Simple techniques for labelling prey and gut content analysis in short-term feeding experiments with fish larvae

Abstract

Techniques were developed for labelling prey, and for gut content analysis in fish larvae. Labelling consisted of a short feeding period of the prey (rotifer and Artemia metanauplii) on black-drawing ink before supplying them to the larvae. Prey labelling was rapid and remained stable for at least 3 h when transferred into seawater. In addition, a method was tested to facilitate the observation of larval gut contents. The method, based on Dawson's technique, involved fixation, removal of lipids and clearance of turbot (Psetta maxima) larvae, which become transparent and ready for gut content analysis. This treatment did not interfere with the black ink label of the ingested prey.