Discussion

Invasive parasites and pathogens are major threats to aquatic biodiversity. However, management strategies directed towards invasive parasite control may detrimentally impact non-target species. For example, the widespread use of the aquatic pesticide rotenone in Norwegian waterways to eradicate the invasive salmonid parasite Gyrodactylus salaris has the potential to inadvertently alter beneficial interactions between native parasites and their hosts. Utilising a multi-lake Norwegian system, I demonstrate how native parasite communities of Arctic charr Salvelinus alpinus and brown trout Salmo trutta populations have responded to a catchment-wide rotenone treatment program. Results indicate approximately 50% of native parasite species are present three years following the rotenone application, however the abundance of most species remains low. This study also suggests that rotenone may have greater impacts on native parasite species with direct lifecycles and those which utilise copepods as intermediate hosts, compared to species utilising snail intermediate hosts. The implications of short- and long-term alterations to native parasite and fish communities are discussed.