Growth of Australian shortfin eel (Anguilla Australis) elvers given different dietary protein and lipid levels

The Australian shortfin eel, Anguilla australis is a potential candidate for intensive aquaculture. The present study was undertaken to evaluate the growth of elvers (5.4 g ± 0.1 initial weight) fed with diets of varying protein and lipid content, and to assess the potential of using soya-bean meal as a dietary ingredient. A 10 week experiment was conducted at 24 (±1.0) °C by rearing fish, in 60 L conical fibre glass tanks using a closed recirculation system. Diets having protein concentrations of 40 or 50% (by dry weight) were tested at three lipid levels (15, 20, 25%); diets being designated P40L15, P40L20, P40L25, P50L15, etc. All these diets contained 5% soya-bean meal. In addition P50L20 diets were formulated to contain 10 and 20% soya-bean meal in the diet (Diets S1 & S2). Shortfin eel grew best on the P50L15 diet, with an average specific growth rate of 2.26%. Food conservation ratio (FCR) and Protein efficiency ratio (PER) ranged from 1.21 (P50L15) to 2.12 (P40L25), and 0.92 (P50L25) to 1.65 (P50L15), respectively. Based on all criteria the best growth performance of shortfin eel was on the P50L15 diet, followed by P40L20 and P40L15. At both protein levels fish reared on diets with 25% lipid performed poorly. The performance of shortfin eel was not affected by the amount of soya-bean meal in the diet, up to a maximum of 20% dietary inclusion. No significant differences in muscle protein were evident in shortfin eel reared on different dietary treatments, nor was the lipid content of muscle related to dietary lipid level.