Non‐native marine species in British waters: effects and controls

 1. The occurrence of non‐native marine macro fauna and flora, which have become established in the wild British waters, are summarized. The effects of these non‐natives on the native fauna and flora and on commercial and recreational interests are reviewed.  2. Sixteen species of marine algae (11 rhodophytes, three chromophytes and two chlorophytes), five diatoms, one angiosperm and 31 invertebrates were identified as non‐native. The majority of these species are red algae, polychaete worms, crustaceans and molluscs.  3. Species were introduced directly from primary sources within their natural range, or from secondary sources to which they had previously been introduced. They have only become established where introduced from similar latitudes of both hemispheres.  4. More than half the total number of species are considered to have been introduced to Britain in association with shipping, whilst half of the non‐native marine algae are believed to have been introduced in association with deliberate introductions for mariculture.  5. Of the species that had spread, the marine plants did so fairly rapidly, while the invertebrates tended to spread more slowly. The methods of spread were often the same as their method of introduction for both flora and fauna.  6. The direct effects of non‐native species on the marine environment in British waters are not as detrimental as those reported from elsewhere in the world. Some commercially important species have been introduced, but some associated pests and parasites have accompanied them.  7. Control methods, where applied to populations of nuisance species, are fairly ineffective and no non‐native marine species have been deliberately eradicated from British waters. Ways of avoiding introduction of further non‐natives by mandatory and voluntary means are discussed. ©1996 by John Wiley & Sons, Ltd.