Trophic analysis and food webs of mangrove fish assemblages from New Caledonia

Fish communities from geomorphologically different mangrove forests showed distinct trophic structures. A mangrove area located near fringing reefs (B ourake) was dominated by large invertebrate (> 2 mm) feeders (40.7 % of tot al wet weight of the fish fauna) and herbivores (26.7 %) whilst an estuarin e mangrove (Ouenghi) was characterized by detritus feeders (28.2 %), pisciv orous (18.2 %) and large invertebrate feeders (17.9 %). In spite of these d ifferences in trophic structure, similar food webs occurred in both areas, whereas the intensity of fluxes between trophic compartments was different. Resident species were usually at the base of the trophic structure. This c omponent of the fish fauna used available sources of energy, such as microa lgae in Bourake or detritus and phytoplankton in Ouenghi. In contrast, tran sient species were high level predators, mainly piscivorous and large inver tebrate feeders. These species actively contributed to net exports of energ y from mangrove areas to nearby coastal habitats. Food webs and energy flux es associated with trophic migration of fishes were particularly important in non-estuarine mangrove forests because of hydrologic conditions (salinit y and turbidity) which were more suitable to the invasion of numerous marin e foraging species (carangids, lutjanids, sphyraenids). (C) Academie des Sc iences / Elsevier, Paris.