Optimal prey size for early turbot larvae ( Scophthalmus maximus L.) based on mouth and ingested prey size

Abstract

Mouth size and gut contents were examined in turbot ( Scophthalmus maximus L.) larvae from first exogenous feeding to day 10. The larvae were fed on three organisms (two Brachionus species and Artemia nauplii) differing in size. A logarithmic relationship was found between mouth size (width and height) and standard length (SL) of larvae, and a linear relationship between prey size and SL of larvae. Considering the mean size of prey found in the guts of larvae fed on a range of prey sizes, the optimal prey size was determined over the study period. The optimal prey width corresponded to 36±1% of the mouth height (MH). The relationship between optimal prey size and mouth width (MW) was more variable (40±4%). Therefore, the former relationship was found to be more adequate in determining optimal prey size. The optimal prey width for first feeding larvae (day 2 posthatching) was found to be 144 μm, increasing to 225 μm at day 10. The relationships were described by mathematical equations that can be useful to optimise both ingestion and growth rates under rearing conditions.