coasts and oceans > factfile > alien species
Alien speciesPosted: 12 Oct 2004
Another form of pollution is the introduction of exotic, or non-native species into marine environments. These marine invaders are on the increase in all the world's seas, probably because of the increase in international shipping.
Most exotics, from micro-organisms to fish, hitch-hike in the ballast waters and cargoes of ships. Some 60 introduced species have been found in the Baltic Sea. In some parts of the Black Sea, up to 90 per cent of the biomass consists of the comb-jelly, Mnemiopsis leidyi, which feeds on the eggs and larvae of many commercially valuable species of fish.