Salinity tolerance of Gyrodactylus salaris (Platyhelminthes, Monogenea): laboratory studies

• Published in: Canadian Journal of Fisheries and Aquatic Sciences
• Main Authors: Soleng, A, Bakke, T A
• Format: Article in Journal/Newspaper
• Language: English
• Published: Canadian Science Publishing 1997
• Subjects: Aquatic Science; Ecology, Evolution, Behavior and Systematics; Atlantic salmon; Salmo salar
• Online Access: http://dx.doi.org/10.1139/f97-089; http://www.nrcresearchpress.com/doi/pdf/10.1139/f97-089

The salinity tolerance of the freshwater monogenean Gyrodactylus salaris, infecting Atlantic salmon (Salmo salar) parr, was studied experimentally. Following direct transfer of infected fish from fresh water to 5.0omicron salinity, parasite population growth increased at the same rate as in fresh water and was positively correlated with temperature (1.4, 6.0, and 12.0°C). In 7.5omicron salinity the populations declined and became extinct after a maximum of 56 days, without any significant difference between 6.0 and 12.0°C. However, some infrapopulations demonstrated short periods of growth. At higher salinities (10.0, 15.0, 20.0, and 33.0omicron) the survival time decreased, and there was a negative correlation between survival time and temperature (1.4, 6.0, and 12.0°C). When transferred directly to sea water (33.0omicron) the parasites became opaque and ceased moving after a few minutes. There was no difference in parasite survival time between direct and gradual transfer from fresh water to 7.5 and 10.0omicron, except for one infrapopulation which demonstrated population growth from day 22 after some fluctuations following gradual transfer to 7.5omicron. The present findings support the hypothesis of brackish water dispersal of G. salaris with infected fish migrating between rivers in fjord systems.