The number of sources of anthropogenic magnetic and electromagnetic fields generated by various underwater facilities, industrial equipment, and transferring devices in aquatic environment is increasing. These have an effect on an array of fish life processes, but especially the early developmental stages. The magnitude of these effects depends on field strength and time of exposure and is species-specific. We review studies on the effect of magnetic fields on the course of embryogenesis, with special reference to survival, the size of the embryos, embryonic motor function, changes in pigment cells, respiration hatching, and directional reactions. We also describe the effect of magnetic fields on sperm motility and egg activation. Magnetic fields can exert positive effects, as in the case of the considerable extension of sperm capability of activation, or have a negative influence in the form of a disturbance in heart rate or developmental instability in inner ear organs.

Analysis of the physicochemical properties of fresh eggs (raw material for caviar production) of the Salmonidae [sea trout ( Salmo trutta L. 1758) and rainbow trout ( Oncorhynchus mykiss, Walbaum 1792)] and the acipenseridae [siberian sturgeon ( Acipenser baeri Brandt, 1869)], as well as sturgeon hybrids ( Acipenser baeri Brandt, 1869 × Acipenser gueldenstaedti Brandt & Ratzeburg, 1833), included determination of basic physicochemical parameters (pH, dry weight, content of protein, fat, fiber and ash), amino acid composition and fatty acid profile. Compared to the Acipenseridae , Salmonidae eggs yielded a 22.5% higher total protein content, a 40.0% higher level of essential amino acids (EAA) and a 57.5% lower crude fat content. The sea trout eggs showed also a completely different fatty acids profile and hence values of lipid indices (lowest PUFA value – 11.72%, highest SFA value – 39.86%). The rainbow trout and sturgeon eggs had a similar fatty acid profile, and were characterized by a high nutritional and dietary value.

This study presents the results of research on energy self-sufficiency, safety and production reliability in a salmonids fish farm. For the needs of the breeding facility under construction in the Recirculating Aquaculture System, energy requirement analyses were carried out and guidelines collected for the implementation of innovative solutions, which ensure the security and continuity of energy supplies and the plant’s energy self-sufficiency. This research included the development of solutions for the reliability of power supply and ensuring the continuity of operation of devices that are key to the fish farming process, i.e., lighting and pumps. In terms of ensuring the necessary amounts of energy, the possibility to diversify electricity sources was analysed, taking into account the possibility of self-production, including primarily from a photovoltaic power plant and from average power wind farms. The profitability of using energy storage was also examined. Recommendations and a list of energy balances for selected cases of potential power sources are presented.

The aim of this study was to determine the levels of Na, K, Ca, Mg, Fe, Zn, Cu, Pb and Cd in the muscle, liver and gills of roach (Rutilus rutilus) and perch (Perca fluviatilis) from three polymictic and eutrophic lakes in poor ecological condition in north-western Poland. Metals in the waters of the lakes, as well as in the muscle, gills and livers of fish, were determined by atomic absorption. Oxygen deficits in summer and high concentrations of Cd and Pb were responsible for the low water quality of the lakes studied. Perch and roach showed a potential to accumulate metals from the water (bioconcentration factor >1). The lowest concentrations of Na, Fe, Zn, Cu, Pb and Cd were found in the fish muscle. The highest concentrations of Cd and Pb were recorded in the liver of both species. Differences in metal concentration between the species were mainly due to significantly higher levels of Fe, Cu and Zn in the muscle of the roach than in the perch (p < 0.05). A portion of 100 g/day of roach or perch muscle can be a complementary source of elements essential to the human diet, because Dietary Reference Intakes were below 2% for Fe, 5% for Na, Ca and Cu, and 10% for K, Mg and Zn. With regard to Pb and Cd levels, consuming the muscle of these fish from the studied lakes should not pose a health risk (Acceptable Daily Intake less than 1%).

Effective protection of lakes against degradation requires a detailed recognition of the factors leading to their eutrophication. This also pertains to small lakes, which constitute an important element of various ecosystems and are crucial for maintaining biodiversity. Therefore, the aim of the study is to determine the trophic state as well as the susceptibility to degradation of three small lakes in north-western Poland: Maszewo, Starzyca, and Nowogardzkie. This study analyzes the morphometric characteristics of the lakes, the impact of the catchment, their actual trophic state, and phosphorus levels. The analysis showed varying regeneration potentials of the lakes. Maszewo Lake is eutrophic-hypertrophic, nonresilient, strongly exposed to influence from the catchment, with phosphorus levels within the norm. Starzyca Lake is a eutrophic lake, not very resilient to the influence of the catchment, with excessive phosphorus levels. Nowogardzkie Lake is a eutrophic lake with moderate resilience to degradation, but with excessive phosphorus levels, which endangers the functioning of this aquatic ecosystem. In all the lakes, phosphorus supply was predominantly internal. Restoration of these lakes could be performed by completely cutting off the inflow of nutrients, as well as reclamation involving the deactivation of phosphorus (e.g., by precipitation) as well as the removal of the bottom sediments responsible for the internal supply of phosphorus.