Absorption and Retention of Fluoride in Atlantic Salmon (Salmo salar), rainbow trout (Oncorhynchus mykiss) and Cod (Gadus morhua) Fed Krill

Traditionally, the diets used for carnivorous fish have been based on meal and oil obtained from fatty fish species. World catches of these species are now at a maximum and alternative nutrient sources are necessary in order to support further growth in f armed fish production. Krill, shuch is found in large quantities in Norwegian waters, is a natural part of the food of wild fish and should be well suited as food source. The suitability of krill as feed was subject of several studies in the late 70s and 80s. The general conclusion was that krill could be used in fish diets, but the results were not followed up partly because of the high fluoride content found in krill species of interest (1000-6000 mg F/kg). To our knowledge, only one publication and one report is as yet available regarding fluoride retention in fish given krill. As EU has set a maximum level for fluoride in feed (150 mg/kg dry feed). More documentation on fluoride retention in different fish spesies is therefore needed before krill commercially can be used in fish feed. This project will be coordinated towards ongoing activities at the Institute of Marine Research (Bergen).