Abstract

The life cycle of most of the reef fish is complex, with potential transitions and movements of individuals between habitats during ontogeny. A recent method showed that isotopic compositions of the crystalline lens of adult individuals can be used to retrace their entire life history. Indeed, lens formation begins as soon as the eggs hatch, and forms new layers as the individual grows, trapping environmental elements in each layer, without renewing or degrading over time. In this study, adult eye lenses of the commercial reef fish species Sparisoma viride were used to trace the life cycle of individuals at several sites around the island of Guadeloupe. Isotopic compositions of carbon, nitrogen, and sulfur (?15N, ?13C, ?34S) were obtained for each lens layer. Comparisons of isotopic fractionations and isotopic compositions were then made to determine whether 1) the isotopic values taken by individuals during their lifetime differed between sites, 2) the isotopic values of individuals at adults stages differed from site to site. The results suggested that the isotopic values taken by individuals over their lifetime differ between sites. The ?13C values tended to remain stable over the lifetime of the fish at site AD, while these values followed a U-shaped curve at sites GCSM and PGV and decreased at site PC. However, adult isotope values did not differ between sites. These differences are probably due to the use of different sources of organic matter as individuals transition to one or more habitats during their growth, and conversely to similar use of resources in adulthood regardless of the site studied. The use of adult lens can therefore be a good way of tracing the entire life cycle of reef fish and acquiring new information to protect the habitats used by commercialized species.