P04 | Mussel die-off off the coast of Gargano

Purpose. This study aims to analyze the causes, consequences, and responses of the Competent Authority to the mussel die-off that occurred in 2024 along the northern coasts of the Puglia Region, with particular attention to the impact on the marine ecosystem and the local economy, in order to provide useful data and recommendations for planning appropriate supply chain intervention strategies and ensuring effective environmental risk management. Methods. The study was conducted between July and October 2024 at 5 mussel farms (Mytilus galloprovincialis) located in Gargano, approximately 3 miles from the coast, using a multi-level approach that involved the three veterinary services and included: • Environmental data analysis: data processing provided by accredited government agencies Copernicus, for temperature and salinity, and Ispra data for chlorophyll and mucilage; • On-site inspection: verification of the operating conditions of the plants, geolocation, and water temperature measurements; • Collection of epidemiological data: recording of mortality rates and assessment of the health status of mussels; • Temporal comparative assessment: comparison and analysis of data related to mussel monitoring plans conducted in previous years to identify correlations with the observed phenomenon. Results. In 2024, the coasts of Gargano recorded a mussel mortality rate exceeding 70% (with peaks close to 100% in some areas). The main contributing factors identified were: • Water temperature exceeding 30°C during certain periods of the year; • Decreased precipitation and the resulting reduced nutrient input; • Reduction in chlorophyll concentration related to the increase in mucilage due to rising water temperatures; •Increased plastic waste pollution (with particular reference to the remains used in mussel farming facilities); Conclusions. The absence of pathogens and parasites in the mussel farming areas studied here excludes direct biological causes: The die-off primarily reflects phenomena related to climate change and the inadequacy of environmental risk management measures. The analysis of temperature and rainfall trends over the last decade highlights a continuous increase in temperatures. To mitigate these risks, it is urgent to define and implement adaptation strategies and promote good operational practices for sustainable mussel farming.