ASSESSMENT OF FIN DAMAGE EXTENT IN AQUACULTURE TROUT IN THE LIKOVO REGION

Fisheries and aquaculture have become vital contributors to human existence and progress. Over the last five decades, the supply of fish has outplaced the growth in the percentage of the world population, and today, fish meat stands as one of the most crucial sources of animal protein. Fin damage in aquaculture trout is a common occurrence in intensive trout production worldwide and in our country. The cultivators are aware of its presence, but they don’t draw attention and regard it as a “cultivation phenomenon” that cannot be influenced. This research was conducted at the fish farm in the village Rezhanovtse (Likovo region). It analyzed the degree of fin damage in rainbow trout (Oncorhynchus mykiss (Walbaum, 1792)) in several months (February, April, June, and September 2023). The study included two groups of fish (<30 g and >100 g.) Among 430 individuals of fish included in the study, analysis revealed that all fins, totaling 2240 were damaged to different degrees, with a frequency of 100%. Superficial scarring was represented by 53%, breakage by 24%, burning by 9%, bleeding by 7%, and wound closure at 5%. Additionally, there were instances of fin folding and shedding of fin rays, each occurring at a rate of 1 %. In the group of fish weighing less than 30 g, the damage rates were as follows: 2.30 for the dorsal fin, 1.13 for the caudal fin, 1.29 for the subcaudal fin, 1.72 for the left pectoral fin, 1.71 for the right pectoral fin, 1.39 for the left ventral fin, and 1.42 for the right ventral fin. For fish weighing over 100 g, the damage rates were higher: 3.11 for the dorsal fin, 1.75 for the caudal fin, 1.90 for the subcaudal fin, 2.72 for the left pectoral fin, 2.70 for the right pectoral fin, 2.14 for the left ventral fin, and 2.17 for the right ventral fin. Additionally, in a small number of fish in the <30 g category, aside from fin damage, deformities (malformations) in their gill cover (operculum). The results of this study revealed that both categories of fish were affected with fin damage, and the dorsal, and pectoral fins were the most damaged fins. In addition to the visual observations of fins, also were analyzed (May and August 2023) the abiotic parameters of the water that supplies the farm’s basins. The values measured in August were higher than those in May, and these changes can be taken as the cause of fin damage in the rainbow trout at this research farm. We hope that this research will result in proposals for the modification of farming practices and the continuous improvement of the fin profile of cultivated rainbow trout.