Day River, OR, U.SA. Statistical models predicting the relative abundance of larvae both among sites (large scale) and among samples (small scale) were ranked using Akaike's Information Criterion (AIC) to identify the ‘best approximating’ models from a set of a priori candidate models determined from the literature on larval lamprey habitat associations. 3. Stream habitat variables predicted patterns in larval abundance but played different roles at different spatial scales. The abundance of larvae at large scales was positively associated with water depth and open riparian canopy, whereas patchiness in larval occurrence at small scales was associated with low water velocity, channel‐unit morphology (pool habitats), and the availability of habitat suitable for burrowing. 4. Habitat variables explained variation in larval abundance at large and small scales, but locational factors, such as longitudinal position (river km) and sample location within the channel unit, explained additional variation in the logistic regression model. The results emphasise the need for spatially explicit analysis, both in examining fish habitat relationships and in developing conservation plans for declining fish populations.     

Strong genetic differentiation in the invasive annual grass <Emphasis Type="Italic">Bromus tectorum</Emphasis> across the Mojave–Great Basin ecological transition zone

Bromus tectorum, an inbreeding annual grass, is a dominant invader in sagebrush steppe habitat in North America. It is also common in warm and salt deserts, displaying a larger environmental tolerance than most native species. We tested the hypothesis that a suite of habitat-specific B. tectorum lineages dominates warm desert habitats. We sampled 30 B. tectorum Mojave Desert and desert fringe populations and genotyped 10–26 individuals per population using 69 single nucleotide polymorphic (SNP) markers. We compared these populations to 11 Great Basin steppe and salt desert populations. Populations from warm desert habitats were dominated by members of two haplogroups (87 % of individuals) that were distinct from haplogroups common in Great Basin habitats. We conducted common garden studies comparing adaptive traits and field performance among haplogroups typically found in different habitats. In contrast to the haplogroup abundant in sagebrush steppe, warm desert haplogroups generally lacked a vernalization requirement for flowering. The most widespread warm desert haplogroup (Warm Desert 1) also had larger seeds and a higher root:shoot ratio than other haplogroups. In the field, performance of warm desert haplogroups was dramatically lower than the sagebrush steppe haplogroup at one steppe site, but one warm desert haplogroup performed as well as the steppe haplogroup under drought conditions at the other site. Our results suggest that B. tectorum succeeds in widely disparate environments through ecotypic variation displayed by distinct lineages of plants. Accounting for this ecotypic variation is essential in modeling its future distribution in response to climate change.     

PHOSPHOGLUCONATE DEHYDROGENASE POLYMORPHISM AND SALINITY IN THE WHITE SANDS PUPFISH

The phosphogluconate dehydrogenase (Pgdh) locus is the only polymorphic allozyme locus observed among 37 loci examined in all four populations of a New Mexico state Endangered species, the White Sands pupfish (Cyprinodon tularosa). We report evidence suggesting that this polymorphism may be associated with salinity. Salinity levels vary widely within and between habitats occupied by White Sands pupfish. The frequency of the Pgdh¹⁰⁰ allozyme was correlated with salinity but not with temperature. Frequency of Pgdh¹⁰⁰ differed between low (3.76 parts per thousand (ppt)) and high (9.23 ppt) salinity sites at Malpais Spring despite no obvious barriers to fish movement. Frequencies of Pgdh¹⁰⁰ in two introduced populations differed from that of the presumptive founding stock and correlated with salinity in the current habitats.     

Response of Endangered Desert Fish Populations to a Constructed Refuge

The U.S. Bureau of Reclamation created a shallow, 110-m channel to provide habitat for two endangered fishes, Cyprinodon elegans (Comanche Springs pupfish) and Gambusia nobilis (Pecos gambusia), at the site of the fishes' former natural habitat. The ciénega (marsh) associated with Phantom Lake Spring in Jeff Davis County, Texas, was destroyed by the creation of an irrigation canal system. In 1993, the endangered fishes were stocked into the refuge with individuals from the irrigation canals, and in the case of C. elegans, hatchery stocks. The condition of habitat, status of fish populations, and fish ecology within the refuge were then monitored for two years. The abundance and density of both species increased in accordance with aquatic plant development. Cyprinodon elegans abundance peaked after one year and stabilized at an average density of 14.7/m² by the end of our study. Juvenile C. elegans were always rare, which may indicate that the population reached the refuge's carrying capacity and that recruitment is low. Gambusia nobilis was the most abundant fish in the refuge (average density 96/m²), used the entire refuge, and outcom-peted nonindigenous G. geiseri. The two Gambusia species used similar habitats but showed almost no dietary overlap. High densities of aquatic plants reduced the amount of open water areas necessary for C. elegans. The refuge will sustain the two endangered fishes at this historic site of endemism while maintaining flow to the irrigation system; however, the refuge is not equivalent to a restored ciénega.     

Long-term trends in the breeding populations of waterbirds (1951–1985) at a sewage treatment plant

Long-term (1951–1985) data on the breeding waterbird populations and habitat modifications at Cape Flats sewage treatment works (Strandfontein) and Rondevlei Bird Sanctuary (Rondevlei) were assessed to establish the main factors affecting the breeding species richness and nest abundance. Fifty-two 'water-associated' breeding species were recorded in the Zeekoe River catchment waterbodies, 46 (88.5%) at Strandfontein, 38 (73.1%) at Rondevlei Bird Sanctuary (Rondevlei), 33 (63.5%) at Zeekoevlei and ten (19.2%) at Princess Vlei. Thirteen (25.5%) of the species were unique to Strandfontein and five (9.8%) to Rondevlei. Sorenson's similarity indices indicated high similarity (C_s = 0.81) in species richness and low similarity in nest abundance pattern (C_N = 0.10) for the paired sites Strandfontein-Rondevlei. The lowest breeding species richness (11 species) was in winter (June) and the peak (42 species) was in spring (October). Twenty-four species joined the breeding population of Strandfontein during 1959–1976 (during which time pond water surface area increased 2372%). The mean breeding species richness increased significantly (χ ² ₂ = 14.42, P <0.001) at Strandfontein during three distinctive periods: 1951–1958 (pre-construction), 1959–1976 (construction) and 1977–1985 (stabilization). At Rondevlei there were no significant differences in breeding species richness during the same periods. However, there were significant differences in the nest abundance pattern between these grouped years, both at Strandfontein (χ ² ₂ = 1472.2, P <0.001) and at Rondevlei (χ ² ₂ = 60.28, P <0.001). It is suggested that the same pool of species use the heterogeneous habitats at all the sites in the catchment according to their availability. The remarkable increase in species richness and nest abundance at Strandfontein after the late 1970s is attributed to higher habitat structural complexity, broad habitat types, stabilization and maturation of pond water and the subsequent increase in food diversity and availability. The decrease in Rondevlei nesting populations after the 1960s is probably related to fluctuations in water levels, cover of mudbanks with vegetation and high density of alien fish. A multipurpose management concept for conservation is proposed for the Zeekoe River catchment area. Strandfontein provides the greatest diversity of aquatic habitats not available elsewhere in the catchment (habitats for rare breeders such as Avocet, Black-winged Stilt, Red-billed Teal and some plovers) Rondevlei has a complementary habitat spectrum (suitable for Great Crested Grebe, Podiceps cristatus, Little Bittern, Ixobrychus minutus, and reedbed species). Zeekoevlei provides a large area of reedbed habitat for colonial breeding species (African Spoonbill and herons) and Princess Vlei is suggested for attracting Laridae.