Aquaculture and NIS introductions in the Lagoon of Venice
The Lagoon of Venice is a known hotspot of Non-Indigenous Species (NIS) introductions within the Mediterranean Sea, hosting all human activities linked with the main pathways of introduction of marine species: commercial shipping, recreational boating, shellfish culture and live seafood trade. A data analysis was performed, and information on the current number of marine NIS updated; the strength of the different vectors of introduction operating in the lagoon was assessed. Data was collected from a variety of sources: scientific literature, ad-hoc field surveys and interviews with local stakeholders. The role of the lagoom as a “sink and source” of NIS at the Mediterranean and European scale was also analysed: species showing outbreaks in the Lagoon of Venice have caused major changes in the lagoon biological communities and this might occur elsewhere.
The number of Non-Indigenous Species (NIS) in Venice Lagoon is increasing at the rate of 1.5 new NIS per year.
The analysis on the vectors of introduction operating in the Lagoon of Venice showed that the current propagule pressure in the area is very high: 4,500 ha devoted to farming exotic clams (seed for restocking is often imported from distant hatcheries); a few facilities for live seafood trade and processing; two harbours that receive intensive international and local ship traffic; 30 marinas attended by small crafts as well as yachts and mega-yachts.
The total number of NIS introduced into the Lagoon of Venice is 68: all the Baltic countries and several Member States on the Atlantic and Mediterranean coasts of Europe have to deal with less NIS than Venice alone1. Almost a half of all NIS recorded in Venice are native to the NW Pacific region. The vector responsible for the highest number of introductions is “aquaculture”, namely the trade of Pacific oysters and clams.
The first introduction event dates back to the XVI century, but it's since the 1970's that introductions have started following a dramatically increasing trend, showing a rate of 1.5 new NIS per year. If the observed trend continues in the next future, and no action is taken to prevent new introductions, the cumulative number of introductions is expected to almost double by 2050.
Venice is a “sink and source” of NIS: both target and non-target species are imported and exported by aquaculture and live seafood trade activities; secondary dispersal is highly favoured by the active movement of small crafts to and from the lagoon.
The majority (76%) of NIS recorded in Venice were already known from other European countries, mainly from France. As regards NIS whose first site of Mediterranean or European record was Venice, more than 50% have further spread elsewhere, especially to other shellfish farming sites such as the Po Delta Lagoon and Pialassa della Baiona pond in the North-Adriatic Sea; the Lagoon of Olbia in the Tyrrhenian Sea; the Mar Piccolo of Taranto and the Lake Faro in the Ionian Sea.
The continuous import/export of live bivalves for farming among these culture sites is likely to have facilitated the spread of several populations of Pacific origin, following a stepping stone colonization process, in which Venice has played the role of sink and source of NIS. A likely route of culture-associated introductions is: first introduction to French shellfish farms (or other shellfish farms in western Europe), then secondary introduction to Venice, then further spread from Venice to other Mediterranean sites. This is the route of invasion suggested for the newly discovered isopod crustacean Paranthura japonica Richardson 1909, but it also applies to several macroalgae. The movement of recreational boats and yachts travelling to distant harbours and marinas is also responsible for further spreading from venice to elsewhere, as in the case of the bryozoan Tricellaria inopinata d'Hondt & Occhipinti Ambrogi 1985 that has reached many localities along the Western European Margins.
Live seafood trade is an underrated and uncontrolled vector of introductions in the Lagoon of Venice.
Direct observations and interviews to the personnel of the Chioggia fish market (Chioggia is a town in the Southern part of the Venice Lagoon) showed that the careless procedures employed during the live seafood trading might be the cause of accidental introductions of NIS in the Lagoon of Venice: loading and unloading of live seafood takes place directly on the docks, very close to the Lagoon waters. It has been shown that about 20 edible species of exotic origin are regularly traded live for fish markets and processed near the lagoon canals, and might be accidentally released in the wild. The analysis of their biological and ecological traits showed that they are tolerant species, able to grow on every kind of substrate, to thrive in low salinity and to endure a broad spectrum of water temperatures.
It has also been observed that residues of the fish markets are often thrown into the lagoon canals at the end of the day. In this way, other non-commercial NIS, such as macroalgae used as packaging material for bivalves sold in the fish market, are also likely to be accidentally released in the Lagoon waters.
Relevance for Policy:
- Alien Invasive Species Directive
- EU Biodiversity Strategy
- Guidelines for the Control and Management of Ships’ Biofouling to Minimize the Transfer of Invasive Aquatic Species
- International Convention for the Control and Management of Ship's Ballast Water and Sediments
- Marine Strategy Framework Directive
Deliverable 2.1.2: Mechanisms of change in Alien and native species outbreaks
Factsheet: Invasive alien species
AquaNIS (Information system on aquatic non-indigenous and cryptogenic species) database
Marchini, A., J.-C. Sorbe, F. Torelli, A. Lodola, and A. Occhipinti-Ambrogi. 2014. The non-indigenous Paranthura japonica Richardson, 1909 in the Mediterranean Sea: travelling with shellfish? Mediterranean Marince Science 15(3): 545-553.
Ferrario, J., D. Savini, A. Lodola, A. Marchini, and A. Occhipinti-Ambrogi. 2013. Risk of non-indigenous species introduction via international seafood trade: the case of Chioggia fish market. Biologia Marina Mediterranea 20(1): 236-237.
Marchini, A., J. Ferrario, A. Sfriso, and A. Occhipinti-Ambrogi. 2014. Current status and trends of biological invasions in the Lagoon of Venice, a hotspot of marine NIS introductions in the Mediterranean Sea. (Submitted paper).
Galil, B.S., A. Marchini, A. Occhipinti-Ambrogi, D. Minchin, A. Narscius, H. Ojaveer and S. Olenin. (2014) International arrivals: widespread bioinvasions in European Seas. Ethology Ecology and Evolution 26(2-3), 152-171.
Data used: Data was gathered from literature, local stakeholders and scientists, collection of samples.
Where it is held: University of Pavia (Italy), Department of Earth and Environmental Sciences
Contact: Anna Occhipinti-Ambrogi, email@example.com