This study aimed to investigate the effects of the probiotic Betaplus® and prebiotic Technomos®as feed additives for Nile tilapia in terms of growth performance, health profiles, and resistance to infection with Aeromonas hydrophila and Pseudomonas fluorescens. A total of 960 healthy juvenile Nile tilapia (1.5 ± 0.01 g) were randomly divided into four experimental variants with three replicates for each variant. Fish were fed a commercial diet (control group, V0), supplemented with BetaPlus® probiotics–1%×BW (V1), TechnoMos® prebiotics–1% × BW (V2), and with BetaPlus® probiotics and TechnoMos® prebiotics in a ratio of 1:1%×BW (V3). Results on growth performance showed the best values in the probiotic variant, correlated with the health profile and the relative survival percentage after the challenge test with A. hydrophila and P. fluorescens. Similarly, the effects of dietary supplementation with probiotics and prebiotics on physiological conditions also recorded beneficial results in the synbiotic variant, where a high survival percentage was obtained after infection with the two pathogenic bacteria. In conclusion, the results of this study indicate that dietary supplementation with feed additives consisting of mentioned probiotics, prebiotic, and their combination as synbiotics has the potential to promote growth performance, improving tilapia immunity and increasing survival after the challenge test.

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The Romanian fishing areas extends over 7000 km2 and 50% of the numbers of authorised fishers conduct their activities in the Danube areas. Inland fisheries are highly important for income, food security and nutrition. Inland peri-rural fisheries face degradation due to climate change. According to the European Commission, the dominant factor driving the change in water resources in Danube River basin is climate change. Global mean surface temperatures have increased, fact which causes a constant increase in water temperature as well. Razim-Sinoie Lagoon System represents the largest lagoon (1145 km2) in Romania and stands out for its ecological, historical and socioeconomic importance. The lagoon is connected to Danube River through the channels Dranov and Dunăvăț and receives significant river intake. This present study points out the vulnerability of fish stocks and Romanian fisheries in the context of climate change and global warming. Thus, the aim is to evaluate the influence of multiannual hydrographic and thermic regime on fish stocks status and structure from Razim-Sinoe Logoon System, between the years 2016-2018. Thus, a strong positive correlation was observed between the water temperature and the total quantity of fish catches. In case of fish stocks, a simultaneous decline of ichthyophagous fish species, while increasing the stocks of non- ichthyophagous fish species, is recorded. It is recommended that similar studies to be conducted also in other areas connected to Danube River hydrographic basin, in order to evaluate the magnitude of climate change and global warming impact on fish stocks status and structure.

Sturgeon farming is practiced in rearing systems with different types of fresh water, such as surface water, depth water (including geothermal water) and industrial water. If at the beginning of twentieth century sturgeon farming was successfully applied in ponds, nowadays, with the need for quantitative and qualitative productions imposed by the principles of economic viability in the context of ensuring the norms of the European Union, high intensity recirculating rearing systems have been developed. Nutrition plays a central role in sustainable aquaculture and, as a result, research on food resources as well as production costs continues to dominate aquaculture worldwide. According to literature, sturgeon fingerlings with a length of 2,5 – 12,5 cm require a daily ration of 5 - 7% of body weight per day. The optimization of feeding rations for Acipenser baerii related to the pre-development stage in a recirculating aquaculture system was carried out accordingly by following the biotechnological indicators (especially the growth increase) which indicate a favourable growth rate of the biomass.

The present written work represents the results of the research of the ichthyofauna from the lower course of the Prut River (including the Manta puddle and the Beleu lake) in terms of succession. It was established that, as a result of anthropogenic actions (drying of over 27-30 thousand ha of puddles, dam of the banks of the Prut River and its tributaries, extraction of sand and river stone from the minor riverbed, irreversible use of water in irrigation and industries, pollution, construction of the Costești-Stânca dam, destruction of wood cuts for lithifile and phytophilic species, etc.) in the ichthyofauna on the lower course of the Prut River, there were significant changes in diversity, quantitative and qualitative composition, and functional status of fish populations.