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In the Central European region, there is a long tradition of breeding fish in artificially constructed ponds. As the area belongs to the temperate zone, farmed fish need to survive cold winter periods. Common carp (Cyprinus carpio L.), which is an omnivorous, bioturbating species, is well adapted to warm and cold periods and the alluvial water environment. Since the Middle Ages, a large scale, efficient carp farming methodology has been developed in the region, where production is based on natural resources (protein and fatty acid sources) of renewable water ecosystems. This summary aims to present this well-developed breedi:ng method through discussing aspects of hydrobiology and energy transfer through the food chain as well. Capabilities and effects of agro-technical treatments such as liming and organic manuring, zooplankton management and possible supplementary feedings are also reviewed. Analysing chemical processes of waters uncovers that biological production has no carbon footprint; no carbon dioxide is released into the atmosphere. In contrast, gaseous carbon dioxide diffuses into pond water containing calcium and/or magnesium, then it accumulates in algae production and, through energy migration to upper trophic levels, increases carp production. Thus, it can be declared that pond-farmed carp provides an environmentally friendly, delicious meat among products of animal origin.

Two experiments were conducted to evaluate the suitability of corn DDGS as a protein source for European catfish (Silurus glanis). The first experiment consisted of an in vivo digestibility assessment to determine apparent digestibility coefficients for protein, lipid, phosphorus and amino acids available in DDGS. One hundred twenty juveniles (average weight, 154.29 ± 2.73 g) were distributed in recirculation water system equipped with six 1m3 fiberglass tanks (20 fish per tank), which were allotted to two experimental group in triplicates. Juveniles were fed either of the two diets, with or without DDGS (DDGS diet or reference diet) ad libitum till saturation 3 times per day for two weeks. Apparent digestibility coefficient of dry matter, crude protein, crude fat and phosphorus of DDGS ingredient for Europeean catfish were found 49.42 %, 73.39 %, 77.38 % and 87.98 % respectively. The second experiment was conducted for eight weeks to evaluate the effect of corn DDGS on growth, nutrient utilization and metabolism of European catfish. Two hundred forty juveniles of European catfish (average weight, 272.7 ± 37.8 g) were stocked in 1000 L glass fibre tanks in a recirculation system in triplicates. Juveniles were fed with either of the four iso-nitrogenous and iso-caloric (37 % crude protein and 6 % crude fat) experimental diets formulated with the inclusion of 0, 10, 20 and 30 % corn DDGS with partial replacement of soybean and wheat. No significant differences were found between the experimental groups regarding growth performance and plasma biochemical parameters. The liver histopathological observations showed that 20 and 30 % DDGS groups had less vacuolized hepatocytes than the other groups. Both experiments conclude that apparent digestibility of corn DDGS is auspicious for European catfish and 30 % DDGS can be included in the diet of European catfish without compromising the growth performance and nutrient utilization.