| Summary: | Gyrodactylus salaris is a monogenean ectoparasite parasitizing salmonids in freshwater. This parasite is highly pathogenic to both Norwegian and Scottish salmon and has decimated the salmon populations in 45 Norwegian rivers after anthropogenic transfer from Sweden. G. salaris has also been found on several occasions in Danish rainbow trout farms but has never been recorded as a pathogenic parasite on Danish wild salmon. In the present study the occurrence of G. salaris and other Gyrodactylus parasites on wild Danish salmon fry and parr were monitored. Electrofishing was conducted in three river-systems (River Skjern, Ribe and Varde) and 0+ and 1+ salmon were collected and sacrificed using an overdose of MS222. During spring or summer time more salmon fry and parr will be collected. The fins were excised and fins and body were conserved separately in 96% ethanol. In the laboratory, the fins and body were examined for Gyrodactylus parasites under a dissection microscope. The location of each parasite was registered and each parasite was isolated for later morphological and genetic typing. The opisthaptor was separated from the body, fixed and mounted using Malmbergs fixative (ammonium picrate-glycerine) on a microscope slide. The morphology of the hamuli and marginal hooklets were examined and used for species discrimination. The body of the parasites will in future studies be used for PCR and species identification will be done by RFLP using restriction enzyme HaeIII. The preliminary morphological results are presented and discussed.
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