Eradication of Gyrodactylus salaris infested Atlantic salmon (Salmo salar) in the Rauma River, Norway, using rotenone

Abstract

Introduced alien species bring potential adverse impacts on biodiversity and ecosystem functions. International shipping is an important vector for such unintentional introductions in aquatic environments. Therefore, in addition to climate change and eutrophication, increasing international shipping may enhance the spread of alien species into areas which have not previously been considered prone to alien invasions. One example of such development might be the recent invasion of the moss animal Pectinatella magnifica into Finnish inland waters, which are generally considered to be hostile to alien species. We took advantage of observations made by the general public and recorded by environmental authorities to describe the invasion history of the species in Finland. The records of P. magnifica were almost exclusively from the Vuoksi watercourse, where the species was most likely introduced by international shipping ca 10-15 years ago. The species occurred mainly in the vicinity of ports of international shipping, but was also abundant in an area with only domestic cargo transport. Only one confirmed observation in Lake Kirkkojärvi was from outside the Vuoksi watercourse. Most colonies were found attached to landing stages or submerged, relatively rigid water plants, and the species seemed to avoid less rigid water plants, such as water lilies. Once established, the species may spread by vectors such as recreational boating or water birds and fish. The species poses some risks to the ecosystem, including a risk to farmed and wild salmonid fish by serving as a potential host for the myxozoan endoparasite Tetracapsuloides bryosalmonae, the causative agent for proliferative kidney disease (PKD), known to be detrimental for salmonid fish.

Full steam ahead: direct steam exposure to inhibit spread of invasive aquatic macrophytes

“…Many of these microscopic juvenile life stages can be frequently dispersed, difficult to detect and often remain impervious to suboptimal conditions and resistant to desiccation for long periods of time (Banha et al 2016;Coughlan et al 2017a). Moreover, determination of the efficacy of steam treatments to prevent the continued worldwide spread of damaging aquatic parasites and pathogens, such as inter alia the salmon fluke, Gyrodactylus salaris (Sandodden et al 2018), the crayfish plague, Aphanomyces astaci (Svoboda et al 2017), and amphibian ranaviruses (Price et al 2017), is urgently required. Many of these organisms can disperse between non-hydrologically connected watercourses, with anthropogenic activities being linked to their continued spread and persistence (Price et al 2017;Sandodden et al 2018;Svoboda et al 2017).…”

Catching the fish with the worm: a case study on eDNA detection of the monogenean parasite Gyrodactylus salaris and two of its hosts, Atlantic salmon (Salmo salar) and rainbow trout (Oncorhynchus mykiss)

“…Altogether, fish in 50 rivers in Norway have been infected by G. salaris and extensive eradication programs, mostly using pesticides such as rotenone, have been carried out in several of these watercourses [ 10 ] since 1981 [ 11 ]. Over the last 15 years [ 12 ], the eradication programs have been highly successful and to date the parasite is present only in seven rivers [ 10 ]. To document the absence of G. salaris in Norwegian river systems and to detect new infections at an early stage, large-scale national surveillance programs are carried out every year [ 10 , 13 ].…”

Maintenance management and eradication of established aquatic invaders

“…Another reported consequence of a freshwater fish eradication was eradication of a parasite from a region by eradicating native host fish populations. A Norwegian government agency eradicated the monogenean salmon fluke, Gyrodactylus salaris Malmberg, 1957, a damaging non-native parasite in Norway of wild Atlantic salmon ( Salmo salar Linnaeus, 1758), by eradicating salmon populations with rotenone, then reintroducing salmon from other locations that are parasite-free (Sandodden et al, 2018 ).…”