In present study the effect of iron (Fe) and manganese (Mn) contamination was assessed by modeling a freshwater food web of water, zooplankton (Daphnia pulex), and zebrafish (Danio rerio) under laboratory conditions. Metals were added to the rearing media of D. pulex, and enriched zooplankton was fed to zebrafish in a feeding trial. The elemental analysis of rearing water, zooplankton, and fish revealed significant difference in the treatments compared to the control. In D. pulex the Mn level increased almost in parallel with the dose of supplementation, as well as the Fe level differed statistically. A negative influence of the supplementation on the fish growth was observed: specific growth rate (SGR%) and weight gain (WG) decreased in Fe and Mn containing treatments. The redundancy analysis (RDA) of concentration data showed strong correlation between the rearing water and D. pulex, as well as the prey organism of Fe- and Mn-enriched D. pulex and the predator organism of D. rerio. The bioconcentration factors (BCF) calculated for water to zooplankton further proved the relationship between the Fe and Mn dosage applied in the treatments and measured in D. pulex. Trophic transfer factor (TTF) results also indicate that significant retention of the metals occurred in D. rerio individuals, however, in a much lower extent than in the water to zooplankton stage. Our study suggests that Fe and Mn significantly accumulate in the lower part of the trophic chain and retention is effective through the digestive track of zebrafish, yet no biomagnification occurs.
European perch (Perca fluviatilis) is a predatory fish species with a high degree of stress sensitivity during rearing in intensive systems. Our study was focused on the effects of contrast between two colours (black and light grey) in different parts of a tank (bottom and sidewall) on the production and antioxidant parameters of juvenile European perch during intensive rearing. The duration of the experiment was 8 weeks. In the first treatment, the bottoms of the tanks were black (DB); in the second treatment, the sides of the tank were black (DS); in the control treatment, the fish were kept in light-grey tanks (K). There were three replicates per treatment, and a total of 180 individuals were used; therefore, 60 individuals were used per treatment, with 20 individuals per tank. The mean body weight of the fish at the start of the experiment was 32.01 ± 0.79 g. At the end of the experiment, the antioxidant parameters (cortisol, glucose, MDA, catalase, vitamin C, GPx, GR, GSH, GSSG, and HSP70) of the fish were determined from blood samples. The results of our experiment show that different levels of contrast between the dark and light tank colours significantly influenced the production and antioxidant parameters of the juvenile European perch.
During the rearing of mealworm (Tenebrio molitor) larvae, the optimisation of the growing substrate has a particular importance. The application of the appropriate substrate is a fundamental pillar for intensive and safe production. The requirements for substrate include the lack of toxins, high nutrient and micro-macro element content. The aim of this study was the evaluation of the effects of different substrates on the production parameters, nutrient and mineral composition of the mealworm larvae. The experiment lasted through 14 days. 5 treatments were set up at, where the variable was the substrate. The test system consisted of 25 units (5 treatments and 5 replicates). 10 mealworm larvae per unit, (total of 250 larvae) were used at the beginning of the experiment. Regarding the substrates, our study included sweet potato (SP), may turnip tuber (MT) and may turnip leaf (ML). In addition to the plant by-products, wheat flour (WF) and wheat semolina (WS) were used as control substrates. Trace element uptake and production parameters of the larvae were determined at the end of the experiment. Regarding the production parameters, it can be stated that the wheat semolina (0.081 ± 0.005 g) and wheat flour (0.069 ± 0.007 g) substrate used as control gave the best results for the final body weight. In terms of plant raw materials and by-products, sweet potatoes (0.063 ± 0.007) can only be recommended as substrate, while may turnip tuber and may turnip leaf produced significantly lower final body weight results (MT=0.034 ± 0.002 g ; ML= 0.036 ± 0.002 g). The nutrient composition of the larvae was not affected by the substrate, these results confirmed the high protein and fat content reported in the literature. The results with the production parameters were contradicted by the micronutrient content. Larvae reared on may turnip leaf (ML) and tuber (MT) showed the highest values for most of the macro- and microelements (potassium, calcium, magnesium, iron, zinc, copper) tested.
Aquaponics is the combined culture of fish and plants in recirculating aquaculture systems, an ecologically sustainable horticultural production technique with long traditions. The objective of this study is to compare flood-and- drain, and the water crossflow system and examine the differences in the water quality, fish yield and plant growth parameters for Common carp (Cyprinus carpio) and basil (Ocimum basilicum). During the study, water quality parameters of two treatments were compared in temperatures, pH, EC and NO3¯N were significantly different (p <0.05). Leaf area of the basil plants grew to an average of 20.37 cm2 (± 9.02 cm2). The plants’ biomass production was significantly different (p< 0.05) in the two systems. The biomass production showed lower yield, 458.22 g (± 214.59 g) in the constant flow system that in the flood- and- drain system 692.9 g (± 175.82 g). Fish Growth parameters were better in constant flow system (FCR 5.48 g/g ± 0.19). However, the specific growth rate (SGR) demonstrated that fish grew faster in flood- and- drain system 1.38 %/day (± 0.29).
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