Seasonal dynamics and persistence of Gyrodactylus salaris in two riverine anadromous Arctic charr populations

Abstract

The seasonal occurrence of the monogenean ectoparasite Gyrodactylus salaris Malmberg infecting Arctic charr, Salvelinus alpinus (L.) in the two rivers Skibotnelva and Signaldalselva in northern Norway was studied in the period from autumn 2003 to autumn 2005. Skibotnelva has been infected with the parasite since 1979, and treated with rotenone twice. Most likely resident Arctic charr avoided the rotenone treatment in small tributary streams, and thus was the source of the repeated re-infection of this river. G. salaris was first recorded in Signaldalselva in the year 2000 and it is still untreated. Unlike Atlantic salmon, which is highly susceptible to G. salaris, Arctic charr can display a wide range of host-responses to G. salaris infections. Arctic charr were sampled by electro fishing with a total sample of 681 Arctic charr. The results from this study demonstrate an evident seasonal dynamic in G. salaris infection in charr in both rivers. Parasite intensities fluctuated with the rise and fall in temperature through the year, with an autumn high and spring low. There was a significantly lower prevalence and mean intensity of G. salaris in Skibotnelva than in Signaldalselva. There were also a lower prevalence and intensity of G. salaris in the older than in the youngest charr. The different history of infection and treatment in the two rivers might be the underlying cause of these observed dissimilarities. The current study indicates that Arctic charr is a good natural host for G. salaris.

Metazoan Parasites of the European Sea Bass Dicentrarchus labrax (Linnaeus 1758) (Pisces: Teleostei) from Corsica

“…Parameters including oceanographic factors (temperature or water circulation) associated with physiological factors (immunological alterations and hormonal changes) are the most frequent causes suggest to explained seasonal fluctuations of parasitic infections. They are highly variable and may vary seasonally or annually (Gonzalez-Lanza et al, 1991, Oliver, 1982Robertsen et al, 2008;Winger et al, 2008).…”

Seasonal population dynamics of the monogeneans Pseudorhabdosynochus coioidesis and P. serrani on wild versus cultured groupers in Daya Bay, South China Sea

“…Consequently, care should be taken when transferring E. coioides to a cultured system for Epinephelus spp., as reported for Gyrodactylus salaris Malmberg on salmons (Soleng & Bakke, 1998. Seasonal fluctuations in infections of monogeneans have previously been reported (e.g., Mo, 1992;Van Damme & Ollevier, 1994;Appleby, 1996;West & Roubal, 1998 Winger et al, 2008) which were due to the different responses of the parasites to seasonal variations in complex environments (Koskivaara, 1992). Temperature has been regarded as an important factor for controlling the rates of reproduction and survival of monogeneans (Scott & Nokes, 1984;Jansen & Bakke, 1991;Bakke et al, 2007;Winger et al, 2008).…”

“…Seasonal fluctuations in infections of monogeneans have previously been reported (e.g., Mo, 1992;Van Damme & Ollevier, 1994;Appleby, 1996;West & Roubal, 1998 Winger et al, 2008) which were due to the different responses of the parasites to seasonal variations in complex environments (Koskivaara, 1992). Temperature has been regarded as an important factor for controlling the rates of reproduction and survival of monogeneans (Scott & Nokes, 1984;Jansen & Bakke, 1991;Bakke et al, 2007;Winger et al, 2008). Some species of monogeneans tend to reproduce at a faster rate at higher water temperatures, whereas others prefer cool water temperatures (Hanzelová & Žitňan, 1985;Pojmaňska, 1994;Ötürk & Altunel, 2006).…”

“…Consequently, investigations into their population dynamics are important for disease control and the maintenance of a healthy relationship between the cultured fish and their environment (Kabata, 1985). Ecological studies on monogeneans of fishes generally focused on single species of hosts in natural systems (e.g., Rawson & Rogers, 1973;Gonzalez-Lanza & Alvarez-Pellitero, 1982;Koskivaara et al, 1991;Mo, 1992;Van Damme & Ollevier, 1994;Appleby, 1996;Winger et al, 2008) or laboratory experiments (Scott & Anderson, 1984). It is, however, difficult to understand the impact of host susceptibility on infection dynamics between farmed and wild hosts.…”

Transmission dynamics of the monogeneanGyrodactylus salarisunder seminatural conditions

“…Whereas this strategy has been successful in several rivers, it has failed in others (Anon 2011). It has been proposed that salmonid fish escaping the rotenone treatment, or migrating from nearby infected regions may reintroduce the parasite into treated populations (Hansen et al 2003, Kristoffersen et al 2005, Winger et al 2008.…”