Potential interaction between cultured and wild Atlantic salmon

Abstract

This paper gives an overview of the potential interaction between cultured and wild Atlantic salmon in respect to disease, parasites, behavior-ecology and genetics. The threat from diseases and parasites is real and, in some cases, serious during interaction between reared and farmed Atlantic salmon. Diseases are a more serious threat to reared than to wild salmon owing to intensive culture, resulting stressful conditions and the ease of transmission of pathogens. Little is known of infections of wild salmon resulting from culture activity. Metazoan parasites can pose serious threats to both farmed and wild salmon. In the examples given, sea lice are of little danger to wild salmon but are a major concern in salmon mariculture. The fluke, Gyrodactylus salaris, is a serious threat to wild salmon in Norway where the parasite has been recently introduced from the Baltic area. Behavioral and ecological interaction between cultured and wild salmon is likely since it has been demonstrated that culture salmon do enter rivers and spawn. It is safe to assume that the two forms do interbreed but the extent is unknown. Cultured salmon quickly become genetically dissimilar to the wild stocks from which they are derived. Wild stocks are believed to have developed unique genotypes which are adaptive to local conditions and life history imperatives. Reasonably precise homing behavior is believed to have been responsible for development of unique genotypes and for helping to maintain this uniqueness. There is no consensus as to possible damage and loss of adaptivenes following inter-breeding a between potentially greatly different genotypes. It is recommended that a long-term study be conducted using farmed and wild salmon in a previously unaffected river to answer vital questions about behavioral interactions and the short- and long-term consequences of interbreeding between farmed and wild salmon.