Investigations on the wastewater of a flow-through fish farming system

European and Hungarian fish consumption has been increasing for years. Intensive fish production is one potential methods to meet the ever-increasing demand of Hungarian consumers. However, for the sustainable growth of production, it is necessary to tackle one of the important problems of this type of fish production: reducing the nutrient content of the effluent water. Wetland can be a perfect application to solve the problem. In this research, we examine the efficiency of wastewater treatment in a fish farm where the effluent feeds the Szarvas-Békésszentandrás oxbow system. The current theoretical nutrient retention capacity of the wetland—based on literary data—is 53–61% for nitrogen (N), 76–84% for phosphorus (P) and 80– 91% for chemical oxygen demand (COD). In recent years, the production capacity of the plant has increased to 500 T/year and a new pre-settling and drum filter were added to the filtration, and thus the deterrent effect of the filtration system in 2014–2017 was 74% for "N", 63% for phosphorus and 83% for COD. The efficiency of the wetland was demonstrated by measurements carried out by an accredited independent laboratory proving that no limit value has been exceeded for the last 15 times. We can conclude that the wetland is able to carry out its tasks in the long term, independently of the season, and to ensure that effluent water does not pose a significant impact to the natural environment

THE HABITAT USE AND SELECTIVITY BY TOPMOUTH GUDGEON (PSEUDORASBORA PARVA)

The topmouth gudgeon is an invasive species of the European fish fauna that causes problems not only as a competitor of native fishes in natural waters but also generates damages in pond fish farming. The behaviour of topmouth gudgeon has already been studied from a number of aspects, however, complex investigations on the habitat use of the species in invaded regions were not carried out yet. Here the habitat use of the fish in a close-tonature pond system was examined with special, non-selective minnow traps and observations were subsequently complemented by aquarium experiments. Our findings revealed that in a pond inhabited by predator fish, topmouth gudgeon preferred the pelagial region, while in a pond free of predator fish, they preferred the littoral zone. The examined abiotic parameters had no effect on the habitat use of the fish. In a simplified artificial environment experiments have yielded the same results. The findings showed that topmouth gudgeon is rather flexible in adapting to the environmental conditions, the available nutrition base, but from the aspect of habitat use the most significant factor is probably the presence of predatory fish. The results can establish an effective suppression method of topmouth gudgeon populations with predator fishes

Optimizing fish structure in angling ponds focusing on white fish

According to new amendments of laws, commercial fishing licenses of natural waters shall not be issued from the calendar year 2016 in Hungary. However, the most settlement of white fish to angler ponds originated from natural waters. Currently, there is no sufficient quantity of fish species belonging to this group available to fulfil the settlement commitments of fish farmers. The aim of this recent study is to develop a breeding and production technology that is suitable for settlement of large quantities of this fish species of appropriate length of (4–5 cm). The following methods are investigated: aquaculture cage system (pond-in-pond system), monoculture and mixed population with different ratio of white fish in fish structure. Due to the different environmental needs of different fish species, many parameters need to be investigated, for example: stocking density, feeding, oxygen level, monoculture or mixed populations, growth potential and mortality. A preliminary experiment was carried out following the artificial propagation of ide (Leuciscus idus) following a 21-day larval rearing experiment in which the effect of different stoking density was investigated for mortality and growth. On the basis of the expected results, the optimal conditions for the aquaculture cage system will be described, regarding to the white fish stock

Cryopreservation of sperm of the adriatic grayling (Thymallus thymallus) and the marble trout (Salmo marmoratus) from the Soča river in Slovenia

A cryopreservation protocol was tested on the sperm of genetically distinct Adriatic grayling (Thymallus thymallus) and the Natura2000-listed marble trout (Salmo marmoratus) from the Soča River basin in Slovenia. Sperm was frozen in an extender composed of 200 mM glucose, 40 mM KCl, 30 mM Tris (pH 8.0) and 10% methanol as a cryoprotectant in the vapour of liquid nitrogen. Sperm dilution ratios of 1:1, 1:4 and 1:9 were tested. The cooling rate was 57 ± 1°Cmin-1 in all cases. In the grayling, the highest ratio of eyed eggs (74 ± 4 % vs. 69 ± 6 % in the control) and the highest hatch percentage (63 ± 6 % vs. 56 ± 10 % in the control) was observed with a dilution ratio of 1:1. In the marble trout, the highest percentage of eyed eggs (84 ± 4 % vs. 88 ± 3 in the control) and the highest hatch rate (70 ± 3 % vs. 76 ± 2 % in the control) was again found using the 1:1 dilution ratio of the sperm. In both species, individual sperm samples had a significant effect on the results. Sperm-to-egg ratios ranging from 2.5 to 5.7 × 104 spermatozoa per egg yielded satisfactory hatch rates (67 ± 7 % to 73 ± 7 %) in the grayling

Biochemical Marker Assessment of Chronic Carbamazepine Exposure at Environmentally Relevant Concentrations in Juvenile Common Carp (Cyprinus carpio)

Worldwide, the anticonvulsant drug carbamazepine (CBZ) is the most frequently identified pharmaceutical residue detected in rivers. Reported chronic effects of CBZ in non-target freshwater organisms, particularly fish, include oxidative stress and damage to liver tissues. Studies on CBZ effects in fish are mostly limited to zebrafish and rainbow trout studies. Furthermore, there are only a few chronic CBZ studies using near environmental concentrations. In this study, we provide data on subacute effects of CBZ exposure (28 days) to common carp (Cyprinus carpio), employing a set of biochemical markers of damage and exposure. CBZ was found to induce a significant change in the hepatic antioxidant status of fish subjected to 5 µg/L. Moreover, with increasing concentrations, enzymatic and non-enzymatic biomarkers of oxidative defence (catalase (CAT), superoxide dismutase (SOD), glutathione reductase (GR), DNA strand breaks)), toxicant biotransformation (ethoxyresorufin-o-demethylase (EROD), glutathione-S-transferase (GST)), and organ and tissue damage (lactate dehydrogenase (LDH), cetylcholinesterase (AChE)) were altered. The AChE, LDH, and lipid peroxidation (LPO) results indicate the occurrence of apoptotic process activation and tissue damage after 28 days of exposure to CBZ. These findings suggest significant adverse effects of CBZ exposure to common carp at concentrations often found in surface waters

Effects of fertilisation on development and nutrient uptake of black locust saplings grown in pots

Currently, black locust is the most important tree species in Hungary with significant economic value. Intensification of its cultivation and the improvement of the timber quality should include the use of highly productive clones and reasonable fertilization. Nutrition management should be based on reliable data from exact experiments. In our trial, nutrition intake of Turbo Obelisk OBE01 clone saplings was examined during a four-month period. Osmocote Pro (18:9:10 + 2Mg) was used as fertilizer at a dose of 2.5 and 5 kg m−3 mixed to a peat-based substrate. At the end of the growing period, saplings reached a height of 260-280 cm and a stem diameter of 16-18 mm. Nutrient intake order was found to be the following: Ca (3.3-4.2 g) > N (3.1-3.6 g) > K (2.1-2.9 g) > Mg (0.35-0.5 g) = P (0.3-0.5 g). Based on our results, a lower N:P and N:K rate fertilizer is recommended, especially if a non-peat based substrate and longer growing period is planned with a higher rate of nitrogen fixation. Considering nitrogen resource, a dose of 5 kg m−3 was proved to be less effective than a concentration of 2.5 kg m−3. However, the higher concentration of phosphorous, potassium and magnesium were well-utilized by the plants