A scientific network has successfully identified the presence of the invasive oyster Pinctada radiata in Punta Javana and Agua Amarga, in the province of Almería. The finding is significant because larval collectors allowed the species to be detected before it was observed in its natural habitat.
In Agua Amarga, researchers recorded three recruits of this species in larval collectors during 2022. The first observation of specimens in the natural environment, specifically in a Posidonia oceanica meadow, did not occur until 2025.
The study, published in Marine Environmental Research, compiles data from 1,014 collectors installed at 132 points across the Mediterranean between 2015 and 2024. The network, integrating eight countries and 25 research teams, allows for tracking the species' colonization of new enclaves.
On the Almerian coast, Punta Javana and Agua Amarga were identified as the first detection points in 2022, with no previous records since 2017. Subsequent monitoring in Punta Javana showed an increase in recruitment, rising from an average of 0.3 individuals per bag in 2022 to 7 in 2024.
The Cabo de Gata-Níjar Marine Reserve, located about 29 kilometers south, did not register recruits during five non-consecutive years of monitoring since 2017, suggesting the species had not yet crossed into the Sea of Alborán during that period. However, later observations in Calahonda (Málaga) and Torreguadiaro (Cádiz) indicate it may have already reached some areas of the western sector.
Pinctada radiata is the first documented Lessepsian migrant, first detected in 1874 in Alexandria after the opening of the Suez Canal. Its pelagic larval stage of about three weeks facilitates its dispersal, in addition to vectors such as maritime transport and aquaculture.
Researchers point to anthropogenic warming as a key factor favoring the expansion of this thermophilic species. Rising temperatures reduce thermal limitations, facilitating its advance. The optimal temperature range for the species in the Mediterranean is between 20 and 27 degrees Celsius.
The study's main contribution is demonstrating that larval collectors function as an early warning system. In Agua Amarga, larvae were detected three years before natural observation. These collectors, mesh bags with artificial substrates, allow for tracking the arrival of new species on a large scale.
The Mediterranean hosts approximately 1,000 introduced species, and Pinctada radiata is considered one of the 100 most problematic due to its potential effects on biodiversity and ecosystems.
In Almería, the presence of larvae in Punta Javana and Agua Amarga, with increased recruitment in Punta Javana up to 2024, and observation in Posidonia in 2025, contrasts with the absence of recruits detected until 2024 in Cabo de Gata-Níjar. This makes the Almerian coast a key point for monitoring the species' expansion.
