Impact of predation by gastropods and crabs recruiting onto culture enclosures on the survival of the scallop Euvola ziczac (L.) in suspended culture

We evaluated the impact of predation from carnivores settling onto suspended culture enclosures on the production of scallops, Euvola ziczac, in the Golfo de Cariaco, Venezuela. Seven potential predator species were found on 70 pearl nets which were immersed from mid-February to mid-April 1994. The crabs Mythrax forceps and Pilumnus caribbaeus and the gastropod Cymatium poulseni, were found on a high proportion of the nets (56, 44 and 48%, respectively). Studies in which the various potential predator were maintained in pearl nets with 25 scallops indicated that six of the seven predators would cause significant mortality within 30 days. A single P. caribbaeus or C. poulseni destroyed 22–25 of the 25 scallops in 30 days. Observations in aquaria of attacks by three species of Cymatium suggested the scallops are subdued using secreted substances. High losses in production due to recruiting predators poses a major problem to growing E. ziczac, and possibly other tropical bivalves, in intermediate suspended culture.  2000 Elsevier Science B.V. All rights reserved.