Separate Ponds Research Articles

Replicated whole‐lake experiment reveals the ineffectiveness of stocking five example fish species in small lakes

AbstractFish stocking is common practice in fisheries management, but its effectiveness to support or increase stock size or catches is debated. In Lower Saxony, Germany, a controlled, replicated stocking experiment of five native fish species in eight gravel pit lakes <20 ha was conducted to examine the potential additive effects of fish releases on abundance, indexed by catch per unit effort (CPUE) in electrofishing and gillnet samples. Fish were stocked twice in four study lakes, while the remaining four control lakes were not subjected to any stocking over a 6‐year study period. Recapture rates of individually marked fishes were extremely low in all five species. Consequently, stocking did not increase species‐specific and total fish community abundance. In additional control experiments in separate ponds all stocked fish species, except bream (Abramis brama), showed high survival in at least one study year, indicating general survival of the stocking material. Fish marking with passive integrated transponders did not affect fish survival, except for roach (Rutilus rutilus), and can thus be ruled out as an explanation for the high post‐stocking mortality. We conclude that stocking failed to enhance stocks of five native fish species in small gravel pit lakes.

Evaluation of Growth Parameters in Post Larvae Catfish in Relation to Feed Types

The aim of this research is to evaluate growth parameters in post larvae catfish in relation to feed types. This study will analyze the trend for length of Claria gariepinus fed on commercial feed, maggot and zooplankton; analyze the trend of weight of Claria gariepinus fed on commercial feed, maggot and zooplankton; analyze the relationship between length and weight and; make forecasts for the length and weight of the fish fed on the specified feed types. Artificial reproduction of African Catfish (C geriepinus) was carried out using the hypophysation technique. Brood stocks were selected from centrally located parent stock holding ponds. Males and females were conditioned in separate ponds. The brood stocks were fed with 20% crude protein formulated feed, acclimatized for three weeks, then transferred into the hatchery holding tanks between 240 Celsius and 270 Celsius to stimulate ovulation after injecting the females with 0.5ml of ovalin. Fertilized eggs were incubated in continuous flow of water until hatching was completed. A commercial starter feed consisting of 8% ash, 6% fiber, 12% NFE, 1.5% calcium, 1.6% sodium, 1.5% phosphorous and sufficient amount of essential vitamins was administered to the larvae. Larvae were randomly distributed into 45 plastic tanks in a flow-through system at a density of 500 fish per tank. Fifteen fries were randomly selected from each holding tank and measurements on weight and length collected daily. Time series analysis and regression analysis were applied in the study. It was found that the length and weight of post larvae fed on mixed zooplankton was consistently lower than the other treatments. The length and weight of the fish fed on the three feed types were successfully modeled and forecasts made for future five periods while the relationship between length and weight was found to be significant on a linear regression model. This certainly adds value as the weight of post larvae catfish is measure with less difficulty and without causing injury or stress to the fish than measurement of length.

С, О, S, Sr-Isotopes in the Osveya Horizon Deposits of the Lower Eifelian on the Territory of Belarus

The complex interpretation of distribution of δ13C and δ18О in carbonates, δ34S and 87Sr/86Sr in gypsum from the Osveya horizon (Lower Eifelian) on the territory of Belarus showed that significance of diagenetic isotope signals is low and variations of the values can be consistently explained within a sedimentation model. Along with intervals of sections with standard marine δ13C values, there are negative excursions of the parameter (up to –7…–11‰) marking segments of sequence with carbonate-sulphate rocks and smaller scale sulphate manifestations. The excursions correspond to evaporite episodes when the basin shallowed and, probably, dismembered into separate ponds. This led to increasing the role of continental water enriched with soil carbon in the geochemical system of sedimentation due to the land runoff activation and/or shallowing. Continental water could come from for a long time exposed land areas where the Eifelian deposits are absent until now as well as from periodically existing islands. Oxygen isotopic composition does not react to δ13C negative excursions by similar shifts due to the possible absence of significant difference between the δ18О values of atmospheric precipitation, giving rise to land water, and seawater in low latitudes where the territory of Belarus was situated in the Devonian. In 40% of the studied samples, the δ18О values range from –4 to –2‰, corresponding to the Eifelian “plateau” (~–3‰) in the generalized chemostratigraphic curve in the generalized chemostratigraphic curve constructed using calcite of brachiopod shells from several regions of the world. The δ18О values higher than –2‰ (44% of cases), probably, are the result of water evaporation, while figures –2‰ (16%) which may decrease up to –7.0…–9.5‰ at the peaks of evaporite episodes, are caused by water heating (sometimes very significant) during the basin shallowing. The activation of continental water role accompanying evaporite episodes is supported by the fact that the 87Sr/86Sr ratio in the Osveya horizon gypsum (0.708402–0.708742) is much higher than that of the Eifelian seawater according to a global estimate (0.70772), while δ34S of gypsum (15.5–21.2‰) in more than a half of the analyzed samples is lower than figures characteristic of the Middle Devonian seawater sulphate (19–20‰).

The functional response and resilience in small waterbodies along land-use and environmental gradients.

There is growing recognition of the essential services provided to humanity by functionally intact ecosystems. Freshwater ecosystems are found throughout agricultural and urban landscapes and provide a wide range of ecosystem services, but globally they are also amongst the most vulnerable. In particular, ponds (lentic waters typically less than 2ha), provide natural flood management, sequester carbon and hold significant cultural value. However, to inform their management it is important to understand (1) how functional diversity varies in response to disturbance and (2) the link between biodiversity conservation and ecosystem function. In this study, a meta-analysis of seven separate pond studies from across England and Wales was carried out to explore the effect of urban and agricultural land-use gradients, shading, emergent vegetation, surface area and pH upon groups of functionally similar members of the macroinvertebrate fauna. Functional effect groups were first identified by carrying out a hierarchical cluster analysis using body size, voltinism and feeding habits (18 categories) that are closely related to biogeochemical processes (e.g. nutrient and carbon recycling). Secondly, the influence of the gradients upon effect group membership (functional redundancy-FR) and the breadth of traits available to aid ecosystem recovery (response diversity) was assessed using species counts and functional dispersion (FDis) using 12 response traits. The effect of land-use gradients was unpredictable, whilst there was a negative response in both FR and FDis to shading and positive responses to increases in emergent vegetation cover and surface area. An inconsistent association between FDis and FR suggested that arguments for taxonomic biodiversity conservation to augment ecosystem functioning are too simplistic. Thus, a deeper understanding of the response of functional diversity to disturbance could have greater impact with decision-makers who may relate better to the loss of ecosystem function in response to environmental degradation than species loss alone.

Characterization of the Life Cycle of a Fish Eye Fluke, Austrodiplostomum ostrowskiae (Digenea: Diplostomidae), with Notes on Two Other Diplostomids Infecting Biomphalaria havanensis (Mollusca: Planorbidae) from Catfish Aquaculture Ponds in Mississippi, USA.

Ocular diplostomiasis is caused by trematode species in the family Diplostomidae, specifically those in the genera Austrodiplostomum, Diplostomum, and Tylodelphys. Diplostomid trematodes are globally distributed parasites of fish. Heavy infections of diplostomids that parasitize the eyes of fish can result in acute mortality while chronic infections are often characterized by impaired vision or blindness. In the southeastern United States, commercial catfish production is threatened by piscivorous birds and the many trematode species that parasitize them. The life cycles typically involve a piscivorous avian definitive host, a mollusk first intermediate host, and a fish second intermediate host. A survey of parasites infecting the snail host Biomphalaria havanensis (= B. obstructa ) in catfish production ponds was undertaken. Snails were collected from 2 separate ponds during the summer of 2014 and observed for the release of trematode cercariae. A total of 1,740 snails were collected. Three distinct longifurcate pharyngeate cercariae were observed and these cercariae were characterized morphologically and molecularly. Sequencing of ∼4,200 base pairs (bp) of the nuclear ribosomal genes and ∼450 bp of the mitochondrial cytochrome c oxidase gene revealed 3 genetically distinct species. One morphotype shared 99-100% sequence identity with metacercariae from the aqueous and vitreous humors of gizzard shad Dorosoma cepedianum and channel catfish Ictalurus punctatus as well as an adult trematode, Austrodiplostomum ostrowskiae, a parasite of the double-crested cormorant Nannopterum auritus. The remaining 2 cercariae morphotypes shared 99-100% sequence identity with an unidentified Tylodelphys sp. and Austrodiplostomum sp. metacercaria from the brain and eyes of several freshwater fish. Herein we molecularly link the cercaria, metacercaria, and adult stage of the life cycle of A. ostrowskiae, identifying the snail host for this parasite, in addition to providing notes on 2 cercariae representing 2 other diplostomids.

Closure to “How Buoyant Flow Control Devices Can Reduce Pond Size Requirements” by Jeffrey S. Glenn, Elizabeth M. Bartell, and Jon Moody

In the original paper, the authors make a claim that a buoyant flow control device, proprietarily named Thirsty Duck (TD), can be installed in a standard detention basin and will reduce the detention volume while simultaneously maintaining the outlet flows to the existing condition. The TD operates by providing a constant outflow at a variety of heads. In essence, it is an orifice that floats upon the water level and rises and falls with the water level. The ASCE proceedings paper provides a summary outline of the results of a much larger paper published online in 2011. This document will be referred to as the TD paper. The underlying computations can be found in RS&H (2011). This document will be referred to as the RSH paper. It is 279 pages in length and provides many pages of computer input and computer output sheets and some summary information. The TD paper indicates that three separate ponds (detention basins) were modeled, listed as Ponds 1, 2, and 3. Pond 3 is the same pond noted as POND33C in the RSH paper. The authors indicate that their hydrologic modeling of Pond 3 shows a reduction in storage volume from 7.61 to 5.07 acre-ft, a savings of 33.4%. It is this claim that the discusser has investigated. The discusser did not review Ponds 1 and 2 in either paper since it was nearly impossible to follow the methods, and the lack of drawings and basic information did not allow a review.

Cannibalism of Embryos and Larvae by Adult Woundfin in Intensive Culture: Application to Conservation Propagation

Abstract Woundfin Plagopterus argentissimus are a small, endangered cyprinid native to the Colorado River basin. Woundfin occur only in the Virgin River in Utah, Arizona, and Nevada, and habitat degradation and competition with invasive species threaten their survival. Three facilities raise woundfin in captivity for use in conservation propagation projects. A suspected limiting factor to pond culture production of woundfin is cannibalistic predation on embryos and larvae. We experimentally measured rates of predation on embryos and larvae by adult woundfin at the Bozeman Fish Technology Center in Montana. Predation was a significant source of mortality on both embryos (W = 210, P < 0.001) and larvae (W = 45, P = 0.004). These rates of predation could translate into the loss of thousands of fish over the course of a spawning season at the conservation propagation facilities. We recommend removing embryos from spawning ponds and rearing them in separate tanks or ponds to reduce predation loss.

An integrated fish–plankton aquaculture system in brackish water

Integrated Multi-Trophic Aquaculture takes advantage of the mutualism between some detritivorous fish and phytoplankton. The fish recycle nutrients by consuming live (and dead) algae and provide the inorganic carbon to fuel the growth of live algae. In the meanwhile, algae purify the water and generate the oxygen required by fishes. Such mechanism stabilizes the functioning of an artificially recycling ecosystem, as exemplified by combining the euryhaline tilapia Sarotherodon melanotheron heudelotii and the unicellular alga Chlorella sp. Feed addition in this ecosystem results in faster fish growth but also in an increase in phytoplankton biomass, which must be limited. In the prototype described here, the algal population control is exerted by herbivorous zooplankton growing in a separate pond connected in parallel to the fish–algae ecosystem. The zooplankton production is then consumed by tilapia, particularly by the fry and juveniles, when water is returned to the main circuit. Chlorella sp. and Brachionus plicatilis are two planktonic species that have spontaneously colonized the brackish water of the prototype, which was set-up in Senegal along the Atlantic Ocean shoreline. In our system, water was entirely recycled and only evaporation was compensated (1.5% volume/day). Sediment, which accumulated in the zooplankton pond, was the only trophic cul-de-sac. The system was temporarily destabilized following an accidental rotifer invasion in the main circuit. This caused Chlorella disappearance and replacement by opportunist algae, not consumed by Brachionus. Following the entire consumption of the Brachionus population by tilapias, Chlorella predominated again. Our artificial ecosystem combining S. m. heudelotii, Chlorella and B. plicatilis thus appeared to be resilient. This farming system was operated over one year with a fish productivity of 1.85 kg/m2 per year during the cold season (January to April).

The Critical Thermal Maximum of Juvenile Red Drum Reared for Out‐of‐Season Stocking in Texas

AbstractHatchery‐propagated red drum Sciaenops ocellatus are released by the Texas Parks and Wildlife Department (TPWD) during the spring, summer, and fall to supplement natural stocks. Reported success of red drum stocked out of season in summer has been low or nonexistent; several potential causes, including mortality due to high temperatures, have been suggested. The present study was devised to determine the critical thermal maximum (CTM) of pond‐raised juvenile red drum that had previously been exposed to diurnal temperatures of the summer season. Laboratory studies designed to mimic the rate of temperature increase (0.25°C per hour) typical of TPWD rearing ponds were used to examine rates of mortality in juvenile red drum that were collected from three separate ponds exposed to the ambient fluctuating temperatures of the summer season. The CTM (temperature that was lethal to 50% of the test fish [LT50]) was significantly lower (P < 0.0001) for two of the fish trials (LT50 = 37.1°C and 37.0°C) than for a third trial (LT50 = 38.7°C). This difference correlated with the size of fish in each trial; the two trials with smaller‐sized fish (range = 18–32 mm total length) had the lower CTMs, whereas the trial with larger‐sized fish (range = 31–50 mm total length) had the higher CTM, suggesting positive size dependence in the CTM. The CTMs obtained here are higher than the maximum temperatures encountered in grow‐out ponds during summer, indicating that high temperature exposure may not be the sole cause for the low success of red drum stocked out of season.

Aquatic insects associated with two morphologically different submerged macrophytes, Lagarosiphon ilicifolius and Vallisneria aethiopica, in small fishless ponds

The study assessed the composition and abundance of insect assemblages associated with two submerged macrophytes, Lagarosiphon ilicifolius and Vallisneria aethiopica, in fishless ponds. Six ponds were used, with each plant occurring singly in two ponds, whilst the remainder had both plants. The insects were sampled using a 500-μm mesh. The number of insect taxa, diversity and total abundance on Lagarosiphon were greater than on Vallisneria when the plants occurred in separate ponds. In ponds comprising both plants, the total insect abundance on Lagarosiphon was greater than on Vallisneria. In all ponds, anisopteran naiads were dominant. Hemicordulia, Diplacodes and Trithemis made up 36.2, 27.1 and 15.2%, respectively, of the total number of insects on Lagarosiphon in single plant ponds. Trithemis was the only odonate in ponds comprised exclusively of Vallisneria and made up 68.7% of insects. In ponds that were cultured with both plants, four anisopteran taxa, Hemicordulia, Diplacodes, Trithemis and Tramea, were collected. In single plant ponds, the body-size class distribution of naiads on Lagarosiphon was characterised by a broader range, with significantly greater numbers of smaller and larger size classes than on Vallisneria (Kolmogorov–Smirnov test, P < 0.05). The study shows that in fishless waters, epiphytic insect assemblages may differ between the two plant species, especially when they are widely separated in space, probably due to greater predator–prey interactions on Vallisneria than on Lagarosiphon. The two plants may also differentially affect water physicochemical conditions, which may possibly influence insect ovipositing behaviour, and so affect insect community assemblage.

Occurrence of the lobose testate amoeba Pseudonebela africana (Amoebozoa, Arcellinida) in the Brazilian “cerrado”

Flagship species are defined as microbial eukaryote species with characteristic morphologies and restricted geographic distributions. These are proposed as ideal systems to elucidate patterns of geographical distribution in microbial eukaryotes. Here we present new records of the putative flagship species Pseudonebela africana, a lobose testate amoeba (Arcellinida) characterized by a cross or clover-shaped aperture and geographic distribution previously believed to be restricted to Africa. We have sampled P. africana from 5 separate ponds in the Central and Southwest Brazillian “cerrado”, and characterized individuals both by light and electron microscopy. We provide a brief description to facilitate further studies on this poorly understood taxon, and show that light microscopy is sufficient for identification, an important feature for ecological and biogeographical studies.

Prevalence and transmission of antimicrobial resistance among Aeromonas populations from a duckweed aquaculture based hospital sewage water recycling system in Bangladesh

In order to investigate the influence of a duckweed aquaculture based hospital sewage water recycling plant on the prevalence and dissemination of antibiotic resistance, we made use of an existing collection of 1,315 Aeromonas isolates that were previously typed by the biochemical fingerprinting PhP-AE system. In these treatment plant, hospital raw sewage water is first collected in a settlement pond (referred to as sewage water in this study) and is then transferred to a lagoon, where the duckweed (Lemnaceae) is grown (referred to as lagoon). The duckweed is harvested and used as feed for the fish in a separate pond (referred to as fish pond). From this collection, representatives of 288 PhP types were subjected to antibiotic susceptibility testing for eight antimicrobials by broth microdilution method. The overall resistance rates among Aeromonas isolates from the treatment plant were highest for ampicillin (87%) and erythromycin (79%) followed by cephalothin (58%), nalidixic acid (52%), streptomycin (51%), tetracycline (31%), chloramphenicol (13%) and gentamicin (8%). A significantly lower prevalence of antibiotic resistance was found in Aeromonas from environmental control water, patient stool samples, duckweed and fish compared to sewage water isolates. The prevalence of resistance in the sewage water was not significantly reduced compared to the lagoon water and fish pond. Throughout the treatment system, the frequencies of resistant strains were found to diminish during the sewage water purification process, i.e. in the lagoon where sewage water is used to grow the duckweed. However, the frequency of resistant strains again increased in the fish pond where sewage grown duckweed is used for aquaculture. Among the selected isolates, two multiresistant clonal groups of Aeromonas caviae HG4 were identified that exhibited indistinguishable PhP and amplified fragment length polymorphism fingerprints and shared a common plasmid of approximately 5 kb. Representatives of both groups were recovered from almost every part of the sewage treatment plant but not in the control ponds nor in human samples, which suggests that specific multiresistant Aeromonas clones are able to persist and spread throughout the entire purification process.

Delineating fine-scale genetic units in amphibians:Probing the primacy of ponds

The population structure of pond-breeding amphibians is shaped by their distinct breeding foci, but it is unclear to what extent this is reflected in the fine-scale distribution of genetic diversity. We used microsatellite genotypes to investigate the genetic signatures of 24 populations of European newts, Triturus cristatus and T. marmoratus, inhabiting 21 ponds in a confined study area (7.5 · 3.5 km) in western France. Employing a Bayesian clustering approach based on individual genotypes that minimises departures from Hardy–Weinberg equilibrium and linkage disequilibrium, no evidence was found for within-pond substructuring. Subjecting all sampled ponds simultaneously to this procedure revealed a clear signal of partitioning, with the most likely number of clusters however below the actual number of ponds (seven in T. cristatus, three in T. marmoratus). A more hierarchical Bayesian approach, with pond as analysis unit, was achieved to separate ponds from genetically more meaningful units, and reduced the T. cristatus populations to 11 clusters, and the T. marmoratus populations to five clusters. We were unable to specify a minimum nearest-neighbour distance where ponds are separate units, probably due to both historical and current demographic processes. The implications for strategies to manage and conserve endangered amphibians in human-altered landscapes are discussed.

Host specificity among Ancyrocephalinae (Monogenoidea) of Nebraska sunfish.

This study addressed the problem of local patterns of host specificity among Ancyrocephalinae (Monogenoidea) on bass and sunfish species, when the hosts occur in different species combinations in separate ponds. One hundred fifty-three fish of the Centrarchidae, from 4 study sites in Nebraska, were collected. Host species included bluegill (Lepomis macrochirus), green sunfish (L. cyanellus), largemouth bass (Micropterus salmoides), black crappie (Pomoxis nigromaculatus), white crappie (P. annularis), and rock bass (Ambloplites rupestris). These fish occurred in different species combinations, depending on the pond sampled. Results indicated that several centrarchid species could inhabit the same pond and yet support distinct monogene communities. Clavunculus bursatus, Onchocleidus helicis, O. principalis, and Syncleithrum fusiformis were found only on largemouth bass, regardless of what other centrarchids were present in a particular pond. Haplocleidus dispar occurred on green sunfish, bluegill, largemouth bass, and black crappie, and H. furcatus occurred on both bluegill and largemouth bass. Onchocleidus cyanellus and O. ferox were found on both bluegill and green sunfish. Rock bass were present in only 1 of the 4 ponds, but were not infected with any monogenes, even though co-occurring centrarchids were often heavily infected. Largemouth bass had the most diverse ancyrocephaline communities. The degree of parasite host specificity among these monogenes was inversely related to the diversity of host species present in a particular pond. In general, the parasites were more host specific than might be inferred from the literature; parasite species did not necessarily colonize supposedly receptive host species even when the latter were present, and host relatedness was the major factor in determining whether host species shared a common parasite species.

Evidence for individualistic species assembly creating convergent predator:prey ratios among pond invertebrate communities

summary Predator : prey ratios are cited as examples of a community level pattern, which suggests underlying assembly rules. Consistent ratios may result from either holistic community interactions or individualistic species assembly. This study tested for evidence of holistic or individualistic explanations for the predator : prey ratios among invertebrate communities of temporary ponds. Macroinvertebrate species were recorded from 30 adjacent experimental ponds, in January and early summer over 4 years. After the first 2 years either additional predatory or prey taxa were added to treatment ponds to skew the natural predator : prey ratios. Species richness and ratios were monitored for the following 2 years comparing treatment ponds subject to augmented predator or prey richness against unmanipulated control ponds. The majority of species added to treatments established in their respective ponds initially creating unusually high or low predator : prey ratios. In the 2 years following manipulation the ratios in treatment and control ponds converged. The convergence resulted from the spread of the additional species across all the ponds rather than acquisition or extinction of species within treatment ponds compensating for the skewed ratios. Convergent predator : prey ratios resulted from the spread of the augmented local species pool across the site rather than holistic community level adjustment within separate ponds. The results support individualistic models of community assembly as the explanation for convergent predator : prey ratios in pond habitats.

Variation in the Pattern of Predator-Induced Damage to Tadpole Tails

Tadpoles in nature are often found with injured tails. We introduce a planimetric technique for compiling data on the injuries sustained by individual tadpoles, which allows us to visualize and quantify the tail damage sustained by a population as a whole. We have used this technique to compare the pattern and severity of damage in tadpoles from seven species (Ascaphus truei, Bufo americanus, Phyllomedusa tomopterna, Pseudacris crucifer, Rana catesbeiana, Rana sylvatica, and Rhinophrynus dorsalis) that differ in microhabitat use (benthic vs pelagic), tail morphology (filamentous vs nonfilamentous) and palatability to predators. We also examined differences in tail damage across developmental stages. Finally, we compared interpopulation variation for R. sylvatica tadpoles from six separate ponds. The tail tip was the most commonly damaged area in all tadpoles, although the pattern and severity of injury varied greatly across species. Unpalatable, benthic larvae sustained small nicks around the margin of the tail, whereas pelagic and palatable species more often had the tail tip sheared off caudally. Little damage was found in any species in the anterior portion of the tail, where most thrust is generated during swimming. Only one species, A. truei, exhibited increased tail damage as the tadpoles aged. Later stage P. crucifer and R. sylvatica larvae in contrast, had significantly less tail damage than younger stage conspecifics. Although this could be the result of different healing rates at different stages, alternatively it suggests that for these species, survivorship is ultimately reduced in individuals that lose a substantial part of the tail when they are young.

Pathology, isolation, and preliminary molecular characterization of a novel iridovirus from tiger salamanders in Saskatchewan.

All iridovirus was confirmed to be the cause of an epizootic in larval and adult tiger salamanders (Ambystoma tigrinum diaboli) from four separate ponds in southern Saskatchewan (Canada) during the summer of 1997. This organism also is suspected, based on electron microscopic findings, to be the cause of mortality of larval tiger salamanders in a pond over 200 km to the north during the same year. Salamanders developed a generalized viremia which resulted in various lesions including: necrotizing, vesicular and ulcerative dermatitis; gastrointestinal ulceration; and necrosis of hepatic, splenic, renal, lymphoid, and hematopoietic tissues. In cells associated with these lesions, large lightly basophilic cytoplasmic inclusions and vacuolated nuclei with marginated chromatin were consistently found. Virus was isolated from tissue homogenates of infected salamanders following inoculation of epithelioma papilloma cyprini (EPC) cells. The virus, provisionally designated Regina ranavirus (RRV), was initially identified as an iridovirus by electron microscopy. Subsequent molecular characterization, including partial sequence analysis of the major capsid protein (MCP) gene, confirmed this assignment and established that RRV was a ranavirus distinct from frog virus 3 (FV3) and other members of the genus Ranavirus. Intraperitoneal inoculation of 5 x 10(6.23) TCID50 of the field isolate caused mortality in inoculated salamanders at 13 days post infection. Field, clinical, and molecular studies jointly suggest that the etiological agent of recent salamander mortalities is a highly infectious novel ranavirus.

Rates and pathways of benthic mineralization in extensive shrimp ponds of the Mekong delta, Vietnam

Benthic mineralization rates and pathways were measured in two extensive shrimp ponds of the Mekong delta, Vietnam. Sediments of both ponds were unconsolidated, oxic to suboxic silt-clays of neutral pH (6.8–7.3). Free sulfides and methane were not detected in the porewater, which was dominated by NH 4 + (up to 400 μM); other interstitial solutes were very variable among replicate cores, ponds, and sediment depths. Particulate C and N concentrations ranged from 2–8% and 0.15–0.36% by sediment dry weight (DW) with few depth differences between ponds. Pyrite was abundant (0.3–5.6% of sediment DW) in both ponds. Total carbon oxidation rates were not significantly different between the pond located separate from mangroves (separate pond) and the pond located within a mangrove forest (mixed pond). Fluxes of O 2 and CO 2 (=total carbon oxidation, T COX) were highly variable, with slow rates of CO 2 release (range: 7.7–30.5 mmol m −2 day −1) but higher rates of O 2 consumption (range: 9.8–135.9 mmol m −2 day −1), especially in the separate pond. A budget of the contribution of the various diagenetic pathways to total carbon oxidation indicates that aerobic respiration accounted for 41–60% of T COX, with active manganese and iron reduction in the mixed and separate ponds, respectively. No denitrification or methane flux was detected from sediments of either pond. Rates of sulfate reduction were slow (range: 0.94–2.73 mmol S m −2 day −1) and highly variable, accounting for 13–26% of T COX. Rates of solute flux across the sediment–water interface were dominated by DOC, NO 2 −+NO 3 −, and Mn. There was no measurable NH 4 + flux. Most light–dark bottle O 2 fluxes indicated no net benthic primary productivity. The slow rates of benthic decomposition and the dominance of oxic and suboxic pathways reflect the slow rates of organic matter input, and phytoplankton and shrimp production in these extensive ponds.

Distinguishing characteristics of temporary pond habitat of endangered northeastern bulrush,Scirpus ancistrochaetus

Habitat characteristics of wetlands that contain the federally endangered sedge,Scirpus ancistrochaetus, were investigated in a one-point-in-time field survey. Sixteen adjacent seasonal ponds, four of which supported populations ofS. ancistrochaetus. were sampled for 26 habitat variables. Using only five of these variables, we were able to separate ponds with and withoutS. ancistrochaetus in a linear discriminant analysis. These five variables are wetland area, percent cover of overlying forest canopy, soil percent organic matter, soil exchangeable [Na], and water [H−]. Ponds containingS. ancistrochaetus had higher soil organic matter content, highet soil [Na], greater area, lower water [H+], and lower percent forest canopy cover compared to ponds that did not support this species. This information can be used toward understanding factors that control the distribution of this species and also toward evaluating possible habitat for reintro-duction of this endangered species.

Improved Utilization of Pond Carrying Capacity by Increasing Initial Stocking Rates and Subsequent Stock Division1

AbstractFingerling channel catfish Ictaturus punctarus were stocked into eight 0.04‐ha ponds at 12,500 fishlha (treatment 1) and 50,000 fish/ha (treatment 2) with four ponds per treatment. At the end of of phase I (59 d) 50% of the fish were removed from each of the ponds in treatment 2 and divided equally into two ponds, forming treatment 3 (eight ponds at a density of 12,500 fish/ha). The remaining fish in treatment 2 (25,000 fish/ha) were maintained in the original ponds until the end of phase II (36 d). At this time, the fish were removed and equally divided at a density of 12,500 fish/ha into separate ponds. These ponds were continued to be denoted as treatment 2. All fish were grown for a total of 188 d. Production characteristics between treatments were compared at phases and at the end of the 188 d. There was no significant difference in feed conversion ratios due to treatment. The individual weights of the fish were higher in treatment I, but the difference occurred only in phase I. Size variabilities in treatments 2 and 3 were also higher than in treatment 1, which may cause a decrease in the percentage of marketable fish. Although there were some adverse effects due to the initial high stocking densities, overall pond production was higher in treatments 2 and 3. Treatment 2 had a daily net production of 49.9 ± 3.43 kg/ha and treatment 3 had 44.6 ± 3.81 kg/ha per d, compared to treatment 1 with only 32.4 ± 1.06 kg/ha per d (mean ± SD).