World Aquaculture March 2019

WWW.WA S.ORG • WORLD AQUACULTURE • MARCH 2019 49 ( C O N T I N U E D O N P A G E 5 0 ) to increase the surface area available in tanks for post- larvae by adding structures such as plates and PVC pipes. After settling it was necessary to clean tanks daily through siphoning because there was a greater accumulation of debris (feces, uneaten food, dead individuals) and animals had greater contact with the sediment. After establishment of post-larvae, the diet consisted of seaweed ( Ulva spp.) produced and collected from earthen ponds at EPPO and a mixture of microalgae ( Isochrysis galbana , Nannochloropsis occulata , Tetraselmis spp., Chaetoceros calcitrans imp3 and the diatom Skeletonoma costatum ). In this way, a nutritionally varied diet was guaranteed by favoring of different ways of eating food: scraping with teeth (seaweed) or by passive intake (microalgae). The growth in diameter of the shell was low (0.03 mm/day) until 58 DAH, when a significant increase occurred between 58 and 77 DAH (0.22 mm/ day). This may have been cause by the ingestion of macroalgae ( Ulva spp.), which was provided daily after 58 DAH. Fattening Fattening tanks for juveniles are managed in flow-through mode with filtered seawater, with a water exchange of about 100 percent/h with seasonally variable temperature. Dissolved oxygen concentration was maintained above 7 mg/L. After four weeks of grow-out (sea urchins of 150 DAH), the biomass reached 1.4 g/L. At this stage, the cultivation was done at a density of 294 individuals/m 2 and a biomass of 2.8 g/L. After 10 weeks of cultivation, densities reached 10 g/L (approximately 4 individuals/L) with an average weight of 2.3 g. The feeding supply was between 5 and 10 percent/d of total biomass and consisted of macroalgae ( Ulva spp.) and corn grain. According to Boudouresque and Verlaque (2013), the sea urchin P. lividus reaches an average diameter of 2 cm in two years. However, in our trials, 35 percent of individuals were greater than 2 cm in diameter in only seven months. The greater growth rate observed may be the result of not only the food provided, but also the higher cultivation temperature. In a trial with four species of seaweed, Cyrus et al . (2015) obtained the best results with Ulva . The size of first maturity for purple sea urchins is reached at a diameter of 20-28 mm (Ouréns et al . 2013), well above the verified size in our work. Sea urchins at 230 days (Fig. 9) had a 30 percent sexually mature individuals (with diameter up to 20.4 mm) and a gonadosomatic index at this age of around 2-4 percent. When fed with good quality nutritious diets, sea urchins improved their reproductive capacity and may direct energy to gonadal development (Fernandez and Boudouresque 2000, Schlosser et al . 2005, Watts et al . 2013). The type of feed should be formulated with consideration to development stage and cultivation objective. An early stage of fattening will be important to the greater development of shell size, allowing the development of gonads in a stage closer to marketing or reproduction. FIGURE 7. Variation in total length and diameter of purple sea urchin during the planktonic phase. Main changes in larval metamorphosis indicated. FIGURE 8. Purple sea urchin at 30 DAH (Photos: João Araújo). FIGURE 9. Juvenile purple sea urchins at approximately 220 DAH, reproduced in captivity (left). Mature gonad of purple sea urchin at 220 DAH (right) (Photo: João Araújo).