Induction of settlement, growth and survival of juveniles of Paracentrotus lividus

The effect of different treatments on the settlement success, survival and growth of sea urchin juveniles has been evaluated. Two experiments were performed for assessing the ability of substrates or seawater to induce settlement. In the first test 500 competent larvae were inoculated in transparent plastic containers conditioned for ten days with: Tetraselmis marina, Cyilindrotheca closterium, Nitzschia sp., Maërl beds, 100 μm filtered natural seawater and 1 μm filtered and UV disinfected seawater. Maximum settlement values were obtained with C. closterium, Nitzschia sp. films and UV treated seawater; and significant differences were only detected between T. marina films and the other treatments. In the second test the following treatments were performed in order to investigate the effects of filtered seawater on settlement: 0.22 μm filtered and autoclaved seawater (negative control), 1 μm filtered and UV treated seawater and C. closterium (positive control). Settlement success was significantly higher for C. closterium than for autoclaved seawater. Survival and growth of juveniles were monitored for 32 days on these treatments: T. marina, C. closterium, Nitzschia sp., Maërl beds and 100 μm filtered natural seawater. Growth of juveniles could be adequately described by linear fitting and maximum growth rate was found for C. closterium film. There were no significant differences between treatments in terms of mortality at days 21 or 32. In general, the results showed that C. closterium biofilms provide good settlement, growth and survival of sea urchin juveniles which would allow improving general performance of these phases of culture compared to the other diets tested.