ABSTRACT
In recent years, species invasions have become recognized as one of the major human-mediated impacts on natural systems. Specifically, invasions in marine environments have caused considerable harm to native communities, as exemplified by San Francisco Bay on the United States (US) west coast. From 1961 to 1995, with an average of one new species invading every 14 weeks, these marine exotics comprised 40 to 100 per cent of the common species within the bay, up to 97 per cent of its species abundance and up to 99 per cent of the species biomass. Due to this high rate of invasion, the bay has become one of the world’s most heavily invaded aquatic ecosystems, a factor that has greatly contributed to its high level of degradation (Cohen and Carlton, 1998). Invasions can therefore have profound effects on ecosystems, with significant implications for ecological and management work.
