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

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 th ree organisms (two Brachionus species and Artemia nauplii) differing in siz e. A logarithmic relationship was found between mouth size (width and heigh t) and standard length (SL) of larvae, and a linear relationship between pr ey size and SL of larvae. Considering the mean size of prey found in the gu ts of larvae fed on a range of prey sizes, the optimal prey size was determ ined 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 relat ionship 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 mu m, increasing to 225 mu m at day 10. The relationships were d escribed by mathematical equations that can be useful to optimise both inge stion and growth rates under rearing conditions. (C) 1999 Elsevier Science B.V. All rights reserved.