Invasive Aquatic Species (IAS)

Some examples of aquatic bio-invasions causing major impact are listed in the table, but there are hundreds of other serious invasions which have been recorded around the world.
Name Native to Introduced to Impact


Vibrio cholerae (various strains)

Various strains with broad ranges

South America, Gulf of Mexico and other areas

Some cholera epidemics are reported to be have been associated with ballast water.

Cladoceran water flea

Cercopagis pengoi

Black and Caspian Seas

Baltic Sea

Reproduces to form very large populations that dominate the zooplankton community and clog fishing nets and trawls, with associated economic impacts.

Chinese mitten crab

Eriocheir sinensis

Northern Asia

Western Europe, Baltic Sea and west coast North America

Undergoes mass migrations for reproductive purposes. Burrows into river banks and dykes causing erosion and siltation. Preys on native fish and invertebrate species, causing local extinctions during population outbreaks. Interferes with fishing activities.

Toxic algae (red/brown/green tides) various species

Various species with broad ranges

Several species have been transferred to new areas in ships’ ballast water

May form harmful algae blooms. Depending on the species, can cause massive kills of marine life through oxygen depletion, release of toxins and/or mucus. Can foul beaches and impact on tourism and recreation. Some species may contaminate filter-feeding shellfish and cause fisheries to be closed. Consumption of contaminated shellfish by humans may cause severe illness and death.

Round goby

Neogobius melanostomus

Black, Azov and Caspian Seas

Baltic Sea and North America

Highly adaptable and invasive. Increases in numbers and spreads quickly. Competes for food and habitat with native fishes including commercially important species, and preys on their eggs and young. Spawns multiple times per season and survives in poor water quality.

North American comb jelly 

Mnemiopsis leidyi

Eastern seaboard of the Americas

Black, Azov and Caspian Seas

Reproduces rapidly (self‑fertilising hermaphrodite) under favourable conditions. Feeds excessively on zooplankton. Depletes zooplankton stocks; altering food web and ecosystem function. Contributed significantly to collapse of Black and Azov Sea fisheries in 1990s, with massive economic and social impact. Subsequent similar impact in Caspian Sea.

North Pacific seastar

Asterias amurensis

Northern Pacific

Southern Australia

Reproduces in large numbers, reaching ‘plague’ proportions rapidly in invaded environments. Feeds on shellfish, including commercially valuable scallop,oyster and clam species.

Zebra mussel

Dreissena polymorpha

Eastern Europe (Black Sea)

Western and northern Europe, including Ireland and Baltic Sea; eastern half of North America

Fouls all available hard surfaces in mass numbers. Displaces native aquatic life. Alters habitat, ecosystem and food web. Causes severe fouling problems on infrastructure and ships. Blocks water intake pipes, sluices and irrigation ditches. Economic costs to United States alone of around US$750 million to US$1 billion between 1989 and 2000.

Asian kelp

Undaria pinnatifida

Northern Asia

Southern Australia, New Zealand, west coast of the United States, Europe and Argentina

Grows and spreads rapidly, both vegetatively and through dispersal of spores. Displaces native algae and marine life. Alters habitat, ecosystem and food web. May affect commercial shellfish stocks through space competition and alteration of habitat.

European green crab

Carcinus maenus

European Atlantic coast

Southern Australia, South Africa, the United States and Japan

Highly adaptable and invasive. Resistant to predation due to hard shell. Competes with and displaces native crabs and becomes a dominant species in invaded areas. Consumes and depletes wide range of prey species. Alters inter-tidal rocky shore ecosystem.