Feeding preference and performance in the tropical sea urchin Tripneustes gratilla

Sea urchin aquaculture has two sequential steps relating to performance, optimising somatic growth followed by conditioning of the gonad (roe) as the end product. Quantifying dietary preferences and consumption on performance is a first step in maximising somatic growth and subsequently optimising gonad conditioning. In this study we evaluate dietary preferences, consumption, and performance in the tropical sea urchin, Tripneustes gratilla across a broad range (29 species) of algae. T. gratilla has strong and consistent preferences for algal species, however, there was less discrimination among brown algae compared to red and green algae. The outcomes of preference (choice) experiments were generally reflected by consumption rates (g.hr^{− 1}) in no choice experiments. Performance experiments with four clearly preferred and abundant species, Sargassum flavicans and Cystoseira trinodis (brown algae), Hypnea pannosa, and Laurencia intricata (red algae), and a mixed diet of all species, provided contrasting outcomes. Brown algae, and the mixed diet, provided the highest growth rates and gonad yields. Red algal diets provided poor growth performance as single species diets, but improved holistic performance in terms of growth, test diameter and gonad yield, when combined with brown algae in a mixed species diet.