Abstract

Queen conch, Strombus gigas, a slow moving marine gastropod, is vulnerable to depressed reproductive activity resulting from density dependent mechanisms such as the Allee effect. Now heavily exploited throughout most of its range, the density of remaining conch populations has become a matter of concern for conservation and recovery of depressed populations, and for management of viable stock densities. In this study we observed individual behaviours and density of neighbours in a Barbados conch population, to determine any patterns and/or ranges in conch densities at which particular behaviours occur. Tagged conch were observed by SCUBA divers biweekly for one year from May 2009 through May 2010. On each occasion the individual’s behaviour (quiescent, buried, feeding, pairing or spawning), water depth and temperature were recorded, together with the number of neighbours within a 20 m radius. Pairing and spawning were only observed at medium (3 - 6 conch per circle or 25 - 50/ha) and high (? 7 conch per circle or ? 58/ha) densities. Feeding was only observed at high densities, whilst quiescent and burying behaviour was observed predominantly at low densi-ties. These results corroborate previous findings of a minimum density threshold for conch spawning and confirm the importance of protecting spawning aggregations.

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