Blue Crab in the Lagoon: Why Thousands of Octopuses Are Now Fighting the Crab Invader
In brief: The invasive blue crab (Italian granchio blu, scientific name Callinectes sapidus) has spent years eating its way through mussel and clam stocks in the Venice lagoon and the Po Delta, at times pushing seafood prices up by as much as 76 percent. Since August 2026 Italy has been trying an unusual biological remedy: the “Octo-Blu” project is releasing tens of thousands of young octopuses into the Adriatic, because octopuses are natural predators of the crab. Alongside it runs a €1.5 million pilot project by the Veneto Region that explicitly includes the Venice lagoon, plus national funding, capture traps, and the marketing of caught crabs as food.
Walk through the lagoon’s fishing villages, browse the Rialto fish market, or eat in Chioggia or Pellestrina, and you’ll run into one topic again and again: the granchio blu. The blue crab, introduced from North America, is now considered one of the biggest threats to Venice’s lagoon economy in decades. In 2026 it is, for the first time, facing a genuinely novel countermeasure: the octopus as natural hunter.
The blue crab conquers the Venice lagoon
The blue crab originates from the Atlantic coast of the Americas and most likely reached the Mediterranean via the ballast water of cargo ships. For a long time, cooler winter months kept its spread in check. But with milder winters and longer stretches of warm water, the crab now stays active and reproductive for much of the year — with consequences across the whole upper Adriatic, from Friuli through the Venice lagoon to the Po Delta. Marine biologist Enrica Franchi (University of Siena) explains the mechanism: the temperature thresholds that used to slow the crab down now occur far less often.
For Venice’s lagoon, this is a problem with two faces. First, the blue crab directly preys on Manila clams (vongole veraci) and other bivalves while they are still young and soft-shelled — entire farmed stocks can be wiped out within weeks. Second, its powerful claws tear apart fishermen’s nets, adding extra costs before any catch is even landed. Veneto Agricoltura confirms the species is now found in practically every coastal and lagoon area of the region.
How much the crab invader has already cost Venice
The figures behind the crisis are striking. Farmers’ association Coldiretti has at times put the total damage to Italy’s shellfish and fishing industry at around €200 million — double its mid-2024 estimate. Environment minister Gilberto Pichetto Fratin has spoken of a total loss of clam production in some affected areas. In the Scardovari lagoon in the Po Delta, one of the most important growing areas for the protected DOP Manila clam, the 2026 harvest fell from roughly 25,000 to about 15,000 quintals. In neighbouring Friuli-Venezia Giulia, the catch from just the first four months of 2026 already matched the entire 2025 catch volume.
Veneto’s own record is just as stark: back in 2023 the region already caught around 326 tonnes of blue crabs, including 84 tonnes in Scardovari and 29 tonnes in Pila in August alone. Studies by Ispra and Arpav documented Manila clam mortality of up to 85 to 99 percent in parts of the lagoon over the winter of 2023/24 — Governor Luca Zaia called it “a tragedy” and requested a national state of emergency. Prices reacted sharply: market observers reported 2023/24 mark-ups for Manila clams of 60 to 76 percent year on year, with some parts of Italy seeing prices triple around the holidays.
The octopus as natural enemy: the “Octo-Blu” project
This is exactly where the most closely watched new countermeasure comes in: the octopus (polpo) as a natural predator of the blue crab. Marine biologists confirm that octopuses actively hunt crabs — using a judo-like grip, they flip their prey onto its back to neutralise the dangerous claws, then inject a paralysing toxin into the gills before eating the crab at leisure. Unlike some other predators, the octopus hunts selectively and only when hungry, not indiscriminately.
This observation underpins the research project “Octo-Blu” run by the University of Bologna and the Emilia-Romagna Region, led by Professor Oliviero Mordenti and researcher Antonio Casalini, with support from the Cesenatico port authority. Since 2024, young octopuses bred in university facilities (so-called paralarvae) have been released into the sea off Cesenatico and at artificial reefs near Riccione. In August 2026 around 40,000 more juveniles were released — the researchers’ stated target is a total of 100,000 to 150,000 released animals. “The octopus is a predator capable of regulating a species that has become too abundant,” says Mordenti.
The idea isn’t without a catch: octopuses themselves are commercially fished in the Adriatic, which limits how far a large-scale “breeding as a remedy” approach can go. Solid data on how many blue crabs the released octopuses actually remove is not yet available — “Octo-Blu” is a scientific experiment, not an instant miracle cure.
Traps, funding and marketing: the other countermeasures
The octopus is only one piece of a much larger puzzle. National and regional authorities are running several more down-to-earth programmes in parallel:
- National intervention plan: The government initially set aside €10 million in early 2025, and the Ministry of Agriculture added a further €44 million. A specially appointed commissioner (Enrico Caterino, in office through the end of 2026) coordinates six measures: protecting biodiversity, developing new capture equipment, properly disposing of unusable catch, containment barriers, limiting damage to the fishing industry, and economic support for businesses. The goal: to remove around 2,600 tonnes of blue crabs from the upper Adriatic (Veneto and Emilia-Romagna) over two years.
- Veneto Region pilot project (€1.57 million): A capture campaign runs from March to October and explicitly covers the Venice lagoon, the Po Delta, and the Caorle lagoon. Fishermen receive €1 per kilogram of non-edible crabs delivered, plus subsidies for boat rental and selective capture gear (traps). The project is funded through the EU’s Feampa programme, the Region, Veneto Agricoltura, and the University of Padua, and runs through the end of December 2026.
- Monitoring: Arpav and Veneto Agricoltura have run regular monitoring campaigns with deployed traps since 2023, mainly in the Po Delta lagoons, to track the crab’s spread and population trends.
- Marketing instead of disposal: The Consorzio Pescatori del Polesine fishing cooperative now sells jarred crab meat and claws. Universities in Sassari and Cagliari are also researching whether chitin extracted from the shells can be used in cosmetics and biotech applications.
From enemy to entrée: lagoon restaurants embrace the crab invader
Another, far less dramatic countermeasure shows up on the menu. In Chioggia, several restaurants have already served granchio blu as a festive-season delicacy — the reasoning: what gets eaten, gets caught, and every portion sold is one less crab in the lagoon. Fine dining has embraced the trend too: Venissa, the Michelin-starred restaurant on the lagoon island of Mazzorbo run by chefs Chiara Pavan and Francesco Brutto, has for years deliberately put invasive and problematic species on its menu — including several blue crab preparations alongside jellyfish, the invasive Rapana sea snail, and the invasive Arca clam. The idea: show diners that dealing with invasive species can also be a culinary answer, even as native specialities like the soft-shell moeche crab become rarer as the lagoon’s conditions change.
What this means for your visit to Venice
| Persona | Relevance |
|---|---|
| Seafood lovers & clam fans | Medium to high — local Manila clams and moeche can be scarcer and pricier in crisis years; try a granchio blu dish too, it’s usually cheaper and plentiful. |
| Day-trippers to Chioggia or Pellestrina | High — both fishing towns depend on the shellfish and crab economy and are directly affected by the crisis; the topic is visibly part of everyday life there. |
| Nature enthusiasts | Medium — the Venice lagoon is a vivid example of how invasive species and climate change reshape a fragile ecosystem. |
| Classic sightseeing visitors | Low — around St Mark’s Square and Rialto the crisis is barely visible, except perhaps on menus or at the fish market. |
Frequently asked questions about the blue crab in the Venice lagoon
What is the blue crab and where does it come from?
The blue crab (Callinectes sapidus, Italian granchio blu) comes from the Atlantic coast of the Americas and was most likely introduced to the Mediterranean via the ballast water of cargo ships. Milder winters and longer stretches of warm water now keep it active and able to reproduce for nearly the whole year, letting it spread rapidly across the upper Adriatic in recent years, including the Venice lagoon.
Why is the blue crab a problem for Venice?
It preys on young Manila clams and other bivalves that traditional lagoon shellfish farming depends on, and its claws destroy fishermen’s nets. Coldiretti has at times estimated total damage to Italy’s shellfish and fishing industry at around €200 million, with clam harvests nearly wiped out in some areas.
What does the octopus have to do with the blue crab?
Octopuses are natural predators of the blue crab. Since 2024, the “Octo-Blu” research project run by the University of Bologna and the Emilia-Romagna Region has released specially bred juvenile octopuses off the coast near Cesenatico — around 40,000 animals in August 2026, with a target of 100,000 to 150,000. Whether the method measurably reduces crab populations has not yet been scientifically confirmed.
Are octopuses also released directly into the Venice lagoon?
No, the “Octo-Blu” releases so far have taken place off the Emilia-Romagna coast (Cesenatico, Riccione). The project is nevertheless meant to benefit Veneto’s Manila clam farming areas too, which together with Emilia-Romagna account for more than half of Italy’s shellfish production. Within the Venice lagoon itself, other, complementary measures are underway, such as the Veneto Region’s capture and funding programme.
Will visitors notice the blue crab crisis on their trip to Venice?
Barely, in the historic centre. But visit Chioggia, Pellestrina, or the Rialto fish market, and you’ll find a topic that shapes local everyday life — from higher Manila clam prices to granchio blu as a new, usually inexpensive dish on the menu.
Can you eat the blue crab yourself?
Yes — it is considered quite tasty and is increasingly being marketed, from jarred crab meat to dishes at lagoon restaurants such as the Michelin-starred Venissa on Mazzorbo. Some fishermen and restaurateurs explicitly see eating it as a way to help limit the species’ spread.