Social status determines behaviour and habitat usage in a temperate parrotfish: implications for marine reserve design

Abstract

Marine reserves should work most effectively for exploited species that are strongly site attached to small home ranges (HRs) contained within reserve boundaries. However, to benefit local fisheries through spillover, the species in the reserves must also be able to migrate to unprotected areas. We evaluated the optimal design of marine reserves for protecting and promoting spillover of a commercially important parrotfish, Sparisoma cretense (Linnaeus, 1758), by empirically quantify- ing short- and long-term movements of individuals originally captured inside and outside a small reserve in the Azores Islands (mid-Atlantic). Movements were quantified using active tracking, passive acoustic monitoring and standard tag-recapture. We found that the dual social organization of the species determined the individuals' movements and habitat use. Haremic fish occupied small HRs associated with permanently established male territories in high energy reef areas. Group (schooling) fish spent most of their time in sheltered reefs but expanded their HRs during the spawning season with daily migrations to the 'territorial' areas. S. cretense HR sizes were consider- ably larger than those previously reported for tropical parrotfishes. Passive acoustic monitoring indicated very high site fidelity and minimal dispersion for up to 30 mo. This study demonstrates that residency of adult parrotfish can last for years. Several individuals emigrated to the reserve from neighbouring areas and some of them relocated thereafter. We suggest that a network of adequately enforced marine reserves of small to medium size (ca. 1 to 5 km 2 ) containing suitable habitat diver- sity can effectively protect core populations of S. cretense, but benefits to adjacent fisheries through spillover will be limited to the areas adjacent to the reserve boundaries.