Discovery of a Prolific Invader
In a surprising revelation, an invasive pearl oyster known as Pinctada imbricata radiata, originally from the Red Sea, has been discovered in Ibiza. This intriguing find has left researchers and marine biologists intrigued as the oyster has been slowly making its way into the Mediterranean waters since the opening of the Suez Canal in 1869. The first reported sighting of this species in the Balearic Islands dates back to 1999, with a single shell found amidst fishing remains in Mallorca. However, it was only in 2020 that researchers from the Balearic Oceanographic Center and UIB (University of the Balearic Islands) conducted a study on its presence in Palma Bay, locating specimens even in areas near Cabrera.
Expanding Presence in the Mediterranean
Recent reports now indicate that Ibiza has become another addition to the list of Mediterranean locations where this Red Sea species has set foot. The discovery of an individual oyster at a depth of ten meters in “es Esculls d’en Ramon,” near the islet of na Plana (ses Bledes), on a Monday, July 31, brought the attention to this invader’s presence in the Pitiusas. Furthermore, as images were shared among divers, marine biologists, and sea enthusiasts, it was confirmed that the oyster has also been spotted in the bay of Sant Antoni, Portinatx, Cala Vedella, and Talamanca. In the latter area, the marine area team of GEN-GOB observed specimens attached to the buoys of the seagrass meadows monitoring stations.
Mysterious Introduction and Dispersal
Experts believe that maritime transport is likely the primary mode of introduction and dispersal of this species into the Balearic waters, either through biofouling on ships or ballast water. The oysters have been found in port environments, indicating that this is the most probable entry point. Lydia Png González, a researcher at the Balearic Oceanographic Center and an expert on alien and invasive marine species, suggests that the specimen found near Cabrera likely arrived there through ship movements.
Monitoring the Impact
While the presence of the pearl oyster in the Balearic Islands is a new revelation, its impact on the marine ecosystem remains to be seen. In many publications, the pearl oyster is highlighted as a high-risk species for the habitats it colonizes. Although there are reports of it forming reefs in certain locations, there have been no observed impacts on the Balearic Islands’ habitat yet.
Staying Vigilant
Experts urge vigilance in monitoring the colonization of this species in the islands. Citizen collaboration is essential in reporting sightings of this and other alien or invasive species. Anyone can communicate such observations through the Balearic Biodiversity Database biodibal.uib.cat, coordinated by UIB, or the national registry managed by CSIC www.gbif.es.
Similar Species and Future Implications
Lydia Png González also points out the existence of two closely related pearl oysters in the Pinctada genus – P. imbricata radiata and P. fucata – which might also reach the Balearic Islands. The presence of the latter might have gone unnoticed, being confused with the former. Monitoring these oyster species and understanding their potential impact on the marine ecosystems will be crucial in the coming years.
Unfolding the Oyster’s Journey
Researchers from the Centre d’Estudis Avançats de Blanes (CEAB-CSIC), in collaboration with the Jaume Ferrer station and the Socio-Environmental Observatory of Menorca, indicate that the species has progressively expanded its distribution to other areas of the Eastern Mediterranean since its first sighting in Alexandria. Over the last 40 years, its presence has been reported sporadically in the Adriatic, Liguria, Strait of Messina, Corsica, Sardinia, Mallorca, Catalonia, and recently, the first established population of this species was identified in the Ebro Delta.
As we continue to uncover the mysteries of this invasive oyster’s journey, researchers and citizens alike must remain vigilant to understand its impact on the marine ecosystems of the Balearic Islands.
