Growth performance and gonad yield of sea urchin Paracentrotus lividus (Lamarck, 1816) fed with diets of increasing protein: energy ratios

Abstract

The establishment of a commercially sustainable aquaculture production of Paracentrotus lividus depends on the development of diets able to fulfil the species nutritional requirement and the production of market valuable roe. As dietary protein level and protein: energy ratio (P:E) are major limiting factors for sea urchin growth and gonad development, six isolipidic (≈ 7%) practical diets of increasing protein content (20, 25, 30, 35, 40 and 46 % dry matter, DM) and protein: energy ratios (P:E) (15, 18, 21, 24, 27 and 28 mg P/kJ) were fed to triplicate groups of adult sea urchins for 107 days to identify the dietary protein level and P:E able to promote the highest nutrient utilisation, best growth and gonad enhancement. The trial results showed that protein apparent digestibility coefficients ranged between 69 and 86 %, without significant differences among groups. Digestible energy intake and feed conversion ratio (FCR) decreased with increasing dietary protein levels and protein: energy ratios, whilst digestible protein intake remained similar in all groups. The retention and gain of protein and energy remained unaffected by dietary treatments, resulting in a specific growth rate of 0.3 % per day across treatments, and in a final body weight between 22 and 24 g. All diets significantly increased the gonadosomatic index (GSI) attaining 7.4–8.5%. Both GSI and gonad protein gain picked with a dietary P:E of 21 mg P/kJ (diet P30), whereas gonad protein content picked when P:E was 24 mg P/kJ (diet P35). These results, in association with the decreasing FCR with increasing dietary protein levels, suggest that diets with 30 % DM of protein and a P:E of 21 mg P/kJ are the most appropriate to promote both high somatic growth and high gonad yield in adult P. lividus.