Abstract

The diets of the most conspicuous fishes were studied in two seagrass beds of the Grand Cul-de- Sac Marin lagoon in Guadeloupe (Lesser Antilles). Fishes were sampled in two sites located at the extremities of a coast-seawards gradient: a coastal seagrass site situated near fringing mangroves and an offshore seagrass site close to the barrier reef. A total of 15 fish species was caught with a seine net. Morphological measures (total length (LT) and weight) and gut-content analyses were performed on each specimen. Prey items were identified to the lowest possible taxon, enumerated, weighed, and the Index of Relative Importance was calculated to evaluate the relative importance of each food item in the fish diets. Dietary analyses showed that fishes from the reefal seagrass site were carnivorous species that mainly foraged on shrimps (Hippolytidae, Palaemonidae, Alpheidae), crabs (Portunidae, Xanthidae) and Paguridae. In the coastal seagrass beds, fishes were carnivorous and omnivorous species and their diets were characterized by the abundance of small Tanaidacea (Crustaceans). These small Crustaceans appeared to dominate in abundance the benthic invertebrate assemblage of this coastal site. In both sites, ontogenetic trophic variations were observed for the species Ocyurus chrysurus (Lutjanidae). Smaller individuals (i.e. 2 – 5 cm in LT) generally preyed on amphipods, whereas larger specimens (i.e. 17 – 19 cm in LT) foraged on larger prey items (i.e. shrimps and fishes). This study showed that fishes adjusted their diets according to their ontogenetic development and to spatial changes in the benthic assemblages and prey abundances characterizing seagrass bed sites.

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