Is cleaning behaviour in lumpfish (Cyclopterus lumpus) parentally controlled?

•We assessed the sea lice grazing of different families of lumpfish.•Differences in behaviour, feeding preferences and mortality were found.•High behavioural interaction with the salmon was linked to lower exploitation of natural food sources.•Higher consumption of sea lice was found in family 2 accompanied by 64–93% lower lice infestation rates on the salmon.

To investigate the possible family influence on sea lice grazing of lumpfish on Atlantic salmon, nine families of lumpfish (N = 360) with a mean (± SD) weight of 169.4 ± 8.3 g were distributed among nine sea cages (5 × 5 × 5 m) each stocked with 400 Atlantic salmon with a mean (± SD) weight of 123.3 ± 12.3 g. For each family, 20 lumpfish were stocked into one of nine sea cages and 20 into another cage thus establishing duplicate treatments for each genetic family giving two families stocked per cage. There were significant differences in behaviour, feeding preferences and mortality between the nine families of lumpfish. Fish from family 2 were found to be more predisposed to exploiting natural food sources within the cage environment and showed a higher incidence of sea lice grazing from Atlantic salmon. Using mixed linear model to analyse the data revealed significant maternal and paternal effect on sea lice grazing. In contrast, fish from family 5 were observed choosing to compete with salmon and consume pellets more than the other eight families and were found to be less inclined in seeking out alternative food sources. Further, there were differences in the mortality rates between the nine families as a result of a Pasteurella spp. outbreak. This is probably the first study in fish aquaculture investigating the variation in a specific behavioral trait linked to different family background.Statement of relevanceThe data presented here are highly relevant for aquaculture.