Improving gonad colour and somatic index in the European sea urchin Paracentrotus lividus

One of the major factors influencing marketability of sea urchins is their gonad colour. The effects of a prepared diet, algal diets, and rotational feeding of these diet treatments on the European sea urchin Paracentrotus lividus were studied to determine a diet that would provide optimal gonad colour and gonadal somatic index (GSI). P. lividus underwent six diet treatments: Ulva lactuca and Gracilaria conferta for 12 weeks (UG-12); prepared diet for 10 weeks followed by administration of Ulva and Gracilaria for 2 weeks (P-10); prepared diet for 8 weeks followed by Ulva and Gracilaria for 4 weeks (P-8); prepared diet for 6 weeks followed by Ulva and Gracilaria for 6 weeks (P-6); prepared diet for 12 weeks (P-12); and Ulva, Gracilaria and prepared diet for 12 weeks (UGP-12). The algae diet produced a dark orange colour but a low GSI. The pellet diet produced a good GSI but pale gonad colour. P. lividus fed the prepared diet for 8 weeks followed by 4 weeks of algal diet produced the optimal combination of desired gonad colour and GSI. The dominant carotenoid in the gonads was echinenone, which the sea urchin synthesises from β-carotene. The higher the echinenone level in the gonads, the more intense their colouration. The lack of echinenone found in the gut and its high accumulation in the gonad, in inverse proportion to the β-carotene profile, indicates bioconversion within the gonad or upon transfer from the gut to the gonad.