Sustainable management of sea urchins. From resource conservation to aquaculture promotion in a circular economy perspective

Sea urchins are among the invertebrates that play a pivotal role in structuring and controlling marine benthic macrophyte communities and can be considered the main grazers in shallow seas around the world. The most studied in Mediterranean Sea is Paracentrotus lividus (Lamarck 1816), since, in addition to being one of the most widespread, it is the one with the greatest commercial interest. Moreover, despite many efforts to start aquaculture processes that cover the entire production cycle of this resource, at present, market demand is almost exclusively based on harvesting, and several examples of depletion of natural stocks due to fishing pressure are reported. However, the decline of P. lividus populations has also been reported in areas like the Ligurian Sea, where the sea urchin is not considered a species of commercial interest. Probably, it is due to the fact that they are very sensitive to indirect anthropogenic impacts: stressors related to climate change and the presence of pollutants can lead to abnormal larval development, reduced survival of larvae and juveniles, and impaired reproductive success of adults due to effects on gamete quality, threatening survival of entire populations. This study had two main objectives, the first being the characterisation of P. lividus populations at different sites in the Ligurian Sea, in order to investigate their health status (abundance and size distribution) and hypothesise the possible causes of their regression. While the second was the promotion of sustainable sea urchin aquaculture through the formulation of new experimental feeds, enriched with high Mg and Ca content biocarbonates and antioxidant substances. Those components were directly derived from the processing of sea urchins waste from gonad-packing industries, in a circular economy perspective.