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Relative gene expression pattern of fatty acid transport proteins (FATP and cd36), intracellular fatty acid-binding proteins (FABP3, FABP10 and FABP11), b-oxidationrelated genes [carnitine palmitoyl transferase II (CPTII), peroxisome proliferator-activated receptor b (PPARb), acyl-CoA oxidase (AOX), long-chain fatty acyl-CoA synthetase (FACS), acyl-CoA dehydrogenase (dehydrogenase)] and uncoupling protein 2 (UCP2) was assessed by RT-qPCR in Atlantic salmon muscle (red and white), liver, heart, myosepta and visceral fat. FABP11, a FABP isoform not previously described in Atlantic salmon, was highly expressed in visceral fat and myosepta and at the lower level in red muscle, white muscle, myosepta and heart. Furthermore, Atlantic salmon were fed either a diet containing fish oil (FO) or a complete replacement of FO with a vegetable oil blend (55% rapeseed oil, 30% palm oil and 15% linseed oil; VO) for the production cycle (27 months from start of feeding and until 4.5 kg mean weight). The expression of genes related to b-oxidation, fatty acid uptake and transport in the white muscle indicate (n = 3) significant down-regulation in VO fed Atlantic salmon and correlated with previously reported white muscle triacylglycerol stores and b-oxidation. FABP11 in visceral fat and myosepta was also down-regulated in VO fed fish. KEY WORDS

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The effects of dietary lipid levels on growth, feed utilization, hepatosomatic index (HSI), liver lipid deposition and tissue fatty acid composition in haddock were investigated. Triplicate tanks of juvenile haddock (6.9 g) were fed graded levels of herring oil to supply 14, 16, 19 and 22% lipid (DM, dry matter) in ®sh meal-based, isonitrogenous diets. Growth and feed conversion ratio of juvenile haddock was not signi®cantly (P < 0.05) affected by increasing the lipid content of the diet. A signi®cant increase in HSI (9.8±12.1%), total liver lipid (63.2±69.0%) and whole body gross energy content (6.03±6.39 kcal g ±1 DM) were observed in haddock fed 14% vs. 22% lipid. Although the HSI of these cultured haddock was high in comparison to wild gadoids, histological analyses of these haddock livers did not reveal any overt pathology. Muscle lipid levels (1.0%) did not increase signi®cantly with dietary lipid. Liver fatty acid levels mirrored dietary fatty acid (FA) composition. The muscle consisted mainly of polar lipid (84.3 T 2.5% of total lipid) and a large proportion (52.6 T 0.8%) of polyunsaturated FA. A dietary lipid level of 14% DM or less is recommended for juvenile haddock.

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