Abstract

Mangroves and seagrass beds are important shelter habitats for juvenile reef fishes, but little is known about their relative importance as fish feeding grounds. We investigated the degree to which these two coastal habitats were used as feeding areas by eight reef fish species in the Grand Cul-de-Sac Marin lagoon in Guadeloupe (Lesser Antilles). Carbon and nitrogen stable isotope analyses were performed on fish species and their potential food sources consisting of plant materials and invertebrates. Carbon isotopic signatures of food sources were significantly different between mangroves (?13C mean = -19.5 ± 1.3‰) and seagrass beds (?13C mean = -12.8 ± 0.4‰) and indicated that most juvenile reef species had isotopic values close to those of seagrass prey items. Two planktivorous (Harengula clupeola, Anchoa lyolepis) and two carnivorous species (Centropomus undecimalis, Lutjanus apodus) had depleted carbon values, suggesting an increased reliance on mangrove prey items in their diets. For these species cited above, mangrove-derived organic matter contributes indirectly to fish diets through the pelagic (i.e. zooplankton) or benthic (i.e. crabs, shrimps) food webs. This study highlighted that reef fishes sheltering in mangroves appeared to actively forage in nearby seagrass beds, thus reinforcing the importance of preserving these interlinked coastal habitats.

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