Non-Native Species


Thousands of marine species and plants and algae are transported from their native range to "new" areas. These species are called non-native species (sometimes referred to as alien or invasive species). Species can be introduced to non-native environments accidentally or deliberately. Introductions and transfer of non-native marine species to their non-native environment mainly occurs by the transport and discharge of ballast water , and to a lesser extent by transport of fouling organisms on hulls or through aquaculture.


Deliberate introductions occur through the import and release of fish and bivalves for commercial purposes in new locations. Other species living in or on these commercial species may be accidentally introduced, at the same time unless careful precautions are taken.

Effects of the introduction of invasive/non-native species
Once established in a new region, non-native species may invade new areas adjacent to the occupied area by natural dispersal, e.g. via transport in water currents in the case of many seaweeds and phytoplankton.
Non-native species may displace native organisms by preying on them or out-competing them for resources such as for food, space or both. In some cases this has led to the elimination of indigenous species from certain areas. Occasionally non-native species can reproduce with native species and produce hybrids, which will alter the genetic pool (a process called genetic pollution), which is an irreversible change. When an invasive species has established itself in the marine environment, it is likely to be impossible to get rid of it.
With the import and introduction of commercial species into European waters, some native species have become threatened.
JNCC publication Non-native marine species in British waters: a review and directory details the introduction of marine fauna and flora to Great Britain (England, Scotland & Wales).
International aspects
UK is bound by international agreements such as the Convention on Biological Diversity, the United Nations Convention on the Law of the Sea, The Convention on the Conservation of Migratory Species of Wild Animals (Bonn 1979), The Convention on the Conservation of European Wildlife and Natural Habitat (Bern1979) and the EC Habitats and Species Directive. All of these aim to protect biodiversity and endangered species and habitats, and include provisions requiring measures to prevent the introduction of, or control of, non-native species, especially those that threaten native or protected species.
In response to the growing concern about the increase in damage caused by non-native species, the International Maritime Organisation (IMO) member countries have agreed to develop a mandatory international Convention to regulate and control ballast water transfers.
In Europe there is a ban on the use of Tributyl tin on hulls of ships that are under 25 metres in length. IMO adopted a resolution in 1999 that prohibits the application of TBT to ships by 1. January 2003, and a complete ban by January 2008.

Ballast water is fresh or salt water that is held in the ballast tank cargo holds of ships to provide stability during voyage. The tanks are most commonly filled with water and emptied off the coastline, in estuaries and in bays where freshwater and saltwater meets.
Antifouling paints are applied to coat the bottom of ships to prevent alga and molluscs becoming attached to the hull of the boat. The use of TBT(Tributyl tin) is very harmful for the marine environment and even very low concentrations have effects on snails, such as altering their reproduction system. It accumulates in the food chain, which results in high concentrations in marine mammals.

Further reading/links to other websites
IUCN Guidelines for the Prevention of Biodiversity Loss caused by Alien Species. A guide to Designing Legal and Institutional Frameworks on Alien Invasive Species".
International Maritime Organisation (IMO).
International Council for the Exploration of the Sea (ICES).
Commission for the protection of the marine environment of the North-East Atlantic (OSPAR).