Food partitioning among flatfish (Pisces: Pleuronectiforms) juveniles in a Mediterranean coastal shallow sandy area

Diets of the four main flatfish species, Arnoglossus laterna, Bothus podas (Bothidae), Buglossidium luteum and Solea solea (Soleidae), inhabiting shallow sandy bottoms near the Gulf of Fos (north-west Mediterranean) were analysed to elucidate food partitioning between their juveniles (1(+) group) in nursery areas. The two Soleidae were principally active during the night, and the two Bothidae during the day. The four species all mainly fed on the three most abundant categories of prey in the area (polychaetes, molluscs and crustaceans) but showed different food preferences. Arnoglossus Interna and B, luteum mainly preyed on crustaceans and molluscs (gastropods and bivalves) whereas Bothus podas and S, solea preyed principally on polychaetes and bivalve molluscs. Food niche width was clearly higher in A. laterna and Buglossidium luteum (13.3 and 14.2 respectively) than in Bothus podas and S. solea (3.2 and 3.6 respectively) Overall food niche overlaps (T) obtained for each pair of fish ranged from 0.33 to 0.58. Overlap was higher between species of the same family but did not reach a significant level. Food niche overlap differed according to the period of the day but did not show any important seasonal variation. Differences in feeding rhythms, food preferences and body sizes, reduced the direct food competition between the juveniles of the four flatfish species, allowing their coexistence within the same nursery zone, despite close periods of settlement.