Macrozoobenthic resources use by teleosts in the Gironde estuary
Stomach contents of the main benthodemersal teleost species of the Gironde estuary (France) were examined in order to analyse diet composition, spatial variation and interspecific trophic overlap. The studied species are spotted seabass Dicentrarchus punctatus (Moronidae), common sole Solea solea (Soleidae), flounder Platichthys flesus (Pleuronectidae), common goby Pomatoschistus microps and sand goby Pomatoschistus minutus (Gobiidae). The macrozoobenthos was simultaneously sampled in order to explore the trophic use of estuarine habitats by teleosts. Except gobies, teleosts show a high feeding activity and diets are characterized by a wide diversity of prey and a spatial variation. Ragworm (Hediste diversicolor, Nereididae), brown shrimp (Crangon crangon, Crangonidae) and mudshrimp (Corophium volutator, Corophiidae) are the most common prey items. Spatial sharing of macrozoobenthic resources by teleosts occurs and trophic overlap is limited, indicating that competition for trophic resources is minimized, especially in the intertidal area where resources are abundant. Differences between the availability of potential preys and teleost diet show that most teleosts do not feed on the most abundant resources in the habitat but on preys with the highest individual biomass value (and possibly the highest energy content) despite their scarcity. This possibly indicates high mobility, habitat connectivity and low fidelity for estuarine habitats. Only the common sole predominantly fed on local prey, which conversely might indicate a narrow range of movement and reduced feeding area for this species.