The modified Johnson-Reid method--a practice model for coccidiosis monitoring in the fattening of young fowl?

Models of coccidiosis-monitoring known from literature are described. A suitable alternative of determining the coccidia status in a broiler population is the "modified Johnson-Reid method". This method makes a standardization of diagnostic finding and evaluation possible as well as a differentiated intestinal localization and the determination of coccidia incidence severity. In addition to the microscopic screening of the caecum contents--as described by Johnson-Reid--it appears necessary to take also swabs from parts of the duodenum and jejunum (near the Meckel's diverticulum). Subsequently this method is an important help for veterinarians working with broiler production, for diagnostic institutions as well as producers of anticoccidial agents, especially in regard to its documentation rate and the resulting consequences. In this way other diagnostic efficiency data in broiler production are significantly completed.     

生态监测（Ecological monitoring）的定义

本刊讯：生态监测（Ecological monitoring）是以生态学原理为理论依据，运用可比的和较成熟的方法，在时间和空间上对特定区域范围内生态系统和生态系统组合体的类型、结构和功能以及组合要素进行系统地测定，为评价和预测人类活动对生态系统的影响，为合理利用资源、改善生态环境提供渔业可持续发展决策依据。生态监测有综合性、长期性、复杂性和分散性的特点。从生态监测类型来看，一般分为：宏观生态监测和微观生态监测两种。     

Fish hepatocyte glycogen phosphorylase – a sensitive indicator for hormonal modulation

The absence of a reproducible method for the assay of glycogen phosphorylase (GPase) in isolated fish hepatocytes has made the interpretation of hormone-induced glycogenolysis data difficult. This study presents such an assay and demonstrates its sensitivity to hormonal activation. The enzyme is assayed in the reverse direction using glucose 1-phosphate (G1-P) and glycogen as substrates and uses standard methods for the quantification of the liberated inorganic phosphate. The assay is highly reproducible, sensitive, and provides an excellent means to follow small and rapid changes in enzyme phosphorylation status following the addition of hormones. We show for hepatocytes isolated from rockfish (Sebastes caurinus) and brown bullhead (Ameiurus (Ictalurus) nebulosus) that small concentrations of three model hormones, namely epinephrine (catfish), norepinephrine, and prostaglandin E₂ (rockfish), lead to the rapid, concentration and time-dependent conversion of existing GPase into the active GPase a form. Some of the enzyme seems to be impervious to hormonal activation, as the highest %GPase a never reaches 100%. We provide evidence that changes in enzyme phosphorylation status provide a better short-term insight into hormone-dependent activation than estimates of glucose or some other end products, that usually must accumulate for long periods before detection is possible. Our data also show that GPase in freshly isolated hepatocytes is already in an activated state and cells should be given a period of rest for several hours before hormonal studies involving glycogen breakdown or the cAMP cascade are initiated.     

Diversified aeration facilities for effective aquaculture systems—a comprehensive review

The growing intensive aquaculture system around the world maintains a high stocking density, wherein it is essential to increase and sustain the optimum dissolved oxygen concentration (DO) through the provision of artificial aeration systems. The selection of an aerator is a crucial aspect of aquaculture operations. The selected aerator must be economically efficient and should be able to fulfill the requirement of oxygen supply in the pond water. The present study provides an extensive literature review on the importance of artificial aeration in aquaculture, the standard method of test for performance evaluation of an aerator, various aeration systems and their mechanisms, method to determine the numbers of aerator requirement, comparative studies of different type of aerators, and economic consideration in selection of aerators. In addition, a thorough analysis has been done to suggest the type of aerator that is economically viable and efficient for different pond volumes based on the performance data reported in the reviews. Therefore, this study may help the end-users (fish farmers) to select the best aerator based on their requirements.

     

Is spawning stock biomass a robust proxy for reproductive potential?

Reference points based on fishing mortality (F) and spawning stock biomass (SSB) are a requirement of many fisheries management frameworks. SSB is assumed to be a proxy for stock reproductive potential (SRP). Limit reference points based on SSB are used to indicate the level of biomass below which productivity is affected. SSB fails to account for changes in fecundity, egg viability and sex ratio, and it has been argued that total egg production (TEP) provides a better reflection of SRP. We explore how accounting for TEP impacts limit reference points and evidence for a relationship between stock and recruit. Time series of SSB and TEP are compared for three North Sea stocks: cod (Gadus morhua), herring (Clupea harengus) and plaice (Pleuronectes platessa). Dynamics based on TEP are different from those based on SSB for cod and plaice, but the stock–recruit relationships were not ‘improved’ using TEP. Shifts in productivity (spawner per recruit) occur in all three time series and SSB underestimated uncertainty. Yet again, it was shown that assumptions of stationarity about fish population productivity are incorrect. We argue that the use of TEP does improve the realism in our understanding of stock dynamics, and demographically, more complex management strategy evaluation is required to develop management procedures that are robust to uncertainty and integrate F and the demographic health of a stock. Empirical feedback control systems based on fisheries independent indices including surveys of eggs, larvae, recruits, juveniles or spawning adults should be evaluated and compared to traditional approaches.     

Is current floodplain management a cause for concern for fish and bird conservation in Bangladesh's largest wetland?

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The teleost pseudobranch: a role for preconditioning of ocular blood supply?

The physiological relevance of the teleost pseudobranch as a remnant of a reduced gill arch is still unclear. Numerous hypotheses have been proposed regarding its physiological role, but direct confirmatory evidence is lacking. The close relationship by serial blood flow arrangement with the fish eye’s choroid rete has sparked the idea that pseudobranchial preconditioning of blood pH may facilitate initiation of the Root effect and thus support the establishment of high oxygen tensions for retinal diffusive supply. This idea was critically tested by studies on isolated pseudobranchs in situ (Oncorhynchus mykiss), perfused with RBC/Ringer or RBC/plasma suspensions of widely varied composition (pH 7.4–8.2). Detailed analysis of inflowing as compared to effluent perfusates indicated normal aerobic metabolism expressed by a rise in Pco₂ (+0.39 ± 0.13 mmHg ), an oxygen utilization of 25% and a high oxygen consumption of ∼400 nmol g⁻¹ min⁻¹. Upon passage of the pseudobranch, pH (corrected for Haldane effect) was only slightly acidified (−0.03 to −0.10), [HCO₃ ⁻] and [lactate] were slightly enhanced (+0.51 mmol l⁻¹ or 0.13 mmol l⁻¹, respectively). In order to test for yet unknown plasma components involved in pseudobranch function, a second series of experiments was conducted using RBC-suspensions in fresh plasma instead of Ringer, with results closely resembling those of the RBC/Ringer series. Lacking any physiologically significant correlation with the level of perfusate pH, the obtained data indicate pseudobranchial basic metabolic activity rather than pH regulatory characteristics. Also the observed absolute changes in pH are negligible in terms of pH regulation towards the Root-threshold. Accordingly, the present experiments as well as plausibility evaluation of mechanisms do not support the idea of blood pH pre-adjustment prior to entry into the choroid rete structure of the teleost eye to facilitate the Root-mediated oxygen release.     

Liquid fat,a potential abiotic vector for horizontal transmission of salmonid alphavirus?

Viral diseases represent serious challenge in marine farming of Atlantic salmon (Salmo salar L). Pancreas disease (PD) caused by a salmonid alphavirus (SAV) is by far the most serious in northern Europe. To control PD, it is necessary to identify virus transmission routes. One aspect to consider is whether the virus is transported as free particles or associated with potential vectors. Farmed salmonids have high lipid content in their tissue which may be released into the environment from decomposing dead fish. At the seawater surface, the effects of wind and ocean currents are most prominent. The aim of this study was primarily to identify whether the lipid fraction leaking from dead infected salmon contains SAV. Adipose tissue from dead SAV‐infected fish from three farming sites was submerged in beakers with sea water in the laboratory and stored at different temperature and time conditions. SAV was identified by real‐time RT‐PCR in the lipid fractions accumulating at the water surface in the beakers. SAV‐RNA was also present in the sea water. Lipid fractions were transferred to cell culture, and viable SAV was identified. Due to its hydrophobic nature, fat with infective pathogenic virus at the surface may contribute to long‐distance transmission of SAV.     

Detecting the brook floater,a freshwater mussel species at risk,using environmental DNA

1. The use of environmental DNA (eDNA) is a promising approach for the detection of aquatic species, including species at risk. One freshwater mussel species of interest in Atlantic Canada, the brook floater (Alasmidonta varicosa), is listed as being of Special Concern under the Species at Risk Act in Canada and as Vulnerable on the International Union for Conservation of Nature Red List. Further scientific data regarding species distribution and critical habitat is needed for the protection and conservation of this species.
2. The aim of this study was to design, optimize, and apply a species-specific quantitative polymerase chain reaction assay for the detection of brook floater from eDNA samples, and to assess temporal variability in brook floater eDNA quantities.
3. Through an eDNA survey performed in New Brunswick rivers in 2017 and 2018, brook floater DNA was found at a total of 16 out of 56 sites sampled. The amount of brook floater DNA detected at all 16 sites was always below the theoretical limit of detection of the assay, and, as such, results were classified as either ‘inconclusive’ or ‘suspected’.
4. The co-detection of eastern pearlshell (Margaritifera margaritifera), a more abundant freshwater mussel species in Atlantic Canada, was successfully used as a natural positive control.
5. Temporal variability in the amount of eDNA found in the water was also assessed at a site with a known brook floater population and minimal variability in eDNA quantities was observed from May to September.
6. These results provide researchers and managers with a new tool for the detection of the brook floater in support of conservation and monitoring efforts.

     

Dead or alive — Old empty shells do not prompt false-positive results in environmental DNA surveys targeting the freshwater pearl mussel (Margaritifera margaritifera L.)

1. Environmental DNA (eDNA) from water samples is increasingly used to detect the presence and distribution of species in aquatic ecosystems. However, before implementing eDNA in monitoring programmes, various species-specific sampling or analytical issues remain to be resolved in order to minimize frequencies of false-positive and -negative results. For example, empty shells from freshwater pearl mussels (Margaritifera margaritifera) contain extractable DNA (chemical extraction from ground-up shells) suggesting a risk of false-positive samples at stream sites with extinct populations but with empty shell material remaining.
2. The aim of this study was to investigate whether empty and naturally degrading shells from M. margaritifera can cause false-positive eDNA signals in water samples.
3. Water samples were collected from outdoor stream channels (in Lemming, Denmark) with living freshwater pearl mussels or empty shell material (density ~10 individuals m⁻²) during a 3-week experimental period. Living freshwater pearl mussels were collected from Hemgravs stream in Sweden and transported to Denmark according to permissions granted by the Swedish and Danish authorities.
4. All water samples from stream channels containing empty shells were negative for eDNA indicating that eDNA traces in stream water are most likely to originate from living individuals located upstream of the sampling site. Water samples collected from stream channels containing living individuals of M. margaritifera were consistently positive for eDNA except for one sample (interpreted as a false negative).
5. The study shows that positive eDNA signals for freshwater pearl mussels most likely reflect the presence of living individuals. Consequently, we suggest that eDNA should be used to locate remaining population fragments of M. margaritifera in deep and turbulent streams, providing a platform for faster and more efficient decision making when launching investigative and mitigation initiatives.

     

Genetic structure of Irish freshwater pearl mussels (Margaritifera margaritifera and Margaritifera durrovensis): Validity of subspecies,roles of host fish,and conservation implications

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Validation of environmental DNA (eDNA) as a detection tool for at‐risk freshwater pearly mussel species (Bivalvia: Unionidae)

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Developing a standard approach for monitoring freshwater pearl mussel (Margaritifera margaritifera) populations in European rivers

1. The freshwater pearl mussel (Margaritifera margaritifera) is an endangered species in Europe, protected nationally and internationally, but with a steadily declining range and abundance owing to pressures such as pollution, river engineering, and illegal exploitation. Despite this, no consistent approaches have been developed around Europe for monitoring pearl mussel populations and their habitats.
2. To address this need, experts on pearl mussel ecology from 11 countries met at a series of workshops in order to develop a protocol for monitoring, published under the auspices of the European Committee for Standardization (CEN). This standard is unique, as it is the first CEN standard dedicated to a single species of conservation concern.
3. The standard is aimed at scientists, conservation bodies, and environmental regulators, and can be used for designing national monitoring programmes as well as reporting on the conservation status of pearl mussel populations under the European Habitats Directive. It contains guidance at the individual site level to determine why populations are failing to recruit, but also addresses the need for a wider‐scale approach to ensure that catchment developments do not have adverse impacts on rivers containing pearl mussels.
4. A pearl mussel monitoring programme needs to investigate the size and viability of populations, as well as the fish hosts (Atlantic salmon, Salmo salar, or brown trout, Salmo trutta) on which pearl mussel larvae depend. Water quality, including variables such as dissolved oxygen, acid–base chemistry, and nutrient levels, is also an essential monitoring component, together with the physical features of the river bed, river flow regimes, and sediment dynamics.
5. It is hoped that this pan‐European approach will improve the ability to compare data across many countries, and will ultimately ensure that the results of monitoring are translated into measures for improving the conservation status of the freshwater pearl mussel throughout its range.

     

Demonstrating the practical impact of studies on biotic interactions and adaptation of a threatened unionoid mussel (Margaritifera margaritifera) to its host fish (Salmo trutta)

1. To understand the ecological factors behind the decline of functionally important threatened species with complex life cycles, many different life‐cycle stages need to be investigated. The highly threatened unionoid freshwater mussels, with their complex life cycle, including a parasitic stage on host fish, often have a large influence on biodiversity and ecosystem functioning.
2. The overall aim of the present article is to summarize and discuss the impact of two articles published in Aquatic Conservation: Marine and Freshwater Ecosystems (AQC) on biotic interactions and adaptation of a threatened unionoid mussel (Margaritifera margaritifera) to its host fish (Salmo trutta).
3. The two AQC publications described research on the influence of population size and density of mussels and host fish, and host–parasite interactions between mussels and their host fish, on the recruitment of juvenile mussels.
4. The results from these publications filled gaps in knowledge and resulted in recommendations and incentives for conservation. The results and method development have been used in practical conservation work with threatened mussel species and have been implemented and cited in management handbooks. The outcome of the publications has been implemented in large conservation and restoration projects, and in several recent scientific publications.
5. Specifically, the results from one publication showed that ecological parameters such as mussel and host fish density and population size influenced recruitment of the threatened freshwater pearl mussel. The results from the second publication showed that understanding host–parasite interactions is important for comparing the suitability of host fish strains, and that host fish strains differ in their suitability for mussel infestations. In combination, the articles show that integrating ecological parameters of threatened mussels and their host fish with host–parasite interaction experiments can be an important influence on conservation recommendations, adaptive management and national management programmes for threatened species.

     

Behavioural and metabolic responses of Unionida mussels to stress

1. The aim of this study was to assess the extent to which the behavioural traits of freshwater mussels provide suitable indicators of stress in individuals, towards the advancement of non-invasive, remote monitoring techniques to examine population condition.
2. Variation in the expression of particular behavioural metrics was examined in accordance with measurements of oxygen consumption, across environmental stressors (aerial exposure and high concentrations of total suspended solids), and between two freshwater mussel species (Margaritifera margaritifera and Anodonta anatina)
3. Aerobic metabolic rate was quantified using intermittent respirometry, and behaviour was observed using time-lapse footage. Comparisons of metabolic response and the occurrence of behavioural traits, across the two stressors, focused on differences between the 24 h pre-exposure period (pre-exposure), the first 3 h of post-exposure (immediate post-exposure), and the time following the initial 3 h of post-exposure until the end of the experimental run (extended post-exposure).
4. The results of this study demonstrated a relationship between the frequency of occurrence of behavioural responses to stress exposure, associated with valve activity, and significant changes in the metabolic functioning of A. anatina and M. margaritifera mussels. The findings from the study also highlighted substantial intraspecific variation across species and stressors.
5. Data from this research could assist in the development of novel biosensors that track mussel valve activity remotely in their natural environment. When coupled with real-time data examining alterations in environmental metrics, this technology could assist in the monitoring of population condition and aid conservation management.

     

Conservation status of two endangered freshwater mussel species in Bavaria,Germany: Habitat quality,threats, and implications for conservation management

1. The freshwater pearl mussel (Margaritifera margaritifera) and the thick‐shelled river mussel (Unio crassus) are relatively widespread across Europe, but are strongly declining and are now protected by the European Habitats Directive. In the course of this study, 20 pearl mussel and 14 thick‐shelled river mussel streams in Bavaria, Germany, were investigated.
2. The mussel populations were mapped to determine population size and age structure. For the assessment of habitat quality, host fish abundance and physicochemical parameters were investigated, e.g. substratum quality, water chemistry, redox potential, and turbidity. Furthermore, potential risks for the populations such as predation or river maintenance were also recorded and assessed.
3. The average population size and recruitment rates of M. margaritifera populations were lower than in U. crassus populations, with 3517 (2.2% juveniles) compared with 5566 (41.4% juveniles) individuals, respectively. On average, 22.3% of particles were smaller than 0.85 mm in diameter at M. margaritifera sites, whereas the mean proportion of fine particles at U. crassus sites was twice as high, at 41.3%. Other parameters such as redox potential or electric conductivity also indicated more favourable habitat conditions in M. margaritifera streams. Unio crassus seems to be less vulnerable to adverse substratum texture and increased nutrient levels than M. margaritifera.
4. The main threats for U. crassus were physical habitat destruction, predation by muskrat, or a lack of host fish, whereas M. margaritifera mainly suffered from siltation leading to a lack of oxygen supply to the interstitial zone, affecting recruitment. Consequently, conservation strategies need to be species‐specific and address stream‐specific reasons for decline. As a basis, accurate and comparable monitoring data are necessary, which implies the standardization of monitoring protocols.