INVERTEBRATE PREDATORS OF ZOOPLANKTON ON GEORGES BANK, 1977-1987

Chaetognaths, primarily Sagitta elegans, were the most abundant and wi despread invertebrate predator on Georges Bank during 1977-1987 MARMAP surveys. They were present in 79% of samples collected, and their ave rage abundance was nearly an order of magnitude greater than that of a ny other predator taxon. Hydrozoan and scyphozoan medusae, euphausiid shrimp, and gammarid and hyperiid amphipods were also abundant. Divers ity and abundance of predators was highest in the central, well-mixed region of the bank. In this region numbers of chaetognaths and cnidari a increased following increased abundances of Calanus finmarchicus. Ho wever, on a larger scale the density of C. finmarchicus populations wa s inversely correlated with number of predators because this herbivore was most abundant in deeper waters surrounding Georges Bank where pre dators were least numerous. Chaetognaths and cnidaria were more abunda nt in 1978-1979 than in other years, and there was a statistically sig nificant decline in the abundance of chaetognaths over the 10 year per iod. Abundance of both these groups was inversely correlated with temp erature. Average numbers of chaetognaths in summer were low following a warm winter. Abundance of cnidaria in summer decreased with increasi ng summer temperatures. Copyright (C) 1996 Elsevier Science Ltd.