• intertidal;
  • subtidal;
  • legislation;
  • special area of conservation;
  • invertebrates;
  • alien species;
  • oyster;
  • Ostrea chilensis;
  • invasive species;
  • Menai Strait


  1. Bioinvasions are known to be highly unpredictable and context-dependent, varying both spatially and temporally, particularly in areas of intense anthropogenic activity and disturbance. Even the most unlikely invader can rapidly become problematic in the absence of frequent, coherent, and flexible management strategies. Using the recent spread of the Chilean oyster (Ostrea chilensis Philippi 1845) within a designated Special Area of Conservation, the paper describes what can happen to seemingly innocuous non-native species under the often complicated and uncoordinated current UK legislation framework.
  2. Following >30 years of containment at Tal y Foel (North Wales, UK), O. chilensis, a species with a highly-reduced natural dispersal capacity, has now spread over a range of >30 km of shoreline. Alternative vectors, including rafting and several anthropogenic activities, are likely to have facilitated the dispersal of O. chilensis away from Tal y Foel.
  3. Areas of high oyster densities (maximum = 232 oysters m-2) have become established both close to and distant from the site of original introduction. The presence of all year classes throughout the observed age range (≤7 and ≤9 years old in the intertidal and subtidal populations, respectively) confirms regular annual recruitment in the area. Information is now urgently required regarding the factors that promote the persistence and spread of O. chilensis within its new environment, as well as the impacts of its increasing localized dominance on the native biodiversity and ecosystem function.
  4. As well as providing valuable, up-to-date information on the recent spread of this non-native species, the paper highlights discrepancies in the current UK legislation framework that allow for the successful establishment and spread of even the most unlikely invaders. the formation of a comprehensive and dedicated EU legal framework for managing invasives is advocated that also promotes coherence and continuity with impending legislative instruments concerning other relevant sectors.

Copyright © 2011 John Wiley & Sons, Ltd.