Experimental Ponds Research Articles

First detection of Erysipelothrix sp. infection in western mosquitofish Gambusia affinis inhabiting catfish aquaculture ponds in Mississippi, USA.

Native and introduced fish can serve as reservoirs for pathogens of cultured fish species. In the current study, 351 archived western mosquitofish Gambusia affinis collected from experimental catfish production ponds in Mississippi, USA, were surveyed histologically to evaluate their potential as vectors for fish pathogens. In addition to epitheliocystis and multiple metazoan parasites, 8 fish had widespread basophilic colonies of small Gram-positive rods associated primarily with stroma supporting the skeletal muscle and bone, as well as connective tissue components of other tissues and organ systems, such as perivascular adventitia and basement membranes. These findings were consistent with spaC-type Erysipelothrix sp. infections in ornamental fish cultured in the USA. The 16S rRNA, gyrase B (gyrB), and surface protective antigen (spa) genes were amplified and sequenced from bacterial colonies excised from paraffin-embedded tissue sections using laser capture microdissection. Molecular data confirmed the identity of a spaC-type Erysipelothrix sp., which grouped phylogenetically with spaC-type Erysipelothrix sp. from diseased ornamental fish. Given the significance of commercial catfish aquaculture in the southeastern USA and the widespread distribution of mosquitofish in catfish ponds throughout the region, infectivity trials with channel catfish Ictalurus punctatus were conducted. Catfish fingerlings were exposed to a spaC-type Erysipelothrix sp. isolate by intracoelomic injection and gavage. No mortality was observed in catfish exposed by either route, and surviving fish demonstrated no significant histopathologic lesions, suggesting channel catfish have low susceptibility to the bacteria. Further research is warranted to investigate the susceptibility of other cultured fish species to this emergent fish pathogen.

Differential oviposition and offspring success of gray treefrogs in the presence of an invasive fish

AbstractFemales often decide where to place their eggs or offspring based on the relative risks and benefits of a location. One trade‐off may be between ovipositing with predators and ovipositing with competitors. Many amphibians show risk‐sensitive oviposition and select oviposition sites based on offspring performance. We examined differential oviposition and offspring success by gray treefrogs (Hyla versicolor) in response to the presence of caged or free‐ranging invasive western mosquitofish (Gambusia affinis) using cattletank mesocosms as experimental ponds. Our experiment sought to answer these questions by comparing the number of eggs laid and tadpoles produced among the experimental treatments: (1) Do gray treefrogs exhibit risk‐sensitive oviposition? and (2) What is the relative importance of pre‐colonization and post‐colonization consumptive and trait‐mediated effects of western mosquitofish? Gray treefrogs laid more eggs in control and caged predator mesocosms than in free‐ranging predator mesocosms. At the end of the experiment, there were more tadpoles in control and caged predator mesocosms than in free‐ranging predator mesocosms. Proportional yield was lower in free‐ranging predator mesocosms than control and caged predator mesocosms. Eggs were laid 7–8 d earlier in control mesocosms than caged and free‐ranging predator mesocosms. Western mosquitofish therefore had a negative effect on the successful colonization of experimental ponds by gray treefrogs, most likely through direct physical interactions. Our results also suggest gray treefrogs shift oviposition preferences as the number of conspecifics reaches a threshold where competition risk outweighs predation risk. Western mosquitofish therefore have great potential to affect the distribution of gray treefrogs through pre‐ and post‐colonization effects.

Effects of rapid evolution on species coexistence

Increasing evidence for rapid evolution suggests that the maintenance of species diversity in ecological communities may be influenced by more than purely ecological processes. Classic theory shows that interspecific competition may select for traits that increase niche differentiation, weakening competition and thus promoting species coexistence. While empirical work has demonstrated trait evolution in response to competition, if and how evolution affects the dynamics of the competing species-the key step for completing the required eco-evolutionary feedback-has been difficult to resolve. Here, we show that evolution in response to interspecific competition feeds back to change the course of competitive population dynamics of aquatic plant species over 10-15 generations in the field. By manipulating selection imposed by heterospecific competitors in experimental ponds, we demonstrate that (i) interspecific competition drives rapid genotypic change, and (ii) this evolutionary change in one competitor, while not changing the coexistence outcome, causes the population trajectories of the two competing species to converge. In contrast to the common expectation that interspecific competition should drive the evolution of niche differentiation, our results suggest that genotypic evolution resulted in phenotypic changes that altered population dynamics by affecting the competitive hierarchy. This result is consistent with theory suggesting that competition for essential resources can limit opportunities for the evolution of niche differentiation. Our finding that rapid evolution regulates the dynamics of competing species suggests that ecosystems may rely on continuous feedbacks between ecology and evolution to maintain species diversity.

Effects of water depth and structural complexity on survival and settlement of white-spotted charr (Salvelinus leucomaenis)

Both climate change and dam operations are affecting water levels in river systems worldwide and their influence can be especially drastic in upper streams, where juvenile salmonids hatch and grow. However, efficient means of mitigating such influence on salmonid populations have not been developed, at least not in a practical manner throughout the world. In this study, we investigated effects of declining water levels and structural complexity on populations of age-0 white-spotted charr (Salvelinus leucomaenis) in tank and pond experiments. Survival of the charr was lower in the shallow tanks (15 cm water depth) than in the deeper ones. Similarly, more fish survived in the tanks with artificial structures (cobbles with Ringlong tape) compared to those without them. The grey heron (Ardea cinerea) was the most frequently observed predator during the tank experiment, and settlement of fish in the shallow ponds increased when artificial structures were provided. These results suggest that declining water levels and the loss of structural complexity may lead to a decrease in populations of white-spotted charr by increasing predation risk and interference competition.

Assessment of Water Quality and Thermal Stress for an Artificial Fish Shelter in an Urban Small Pond during Early Summer

: This study evaluated water quality variations in an artificial deep pool (ADP), which is an underground artificial structure built in a shallow pond as a fish shelter. The water temperature, pH, dissolved oxygen (DO), and electrical conductivity (EC) were measured on an hourly basis in the open space and inside the ADP, and a phenomenological study was performed, dividing seasons into normal and rainy seasons and environments into stagnant and circulating conditions. The results showed that the water quality parameters inside the ADP exhibit lower fluctuations and diurnal variations compared with the open space. On average, the water temperature inside the ADP is lower than outside it by 1.7–3.7 °C in stagnant conditions, and by 0.6–0.7 °C in circulating conditions during early summer. Thermal stratification occurs inside the ADP but is temporarily disturbed due to the mixing from the forced circulation and the rainwater input through rainfall events. The ADP provided a constant and optimal water temperature for living and spawning for bitterling (i.e., 15.0–21.0 °C), which dominated in experimental pond during spring to summer. Most importantly, the ADP was able to significantly reduce the thermal stress of the fish in the study site, and as a result, the bitterling, a cool water fish species, could successfully become dominant. Finally, the deployment of the ADP appears to provide a practical alternative for effective fishery resources management to improve species diversity and fish communities in an artificial freshwater ecosystem (garden pond, park pond, other artificial wetlands, etc.).

Competition during early ontogeny: Effects of native and invasive planktivores on the growth, survival, and habitat use of bluegill

Abstract Early life stages of fishes are sensitive to ecological and environmental disturbances and experience very high mortality rates. During early ontogeny, the growth and survival of larval fish often depends on food availability. Because habitat and diet shifts are strongly tied to individual body size, factors that influence the growth rates of individuals (e.g. resource limitation, competition) also affect other aspects of ontogeny including the timing of habitat or diet shifts. In the context of biological invasions, non‐native species can potentially disrupt the interaction of larval fish with their food via competition for shared prey, reducing growth and survival during a vulnerable period of an organism's life history. We hypothesised that invasive planktivores negatively affect native species through the vulnerable larval life stage via competition for zooplankton resources. To test this hypothesis, we conducted a series of experiments to assess and contrast the effects of invasive (bighead carp, Hypophthalmichthys nobilis) and native (golden shiners, Notemigonus crysoleucas) planktivores on zooplankton densities, and their effects on the growth, survival, abundance, and habitat use of larval bluegill (Lepomis macrochirus). Overall, the effects of the invasive planktivore were consistently greater than the native planktivore in terms of reduced prey densities, reduced bluegill growth rates, and delays to the timing of ontogenetic habitat shifts. Growth rates of bluegill larvae were reduced by 58–87% in the presence of bighead carp and 37% in the presence of golden shiners (relative to controls), but such reductions did not consistently lead to reduced survival (in mesocosm experiment) or relative abundance (in pond experiment). However, we estimated that bighead carp and golden shiners delayed ontogenetic habitat shifts in bluegill by 9–24 and 1–3 days, respectively. Although we did not detect an effect of planktivores on the numbers of larval bluegill, our findings suggest that bighead carp may still affect bluegill ontogeny and freshwater food webs by disrupting the timing of ontogenetic habitat shifts. By affecting the coupling of habitats via organism movements during early ontogeny, bighead carp may indirectly disrupt predator–prey interactions of native taxa.

Megalobrama amblycephala grazes preferentially on Hydrilla verticillata but makes more efficient use of Vallisneria denseserrulata: implications for biological control of submerged macrophytes

Growth of the meadow-forming macrophyte Vallisneria denseserrulata is often negatively impacted as result of shading by the canopy-forming Hydrilla verticillata. Grazing by the herbivorous cyprinid Megalobrama amblycephala is thought to control H. verticillata. We hypothesized that M. amblycephala would prefer H. verticillata over V. denseserrulata, and that where the latter is grazed, its growth will not be wholly compromised, due in part to the efficiency with which it is metabolized by the grazer. In a pond experiment, macrophytes were planted with monocultures of H. verticillata and V. denseserrulata, and in mixed cultures of the two species, with and without grazing by M. amblycephala. The results showed that in the absence of fish, the growth rate of V. denseserrulata was significantly reduced in the presence of H. verticillata. In the mixture, M. amblycephala had a significant negative effect on the growth of H. verticillata but not on V. denseserrulata. Grazing was associated with reductions in plant height, plant fresh weight and leaf fresh weight but the leaf number, maximum root length, maximum blade width, root weight and stem weight in V. denseserrulata increased. The food utilization ratio of M. amblycephala was significantly higher when grazing solely on V. denseserrulata than when grazing on H. verticillata or the mixture. Our results imply that V. denseserrulata is protected from overgrazing by the ability of M. amblycephala to make more effective metabolic use of ingested material than for H. verticillata. Furthermore, M. amblycephala is beneficial to V. denseserrulata in reducing competition from H. verticillata.

Influence of the Quality of Maintenance of Fish Ponds on the Biomass of Zooplankton <i>in situ</i> in Tropical Zone (Yaoundé-Cameroon-Central Africa)

A comparative study of the biomass of zooplankton of four semi-intensive fish ponds found in the ecological area of Yaounde in Cameroon was sampled for 9 months, which made it possible to evaluate the influence of the maintenance quality of the water bodies on their productivity. There were three ponds E1, E2, and E3 fertilized with organic and mineral matter, sampled from March to November 2012 on the one hand and on the other hand an experimental pond ET serving as a control, which was sampled from March to November 2014. ET was fertilized with mineral and organic matter and received particular attention during the first three months of breeding. The breeding method recommended in these ponds was the polyculture of Clarias gariepinus and Oreochromis niloticus. The samples were collected twice a month at 20 cm depth. Physico-chemical and biological analyses were measured using appropriate techniques. Zooplankton biomass remained very high in ET relative to E1, E2 and E3 (90% vs. 10%), creating an uneven profile in all water bodies. Minimum biomass values were 119 mg C / L in E1, 200 mg C / L in E2, 40 mg C / L in E3 and 781 mg C / L in ET; the maximum values being 748 mg C / L, 2643 mg C / L, 474 mg C / L and 67010 mg C / L in E1, E2, E3 and ET respectively. The largest contributors to this biomass were rotifers followed by Cladocerans in ET and E2 and Copepods followed by rotifers in E1 and E3. Food resources were thus limited in these last two water bodies compared to others. Abiotic and biological analyses indicate that these water bodies were oligomesotrophic (E1 and E3), mesotrophic (E2) and eutrophic (ET). ET under these conditions enabled the production of a satisfactory fish yield. It is therefore recommended that, fish farmers should improve the quality of maintenance of fish ponds which together with good fertilization will generate maximum productivity.

Effects of periphyton on monoculture of Puntius gonionotus

An experiment was carried out on the effects of periphyton on monoculture of Thai sharputi, Puntius gonionotus at the Department of Fisheries Management, Bangladesh Agricultural University, Mymensingh during 7th August to 8th November. In treatment-1 bamboo poles were used as artificial substrate for periphyton production and in treatment-2 there was no artificial substrate (control). Each of the six ponds was stocked with 150 fingerlings of average size 6.41 cm and 3.60 g. The ponds were fertilized fortnightly with manure (cow dung) at a rate of 10 kg decimal-1, urea 60 g decimal-1 and triple super phosphate 90 g decimal-1. During the experimental period, the ranges of physico-chemical parameters viz. air temperature (31.0-35.50C), water temperature (29-320C), water depth (0.56-0.84 m), transparency (32-63 cm), dissolved oxygen (3.5-7.8 mg L-1), pH (6.8-7.9), total alkalinity (44-92 mg L-1), free CO2 (1.5-4.0 mg L-1), phosphate-phosphorus (0.31-1.07 mg L-1) and nitrate-nitrogen (1.12-2.30 mg L-1) were within the productive range and more or less similar in the ponds under treatments-1 and 2. Among the observed biological parameters, there were 35 genera of phytoplankton composed of five groups and 13 genera of zooplankton composed of four groups in the experimental ponds. Thirty three genera under the groups of Bacillariophyceae, Chlorophyceae, Cyanophyceae and Euglenophyceae formed the periphyton on bamboo poles in the experimental ponds. Net fish production of the ponds with periphyton under treatment-1 was about 1.5 times higher than those of the ponds without periphyton (treatment-2). By analysis of variance, it was found that the net fish production of Thai sharputi under treatment-1 was significantly higher than that under treatment-2 (p< 0.05). Finally, it can be concluded that periphyton is one of the preferable food item of Thai sharputi and it is also suggested that growth and production of Thai sharputi can be increased if arrangement is made for periphyton production.
 Int. J. Agril. Res. Innov. & Tech. 8 (2): 13-23, December, 2018

Effects of different amounts of organic fertilizers on growth and production of tilapia in monoculture

The experiment was conducted to determine the effects of different amounts of organic fertilizers on growth and production of Tilapia (monosex GIFT tilapia) in monoculture system for a period of 120 days. The experiment was carried out in six earthen ponds, which were situated at the south-east corner of the Fisheries Faculty Building under the Department of Fisheries Management, Bangladesh Agricultural University, Mymensingh. The experiment was designed with three treatments and each of them consisted of two replications. Fish population density was 120 fish per decimal for all the treatments. Ponds were treated with organic fertilizers (cow dung) at the rate of 2 kg, 4 kg and 6 kg per decimal were supplied fortnightly for treatment-I, treatment-II and treatment-III, respectively. The ranges of water temperature, transparency, dissolved oxygen, total alkalinity, free CO2, phosphate-phosphorus and nitrate-nitrogen found were 15.82 to 24.49 ºC, 17.00 to 32.00 cm, 7.00 to 10.30 mg L-1, pH 7.20 to 7.90, 140.00 to 192.00 mg L-1, 2.00 to 6.00 mg L-1, 1.40 to 1.95 mg L-1 and 3.30 to 3.73 mg L-1, respectively. All the physical and chemical parameters except temperature were within the productive range and more or less similar among all the ponds under three treatments. 18 genera of phytoplankton under five major groups and 9 genera of zooplankton under three major groups were identified in the experimental ponds. Average survival rate of fish under treatment-I, treatment-II, and treatment-III were 94.50%, 94.00% and 95.00%, respectively. The calculated net fish production under treatment-I was 3.554 ton ha-1 yr-1 and that under treatment-II was 3.648 ton ha-1 yr-1 and under treatment-III was 2.919 ton ha-1 yr-1. The net fish productions under treatment-II and treatment-III were 102.64% and 82.13% comparing with treatment on which was taken for 100%. According to cost-benefit analysis, the ratios of net profit under treatments I, II, and III were 1:0.81, 1:0.54, and 1:0.04. According to specific growth rate, treatment-II was the best and survival rate of treatment-III was the best, and according to cost-benefit analysis, treatment-I (ratio 1:0.81) was the best. So, organic fertilizer at the rate of 2 kg per decimal (treatment-I) was considered the best among three treatments in this experiment.
 Int. J. Agril. Res. Innov. & Tech. 8 (2): 24-31, December, 2018

PERTUMBUHAN, SINTASAN DAN PRODUKSI IKAN NILA MERAH (Oreochromis niloticus) YANG DIBERI KOMBINASI PAKAN KOMERSIL DAN AMPAS TAHU HASIL FERMENTASI

The study aimed to evaluate the combination between commercial feed and fermented tofu waste feeding for growth, survival rate and production of red Tilapia Oreochromis niloticus in pond. The study was conducted in Experimental Pond Installation of Research Institute for Coastal Aquaculture, Maros, South Sulawesi, using eight ponds with 2,500 m2 in size. Red Tilapia fingerlings (±8 cm in length) were reared for 112 days with 1 individu/m2 of stocking density. The feeding treatments were of 100% commercial feed (A), 75% commercial feed + 25% fermented tofu waste (B), 50% commercial feed + 50% fermented tofu waste (C), and 25% commercial feed + 75% fermented tofu waste (D). Feeding frequency was given twice a day using concentration 10% of biomass weight in the first month, and decreased by 3% of biomass weight in the fourth month. Experimental was designed by a completely randomized designed consisted of four treatments and two replications for each treatment. Observed variables were growth, survival rate, feed conversion ratio, production, and water quality. Present study indicated that different levels of combination of commercial feed and fermented tofu waste had significant effect on growth (P<0.05), but did not have significant effect on survival rate, production, and feed conversion ratio (P>0.05). Feeding by combination of 75% commercial feed + 25% fermented tofu waste could be utilized optimally by Tilapia. During experiment, pond water quality was in conducive condition to support the growth and survival rate of red Tilapia.

Bottom-up and top-down effects of browning and warming on shallow lake food webs.

Productivity and trophic structure of aquatic ecosystems result from a complex interplay of bottom-up and top-down forces that operate across benthic and pelagic food web compartments. Projected global changes urge the question how this interplay will be affected by browning (increasing input of terrestrial dissolved organic matter), nutrient enrichment and warming. We explored this with a process-based model of a shallow lake food web consisting of benthic and pelagic components (abiotic resources, primary producers, grazers, carnivores), and compared model expectations with the results of a browning and warming experiment in nutrient-poor ponds harboring a boreal lake community. Under low nutrient conditions, the model makes three major predictions. (a) Browning reduces light and increases nutrient supply; this decreases benthic and increases pelagic production, gradually shifting productivity from the benthic to the pelagic habitat. (b) Because of active habitat choice, fish exert top-down control on grazers and benefit primary producers primarily in the more productive of the two habitats. (c) Warming relaxes top-down control of grazers by fish and decreases primary producer biomass, but effects of warming are generally small compared to effects of browning and nutrient supply. Experimental results were consistent with most model predictions for browning: light penetration, benthic algal production, and zoobenthos biomass decreased, and pelagic nutrients and pelagic algal production increased with browning. Also consistent with expectations, warming had negative effects on benthic and pelagic algal biomass and weak effects on algal production and zoobenthos and zooplankton biomass. Inconsistent with expectations, browning had no effect on zooplankton and warming effects on fish depended on browning. The model is applicable also to nutrient-rich systems, and we propose that it is a useful tool for the exploration of the consequences of different climate change scenarios for productivity and food web dynamics in shallow lakes, the worldwide most common lake type.

Positive correlation between dispersal and body size in Green Frogs (Rana clamitans) naturally colonizing an experimental landscape

Dispersers are often assumed to have the mean phenotype observed across the entire metapopulation, despite growing evidence of dispersal–phenotype correlations. We examined three dispersal–phenotype correlations in Green Frogs (Rana clamitans Latreille, 1801 = Lithobates clamitans (Latreille, 1801)). Two were in traits that have been previously tied to fitness (body size and body condition), while a third (relative hindlimb length) has been linked to movement performance. We constructed a spatially dispersed array of experimental ponds in close proximity to source ponds known to support Green Frog breeding populations. Over the course of two breeding seasons (four sampling periods), we measured phenotypes of all Green Frogs that had colonized the experimental ponds and a sample of individuals from the source ponds. After only 1 month, a positive correlation was detected between dispersal and body size within the population of dispersers occupying the experimental ponds. After a 2nd month, this positive dispersal – body size correlation was also present when comparing the population of dispersers to the population of nondispersers remaining at the source ponds. Even if generated solely by plasticity, a positive correlation between dispersal and body size (a trait tightly linked to fitness) has the ability to alter metapopulation capacity and thus the probability of regional species persistence.

Multiple density-dependent processes shape the dynamics of a spatially structured amphibian population.

Understanding the mechanisms that regulate the dynamics of spatially structured populations (SSP) is a critical challenge for ecologists and conservation managers. Internal population processes such as births and deaths occur at a local level, while external processes such as dispersal take place at an inter-population level. At both levels, density dependence is expected to play a critical role. At a patch scale, demographic traits (e.g., survival, breeding success) and the population growth rate can be influenced by density either negatively (e.g., competition effect) or positively (e.g., Allee effects). At the scale of an SSP, although positive density-dependent dispersal has been widely reported, an increasing number of studies have highlighted negative density-dependent dispersal. While many studies have investigated the effects of density on population growth or on dispersal, few have simultaneously examined density-dependent effects at the scale of both the local population and the entire SSP. In this study, we examine how density is related to demographic processes at both the pond level (survival and population growth) and the SSP level (between-pond dispersal) in a pond-breeding amphibian, the great crested newt (Triturus cristatus). The study was based on 20years of individual capture-recapture (CR) data (from 1996 to 2015) gathered from an SSP made up of 12 experimental ponds ("patches"). We first used a CR multievent model to estimate both survival and dispersal rates in specific ponds as a function of distance between ponds. Then, using a second CR multievent model, we examined whether survival and recapture rates were influenced by population density in a pond. Lastly, we used state-space time series models to investigate whether density affected population growth in each pond. Our results found a positive density-dependent effect on survival and a negative density-dependent effect on departure. In addition, the findings indicate that population growth was negatively related to density in all 12 ponds. These results support the hypothesis that in SSPs, density may have multiple and contrasting effects on demographic parameters and growth rates within local populations as well as on dispersal. This study underlines the need to better understand how density dependence may influence potential trade-offs between life-history strategies and life-history stages.

Context-dependent dispersal, public information, and heterospecific attraction in newts.

Dispersal is one of the main processes that determine community structure. Individuals make dispersal decisions according to environmental and/or social cues that reflect the fitness prospects in a given patch. The presence and abundance of heterospecifics within the same ecological guild, and/or their breeding success, may act as public information that influences movement decisions. To date, most studies investigating the role of heterospecific attraction have focused on habitat choice, using both experimental and correlational approaches. The present study is the first to examine how long-term variation in heterospecific density in breeding patches may affect dispersal patterns in spatially structured populations. We investigate how the dispersal decisions of the great crested newt (Triturus cristatus) are related to the variable density of two other newt species, the alpine newt (Ichthyosaura alpestris) and the palmate newt (Lissotriton helveticus). To examine this issue, we used capture-recapture data collected in an experimental pond network over a 20-year period. The results revealed that the great crested newt's dispersal is context dependent and is affected by variation in heterospecific density: individuals were less likely to emigrate from ponds with high heterospecific density and were more likely to immigrate to ponds with high heterospecific density. These findings suggest that individuals adjust their dispersal decisions at least partly based on public information provided by heterospecifics. This mechanism may play a critical role in the dynamics of spatially structured populations and community functioning.

Review on Solar Ponds in Libya

Solar and renewable energies applications got great interest and attention in the last few decades. Problems related to CO2 emissions, air pollution, Ozone layer depletion, global warming, and environmental issues raise the necessity for getting clean and safe energy. For this purpose, the Center for Solar Energy Studies (CSERS) in Libya conducted huge research work in different applications for solar and renewable energies. One of these important activities is the Solar Gradient Solar Pond technology. It is an effective solar energy collection and storage system which presents a relatively simple and economic method of providinglow-grade energy with the advantage of an annual storage cycle.This paper presents a general review of researches and studies on solar ponds that were conducted by the CSERS research team. Tajoura’s Experimental Solar Pond (TESP) is designed as an experimental facility enabling the investigation of various aspects of pond performance. It is constructed by the Center for Solar Energy Studies, in joint cooperation with a Swiss company, with a surface area of about 830 m2, and a depth of 2.5 m, coupled with an evaporative pond of 105 m2 area and 1.5 m deep, equipped with all necessary equipment and measuring control system.The paper also shows the experience of operating MSF desalination unit coupled with TESP solar pond. Finally, other factors affecting the solar pond’s thermal stability were also discussed.

ВЛИЯНИЕ ПОКАЗАТЕЛЕЙ РАЗВИТИЯ ЗООПЛАНКТОНА НА РОСТ РАЗЛИЧНЫХ ВОЗРАСТНЫХ ГРУПП РУССКОГО ОСЕТРА, ВЫРАЩИВАЕМОГО В ПРУДАХ РЫБОВОДНОГО ХОЗЯЙСТВА АЛМАТИНСКОЙ ОБЛАСТИ

The article studies the species composition of zooplankton in experimental hatchery ponds for breeding Russian sturgeon using the observations of 4-year data. The data onabundance and biological mass of zooplankton in experimental ponds used for breeding Russian sturgeon in the age 2-5 years has been presented. The dynamics of these parameters during the fish-breeding season is shown. The part of zooplankton organisms which can be considered as valuable feeding for Russian sturgeon (cladoceras) in relation to the total mass of zooplankton has been determined;their population and biological mass within a reproduction periodhave been presented. The prevalence of cladocerasin the number and biological mass above other zooplankton organisms in experimental ponds has been shown. The equations of regression of mass growth and zoological length of a body of 2-year, 3-year, 4-year and 5-year Russian sturgeon speciesgrown in experimental ponds have been presented. Great practical value have calculations of zooplankton biological mass which is optimal for breeding Russian sturgeon in the ponds of the Chilik hatchery of the Almaty region. There has been determined a connection between zooplankton biological mass and coefficients of mass and linear growth of different age groups of Russian sturgeon. There has been found correlation between the parameter of growth rate of zoological length of a body and the mean biological mass of zooplankton; weak correlative relation was observed between the growth parameter in the equation of weight growth of age groups of Russian sturgeon (3-year, 4-year and 5-year old species) grown in ponds, and average biological mass of zooplankton in these ponds. The recommendations on optimization of growing zooplankton in ponds of carp hatcheries used for breeding Russian sturgeon in order to raise their feeding status have been given.

Embracing scale‐dependence to achieve a deeper understanding of biodiversity and its change across communities

Because biodiversity is multidimensional and scale-dependent, it is challenging to estimate its change. However, it is unclear (1) how much scale-dependence matters for empirical studies, and (2) if it does matter, how exactly we should quantify biodiversity change. To address the first question, we analysed studies with comparisons among multiple assemblages, and found that rarefaction curves frequently crossed, implying reversals in the ranking of species richness across spatial scales. Moreover, the most frequently measured aspect of diversity - species richness - was poorly correlated with other measures of diversity. Second, we collated studies that included spatial scale in their estimates of biodiversity change in response to ecological drivers and found frequent and strong scale-dependence, including nearly 10% of studies which showed that biodiversity changes switched directions across scales. Having established the complexity of empirical biodiversity comparisons, we describe a synthesis of methods based on rarefaction curves that allow more explicit analyses of spatial and sampling effects on biodiversity comparisons. We use a case study of nutrient additions in experimental ponds to illustrate how this multi-dimensional and multi-scale perspective informs the responses of biodiversity to ecological drivers.

Poststocking Survival of Conditioned and Pond‐Reared Compared to Indoor Pellet‐Reared Advanced Fingerling Florida Bass

AbstractSupplemental stocking of hatchery Largemouth Bass Micropterus salmoides and Florida Largemouth Bass Micropterus salmoides floridanus (hereafter, Florida Bass) is a common practice around the world, but the results commonly do not meet expectations. Predation upon stocked fish and the inefficiency of stocked fish in capturing wild prey are common reasons for low poststocking survival rates of hatchery fish. Standard protocol for rearing Florida Bass in Florida includes growing fish out in indoor raceways with pellet feed until 5 d prior to stocking, when live prey is introduced. We conducted a 3‐year study to determine whether extended conditioning in outdoor ponds, exposure to predators prior to stocking, or rearing in ponds rather than indoor raceways could increase the survival of hatchery‐reared Florida Bass. One month after stocking, mean survival for standard hatchery‐reared fish that received pellets was 36% (SE = 4.3) across all 3 years. Mean survival was 63% (SE = 4.7) for experimental fish conditioned with predators (E‐CWP), 41% (SE = 4.8) for fish conditioned without predators (E‐CWOP), and 63% (SE = 5.4) for fish raised on live prey in outdoor ponds in the absence of predators (E‐PR). While stocked in research ponds, E‐CWP and E‐PR fish had higher growth rates than standard pellet‐reared fish. During laboratory trials to measure predator avoidance rates, which began 24 h after experimental ponds were stocked, standard pellet‐reared fish had a mean 48‐h survival rate of 84% (SE = 6.6). Mean 48‐h survival for the E‐CWP, E‐CWOP, and E‐PR groups was 96% (SE = 1.9), 84% (SE = 7.2), and 95% (SE = 3.1), respectively. Our experiments indicate that being reared outside or conditioning to a natural environment and exposure to predators may increase poststocking survival of hatchery‐reared Florida Bass.

ВЛИЯНИЕ УСЛОВИЙ ВЫРАЩИВАНИЯ НА МОРФО-БИОЛОГИЧЕСКИЕ ОСОБЕННОСТИ СЕГОЛЕТОК СТЕРЛЯДИ (ACIPENSER RUTHENUS (LINNAEUS))

Paper shows research data considering investigation and analysis of specific technological parameters due to external and internal marks of sterlet. Our research goal is to analyze influence of specific sterlet rearing conditions on the morphological, biochemical and hematological marks. Sterlet fry and fingerlings were the object of investigation. Sterlet fingerlings rearing was conducted in experimental ponds (2 ha square) of Dnieprovsky surgeon fish hatching facility. Three variances were formed: І – without fertilizers; ІІ – with organic (3 t/ha) and inorganic fertilizers (50 kg/ha); control – with organic fertilizers (5 t/ha). Stocking density in ponds ranged 95k-100k fishes/ha, stock bodymass ranged from 77,5 to 85,0 mg. Analysis of hydrochemical, morphometric and fishery marks was made according to well-known methods. Water temperature was ranged from 20°С to 27°С, average 24,2–25,4°С. Dissolved oxygen was about 4,6-10,4 mgО 2 /dm 3 . Phytoplankton biomass in I variance ponds ranged from 9,95 to 11,05 g/m 3 , in II variance ponds – 13,6-16,0 g/m 3 . The most abundant zooplankton and zoobenthos was registered in second variance, which was caused by using organic and inorganic fertilizers. Thus, zooplankton biomass was about 8,3–8,6 g/m 3 , zoobenthos –6,69–7,71 g/m 2 . As a result of rearing we received sterlet fingerlings with average individual bodymass 3,2±0,25 g (I variance), 4,17±0,30 g (II variance). The best survival rate (69.55%) and fish productivity (267kg/ha). We can see apparent difference in morphometric if we compare body length (M diff = 3,28-4,08.), pectoventral distance (M diff = 3,10-3,28) and bodymass (M diff = 3,22-3,96). Fulton’s condition factor was ranged from 0,70 in I variance (Cv = 28,21%) to 0,80 in II variance (Cv =27,73%). Analyzing chemical composition of sterlet fingerlings muscle tissue, we defined that moisture was about 80,0–82,2%, lipids – 1,8–2,0%, inorganic – 0,9–1,4%. Protein ranged from 12,6-12,9% (I variance) to 15,0-15,4% (II variance). Overall, biochemical marks of sterlet fingerlings corresponded to physiological standard for this age category. Sterlet fingerling muscle tissue contained less than 0,05% of ammonia, 35,6-50,0 mg/kg of nitrates, 0,6-1,8 mg/kg of nitrites, 190,0-220,0 mg/kg of phosphorus, 0,2-0,22% of NaCl. Acid value for lipids ranged from 0,1 to 0,3 mgКОН. Comparative hematology analysis defined that haemoglobin concentration in different variances ranged from 85 to 159 g/l. Red blood cells concentration was about 0,51-0,93 Т/l, leucocytes - 153-208 g/l, thrombocytes – 25-106 g/l. Relative standard deviation for red blood cells – from 11,8 to 36,4%. Mathematical analysis allowed us to build polynomial equations with coefficient of determination as much as 0,7892–0,9083. Also we investigated influence of rearing conditions in ponds of different fish farms on the separate blood marks. We defined reasonable correlation between level of intensification and main fishery indexes, such as bodymass, fish productivity and survival rate and biochemical marks. Obtained data complement existing technology of sterlet combined rearing in ponds of Southern Ukraine due to its later introduction into natural water reservoirs. Also obtained data may be used in modern aquaculture according to its rearing goals. Keywords: sterlet, fingerling, pond rearing, intensification, fertilizer, survival rate, average individual bodymass, fish productivity, red blood cells, protein, fat.