Not All Aliens Come to Harm (Maybe): Pinctada radiata (Leach, 1814) Population and Habitat From a Coastal Lagoon (Central Mediterranean Sea)

Pinctada radiata, Leach, 1814, is considered the first Indo-Pacific bivalve introduced in the Mediterranean Sea after the Suez Canal opening and it is now reckoned among the 100 most invasive species within the basin. It is important to assess and describe its established populations in Mediterranean coastal ecosystems to understand the dynamics of this successful invasion and its adaptability. Present research aims to describe the population of P. radiata inhabiting the Capo Peloro Coastal Lagoon (Central Mediterranean Sea, Italy) also analyzing morphometric relationships and growth dynamics. Visual monitoring was carried out along the infralittoral fringe of the Faro Lake and the Faro Canal. Three representative sites have been chosen to investigate their distribution, abundance and associated habitats using the visual census technique, and performing seven strip transects, parallel to the coastline and with constant depth. All the P. radiata specimens present have been counted and 115 individuals have been randomly sampled during the entire study period. Several morphometric measurements have been recorded for morphometric relationships and growth dynamic analyses, assessing the growth indexes, natural mortality parameters and recruitment patterns. Results showed the presence of a mature P. radiata population, organized in banks and patches, confirming the ability of this species to widely colonize the host environments. The information on morphometric relations and growth dynamics showed that the studied area can promote the growth and the well-being of this species. Future studies are needed to fully understand the negative or positive effects of the spreading of this species.