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Abstract

The aim of the study was to analyze and assess the possibility of using a two-stage filtration system with ceramic membranes: a 3-tube module with 1.0 kDa cut-off (1st stage) and a one-tube module with 0.45 kDa cut-off (2nd stage) for treating effluent water from a juvenile African catfish aquaculture. The study revealed that during the 1st filtration stage of the effluent water, the highest degrees of retention were obtained with respect to: suspended solids SS (rejection coefficient RI=100%), turbidity (RI=99.40%), total iron (RI=89.20%), BOD5 (RI=76.0%), nitrite nitrogen (RI=62.30%), and CODCr (RI=41.74%). The 2nd filtration stage resulted in a lower reduction degree of the tested indicators in comparison to the 1st filtration stage. At the 2nd stage, the highest values of the rejection coefficient were noted in for the total iron content (RIV=100%), CODCr (RIV=59.52%; RV=64.28%, RVI=63.49%) and turbidity (RIV and RV = 45.0%, RVI=50.0%). The obtained results indicate that ceramic membranes (with 1.0 and 0.45 kDa cut-offs) may be used in recirculation aquaculture systems as one of the stages of effluent water treatment.

Abstract

Eutrophication process is a serious problem in water ecosystems. There is a great need to study the relation between the physico-chemical condition of water and the influence of these parameters on the diversity of biological life, especially on changes in the structure of microbiocenoses. The most interesting are bacteria and microalgae, due to the important roles they play in maintaining the balance of the aquatic environment. In this study, biodiversity analysis of eukaryotic microalgae and bacteria in two artificial water ecosystems - fish farming ponds - was performed. Aquaculture was based on IMTA technology, in which every part of the trophic chain plays a significant role in maintaining the balance in the ecosystems. Experimental intensive - extensive systems differed in terms of nutrient loads, ponds were characterized by high loads of organic and inorganic nitrogen and phosphorus. During the experimental period, the physicochemical conditions, quantitative genotypic structure of the two biocenoses being studied and the relation between these factors were monitored and investigated. For the biodiversity analysis, the PCR - DGGE technique was used. The results of preliminary research showed that there is a correlation between nutrient loads, diversity expressed in the Shannon-Wiener Index and the overall condition of experimental systems. Higher loadings of nutrient promote the development of bacteria and microalgae without any influence on the balance in the artificial ecosystem being tested.

Abstract

Within the scope of the present study a field survey in the area of “Strandzha” Natural Park in south-east Bulgaria was carried out. The main goal of the investigation was to gain more detailed information on the diet of the European otters (Lutra lutra) that inhabit the park. As indicators for the presence of the mustelids a set of standard procedures, such as footprints tracking and inspecting the terrain for otter spraints were used. A total of 204 excrements were found, measured, documented and then disintegrated in water. The food rests in the faeces were investigated and the diet of the local population was documented. On the base of the results we separated the excrements into six groups and analysed the relations between the contents of the spraints and the characteristics of the habitat where they were found. We discovered a clear tendency toward piscivory in the middle and down streams of the studied rivers in the Natural Park. In the upper streams, otters relied almost exclusively on invertebrates like bivalves and crayfish as food source. The fact, that even suboptimal habitats, which offered invariable menu, were exploited by the otters is an indication for the stability of the local population.

Abstract

The results of observations of intensive sturgeon production integrated with an extensive earthen fish pond are described. The main objective of the study was to show how technological modifications applied to enhance nitrogen assimilation in ponds and nutrient retention in aquaculture products influenced fish production. Each of two integrated systems, A and B, consisted of four intensive fish tanks stocked with sturgeon and one extensive carp pond stocked with carp (Cyprinus carpio L.), silver carp (Hypophthalmichthys molitrix (Val.)) and common nase (Chondrostoma nasus L.). The fish tanks were supplied with water from the extensive pond and the effluent from the tanks was discharged into the same pond, which acted as a biological filter for fish production. System B pond was supplemented with carbohydrates (methanol) and plastic substrates for periphyton development that were installed to increase nutrient utilization. The results of the observations showed better water quality and higher fish production in pond B, but no differences were noted in sturgeon growth performance in system A. The combination of these modifications appeared to be an efficient way of increasing nutrient retention and improving water quality.

Abstract

Common carp Cyprinus carpio was introduced from Thailand to Pakistan in 1964 for the purpose of aquaculture. Due to its high tolerance to temperature and turbidity, and prolific pond breeding habit, it was established promptly in most of natural inland waters, including rivers, lakes, streams, canals, wetlands and even village ponds of the country. Although common carp became one of the most abundant cyprinid species in inland waters and important food fish in Pakistan, its impact is not well documented. Fish farming of common carp has been carried out in Pakistan since 1970; initially it grew slowly but now it is playing an important role in the economy of the country by employing more than 400,000 people. Nowadays, farming of freshwater carps is present throughout Pakistan, especially in the provinces of Punjab and Sindh. There is a huge potential in common carp farming and it could help increase the livelihood of people and gross domestic product (GDP) of the country as well. Still, there is a need to improve the fish farming practice to meet the world-class demands that could only be possible by the keen interest of policy makers and stake holders with better management.

Abstract

This study was conducted in Hammam Debagh Reservoir located in northeastern Algeria, which was first the subject of fish farming tests in 2001. The species tested included Chinese carp, royal carp, common carp, pikeperch, and common bream. The present work aimed to determine the age and growth of one of the most frequently caught species in the reservoir, common bream, Abramis brama. This information is essential to the knowledge of fish biology, and thereby to solving many of the problems of fish research and development. A sample of 100 common bream, A. brama, was caught with gillnets over a period of six months from December 2017 to May 2018. The results obtained fit well with the growth model and were similar to those published regarding other environments. Scales from a sample of 50 fish were read under an optical microscope, which permitted identifying five age groups. The value of the overall sex ratio (4.88) revealed a strong imbalance in favor of males throughout the study period. The relationship linking length-weight is of the minor allometry type with b < 3.

Naravovarstveno Vrednotenje Avifavne Območja Zadrževalnika Medvedce (SV Slovenija) in Dejavniki Ogrožanja

Abstract

The Chociwel region is part of the Szczecin Trough and constitutes the northeastern segment of the extended Szczecin-Gorzów Synclinorium. Lower Jurassic reservoirs of high permeability of up to 1145 mD can discharge geothermal waters with a rate exceeding 250 m3/h and temperatures reach over 90°C in the lowermost part of the reservoirs. These conditions provide an opportunity to generate electricity from heat accumulated in geothermal waters using binary ORC (Organic Rankine Cycle) systems. A numerical model of the natural state and exploitation conditions was created for the Chociwel area with the use of TOUGH2 geothermal simulator (i.e., integral finite-difference method). An analysis of geological and hydrogeothermal data indicates that the best conditions are found to the southeast of the town of Chociwel, where the bottom part of the reservoir reaches 3 km below ground. This would require drilling two new wells, namely one production and one injection. Simulated production with a flow rate of 275 m3/h, a temperature of 89°C at the wellhead, 30°C injection temperature and wells being 1.2 km separated from each other leads to a small temperature drop and moderate requirements for pumping power over a 50 years’ time span. The ORC binary system can produce at maximum 592.5 kW gross power with the R227ea found as the most suitable working fluid. Geothermal brine leaving the ORC system with a temperature c. 53°C can be used for other purposes, namely mushroom growing, balneology, swimming pools, soil warming, de-icing, fish farming and for heat pumps.

Natural conditions for the reconstruction of fish ponds and possibilities of their use in ecotourism

The paper comprises an analysis of the environmental impact of restoring small water retention in the Świergotka River. Hampering water flow due to river damming by 0.5 m and reconstruction of ponds will have a favourable effect on the valley's nature but may result in excessive water eutrophication in case of using these reservoirs for fish-farming.

Abstract

The Sevan is one of the world’s largest highland lakes and the largest drinking water reservoir to the South Caucasus. An intensive drop in the level of the lake that occurred over the last decades of the 20th century has brought to eutrophication. The 2000s were marked by an increase in the level of the lake and development of fish farming. To assess possible effect of these processes on water quality, creating a state-ofthe- art water quality monitoring system is required. Traditional approaches to monitoring aquatic systems are often time-consuming, expensive and non-continuous. Thus, remote sensing technologies are crucial in quantitatively monitoring the status of water quality due to the rapidity, cyclicity, large-scale and low-cost. The aim of this work was to evaluate potential applications of the Landsat 8 Operational Land Imager (OLI) to study the spatio-temporal phytoplankton biomass changes. In this study phytoplankton biomasses are used as a water quality indicator, because phytoplankton communities are sensitive to changes in their environment and directly correlated with eutrophication. We used Landsat 8 OLI (30 m spatial resolution, May, Aug, Sep 2016) images converted to the bottom of atmosphere (BOA) reflectance by performing standard preprocessing steps (radiometric and atmospheric correction, sun glint removal etc.). The nonlinear regression model was developed using Landsat 8 (May 2016) coastal blue, blue, green, red, NIR bands, their ratios (blue/red, red/green, red/blue etc.) and in situ measurements (R2=0.7, p<0.05) performed by the Scientific Center of Zoology and Hydroecology of NAS RA in May 2016. Model was applied to the OLI images received for August and September 2016. The data obtained through the model shows that in May the quantity of phytoplankton mostly varies from 0.2 to 0.6g/m3. In August vs. May a sharp increase in the quantity of phytoplankton around 1-5 g/m3 is observable. In September, very high contents of phytoplankton are observed for almost entire surface of the lake. Preliminary collation between data generated with help of the model and in-situ measurements allows to conclude that the RS model for phytoplankton biomass estimation showed reasonable results, but further validation is necessary.