Cannibal jellyfish Venice lagoon is no longer just a dramatic headline—it is an unfolding ecological crisis in one of Europe’s most famous and fragile waterways. Scientists and fishermen are warning that an invasive marine species known as the sea walnut is spreading rapidly through Venice’s lagoon, threatening fish populations, damaging fishing livelihoods, and destabilizing the entire ecosystem.
Venice, a city visited by tens of millions of tourists every year, is now facing a quieter but potentially devastating invasion beneath its iconic canals. The culprit is Mnemiopsis leidyi, a gelatinous creature often mistaken for a jellyfish but belonging to a different biological group altogether.
What are the cannibal jellyfish in Venice lagoon?
Despite their common name, the cannibal jellyfish Venice lagoon residents are encountering are not true jellyfish. They are comb jellies, also called ctenophores, which belong to a separate phylum.
Unlike true jellyfish:
- They do not sting
- They move using rows of tiny hair-like structures called ciliary combs
- Their bodies are transparent and soft, with an iridescent shimmer
The species at the center of the invasion is commonly known as the warty comb jellyfish or sea walnut. Native to the western Atlantic Ocean, it has now firmly established itself in the Adriatic Sea.
How cannibal jellyfish Venice lagoon arrived
Scientists believe the cannibal jellyfish Venice lagoon invasion began unintentionally. The leading theory is that the species was transported across the ocean in the ballast water of cargo ships.
Ballast water is taken onboard ships to maintain stability during long voyages. When ships unload this water at foreign ports, they also release microscopic organisms—sometimes invasive species—into entirely new environments.
Once introduced to Venice’s lagoon, the sea walnut found nearly perfect living conditions.
Why Venice lagoon is ideal for cannibal jellyfish
Venice’s lagoon is shallow, warm, and rich in nutrients—conditions that strongly favor the survival and reproduction of Mnemiopsis leidyi.
A recent two-year scientific study revealed that:
- The species tolerates wide temperature ranges
- It survives in varying salinity levels
- It reproduces rapidly during spring and summer
These traits allow the population to explode in number, especially during warmer months.
Climate change worsening cannibal jellyfish Venice lagoon spread
Climate change is playing a major role in accelerating the cannibal jellyfish Venice lagoon problem.
Researchers have linked population booms to:
- Rising sea temperatures
- Longer warm seasons
- More stable salinity levels
As the Adriatic Sea warms, conditions increasingly favor invasive species over native marine life. Scientists warn that unless global warming slows, the sea walnut’s presence in Venice could become permanent and far more destructive.
Why these jellyfish are called cannibal
One of the most disturbing facts about the sea walnut is its cannibalistic behavior. When food becomes scarce, it will consume its own offspring to survive.
Even more bizarre, the species has a temporary anus that forms only when waste needs to be expelled, then disappears again. While fascinating to biologists, these traits do nothing to soften the creature’s ecological impact.
Cannibal jellyfish Venice lagoon impact on fish populations
The most serious damage caused by cannibal jellyfish Venice lagoon populations is their effect on the food web.
Sea walnuts feed aggressively on:
- Plankton
- Fish eggs
- Fish larvae
These are the foundational elements of the lagoon ecosystem. By consuming them in massive quantities, the comb jellies prevent fish populations from regenerating.
As a result:
- Fish stocks are declining rapidly
- Native species struggle to reproduce
- Biodiversity is under threat
Fishing industry hit hard
For local fishermen, the invasion is already a financial disaster.
The gelatinous bodies of the sea walnuts:
- Clog fishing nets
- Make nets heavier and harder to retrieve
- Reduce fishing efficiency
At the same time, fewer fish are reaching adulthood due to egg and larvae loss. Venice’s fishing industry, worth billions of euros, is now under growing strain.
Many fishermen report lower catches and higher costs, with no clear solution in sight.
Scientific warnings about long-term damage
Scientists from the University of Padua and the National Institute of Oceanography and Applied Geophysics have warned that the situation could worsen significantly.
Their study states that continued climate change may:
- Increase jellyfish aggregation
- Expand their seasonal presence
- Amplify ecosystem-wide damage
Once established in large numbers, removing invasive comb jellies becomes nearly impossible.
Cannibal jellyfish Venice lagoon not the only invader
The sea walnut is not the only invasive species troubling Venice’s waters. Another growing threat is the Atlantic blue crab, which preys on clams and mussels—key species for both ecology and local cuisine.
Together, these invaders create a double pressure on:
- Marine biodiversity
- Traditional fishing practices
- Economic stability
Why controlling the invasion is difficult
Unlike fish or crabs, comb jellies are extremely difficult to manage because:
- They have no natural predators in the Adriatic
- They reproduce rapidly
- Physical removal is ineffective at large scales
Once populations reach a critical mass, control options become limited to long-term environmental management rather than direct intervention.
What this means for Venice’s future
Venice has survived floods, sinking foundations, and mass tourism—but the cannibal jellyfish Venice lagoon invasion represents a quieter, less visible danger.
If left unchecked:
- Fish populations may continue to collapse
- Fishing traditions could disappear
- The lagoon ecosystem may permanently shift
Scientists stress that invasive species are often symptoms of larger problems, including climate change and global shipping practices.
A warning beyond Venice
While the focus is currently on Venice, experts warn that similar invasions could occur elsewhere. As oceans warm and global trade increases, invasive marine species are likely to spread to new regions.
The sea walnut has already caused ecological disasters in other parts of the world, and Venice may now be facing a similar long-term struggle.