New insights into the biology of the commercial holothurian Parastichopus regalis (Cuvier, 1817) and their ecological implications

Abstract Holothurians provide important ecosystem services by enhancing sediment health through bioturbation. The sea cucumber Parastichopus regalis has a wide distribution in the Mediterranean Sea. Even though it is a commercially exploited species, little is known about its ecological traits and there is no information on the bioturbation potential resulting from its feeding activity. To address these knowledge gaps, the population density, demographic structure, musculature and evisceration of P. regalis were investigated on Arenys de Mar, NW Mediterranean. Food assimilation efficiency, and feeding and bioturbation rates were assessed through field and laboratory experiments. The exploited population exhibited a healthy distribution of sizes/ages, and the density values were similar to or greater than those described in other Mediterranean areas. This species did not show seasonal evisceration, and seasonal patterns in muscle weight depended on year and body size. The field results indicated that P. regalis selected organic matter from the sediment as food. The average individual feeding rate was 8.6 g wet sediment d −1 . The bioturbation role of the P. regalis population in the studied area was especially important at depths between 81 m and 124 m, where it consumed between 7.6 and 13.8 t of wet sediment y −1 km −2 . These results highlight the important role that this species play in deep habitats as sediment bioturbator, controlling the accumulation of dead organic matter.