The effects of krill hydrolysate-supplemented soya-bean based diets on thegrowth, colouration, amino and fatty acid profiles of juvenile American lobster, Homarus americanus

The feasibility of soya-based diets for pounded American lobster, Homarus a mericanus, was investigated using diets (40% protein) of low-fat soya-bean meal (SBM) containing various proportions of freeze-dried krill hydrolysate (FDKH) at 0, 12.5, 25, 50, 75, and 100% of dietary protein, in a 60-day tr ial using stage 5 juveniles. Diets of fresh blue-mussel, Mytilus endulis, a nd a diet of 100% of protein from fish meal (FM), approximating the industr y diet of fish, were included for comparison. Specific growth rates (SGR) w ere not significantly different in all krill-containing diets, 100% FM and mussel diets. Juveniles on the mussel diet and the 75 and 100% FDKH diets h ad significantly higher maximum body weight gains (BWG), longer survivals ( days in culture) and shorter moulting cycles. Juveniles deriving 100% of di etary protein from SBM failed to moult and had the lowest SGR and BWG, and the shortest survival period. Carotenoid content (mg kg(-1) dry weight), n- 3 HUFA profiles (% of total fatty acids) and arginine (% of total amino aci ds) in the carcass correlated with dietary profiles (% of dry diet) and the level of dietary FDKH. Dietary SBM increased carcass 18:2n-6. Soya-bean me al supplemented with FDKH may provide up to 87.5% of dietary protein in art ificial diets without compromising short-term BWG.