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
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
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
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
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 www.invasivespeciesinfo.gov
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
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.
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.
Chinese mitten crab. Image courtesy of the New Zealand Ministry
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
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).