PREDATION OF JUVENILE JELLYFISH RHOPILEMA ESCULENTUM ON FLOUNDER PARALICHTHYS OLIVACEUS EGGS AND NEWLY-HATCHED LARVAE
海蜇(Rhopilema esculentum)浮游幼体对褐牙鲆(Paralichthys olivaceus)卵和初孵仔鱼捕食的比较研究

This study investigated the predation of different-sized juvenile jellyfish Rhopilema esculentum(2.5±0.1), (4.1±0.2), (11.7±0.5), and (21.1±0.6)mm in umbrella diameter] on flounder Paralichthys olivaceus eggs (0.92±0.01)mm in diameter] and newly-hatched larvae (3.01±0.08)mm in total length] at different prey densities (10, 30, 50, 80ind/L). In addition, the predation rates of juvenile jellyfish (21.1±0.6)mm in umbrella diameter] on newly-hatched larvae at different predation duration (0.5, 1, 2, 3, 4, 5h) were examined. In all size-groups, the predation rates on eggs were significantly lower than that on newly-hatched larvae at all prey densities. Neither egg density nor jellyfish size had significant effect on the predation rates. Predation rates on larvae increased significantly with the increase of jellyfish size and larval density. Predation rates on larvae by the juvenile jellyfish (21.1mm in diameter) reached a maximum of 17.3ind/(predator·h) at 1h, and then dropped gradually as the predation duration was prolonged. It is assumed that predation on eggs and larvae by juvenile jellyfish could influence the embryonic and larval survival of the flounder if the predators and prey were spatially and temporally matched in nature, which could subsequently affect the recruitment or the population dynamics of the flounder populations.