Abstract
Norway leads the world aquaculture production of Atlantic salmon Salmo salar and farmed Norwegian Atlantic salmon is currently consumed around the globe. However, sea lice infestation is a major problem faced by the salmon aquaculture industry in Norway and elsewhere. The use of wild-caught cleaner fish, mainly wrasses, has been recommended over the other available methods as the most economical and environmentally friendly option to control sea lice infestation in salmon farming. Here, we review the development of the Norwegian wrasse fishery and the use of wrasses as cleaner fish. In this document, we address the sea lice problem and introduce the main wrasse species employed as cleaner fish, document the cleaning behaviour of wrasses, present the development of a new wrasse fishery associated with the salmon aquaculture industry, and finally, we identify the main challenges associated with the intensive use of wild-caught cleaner wrasses and provide some insight for future directions of the wrasse fishery and further development of aquaculture techniques to supply salmon facilities with domesticated cleaner fish.
Highlights
Atlantic salmon Salmo salar is one of the most important aquaculture species in the world representing 8.5% of the total global value, approximately $13 billion [1]
Sea louse is the common name given to two species of ectoparasites commonly found on Atlantic salmon: Lepeophtheirus salmonis and Caligus elongatus
Farmed Atlantic salmon is initially infested by C. elongatus while infestation by L. salmonis occurs at a later stage [13]
Summary
Among the 208 fish species documented to display symbiotic cleaning behaviour [24], biological treatment against sea lice infestation in Norwegian salmon farms relies on the use of five main species as cleaner fish, namely: corkwing Symphodus melops, goldsinny Ctenolabrus rupestris, ballan Labrus bergylta and rock cook Centrolabrus exoletus wrasses (Fig. 2), and lumpfish Cyclopterus lumpus to a lesser extent [22, 25] (Statistics Norwegian Directorate of Fisheries: http://www.fiskeridir.no/Akvakultur/Statistikk-akvakultur/Akvakulturstatistikk-tidsserier/Rensefisk/, “Accessed 17 January 2017”). Each species presents unique colour patterns and morphological features, which make it differentiated from the other cleaner wrasses [27,28,29,30], while they share some common attributes. All species are commonly observed inhabiting shallow rocky areas along the Northeast Atlantic, and Norway stands at the northern limit of their distribution range [29,30,31]. Their abundance in Norwegian waters has increased in recent times in connection to the increase in sea water temperatures [33, 34]. In addition to the above-mentioned common attributes, each species presents additional features in its life history of particular relevance for the development of the fishery
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