Comparative diets and feeding habits of Boops boops and Diplodus sargus larvae, two sparid fishes co-occurring in the northwestern Mediterranean (May 1992)

Larval diet composition and feeding habits of the marine fishes Boops boops and Diplodus sargus larvae (Pisces: Sparidae), species co-occurring in the Catalan Sea during spring (May 1992), were compared. Copepod nauplii were the dominant prey in B. boops diet, while in D. sargus, in addition to copepod nauplii, calanoid copepod eggs and cladoceran species (Evadne nordmanni and Podon intermedius) were also important. Prey width, number and variety increased as larvae of both species grew. This tendency was more obvious in D. sargus larvae which showed a greater diversity of food items in larvae > 4 mm. Diet overlap decreased as larvae grew, from almost 100% in small larvae to 40% in larger larvae. Analysis of covariance found that prey size increased with larval size in both species, but the prey consumed by D. sargus larvae were larger than prey of B. boops larvae (P < 0.001). Comparison of larval diets of these species with abundance of microzooplankton in the environment revealed a significant prey selection (P < 0.001). B. boops larvae selected copepod nauplii, while D. sargus larvae tended to select cladoceran and calonoid copepod eggs, prey with lower escape reactions than copepod nauplii. Results indicated that these two sparid species of similar morphology and spatial and temporal co-occurrence, have different feeding habits and avoid niche overlap.