Venice's Lagoon Under Siege by Invasive Jellyfish and Blue Crabs

Two invasive species are causing growing problems in Venice's lagoon and the wider Adriatic region. The warty comb jelly, a fast-spreading predator, has been named one of the world's 100 most harmful invaders. Meanwhile, blue crabs—another unwelcome arrival—are damaging fishing gear and seafood stocks across the area.

The warty comb jelly, also called the sea walnut, has rapidly taken over the Venetian lagoon. Researchers at the Istituto di Scienze Marine (ISMAR) of the Italian National Research Council (CNR) spent two years studying its spread. The species likely arrived in ballast water from cargo ships travelling from the western Atlantic.

Warmer waters and ideal salinity levels, linked to climate change, have helped the jelly's population explode. It clogs fishing nets and devours fish eggs, larvae, and plankton, disrupting the lagoon's delicate food chain. Scientists warn that ongoing climate shifts could make the problem worse, threatening the entire ecosystem.

The Adriatic is also battling an invasion of blue crabs, another Atlantic species believed to have hitched rides in ballast water. These crabs tear apart fishing nets and prey on clams and mussels, causing millions in losses. Italy is now pushing for their consumption in supermarkets and restaurants to curb their numbers.

Both invasions pose a serious risk to the Adriatic fishing industry, which generates billions of euros annually. Clam and mussel harvests, in particular, face increasing pressure from these aggressive newcomers.

The spread of warty comb jellies and blue crabs is putting Venice's lagoon and the Adriatic's seafood trade under strain. Efforts to control their numbers include scientific research and promoting crab consumption. Without intervention, the damage to fishing and marine life could worsen in the coming years.