This study describes the presence of the royal cucumber Parastichopus regalis (Cuvier, 1817) in The Natural Park of Ria Formosa (NPRF), Portugal. A single individual was observed during a monitoring scuba dive at a depth of 3 m inside this shallow mesotidal lagoon. The most plausible explanation for this occurrence is attributed to the rejection by trawlers when returning to their home port from their fishing grounds. This marine species has a deeper distribution outside the lagoon and is commonly captured as by-catch and subsequently discarded. This study also alerts us to the growing presence of non-indigenous species and the emergent threat of new invasions, highlighting the need to adopt biosecurity measures, like good practices for fishers when dealing with discards to avoid new species introductions in this fragile coastal marine habitat.
