MIT Sea Grant Center for Coastal Resources

Live and Fresh Seafood Industry

The seafood industry deals with live, fresh, frozen, and processed freshwater and marine organisms such as finfish, crabs, lobsters, clams, oysters, mussels, urchins, sea cucumbers, and sea squirts. Non-native live and fresh seafood that is dumped or released either accidentally or intentionally into local waters may introduce diseases (such as viruses and bacteria), parasites, and other hitchhikers into the environment. Introduced diseases and parasites may cause native species to become ill, while introduced live seafood and their hitchhikers may become invasive as they reproduce and establish self-sustaining populations that compete with native species. Releasing non-native fish and turtles into the wild without a permit is illegal.

What are the impacts of introducing seafood products into the wild?

1. Introduced seafood can spread diseases…

Many seafood consumers are not aware of the dangers of dumping or releasing nonindigenous fresh and live seafood, and their waste products, into local waters. Fresh and live seafood can carry harmful diseases, which can be transmitted to other marine/aquatic animals and, sometimes, people. Carp and koi (Cyprinus carpio, Ctenopharyngodon idella, Aristichthys nobilis, Hypophthalymichthys molitrix, and Carassius carassius) have been known to spread diseases such as spring viremia (Petty et al. 2002) and koi herpes virus (Hartman et al. 2004). Japanese eels sick with the parasite Anguillicola crassus have spread the parasite to local eel populations (Blakenship 1998). Fish can also spread mycobacteriosis to other fish and humans (Virginia Institute of Marine Science, 2006). In one extreme case, supermarket fish tanks in Hong Kong harbored cholera that was transmitted to humans (CHINAdaily 2003).

2. Introduced seafood can become invasive…

Introduced live seafood may become invasive. Invasive species compete with and prey on native species. They may diminish populations of food fish and other organisms sought after as food, harming the recreational fishing, commercial fishing, and seafood industries. Certain invasive species can also cause environmental damage. For instance, the Chinese mitten crab (Eriocheir sinensis), introduced to the West Coast from Asia, has eroded the banks of the San Francisco estuary and other areas where it has become established (Washington Sea Grant 2000; Central Valley Bay-Delta Branch 1998). Erosion destabilizes natural environmental features in addition to human-made structures such as levies and bridges, leaving these structures prone to damage. Erosion can also lead to flooding.

3. Managing introduced species is expensive…

It is nearly impossible to remove invasive species once they have become established in a new environment, and so it is necessary to deal with the problems they present, such as erosion, continually. Controlling invasive species and dealing with the problems they pose can quickly become very expensive. In 1999, it was estimated that the total cost of managing invasive species in the United States was around $120 billion per year (Pimentel et al. 2004). With the introduction of new species each year that number is likely on the rise.

4. Introduced seafood can introduce hitchhikers…

Introduced species and their shells, scales, and other discarded parts often carry hitchhikers that may become invasive or introduce disease. The American lobster (Homarus americanus), crabs, and clams are often packaged in seaweed, which may harbor small hitchhikers such as mussels, clams, snails, crabs, amphipods, copepods, and worms. The European green crab (Carcinus maenas) probably came to the west coast hidden in seaweed packing material (Grosholtz and Ruiz 1995). The green crab and other organisms that can survive in seaweed out of water for long periods of time are frequent invaders in new areas. Sometimes hitchhiking organisms are obvious (e.g. barnacles on oyster shells) and others are not visible to the human eye (e.g. small plants that form a crust on shells and parasites that cause diseases). In some cases the seaweed packing material may itself become invasive if dumped into the environment (The Mercury News 2004).

Examples of invasive seafood

One of the most well-known examples of an invasive food fish is the northern snakehead fish (Channa argus). Snakeheads are large predatory fish native to Eastern Asia, and considered a delicacy in China, Vietnam, and Thailand. There are 30 species of snakehead fish, many of which are warm water species which have been sold as aquarium pets in the United States. A few species such as the northern snakehead are able to survive in colder climates.

In May of 2002, several northern snakehead fish were found in the Potomac River in Maryland (U.S. Fish and Wildlife Service 2002). Since then hundreds of snakeheads have been found in lakes and rivers along the east coast and in the Midwest, including New York City and Boston. It is thought that they were imported to the US, purchased as seafood or as pets, and then accidentally or intentionally introduced into rivers and ponds. In addition, since they are able to use their fins to drag themselves overland for short distances they may have spread beyond the environments where they were initially introduced. Snakeheads have altered species compositions, decreasing population sizes of prized recreational food fish. Most of the warm water species only pose a threat to the southern United States; however, the giant snakehead (Channa micropeltes) has been found as far north as Maine.

In addition to the Chinese mitten crab and northern snakehead fish, other examples of invasive species that have been introduced most probably through the live seafood trade include the green-lipped mussel and brown mussel. Other animals such as tilapia, carp, catfish, and the European oyster (Ostrea edulis) were introduced to the wild via aquaculture which is closely tied to the live seafood trade.

What can we do about the problem?

You can take action! Here’s what you can do…

• Seafood should always be used as food, never released. If you purchase seafood and decide not to use it immediately you should freeze it for later use. Never release seafood, whether freshwater or marine, into the wild. If you do not want to freeze it, you should kill it and put it in the trash.

• Never release or dump live or fresh seafood waste products (including shells, fish heads, intestines, and fish scales) that you have purchased into the wild. Always put them in the trash. Remember live seafood and seafood waste can spread disease and releasing non-native live fish and turtles into the wild without a permit is illegal! If caught, you could be fined or jailed.

• Ask where your seafood comes from and take extra precaution with non-native fresh or live seafood.

• Spread the word! Share your concerns about invasive species with others. Download multi-lingual copies of our new educational pamphlet Live and Fresh Seafood: Into the pan, not into the wild and give them to your friends. Visit to learn more about invasive species and the problems they pose.

Imported seafood passes through many hands before reaching the consumer. Seafood importers, wholesalers, and retailers in addition to seafood consumers should be careful not to intentionally or accidentally release live or fresh seafood or seafood waste products into the wild.

Current Research

The MIT Sea Grant Program conducted a study on the live seafood trade during the winter and spring of 2006. The goal of the study was to better understand the live seafood trade in the Northeast by determining which species are available in markets, where live food fish is available for purchase, and which ethnic groups are involved in the trade. An educational pamphlet Live and Fresh Seafood: Into the pan, not into the wild was created to raise awareness on proper seafood handling and disposal practices which minimize the chance of invasive species introductions through the live seafood vector. It was translated into Chinese, Vietnamese, Khmer, Korean, and Spanish. For copies or for more information on this important topic please click on the above link.

Seafood References

Northern SnakeheadNorthern snakehead. Image courtesy of the U.S. Geological Survey Archives, U.S. Geological Survey,




Live Seafood: Freshwater and marine plants and animals sold alive in markets and grocery stores for use as food.

Fresh Seafood: Seafood that has recently been killed and chilled, but not frozen.

Hitchhikers: Organisms that travel on or with seafood that is being transported.

Invasive species: Organisms that are introduced into a new environment where they breed and thrive.


A Chinese mitten crab. Image courtesy of the New Zealand Ministry of Fisheries.


Diseases Spread by Seafood

Spring Viremia: A viral disease that can infect species used in aquaculture such as common carp (Cyprinus carpio), grass carp (Ctenopharyngodon idella) bighead carp (Aristichthys nobilis), silver carp (Hypophthalymichthys molitrix), and Crucian carp (Carassius carassius). The disease is spread in fish feces. Fish infected with spring viremia may become lethargic and less able to escape from predators. Mortality rates can be as high as 70% (Petty et al. 2002).

Koi Herpes Virus (KHV): A highly contagious DNA-virus that infects common carp (Cyprinus carpio). The disease is spread by direct contact with infect fish or their fluids. Infected fish usually die within several weeks of exposure to the virus (Hartman et al. 2004).

Anguillicola crassus parasite: A parasitic worm traditionally found in Japanese eels, which has recently been found in European and American eels. The worm penetrates the wall of the fish’s swim bladder to lay its eggs (Blakenship 1998). The eel has trouble swimming without full use of its swim bladder and is less able to escape from predators. Eel populations in the United States have decreased dramatically in the past several years due to fishing pressures and disease.

Mycobacteriosis: A bacterial infection that can infect any species. Humans can contract the disease through contact with an infected fish or infected water. Usually the bacteria enter through skin cuts and can cause sores, lesions, and inflammation. It can be treated with antibiotics (Virginia Institute of Marine Science 2006).

Cholera: A bacterial infection resulting in severe diarrhea caused by the bacterium Vibrio cholerae. The bacteria can live in coastal waters and people have contracted the disease by eating undercooked shellfish (CDC- Cholera 2005).

Salmonella: There are several species of Salmonella that affect humans and wildlife. In humans salmonella infections usually cause diarrhea and fever. The bacteria can be carried by animals and transmitted in their feces (CDC- Salmonella Infection and Animals 2005).





:: Home :: MIT Sea Grant :: Site Map :: Contact ::
  this page last updated on: 2 May, 2006