A novel method for tagging and recapturing animals in complex habitats andits use in research into stock enhancement of Trochus niloticus

Researchers into stock enhancement, fisheries and ecology must use a range of techniques to recapture tagged animals effectively. During research into stock enhancement of Trochus niloticus L. (trochus), we used an underwater metal detector to recapture juvenile (16-25 mm) trochus tagged with metal tags. In this paper, we assess its effectiveness. Tagged animals buried up to 8 cm in complex coral reef habitats were successfully recaptured using t he technique. In pilot trials, 86% of a known number of individuals were co nsistently recaptured from a typical reef. Folded aluminium foil tags remai ned attached to trochus shells and were reliably detected for a maximum of 3 months; modified tags could potentially last significantly longer and be used to identify individuals. The tags had no significant effect on the sur vival of juveniles. The technique is applicable to the recapture of a wide range of benthic invertebrates in complex habitats and we discuss other pot ential uses in aquatic research. (C) 2001 Elsevier Science B.V. All rights reserved.