Pond Populations Research Articles

Rapid evolution of consumptive and non-consumptive predator effects on prey population densities, bioenergetics and stoichiometry.

Predators can strongly influence prey populations not only through consumptive effects (CE) but also through non-consumptive effects (NCE) imposed by predation risk. Yet, the impact of NCE on bioenergetic and stoichiometric body contents of prey, traits that are shaping life histories, population and food web dynamics, is largely unknown. Moreover, the degree to which NCE can evolve and can drive evolution in prey populations is rarely studied. A 6-week outdoor mesocosm experiment with Caged-Fish (NCE) and Free-Ranging-Fish (CE and NCE) treatments was conducted to quantify and compare the effects of CE and NCE on population densities, bioenergetic and stoichiometric body contents of Daphnia magna, a keystone species in freshwater ecosystems. We tested for evolution of CE and NCE by using experimental populations consisting of D. magna clones from two periods of a resurrected natural pond population: a pre-fish period without fish and a high-fish period with high predation pressure. Both Caged-Fish and Free-Ranging-Fish treatments decreased the body size and population densities, especially in Daphnia from the high-fish period. Only the Free-Ranging-Fish treatment affected bioenergetic variables, while both the Caged-Fish and Free-Ranging-Fish treatments shaped body stoichiometry. The effects of CE and NCE were different between both periods indicating their rapid evolution in the natural resurrected population. Both the Caged-Fish and Free-Ranging-Fish treatments changed the clonal frequencies of the experimental Daphnia populations of the pre-fish as well as the high-fish period, indicating that not only CE but also NCE induced clonal sorting, hence rapid evolution during the mesocosm experiment in both periods. Our results demonstrate that CE as well as NCE have the potential to change not only the body size and population density but also the bioenergetic and stoichiometric characteristics of prey populations. Moreover, we show that these responses not only evolved in the studied resurrected population, but that CE and NCE also caused differential rapid evolution in a time frame of 6 weeks (ca. four to six generations). As NCE can evolve as well as can drive evolution, they may play an important role in shaping eco-evolutionary dynamics in predator-prey interactions.

Regional and fine-scale local adaptation in salinity tolerance in Daphnia inhabiting contrasting clusters of inland saline waters.

Understanding the spatial scales at which organisms can adapt to strong natural and human-induced environmental gradients is important. Salinization is a key threat to biodiversity, ecosystem functioning and the provision of ecosystem services of freshwater systems. Clusters of naturally saline habitats represent ideal test cases to study the extent and scale of local adaptation to salinization. We studied local adaptation of the water flea Daphnia magna, a key component of pond food webs, to salinity in two contrasting landscapes-a dense cluster of sodic bomb crater ponds and a larger-scale cluster of soda pans. We show regional differentiation in salinity tolerance reflecting the higher salinity levels of soda pans versus bomb crater ponds. We found local adaptation to differences in salinity levels at the scale of tens of metres among bomb crater pond populations but not among geographically more distant soda pan populations. More saline bomb crater ponds showed an upward shift of the minimum salt tolerance observed across clones and a consequent gradual loss of less tolerant clones in a nested pattern. Our results show evolutionary adaptation to salinity gradients at different spatial scales, including fine-tuned local adaptation in neighbouring habitat patches in a natural landscape.

Relaxed risk of predation drives parallel evolution of stickleback behavior.

The occurrence of similar phenotypes in multiple independent populations derived from common ancestral conditions (viz. parallel evolution) is a testimony of evolution by natural selection. Parallel evolution implies that populations share a common phenotypic response to a common selection pressure associated with habitat similarity. Examples of parallel evolution at genetic and phenotypic levels are fairly common, but the driving selective agents often remain elusive. Similarly, the role of phenotypic plasticity in facilitating early stages of parallel evolution is unclear. We investigated whether the relaxation of predation pressure associated with the colonization of freshwater ponds by nine-spined sticklebacks (Pungitius pungitius) likely explains the divergence in complex behaviors between marine and pond populations, and whether this divergence is parallel. Using laboratory-raised individuals exposed to different levels of perceived predation risk, we calculated vectors of phenotypic divergence for four behavioral traits between habitats and predation risk treatments. We found a significant correlation between the directions of evolutionary divergence and phenotypic plasticity, suggesting that divergence in behavior between habitats is aligned with the response to relaxation of predation pressure. Finally, we show alignment across multiple pairs of populations, and that relaxation of predation pressure has likely driven parallel evolution of behavior in this species.

Asynchrony, density dependence, and persistence in an amphibian.

Understanding drivers of metapopulation dynamics remains a critical challenge for ecology and conservation. In particular, the degree of synchrony in metapopulation dynamics determines how resilient a metapopulation is to a widespread disturbance. In this study, we used 21 years of egg mass count data across 64 nonpermanent freshwater ponds in Connecticut, USA to evaluate patterns of abundance and growth and to assess regional as well as local factors in shaping the population dynamics of wood frogs (Rana sylvatica=Lithobates sylvaticus). In particular, we asked whether a species known to undergo metapopulation dynamics exhibited spatial synchrony in abundances. With the exception of a single year when breeding took place during severe drought conditions, our analyses revealed no evidence of synchrony despite close proximity (mean minimum distance < 300 m) of breeding ponds across the 3213-ha study area. Instead, local, pond-scale conditions best predicted patterns of abundance and population growth rate. We found negative density dependence on population growth rate within ponds as well as evidence that larger neighboring pond populations had a negative effect on focal ponds. Beyond density, pond depth was a critical predictor; deeper ponds supported larger populations. Drought conditions and warm winters negatively affected populations. Overall, breeding ponds vary in critical ways that either support larger, more persistent populations or smaller populations that are not represented by breeding pairs in some years. The infrequency of spatial synchrony in this system is surprising and suggests greater resilience to stressors than would have been expected if dynamics were strongly synchronized. More generally, understanding the characteristics of systems that determine synchronous population dynamics will be critical to predicting which species are more or less resilient to widespread disturbances like land conversion or climate change.

Population structure and genetic diversity of the threatened pygmy newt Triturus pygmaeus in a network of natural and artificial ponds

Pond physical characteristics (connectivity, hydroperiod) have shown to be highly relevant in explaining species presence, reproductive success, and survival in breeding-pond amphibians. However, few studies have addressed the influence that these factors may have on the genetic variability of pond populations. We examined genetic variation at 11 microsatellite loci in Iberian endemic, the pygmy newt (Triturus pygmaeus), from 58 breeding ponds in the Doñana National Park (Andalusia), including both temporary ponds and artificially deepened ponds that remain wet during the whole year. Temporary ponds are located in the North part of the region where the surrounding habitat-wet meadows-facilitates the connectivity among populations, whereas the deepest ponds (‘zacallones’) are located in the southern edge embedded in a matrix of unsuitable habitat (thickets and dry underbrush). We investigated genetic diversity and structure within and among ponds. Our results show that both regions (Doñana-North and Doñana-South) are well-differentiated and form two main clusters. We found higher genetic diversity within ponds from the North region, which also exhibited a higher degree of genetic admixture in comparison with populations from the southern edge. Although we found an isolation-by-distance pattern within each cluster, it arose due to the effect of a few isolated ponds located on the edge of each zone, suggesting the existence of substantial gene flow between ponds in the core area. According to our findings, landscape’s permeability to movement (pond connectivity) may constitute a more important factor than hydroperiod length in determining the genetic diversity and viability of pygmy newt populations in this area. Although Doñana populations show a good state, more peripheral and isolated populations present a more worrisome condition as a result of fragmentation and thus, require conservation efforts. Our study provides key insights that could help guide management practices of this threatened and poorly-studied salamander.

Genetic Diversity and Structure of Anax imperator Leach, 1815 Populations (Odonata: Aeshnidae) in Ponds at Regional and European Scales

Anthropogenic activities cause loss and fragmentation of natural habitats and have strong effects on population maintenance by increasing their isolation. Pond ecosystems are scattered waterbodies that can interact as a network connected by dispersal events of freshwater organisms. Identifying local genetic differentiations and understanding how gene flow occurs across these networks is essential to prevent risks associated with environmental perturbations. This study aimed to investigate genetic diversity and structure of Anax imperator Leach, 1815 populations at both regional and European scales using seven microsatellites markers. Seven populations of A. imperator were sampled in northwestern France and four populations were sampled in Italy (Sicily), Czech Republic, Switzerland and United Kingdom (U.K.). French populations presented a low genetic differentiation indicating a high gene flow and confirming dispersal events of this species between ponds at regional scale. No pattern of isolation by distance was found at the European scale. The populations presented a low genetic differentiation and no pattern of isolation by distance, suggesting historical or current movements of individuals. Only the U.K. population presented a significant genetic differentiation from other European populations, suggesting that the English Channel might act as a barrier to gene flow for A. imperator. However, Bayesian analysis showed that some dispersal events could occur between the U.K. and France (Normandy), probably facilitated by prevailing winds.

Preliminary Data on the Taxonomic Composition and the Spatio-Seasonal Variation of the Zooplanktonic Population of Fish Ponds in Kisangani, DR Congo

The overall objective of this study was to determine the taxonomic composition and spatial seasonal variation of the zooplankton population in fish ponds in Kisangani, DR Congo. The collection of zooplankton in fishponds was carried out using plankton nets in the Artisanal and Plateau boyoma districts for four months, two months per season. At the end of this study, 3 sub-classes, 13 families and 22 species were listed. The subclass Monogononta (Rotifers) was the best represented with 7 families and 14 species identified. On the other hand, the family Brachionidae was the richest with 6 species. The high specific richness of zooplankton according to site and season was recorded in the Artisanal district with 19 species and in the rainy season with 22 species. Thus, it should be noted that the fish ponds of Kisangani have a high specific diversity of zooplankton that can vary according to the sites and seasons. Certain species such as Tropocyclops prasinus prasinus, Moina macrocopa, Brachionus falcatus, Thermocyclops sp and Brachionus calyciflorus are more abundant than others present. However, the list of species presented is not exhaustive given the sampling period, which was only 4 months, and the collection effort, which was only carried out at two sites.

Rapid microgeographic evolution in response to climate change.

Environmental change is predicted to accelerate into the future and will exert strong selection pressure on biota. Although many species may be fated to extinction, others may survive through their capacity to evolve rapidly at highly localized (i.e., microgeographic) scales. Yet, even as new examples have been discovered, the limits to such evolutionary responses have not often been evaluated. One of the first examples of microgeographic variation involved pond populations of wood frogs (Rana sylvatica). Although separated by just tens to hundreds of meters, these populations exhibited countergradient variation in intrinsic embryonic development rates when reared in a common garden. We repeated this experiment 17 years (approximately six to nine generations) later and found that microgeographic variation persists in contemporary populations. Furthermore, we found that contemporary embryos have evolved to develop 14-19% faster than those in 2001. Structural equation models indicate that the predominant cause for this response is likely due to changes in climate over the intervening 17 years. Despite potential for rapid and fine-scale evolution, demographic declines in populations experiencing the greatest changes in climate and habitat imply a limit to the species' ability to mitigate extreme environmental change.

The time course of molecular acclimation to seawater in a euryhaline fish

The Arabian pupfish, Aphanius dispar, is a euryhaline fish inhabiting both inland nearly-freshwater desert ponds and highly saline Red Sea coastal lagoons of the Arabian Peninsula. Desert ponds and coastal lagoons, located respectively upstream and at the mouths of dry riverbeds (“wadies”), have been found to potentially become connected during periods of intense rainfall, which could allow the fish to migrate between these different habitats. Flash floods would therefore flush Arabian pupfish out to sea, requiring a rapid acclimation to a greater than 40 ppt change in salinity. To investigate the molecular pathways of salinity acclimation during such events, a Red Sea coastal lagoon and a desert pond population were sampled, with the latter exposed to a rapid increase in water salinity. Changes in branchial gene expression were investigated via genome-wide transcriptome measurements over time from 6 h to 21 days. The two natural populations displayed basal differences in genes related to ion transport, osmoregulation and immune system functions. These mechanisms were also differentially regulated in seawater transferred fish, revealing their crucial role in long-term adaptation. Other processes were only transiently activated shortly after the salinity exposure, including cellular stress response mechanisms, such as molecular chaperone synthesis and apoptosis. Tissue remodelling processes were also identified as transient, but took place later in the timeline, suggesting their importance to long-term acclimation as they likely equip the fish with lasting adaptations to their new environment. The alterations in branchial functional pathways displayed by Arabian pupfish in response to salinity increases are diverse. These reveal a large toolkit of molecular processes important for adaptation to hyperosmolarity that allow for successful colonization to a wide variety of different habitats.

Comparing Regression Models with Count Data to Artificial Neural Network and Ensemble Models for Prediction of Generic Escherichia coli Population in Agricultural Ponds Based on Weather Station Measurements

Indicator microorganisms are monitored in agricultural waters to foster produce safety. Various prediction models are used to estimate the population of indicator microorganisms and pathogens when no observation is available. The purpose of this study was to compare the performance of regression models with count data (zero-inflated Poisson and hurdle negative binomial) to artificial neural network and ensemble models (random forest and AdaBoost) for the prediction of generic Escherichia coli population in agricultural surface waters in relation with weather station measurements. Two-part count data models were built on E. coli population count frequencies (0, [1,10), [10,100), [100,1000), [1000, 10000), (>=10000)) based on the data structure. The use of artificial neural network, AdaBoost, and random forest were determined based on the mean absolute error (MAE) value over pre-tested six models. The MAE was also used to compare the performance of two-part count data models with artificial neural network and ensemble models. Over-dispersed E. coli population count frequencies was calculated between 2.2 and 52.2% for all ponds. Observed and predicted zero E. coli population counts for all ponds were matched from 82 to 100% for zero-inflated Poisson and 100% for hurdle negative binomial regression models. Overdispersion reduced the performance of tested models. AdaBoost-Twelve Estimators had the best performance with the lowest MAE values for all ponds (from 0.87 to 46.60). The ensemble models used in this study provided more promising performance when compared to tested regression models with count data.

Consistency in the life history traits of four invasive pseudorasbora parva populations in Southern England

Life history plasticity can be a strong predictor of the establishment and invasion success of introduced fishes. Here, the life-history traits of four P. parva populations in adjacent ponds in Southern England were measured throughout 2013 to determine the timing and length of their reproductive season and the extent of trait plasticity. The relative abundance of the populations (as catch per unit effort) was similar, with low variability in their traits relating to reproductive effort and somatic growth. All the populations were male dominated. Both sexes matured at small body sizes, with fish as small as 30 mm being mature in both sexes, with the age at maturity for both sexes being age 1+ years. The peak spawning period, characterised by female fish investing heavily in reproduction when their gonado-somatic index (GSI) values were highest and declined thereafter, occurred in May and June, and after a mean of 212 ± 24 degree-days >12°C, and with water temperatures being 13.2–14.6°C. There were no further peaks in GSI, despite the species being considered to have prolonged spawning periods across spring and summer. These results also suggest that whilst the expression of life-history traits of invasive fishes often vary with density, they can be highly consistent between populations at similar abundances and locations.

Suckermouth armoured catfish (Pterygoplichthys spp.) menace in freshwater aquaculture and natural aquatic systems in Andhra Pradesh, India

Suckermouth armoured catfish (Pterygoplichthys spp.) which is popularly called “Devil fish” in Andhra Pradesh, was recorded in 93.33% of fish ponds out of 600 ha surveyed in Krishna and West Godavari districts including mesohaline ponds wherein salinity ranges from 2 to 20‰. Pterygoplichthys spp. have ranged from 150 to 600 kg/ha that accounts to 2.01-7.50% of total biomass of fish harvested in aquaculture ponds leading to escalation of feed conversion ratio by 25.76%. Consequently, carp production has diminished by 18.88% to 22.92% leading to economic losses to fish farmers up to 13.40%. Food chain disruption by this alien fish is not only confined to benthic algae and periphyton but also foraging on supplementary feeds leaving primary fishes deprived from availing feed. Abundance of Pterygoplichthys spp populations in culture ponds as also in canals was high in monsoon season when compared to winter. Invasion and abundance of Pterygoplichthys spp in various river systems in Andhra Pradesh has become major concern for fishers causing extensive damage to nets and gears as also retarded catch per unit effort resulting in minimization of their income by 30%. Efforts to extract fish hydrolysate from Pterygoplichthys spp were futile due to intense bony skeleton and poor recovery rate which projected utilization of this fish for allied activities to minimum. Abundance of Pterygoplichthys spp is increasing in confined and open water bodies due to their tolerance and ability to grow and breed in variety of aquatic habitats including polluted environments as also lack of effective predators thus poses a high risk and threat to native freshwater species in any ecosystem in which they get established.

Molecular identification and population differentiation of Aurelia spp. ephyrae in sea cucumber aquaculture ponds of northern China

Aurelia spp. ephyrae have been reported to form blooms in sea cucumber aquaculture ponds in the Bohai and Yellow Seas. To identify the species, we carried out a genetic analysis of Aurelia spp. ephyrae and medusae based on mitochondrial 16S rRNA gene. Samples of four Aurelia sp. ephyrae populations were collected in sea cucumber aquaculture ponds and samples of four Aurelia sp. medusae populations were collected in coastal waters. Using a BLASTn search, we found that both the ephyrae collected in the aquaculture ponds and medusae collected in coastal waters belong to Aurelia coerulea. Seventeen haplotypes were recovered from the 16S rRNA gene. The overall haplotype diversity and nucleotide diversity of the 166 A. coerulea individuals were 0.686 and 0.329%, respectively, indicating high haplotype diversity and low nucleotide diversity. Moreover, the haplotype diversity of ephyrae populations were generally lower than that of medusae populations with close sampling points. The genetic differentiation between ephyrae populations collected in the sea cucumber aquaculture ponds and A. coerulea medusae collected in coastal waters was not significant, suggesting the ephyrae populations in the sea cucumber culture ponds were part of the same genetic group as the medusae populations in the coastal waters. Phylogeographic analysis of the 16S rRNA region revealed that there was no significant correlation between the haplotypes and the geographic distribution of populations. Pairwise fixation index values showed significant genetic differentiation and limited gene flow between A. coerulea population of Weifang and other locations.

Demographic characteristics of young-of-year freshwater mussel populations in ponds

We describe demographics of young-of-year (YOY) Pondmussels (Ligumia subrostrata) and Giant Floaters (Pyganodon grandis) in ponds during 2009 and 2011. YOY attained large size by approximately 6 months (Pondmussel, mean = 48.5 mm; Floater = 57.5), most individuals were sexually mature, and most females were gravid. Size and sex ratios varied among ponds. Pondmussel size was negatively related to mussel density, suggesting food competition; Floater size was not related to density. Size was not related to glochidial infestation pressure on fishes, suggesting that acquired immunity did not affect YOY performance. The percentage of gravid female Pondmussels varied between years from 27 to 100%, and 91% of female Floaters were gravid in 2011. Mean fecundity was high (Pondmussel = 34,311; Floater = 38,873). The proportion of gravid females and mean fecundity were not related to male density, showing that fertilization was efficient. Variation in size, sex ratios, and gravidity among ponds suggests that small differences in environmental conditions or demographic stochasticity can have large effects on populations. Rapid growth, early maturity, efficient fertilization, and high fecundity of YOY are contrary to traditional views of mussel life history, but these traits may allow Pondmussels and Floaters to rapidly colonize disturbed, unstable habitats.

Azomite Application Does Not Positively Influence Water Quality, Phytoplankton Populations, or Zooplankton Populations When Preparing Mississippi Channel Catfish Nursery Ponds for Stocking

AbstractAzomite is a hydrated sodium calcium alumina silicate that is mined from a volcanic deposit in Utah. The product contains many micronutrients that may be beneficial in preparing catfish nursery ponds for stocking. In northwest Mississippi, a 5‐week study was conducted to compare water quality, phytoplankton populations, and zooplankton populations in Channel Catfish Ictalurus punctatus nursery ponds treated with Azomite at 0, 50, or 100 kg/ha. The study was conducted in 0.04‐ha ponds during April, when fry ponds are prepared for stocking. Azomite application did not affect ammonia concentrations. Over time, nitrite concentrations increased more in control ponds compared to Azomite‐treated ponds; however, nitrite concentrations were low in all ponds. Chlorophyll‐a concentrations were also unaffected by Azomite application. The pH did significantly increase with increasing Azomite application rate. Azomite application had no effects on phytoplankton or zooplankton populations. Overall, there were no beneficial effects of adding Azomite to Channel Catfish nursery ponds in northwest Mississippi.

Using quantitative polymerase chain reaction (qPCR) and occupancy models to estimate atypical Aeromonas hydrophila (aAh) prevalence in catfish

A strain of atypical Aeromonas hydrophila (aAh) has caused issues within the channel catfish Ictalurus punctatus industry of the southeastern United States since 2009. These atypical pathotypes cause acute mortality events resulting in catastrophic losses, as opposed to more chronic mortality and lesions seen in typical infections of motile aeromonas septicemia (MAS). This study provides a basic framework for rapid field sampling negating the need for re-isolation or enrichment culture, thereby reducing the time between sampling and detection. Rapid and accurate quantitative PCR based methods for detection of aAh have been described and are important confirmative tools in research and diagnostic settings. These methods also have application in epidemiological surveys investigating the spread of disease and elucidating pathogen dynamics that may lead to outbreaks. To date, no field-based sampling technique for rapid aAh detection in resident pond populations has been explored. In this study, culture swabs taken from the gills and lower intestine of pond-raised catfish were assessed for their suitability as rapid field-based collection methods for downstream applications. Results showed the state of the pond has a significant effect on which swab location yields the highest proportion of PCR positive results. During an active outbreak, gill swabs identified more fish as aAh-positive; however, in apparently healthy populations, swabs taken from the lower intestine identified significantly more aAh-positive fish than gill swabs, despite no statistical difference in the concentration of aAh cell equivalents between swab sites. Naïve prevalence estimates from the two swab types were compared to estimates provided by a hierarchical occupancy model. Prevalence estimates from gill swabs was 0.95% while vent swabs showed a prevalence of 2.2%; however, estimates based on the occupancy model were 6.6% and 9.8%, respectively. This multi-fold increase in prevalence estimates highlights the importance of accounting for imperfect detection in epidemiological studies and in assessing potential outbreak risk. Furthermore, occupancy models based on these data indicate resident fish can be aAh-positive carriers with no gross signs of infection, providing evidence aAh can reside in catfish ponds in the absence of disease. The presence of a carrier state indicates the pathogen may pose minimal risk to the host is compromised or a mechanical portal of entry into the blood stream is available. This provides an important direction for future research in understanding the mechanisms of aAh outbreaks in catfish aquaculture ponds.

Flow cytometry for rapid characterisation of microbial community dynamics in waste stabilisation ponds

Algal and bacterial communities play a major role in the treatment performance and efficiency of waste stabilisation ponds (WSPs); however, the study of these WSP microbial communities has been challenging. Flow cytometry (FCM) has been used widely as a rapid, culture-independent method of characterising algae and/or bacteria in a range of freshwater and marine environments, and in conventional wastewater treatment processes, but its application to WSP wastewater has been underexplored. In this study, a method for the characterisation of both algal and bacterial microbial populations in WSP wastewater is presented and standardised, using cultures and field samples. We show that SYTO 16 dye is more effective than SYBR Green I for the concurrent detection of both algae and bacteria in samples. Through gating and phenotypic diversity analysis, the FCM results show both spatial and temporal shifts in pond microbial communities. The ability to rapidly determine the spatiotemporal shifts in pond populations is not only important for the improvement of pond operation and monitoring strategies, but also for the planning and management. Flow cytometry has the potential to become a diagnostic tool for ponds to assess treatment performance and determine the most optimal operating conditions.

Predation differentially structures immature mosquito populations in stormwater ponds

1. Understanding the factors underlying the abundance and distribution of species requires the consideration of a complex suite of interacting biotic and abiotic factors operating on multiple spatial and temporal scales. Larval mosquitoes inhabiting small human‐constructed ponds represent a unique opportunity to investigate the relative importance of these structuring mechanisms while simultaneously generating applied knowledge on mosquito control.2. A multi‐year field survey of 32 stormwater ponds was conducted in central Illinois (Champaign County). From each pond, data were collected on pond structure type and hydroperiod, the presence/absence of cattails (Typha spp.), and measures of total nitrogen, phosphorus, and organic carbon, and chlorophyll a. The communities of crustacean zooplankton and aquatic insects were characterised, and these taxa were assigned into two main groups: predators and competitors of larval mosquitoes. Structural equation modelling was used to explore the direct and indirect effects of these biotic and abiotic factors on larval density for three species of culicine mosquitoes (Culex pipiens, Culex restuans, and Aedes vexans).3. Hydroperiod had an indirect negative effect on C. pipiens density. However, this effect was mediated by predator density; more permanent ponds had more predators, which therefore reduced the density of C. pipiens larvae. Aedes vexans density was positively correlated with predator density. No predictor variables were found that explained variation in C. restuans density.4. This study show that the relative importance of these biotic and abiotic factors varies among species of culicine mosquitoes inhabiting stormwater ponds.

Influence of Types and Doses of Fertilizer on the Physicochemical Characteristics of Water, Composition and Structure of Zooplankton Populations in Ponds

In order to improve fish productivity, an essay on the evaluation of the comparative effect of chicken and pig manure on the composition and structure of <i>Zooplankton</i> was conducted at the Application and Research farm from the University of Dschang (LN: 5º44’-5 °36 and LE: 10º06’-9 ° 85’). For this purpose, 15 ponds (5.7 x 5.7 x 1m), three doses of 0 (control); 800 and 1000kg/ha of chicken manure as well as pig dung were used. At each of the randomly selected ponds was administered one of the fertilizer doses every 7 days.

Influence of Types and Doses of Fertilizer on the Physicochemical Characteristics of Water, Composition and Structure of Zooplankton Populations in Ponds

In order to improve fish productivity, an essay on the evaluation of the comparative effect of chicken and pig manure on the composition and structure of <i>Zooplankton</i> was conducted at the Application and Research farm from the University of Dschang (LN: 5º44’-5 °36 and LE: 10º06’-9 ° 85’). For this purpose, 15 ponds (5.7 x 5.7 x 1m), three doses of 0 (control); 800 and 1000kg/ha of chicken manure as well as pig dung were used. At each of the randomly selected ponds was administered one of the fertilizer doses every 7 days.