Water quality, welfare and pathology of fish cultured in sport fishing lakes and ponds from Romania

Fish welfare and their health depend on a large extent on the water quality where they live.Variation in physical, chemical or biological characteristics, in limits too high or very short time,represent serious stress factors for fish. Stress factors reduce the animal’s overall resistance to pestsand diseases and increase the virulence of some pathogenic biotic agents or conditioned pathogens.This research has proposed emphasizing the impact of medial water parameters situated at the limit ofdiscomfort, or even normal limits by point of view by Order 161/2002, correlated with fish welfareassessed by relationship with some morbid states occurring in fish populations in lakes and pondsstudied. Our observations have led to identification and description of interesting episodes caused bythe impact of physical-chemical parameters of water and some biotic pathogenic agents, and theiraction over fish health. Mortality of fish was found in summer season when water quality depreciationnoted in terms of main indicators: increasing water temperatures, decrease of dissolved oxygen levels,increases in pH and organic matter decomposition which led to the installation of hypoxia.Haemorrhagic septicemia was favored by conditions of biotic stress and abiotic factors, being recordedin the case of Asian cyprinids: Ctenopharyngodon idella and Hypophthalmichthys molitrix. Due to thelack of quarantine ponds, prophylactic bathing conditions and due to other technological neglects,several frequent problems were observed, such as: bleeding and skin lesions, infestation of entire fishstock in lakes or ponds with Argulus foliaceus, infestation with Saprolegniaceae. Excessiveadministration of manure to ponds led to water degradation in short time and installation of mortalityin juvenile carp at 21 days.