Variations in mucous cell numbers in gills of Atlantic salmon (Salmo salar) presmolt in commercial freshwater farms in Norway

Abstract

Traditionally, salmon (Salmo salar) smolt have been reared in landbased facilities using water from nearby rivers or lakes which flow through the production site. Flow-through farms (FT farms) depend on high water quality from the source, as means of regulating different water parameters are limited (Kristensen, Åtland, Rosten, Urke, & Rosseland, 2009). Recirculating aquaculture system (RAS) technology has developed rapidly over the last years and has been preferred in new production facilities for rearing of salmon in the freshwater stage. Because RAS technology allows close to 100% recirculation of water, it is possible to produce more fish with restricted resources (Dalsgaard et al., 2013). However, reuse of water demands efficient handling of accumulating waste products, such as particles, which

Mitigating human impacts including climate change on proliferative kidney disease in salmonids of running waters

“…There are some indications that the high prevalence of PKD in Atlantic salmon strains from Norway (Sterud et al., 2007) is not matched by the prevalence of Atlantic salmon in central Europe (Germany, Switzerland) and the Baltic (Estonia) (Lauringson et al., 2021; Thomas Wahli & Zopfi, 2016b). Here, it would be interesting to study whether differences in mucus‐facilitated spore penetration success might play a role (Grabner & El‐Matbouli, 2010) as there is large strain variation in Atlantic salmon in mucus composition and/or gill goblet numbers (Persson et al., 2021). Although mature fish malacospores have been found in the kidney of Atlantic salmon (Svavarsdottir et al., 2021), parasite transmission studies showing shedding of the parasite and successful infection of bryozoans have so far not been carried out for this species.…”

“…Here, it would be interesting to study whether differences in mucusfacilitated spore penetration success might play a role (Grabner & El-Matbouli, 2010) as there is large strain variation in Atlantic salmon in mucus composition and/or gill goblet numbers (Persson et al, 2021).…”