Tissue fluoride accumulation and kidney lesions in freshwater-reared Atlantic salmon (Salmo salar) fed with high dietary fluoride concentrations

Abstract

Antarctic krill (Euphausia superba) and other marine zooplankton may contain high levels of fluoride. The aim of the present experiment was to determine whether dietary fluoride from Antarctic krill at levels similar to the old and the new EU allowable limits in fish feeds (150 and 350 mg kg−1) would induce kidney lesions in freshwater-reared Atlantic salmon (Salmo salar). In addition to the diets containing krill, two high-sodium fluoride (NaF) diets (1500 and 3500 mg kg−1) were used to investigate the effect on growth, feed intake, faecal excretion of minerals and accumulation of fluoride in various tissues. No major effects on growth or feed intake were observed. A higher proportion of the ingested fluoride was absorbed in salmon fed with the NaF diets compared with fish fed with krill shell diets. Fluoride accumulated in liver, kidney and especially bone. Faecal excretion of calcium and magnesium was higher for the NaF-fed fish compared with fish fed with the control and krill shell diets, whereas the levels of these minerals in plasma were unaffected. Dietary fluoride from krill shells did not induce kidney lesions. One-third of the salmon fed with the highest NaF diet showed signs of crystal formation within the distal tubules and/or collecting ducts in the kidney.