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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.
The research objective was to assess the health of sea trout from the Pomeranian rivers Słupia, Wieprza, Parsęta, and Rega in 2010. Microbiological, hematological, and immunological examinations were performed. In total, twelve gram-negative bacteria species were isolated and identified; they belonged to the families Pseudomonadaceae, Enterobacteriaceae, and others. The gram-positive bacteria isolated belonged mainly to the genus Streptococcus. Immunological and hematological examinations did not reveal statistically significant differences among samples. In comparison to previous examinations, the quantity of infected fish was significantly lower.
The present paper demonstrates results of analysis of 247 alimentary tracts of sea trout smolts (Salmo trutta m. trutta) grown in the drainage area of the river Rega (Pomerania). Frequency of occurrence of acanthocephalans and cestodes in the alimentary tract was determined, as well as their impact on fish condition.
The paper deals with two morphologically similar but molecularly clearly different species of Gyrodactylus: G. derjavinoides sp. nov. on Salmo trutta trutta L. in Western Europe and G. derjavini Mikailov. 1975 collected on Salmo trutta caspius Kessler in Iran. The new species is described and its opisthaptoral hard parts compared to those of G. derjavini. Our molecular analysis of G. derjavinoides and G. derjavini confirmed that the morphological differences between them are species differences and not intraspecific variations. Phylogenetic analysis using the ITS rDNA region placed both species within the subgenus G. (Limnonephrotus) and within the G. wageneri-group, quite in accordance with morphological results. The two species, however, did not cluster as sister taxa. The correspondence between molecular-based clades within G. (Limnonephrotus) and the morphological shapes of marginal hooks within these clades are discussed. The importance of combined molecular and morphological analyses when describing or redescribing Gyrodactylus species is stressed.
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