The sea urchin Tripneustes depressus is a potential fishing resource on the coasts of Baja California Sur due to the quality of its gonads for human consumption. An alternative to increase gonadal quality in captivity is to control the nutritional balance of the food. The consumption and protein content of different diets formulated based on algae were evaluated in T. depressus organisms.
According to the results of the selectivity experiments (evaluating 4 algae) three balanced foods were formulated and produced, two based on the selected algae (Eisenia arborea, Sargassum sinicola), and one mixed combining both; with a stability greater than 90%. Sixty organisms (8-11 cm diameter) previously acclimatized without feeding (three replicates of 20 organisms for each treatment) and three controls with each type of natural algae were placed in the laboratory. The organisms were fed ad libitum for three months. Food consumption was evaluated, as well as the amount of protein consumed weekly; and at the end of the experiment, the gonadal protein efficiency ratio (GPER) was determined, using the gonad wet weight for each treatment.
In general, the consumption of balanced feeds during the whole experiment was higher than 50%, which suggests that all the feeds were well accepted by the organisms. In the case of natural algae, it was between 30-50%, except for S. sinicola, which was higher than 60%. The protein contribution per feed consumption was lower for the formulated feeds compared to the natural algae; the former provided approximately 30% of proteins, while in the natural algae it was higher than 50%. The GPER was higher in the natural algae E. arborea treatment (90%), compared to the rest of the treatments, due to the higher gonadal weights present in these organisms. Among the formulated feeds, the highest GPER was in the feed based on E. arborea (55%).
The use of the natural algae E. arborea was favorable in the gain of gonadal weight, as well as in the protein contribution to the organisms. Future studies focused on this could contribute to improving the gonadal quality of T. depressus in captivity, and, therefore, to the development of aquaculture in Mexico of this resource.