The sea urchin Paracentrotus lividus is a valuable European fishing resource where local populations have been heavily exploited. The interest on echinoid aquaculture has been increasing in the last two decades., however its production constitutes a challenge, mainly due to the existence of different stag es over the lifecycle and the complex biotic relationships that occur through larval and post-larvae phase transitions .
The Aquaculture Research Station (EPPO) began in 2017 production trials of P. lividus in order to develop and improve cultivation techniques as well as to promote its production at a commercial level, in Portugal. The wild breeders were collected in rocky areas of the Algarve coast (south of Portugal). S pawning induction was performed by injecting 1 ml of KCl 0.5 M into the coelom via the peristomial membrane . Fertilized eggs are hatched in cylindrical fiberglass tanks with soft aeration for, approximately, 48h. During the planktonic stage sea urchins' larvae are fed with various species of microalgae. Around 18 DAH larvae b egin to undergo metamorphosis and settlement, reaching then the benthon ic stage (juvenile). Afterwards juvenile s began feeding macroalgae and maize (Zea mays) . EPPO is currently developing several studies on the different stages, focusing on larvae feeding trials and juveniles nutrition, and ongrowing production in the sea in several commercial in situ available.
Recently, high survival rates at 15DAH larvae (75.7 ± 9.7 %) in feeding trials have revealed benefits in survival and development when using multi microalgae species when compared with single species diets. The nutrition tests of juveniles show that the diet has an important impact on the development of sea urchins , with special relevance in sexual maturation also reflected in the fatty acids profile. Sea urchins fed with mixed diets, macroalgae (Ulva spp. ) and maize, presented a higher gonadosomatic index, however nutritionally inferior to the individuals fed only with macroalgae. This last group have shown excellent fatty acid profiles, revealing better levels of ω3 fatty acids.
Currently, EPPO is developing sea ongrowing trials, where different location and production systems are being tested: a) o n the southwest rocky coast , sea urchins are being raised on mussel longline system 1 miles off-shore; b) i n Ria Formosa (a coastal lagoon ) sea urchins are growing on a traditional oyster farm; c) more r ecently a new system was settled on a tuna trap, located 3 miles off-shore the southeast sandy coast of Olhão . Preliminary results have shown good adaptation and growth of farmed sea urchins. The first stock of commercially sized individuals, for which nutritional analysis and organoleptic tests will be carried out, is expected soon.
Acknowledgment: Project DIVERSIAQUA I (Mar2020 16-02-01-FMP-0066), DIVERSIAQUA II (MAR2020-P02M01-0656P) and Project OURIÇAQUA (Fundo Azul) for the financial support of this study.