MORTALITY-RATES IMPOSED BY 3 SCYPHOZOANS ON RED DRUM (SCIAENOPS-OCELLATUS LINNAEUS) LARVAE IN-FIELD ENCLOSURES

Field experiments were conducted in enclosures (2 mj) to estimate the predation potentials of three scyphozoan jellyfish on larvae of the re d drum (Sciaenops ocellatus Linnaeus). The vulnerabilities of four age classes of larvae (1-13 days post-hatching) were tested with each of three jellyfish predators, Stomolophus meleagris Agassiz, Chrysaora qu inquecirrha Desor, and Aurelia aurita Linnaeus. Rates of instantaneous mortality among larvae were high and variable. There were no signific ant differences in mortality of larval red drum among predator species , however there was a significant effect of larva age on mortality. Ag e effects were most prominent in S. meleagris where instantaneous mort ality ranged from 0.17 . h(-1) for yolk-sac larvae (1 and 2 days post hatching, DPH) to 0.003 . h(-1) for later stage larvae (12 and 13 DPH) . Regression equations developed to describe the relationship between larva age and mortality indicate that scyphozoan jellyfish may inflict substantial mortality on early-stage red drum larvae. Our results als o suggest that growth and development may decrease vulnerability of la rvae to predation by these gelatinous animals, supporting the hypothes is that rapid growth through the larval stage may provide larvae with some refuge from predation. (C) 1997 Elsevier Science B.V.