A SORTING METHOD FOR ELIMINATING FISH LARVAE WITHOUT FUNCTIONAL SWIMBLADDERS

We describe a simple sorting method for separating cultured fish larvae with functional swimbladders from those without based on density differences. The whole population was first anaesthetized with MS 222 and then the fish were separated: fish with a functional swimbladder float and those without sink. The efficiency of the separation method was tested at several anaesthetic doses (0.02 to 0.1 g l-1) with sea bass (Dicentrarchus labrax) and sea bream (Sparus auratus) larvae in the 6-34 mm (total length) range. The minimal sorting size was 15 mm for sea bass with an optimal anaesthetic dose of 0.07 g MS 2221 l-1. There were not enough data to draw conclusions for sea bream. The method was satisfactory when applied in real conditions to a large (90 000) population of sea bass fry with an efficiency ratio of over 80%.