Regulatory processes in the monogenean Gyrodactylus salaris Malmberg—Atlantic salmon (Salmo salar L.) association. II. Experimental studies

The development of infrapopulations of Gyrodactylus salaris on wild Atlantic salmon parr (Salmo salar) from the River Lierelva was followed under experimental conditions, to assess the impact of various processes on this host-parasite system. Two experiments were performed. (1) The development of infrapopulations was followed from January to May 1991 on 24 naturally infected 1 + and older salmon parr. The fish were held individually isolated in two larger tanks in a fish farm in constantly flowing water supplied directly from the tributary River Glitra. (2) The development of infra-populations was followed in five consecutive groups, covering approximately 1 year, of about 20 1 + and older naturally infected and individually marked salmon parr. The fish were held in two parallel cages submerged in a channel connected to the River Lierelva.