Fish is a nutrient rich food and possesses many components that have positive impact on human health. Nowadays, the fish come to the market from wild-capture fisheries and aquaculture. Latter becomes increasingly global for human consumption, thus total finfish aquaculture includes over 300 species farmed in ponds, floating net cages and recirculating aquaculture systems (RAS). It is reasonable to assume that the chemical composition of farmed fish will vary compared to wild-caught ones due to the different rearing conditions and artificial diets used for feeding the fish. This study gives an overview of basic chemical composition of pikeperch (Sander lucioperca) and rainbow trout (Oncorhynchus mykiss). We analysed the muscle flesh composition of fresh and frozen pikeperch obtained from the local commercial tank-based recirculating aquaculture system together with rainbow trout obtained from river-based net cage farming system. We determined that fresh pikeperch contained 78.27±0.34% moisture, 18.95±2.45% protein, 1.34±0.18% fat and 1.62±0.21% ash, while frozen ones had 78.26±0.44, 20.91±0.62, 0.77±0.15 and 0.99±0.09% respectively. Statistically significant differences were found for fat and ash content (p<0.05). In both cases, artificially cultivated pikeperch has high nutritional value and fit for human consumption. The chemical composition of trout was the following: 69.61±1.33% moisture, 17.78±0.48% protein, 11.41±2.24% fat and 0.88±0.01% ash. After reviewing the literature, we found that farmed trout has considerably higher fat content than wild trout. This primarily can be explained by use of lipid-rich diets and lower mobility in cages.

The second stage of development of northern pike artificial reproduction technology for stocking with larvae and fry in the Kaliningrad lagoon basin is considered in this paper. Today northern pike natural stocks in the Kaliningrad lagoon basin are not numerous due to unregulated fishery and limited spawning habitat. Since the 1990s, in many countries of the world, the number of natural stocking northern pike has gradually decreased and at present does not exceed several thousand tons. This problem is also relevant for the Baltic Sea basin, where the modern catches of northern pike in the Curonian and Kaliningrad lagoons make 7,2 and 0,6 tons respectively. At the present time different scientific programs and actions are realized in many countries to restore natural stocks of northern pike. One of the most promising solutions of low northern pike numbers problem is organization of northern pike artificial reproduction in the territory of the Kaliningrad Region. Based on our earlier research in the Curonian lagoon basin, the second stage of development of the technology of northern pike artificial reproduction was carried out on the basis of the educational and experimental farm of KSTU in 2020. Prespawning maintenance of 25 northern pike producers with the use of cages from deli, ponds and reclamation canal was carried out, as well as egg incubation and holding of prelarvae in RAS. As a result of the conducted researches, it was established, that the reproductive products of northern pike producers have high quality and the prelarvae at the stage of incubation have high survival rate (82,2–91,7%). The calculated of biometric parameters of producers and their reproductive products, confirmed the correlation between the weight of females and their fecundity, which was 0,86 and 0,95. The scheme of keeping of producers and incubation of northern pike eggs tested at the second stage has shown the prospect of providing 50% of the need in stocking of young northern pike in the Kaliningrad lagoon with the use of 100% stock of producers.