Occurrence and seasonality of Gyrodactylus salaris and G. salmonis (Monogenea) on Arctic char (Salvelinus alpinus (L.)) in the Fustvatnet lake, Northern Norway

Gyrodactylus spp. (Monogenea) were found on 16.9% (233 out of 1376) Arctic char, Salvelinus alpinus (L.), sampled from September 2010 to October 2011 in the Fustvatnet lake, Northern Norway. Two species were identified: G. salaris Malmberg, 1957, and G. salmonis Yin and Sproston (Sinensia, 19, 1948). Gyrodactylus salaris was only found on Arctic char larger than 28 cm and only in samples obtained in the autumn (September and October). Gyrodactylus salmonis was found on Arctic char of all sizes (11-47 cm) and throughout the year, with a small peak in abundance in the late autumn (November). Gyrodactylus salaris was found to prefer the tail and dorsal fin. Based on the results, we recommend that surveys of Arctic char for the presence of G. salaris are based on the examination of the fins of large fish sampled during the spawning season (autumn).

Automated summary

Gyrodactylus spp. (Monogenea) were found in 16.9% of Arctic char, Salvelinus alpinus (L.), sampled in the Fustvatnet lake, Northern Norway. Two species, G. salaris and G. salmonis, were identified. G. salaris was found only in Arctic char larger than 28 cm and only in samples collected in the autumn. G. salmonis was found in Arctic char of all sizes (11-47 cm) throughout the year, with a peak in abundance in late autumn. G. salaris preferred the tail and dorsal fin. Based on the results, we recommend surveying the fins of large Arctic char sampled during the autumn spawning season for the presence of G. salaris.