The depletion of natural resources such as freshwater and cropland makes it necessary to find a new solution for sustainable food production. Aquaponic systems seem to be a great alternative to traditional agriculture, however, there are still many unknowns that need to be explored. It is already known how fish stocking affects water quality in aquaponic systems, but not how it affects the plants’ growth, and especially on chlorophyll fluorescence. In this study, we examined how the density of 0, 2, 4, 8, and 16 stocking fish in five aquaria affects lettuce growth. The first tank was only a hydroponic system with plants but without fish (control). In the remaining four aquaria – 2, 4, 8 and 12 specimens of common carp fry with an average weight of 20 grams (average 8.5–33.2 g) were placed in the aquaponic growing system. Physicochemical analysis of water was conducted to determine the levels of pH, electrical conductivity ( EC), N-NO ₃, N-NO ₂, N-NH ₄, P-PO ₄, O ₂ and physiological parameters of plants (nitrogen balance index – NBI, chlorophyll content index – CCI, quantum yield – QY, flavonoid content – Flv) were analysed. The results showed that fish stocking density has different effects on plant physiological parameters, but in most cases, was insignificant. It seems that the greater number of fishes and higher density indirectly causes growth inhibition (lower photosynthetic efficiency) due to the increase of N-NO ₃ and a decrease of O ₂ in the water.

The hemostasis system is designed to ensure the integrity of the body’s internal environment, stop bleeding, and maintain a liquid state of blood in the vascular channel. Modern biological and veterinary science presents highly fragmented and scarce data containing clinical and diagnostic clotting characteristics in different fish species. An essential point emphasising the practical component of such studies is spontaneous thrombus formation in fish farming described in the literature. The present research is devoted to the study of the functional state of plasma hemostasis in some ray- finned commercial fishes: phylogenetically more ancient cartilaginous ganoids – sturgeon Acipenser baerii and hybrid of sterlet A. ruthenus and starred sturgeon A. stellatus, as well as bony fishes – carp Cyprinus carpio and tilapia Oreochromis niloticus. It should be noted that the current study was performed at the aquaculture development center “AquaBioCenter” of VSDFA from 2015 to 2020. Species-specific features of clotting were revealed: activation by common and extrinsic pathways, characterised by thrombin time ( TT), prothrombin time ( PT), and fibrinogen concentration, is several times faster in cartilaginous ganoids than in both bony fish species; hemostasis with activation of the intrinsic pathway, characterised by activated partial thromboplastin time ( APTT), is faster in hybrids and tilapias, in contrast to carps and sturgeons. Content of soluble fibrin monomer complexes ( SFMC) in all fish was higher than in dogs and humans but lower than in cattle. The highest amount of SFMC was detected in carps, the lowest – in cartilaginous ganoids.