GROWTH AND CONVERSION EFFICIENCY OF JUVENILE AMERICAN LOBSTERS (Homarus americanus) IN RELATION TO TEMPERATURE AND FEEDING LEVEL

Abstract

ABSTRACTJuvenile lobsters were maintained in recirculating seawater systems at temperatures of 10, 15, 20 and 25°C. At each constant temperature, groups of 25 lobsters were fed rations of 0, 1, 2 and 4% of their body weight per day; 25 lobsters were also fed to excess at each temperature.For the starvation groups, time to 50% mortality (LT50) varied inversely with temperature. At 10°C the LT50 was 114 days while at 20°C it was only 47 days. Survival was high in all cases except for those groups starved or fed to excess, the latter indicating toxic effects from the decomposition of unconsumed food. Growth was exponential as described by the general growth equation W = αekt where W is weight, t is time and α and k are fitted parameters. Specific growth rate ranged from a low of 0.43% increase wet body weight per day at 10°C and a 1% feeding level to 1.38% at 25°C and a 4% feeding level. Gross conversion efficiency (increase in wet weight divided by dry weight of food fed) ranged from 30% at 10°C and a 4% feeding level to 91% at 15°C and a 1% feeding level. Efficiency values decreased with age. Feeding levels promoting most efficient growth and maximum growth increased with increasing temperature. The optimum combination of temperature and feeding level appears to be near 20°C and 2% of body weight.