Introduction
Purple sea-urchin aquaculture has been increasing in the last two decades but is a still challenge mainly due to the existence of different stages throughout their life cycle. Nutrition is a crucial issue for its production. The main objective of this work was to compare the performance of both artificial and control diets (macroalgae) on body growth and gonad development.
Materials and methods
Three groups of sea urchins (3.73 ± 0.39 cm test-diameter ) produced at EPPO-IPMA were fed with two formulated diets and a natural diet (Ulva sp.) each group, for 183 days. For each treatment, three replicates of 50 individuals were constituted and kept in Hexcyl ® baskets suspended inside fiberglass tanks. The resulting growth parameters, gonadosomatic index and fatty acid profile of gonads were analyz ed to evaluate to evaluate and compare the three diets.
Results and discussion
It was found that the sea urchins fed with both diets showed a higher growth compared to the control (Ulva sp.). Growth rates were 0.76, 0.82 and 0.39 mm/month for sea urchins fed D1, D2 and control diets, respectively. S pecific growth rate (weight increase index) calculated for sea urchins fed with D2 was 0.31%, higher than D1 (0.25%) and control (0.15%) . During the. No mortality was found during the experiment. At the end of the experiment , the sea urchins’ gonads fed with natural food (control) had a total amount of fatty acids (absolute value of 130. 9 ± 56,6 mg/g) slightly higher than those fed with f ormulated food, especially because of the higher content of monounsaturated fatty acids. It was found a high value of DHA observed in animals fed with ration, compared to the control . There was also a significant content of some non-existent or trace fatty acids in the diets used in the gonads, suggesting a biosynthetic activity by sea urchins (20:4 ω 6, 16:4 ω 3 and 20:3 ω3)
Food quality is undoubtedly an important factor for each stage of sea urchin cultivation. In this work it was found that animals fed with formulated food present a body growth significantly higher than those fed with natural food (Ulva sp .). T he development of the gonads was greater in the ones fed with artificial feed . However, the analysis of the fatty acid profile reveals little difference in the composition of the gonads of the three treatments. This low relation suggest s a greater importance of protein and glycogen in gonad development. In conclusion, the formulated diet showed great potential both in the growth and development phases of the gonads, without altering the lipid composition of the edible part.
This work has been financed through the OURIÇAQUA (Fundo Azul) project.