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Improving sea lice grazing of lumpfish (Cyclopterus lumpus L.) by feeding live feeds prior to transfer to Atlantic salmon (Salmo salar L.) net-pens

Imsland, Albert K.D., Frogg, Nina, Stefansson, Sigurd O., Reynolds, Patrick
Aquaculture 2019 pp. 734224
Artemia, Caligidae, Cylopterus lumpus, Salmo salar, adults, females, grazing, lice, live feeds, males, net pens, pelleted feeds, salmon, tanks
Two groups of PIT-tagged lumpfish (initial mean weight ± SD, 22.3 ± 2.5 g) were established in land-based tanks. One group received marine pelleted feed (MF group) whilst the other received a mix of pelleted feed, live adult Artemia and frozen sea lice (LF group), both groups with a feeding rate of 2% body weight−1 per day for a period of 122 days. After this period 60 lumpfish (mean weight ± SD, 118.1 ± 7.7 g) mean from each group were Floy-tagged and transferred to four 5 × 5 × 5 m sea-pens containing 300 Atlantic salmon (mean weight ± SD, 668.4 ± 13.9 g), 30 lumpfish in each replicate sea pen. Two sea pens containing salmon only acted as controls. The sea pen study period lasted for 62 days. Individual weights and behaviour of the lumpfish were recorded every other week throughout the study period. In addition, regular lice counts were done, and the salmon were bulk-weighed at the start and end of the study period. Lower average numbers of female lice, pre-adult and combined pre-adult and mature male lice were recorded on the salmon in the presence of lumpfish from the LF group compared to lumpfish from the MF group. The behaviour of the two groups of lumpfish differed, as lumpfish from the LF group were more predisposed in locating natural food sources than fish from the MF group. The present study suggests that lumpfish exposed to live Artemia and frozen sea lice are more efficient in reducing lice counts on salmon after transfer to sea-pens.