Growth assessment on three size classes of the purple sea urchin Paracentrotus lividus using continuous and intermittent feeding regimes

A 6 month experiment (March '05–September, '05) was conducted to assess the somatic and gonadal growth of three different size classes (small, medium and large) of the European sea urchin Paracentrotus lividus under two feeding regimes. For each size class, four replicate cages were fed continuously in which feed was replenished every seven days and four replicate cages were fed intermittently (an alternating weekly regime of feeding/fasting). Test diameter was measured on a monthly basis while gonad index was determined at the end of the experiment. Small sea urchins (10.0–12.9 mm) were significantly affected by intermittent feeding and showed high mortality rates across the experimental period (39.4 ± 3.32%). Continuous feeding supported somatic growth in small and medium sea urchins (10.0–23.0 mm). Feeding regimes did not affect somatic growth of large sea urchins (29.0–33.5 mm). However, large sea urchins on a continuous feeding regime had greater gonad indices (15.76 ± 1.13%) than those on an intermittent regime, which suggests that an intermittent feeding regime cannot support gonadal production.