Morphological diet analysis of the lumpfish (Cyclopterus lumpus): a cleaner fish inside Newfoundland salmon sea cages

The lumpfish (Cyclopterus lumpus) is a highly opportunistic cleaner fish used as a biological control in Atlantic salmon sea cages for an economically important ectoparasite, the salmon louse (Lepeophtherius salmonis). The objective of my research was to determine the relationship between lumpfish size and whole diet composition to assess which sizes of lumpfish would be more likely to consume salmon lice. Principal component analysis of morphologically-identified gut contents showed that PC3 was a contrast of salmon pellets and diurnally-migrating krill. MANCOVA found a significant relationship between PC3 scores and two covariates: body and stomach weight. In conclusion, larger lumpfish (>150g) with fuller stomachs consumed more salmon pellets, and fewer free-living invertebrates. My work suggests large lumpfish >150g may not be suitable as biological controls in salmonid aquaculture because of their preference for pellets being fed to the salmon over natural crustacean prey.