Sea lice remains one of the largest challenges of the salmon aquaculture industry, and there is an increasing demand for de-licing strategies that do not negatively affect the health of the fish. The use of cleaner fish as a method of controlling infection has become well established in the European salmon aquaculture industry in recent years, and farmers indicate good efficiency,
reducing the need for medical or mechanical treatments.
Lumpfish (Cyclopterus
lumpus ) are well adapted to colder temperatures and are less complicated to farm than other lice eaters such as Ballan wrasse (Labrus
bergylta) . Nutrient- dense feed is a factor believed to influence rapid growth, development and health of lumpfish . However there is a request from the market to reduce the growth rate to comply with vaccination guidelines from manufacturers (i.e. 500 degree days from vaccination to sea transfer) and still have efficient lice eaters in the cages .
In this RFF Nord-funded project in collaboration with Nofima (#267738) a feeding trial was carried out at Tromsø Aquaculture Research Station, with fish delivered from Center of Marine Aquaculture. Triplicate groups of lumpfish juveniles (average initial weight 2 g) were fed 3 die ts with 2 different gross energy and protein levels
for 12 weeks. A functional additive pack including krill, immunostimulatory components, prebiotics , and increased levels of vitamins was present in all diets, however the third diet contained a slightly modified additive pack.
Survival was high throughout the growth period, with average survival above 93% for all diets and an average final weight of 57g. No difference in feed intake or growth performance was observed between the 3 tested diets. Cataracts presence was evaluated after 12 weeks of feeding with clear differences between diets. Liver pigmentation was also enhanced by the diets. At the end of the feeding trial, randomly selected fish from the two best performing diets were labelled and transferred to duplicate challenge tanks for atypical Aeromonas salmonicida bath challenge. After 41 days, survival was improved with 30% between diets. These results indicate that a well-balanced reduced nutrient diet has a positive impact on various health parameters, however an impact on growth was not identified.