Action: Use an alternative protein source: krill
- Two replicated studies in Norway found similar final weight gain between salmon that were fed diets containing fish meal only or a krill meal substitute. When the krill were de-shelled, growth rates were closer to salmon fed fish meal, compared to leaving the krill whole.
- Feed conversion ratios were found to be similar in both the fish meal and krill meal diets.
- The number of aerobic bacteria in the hindgut of salmon fed fish meal and krill meal were higher and composition of the bacterial flora was different.
Supporting evidence from individual studies
In 2002, a replicated, controlled study in Norway (Ringø et al., 2006) found that salmon, Salmo salar, had similar final weights and feed conversion ratios when fed diets containing fish meal or fish meal and krill meal. Fish weighed an average of 105g at the start of the study and increased to 169.0g and 167.2 g in the fish meal and krill meal groups, respectively. Feed conversion ratios were 0.68 and 0.69, respectively. There was a difference in the composition and number of aerobic bacteria colonizing the hindgut of salmon between fish meal and krill meal diets (2.2 x 106 and 8.5 x 104, respectively). Salmon were fed either a diet containing fish meal as the protein source (58.9% of the diet) or a diet containing a 1:1 mix of fish meal and krill meal (64%) for 46 days. Three hundred salmon were stocked in 1.5 m3 x 1.5 m3 x 1m3 fibreglass tanks for the duration of the experiment. On day 46, fish were anaesthetized and measured for weight and feed conversion.
A replicated study in Norway (Hansen et al., 2010) found that salmon, Salmo salar, fed partially de-shelled krill meal had similar growth rates to those fed a whole krill meal diet. During the first 56 days, growth rates of 0.86% and 0.76% were recorded, respectively. Average final weights of salmon were 1060g, 1100g and 956g in fish fed diets containing fish meal, de-shelled krill and whole krill meal, respectively. Three diets were fed to 225 salmon for 100 days: a control diet based on high-quality fish meal or one of two experimental diets where the fish meal was substituted with either partially de-shelled or whole krill meal. Growth rates and final weights were recorded.
- Ringø Einar, Sperstad Sigmund, Myklebust Reidar, Mayhew TerryM., Mjelde Agnar, Melle Webjørn & Olsen RolfErik (2006) The effect of dietary krill supplementation on epithelium-associated bacteria in the hindgut of Atlantic salmon (Salmo salar L.): a microbial and electron microscopical study. Aquaculture Research, 37, 1644-1653
- Hansen J.Ø., Penn M., Øverland M., Shearer K.D., Krogdahl Å., Mydland L.T. & Storebakken T. (2010) High inclusion of partially deshelled and whole krill meals in diets for Atlantic salmon (Salmo salar). Aquaculture, 310, 164-172