The study reported here was undertaken to collate details and review information about introductions of marine fauna and flora to Great Britain (England, Scotland and Wales). The focus of this review is on nature conservation and the work will be used to formulate policy on marine introductions in relation to nature conservation interests.

 

The study evaluates non-native macro fauna and flora, which have been introduced from outside their natural range and have become established in the wild in British waters. This report evaluates their origin, date and method of introduction, the reasons for their success, rate of spread, current distribution, actual and potential effects on native ecosystems and nature conservation as well as commercial interests, and methods of control. Micro-organisms (< 20 µm) are not considered.

Fourteen species of marine alga (or 15 taxa including two subspecies of a single species of green alga), five diatoms, one angiosperm and 30 invertebrates have been identified as non-native and aspects of their introduction and subsequent effects described. The majority of these 50 species are red algae, polychaete worms, crustaceans and molluscs. No non-native sponges, bryozoans or echinoderms have been found in British waters. Although the frequency with which introduced species have been recorded in Europe has increased with time, there is no trend in the number of non-natives which have become established in Britain. Species have been introduced directly from primary sources or areas within their natural range or from secondary sources to which they had previously been introduced. In general, species were found to have only become established if they were introduced from similar latitudes of either hemisphere. More than half the total number of species described here are considered to have been introduced to Britain in association with shipping, whilst half of the non-native marine algae found in Britain are believed to have been introduced to Europe in association with deliberate introductions of shellfish for mariculture.

Of the species deliberately introduced for aquaculture, only some of the bivalve molluscs have become established in the natural environment beyond the confines of their cultivation.

 

The success of the non-natives described here has, where known, been due to a combination of reasons. Of the species that have spread, the marine algae did so fairly rapidly, while the invertebrates tended to spread more slowly. The method of spread, e.g. in association with shipping, was often the same as their method of introduction for both fauna and flora.

The direct effects of non-native species on the marine environment in British waters are in general not as detrimental as reported from elsewhere in the world. Commercially, some economically important species have been introduced, but some associated pests and parasites adversely affecting native species have also been unintentionally introduced. Control methods, where applied to nuisance species, are fairly ineffective and no non-native marine species have yet been successfully eradicated from British waters. The different aspects of the biology and etiology of non-natives are discussed in relation to determining their presence and monitoring their distribution, and developing ways of avoiding further introductions.