Timing and Factors Affecting Cannibalism in Red Drum, Sciaenops ocellatus, Larvae in Captivity

Since 1987, when the red drum, Sciaenops ocellatus, was introduced into Taiwan, research has been concentrated on its feasibility and biological studies applied to aquaculture. As a part of these biological studies, an experiment was conducted to investigate the timing and factors affecting cannibalism in red drum larvae in captivity. Experimental larvae were graded into small and large sizes. Four treatments were then applied: (1) the control group, (2) water turbidity increased by adding green algae, (3) density of larvae increased twofold, and (4) satiation feeding with Artemia nauplii. Each treatment was triplicated, each in a 12 l test tank stocked with 20 large and 20 small test larvae except those with doubled density of larvae. In a period of three days, the size difference in test larvae was found to be the most important factor affecting cannibalism, whereas water turbidity and density of larvae showed no apparent effect. Satiation feeding significantly decreased but did not stop cannibalism. The peak stage of cannibalism for red drum larvae was likely to occur at a total body length of 1.8–1.9 cm, when the ratio of lower jaw length to total body length was at its maximum.