Ocena liczebności, kondycji oraz stanu zdrowotnego tarlaków troci (Salmo trutta trutta) i łososi (Salmo salar) zagrożonych chorobą UDN w niektórych polskich rzekach w 2010 roku

In 2010 studies were continued that focused on determining the abundance, condition, and health of sea trout and salmon spawners caught in the Vistula and the Drwęca and other Pomeranian rivers. These results are compared with those of previous years, and the pathogenic factors that could have an impact on the occurrence of disease are determined. Substantial decreases in the numbers of fish ascending to spawn were confirmed in all of the rivers investigated. The number of individuals exhibiting disease symptoms also decreased. Pathogenic changes were observed in sea trout caught in four Pomeranian rivers: Reda, Parsęta, Wieprza, and Słupia, and also in one salmon specimen from the Rega River. No symptoms of disease were observed in sea trout or salmon from rivers in the eastern part of the coast (Łupawa, Łeba, Vistula, Drwęca). The bacteria isolated from fish in 2010 was more abundant than in 2009, but, as in the previous year, it was not possible to determine unequivocally the pathological factor. Mycological tests performed on samples taken from symptomatic body surfaces confirmed the occurrence of yeast from the genus Rhodotorula and fungus from the family Saprolegniaceae, which can be secondary pathogens.