JellyWatch 

Historically, jellyfish are a familiar presence in the Mediterranean Sea, yet the phenomenon of “jelly blooms” has escalated markedly over the past eight years. These substantial swarms of gelatinous organisms have become a common sight along coastal areas, posing inconveniences to swimmers and, in some cases, presenting significant health risks. Fishermen regard these blooms as detrimental, as jellyfish not only clog nets but also deter fish and consume their larvae. Additionally, several industrial marine cooling systems have experienced temporary shutdowns due to jellyfish obstructing underwater infrastructure.

The socio-economic repercussions of these blooms are evident, affecting both tourism and sectors reliant on coastal and marine resources. From an ecological standpoint, the frequency and synchronization of jellyfish outbreaks across both western and eastern Mediterranean basins suggest a potential shift in the marine ecosystem balance, moving from fish-dominated environments towards a “gelatinous sea.” Factors such as overfishing, coastal habitat degradation, and climate warming are likely contributors to these changes, though pinpointing precise causes and mechanisms remains challenging due to a scarcity of baseline data.

The CIESM Jelly Watch Program was established to collect baseline data on the frequency and scale of jellyfish outbreaks throughout the Mediterranean Sea for the first time. Following a successful pilot phase in several countries, a uniform, standardized protocol has been implemented. This protocol encompasses systematic recording of both presence and absence data for jellyfish swarms across the entire Basin, from coastal areas to open seas. This approach facilitates an impartial evaluation of the geographic and temporal extent of these phenomena, thereby supporting trend analysis and enabling short-term forecasting of ellyfish bloom movements.