November 14, 2012

Does this snail look sufficiently "alien"?

The European Commission has recently issued a decision according to which the so called apple snails shall not be imported into or spread within the European Union (see Implementing Decision of 8 November 2012).

The new legal provision targets any organisms of the genus Pomacea, and regulates the introduction into and the movement within the region of all plants that might represent an effective pathway for such freshwater snails e.g. all plant species for planting that can only grow in water or soil that is permanently saturated with water.

Apple snail Pomacea canaliculata © Riccardo Scalera
Apple snail Pomacea canaliculata © Riccardo Scalera 

The apple snails are mollusks characterised by a very large shell, which may reach the size of an apple as the name suggests. They are native to South America and have been introduced in many countries of the world, particularly in North America and Asia, both intentionally or accidentally as a consequence of the food and the aquarium trade (see for example the case of Pomacea canaliculata as reported by the GISD). In Europe the only known record of occurrence of apple snails is in Spain. 

In fact the EC decision come in response to a risk assessment analysis made by the European Food Safety Authority (EFSA) and the Spanish authorities, following the discovery of the presence of the apple snail (Pomacea insularum) in the Ebro delta, where it has been causing damage to rice production and the natural environment. According to the risk analysis (PRA), a legislative ban on import of the entire genus Pomacea was the only risk reduction option identified that could reduce the probability of entry of this potentially invasive alien species. Besides, the PRA established that: a) the potential consequences of the organism for rice crops are major; b) the probability for establishment of the organism is very likely and c) the probability of spread is estimated as likely. Thus, while rice fields and natural wetlands are known to be at risk, many other aquatic environments could also be threatened, due to the snail's voracious appetite for water plants and the fact that it can survive in a wide range of climatic conditions.

The objective of the legal provision is to prevent the further release of the snail into the environment, either intentionally or accidentally. In fact, in the absence of less restrictive measures efficiently combating the threat posed by that organism there is a high risk of spreading of this freshwater snail to fields and watercourses, lakes, ponds and swamps. The provision does not focuses only on Pomacea insularum (the species reported in Spain) because other species might be available in the market to replace it, and in any case many other species from the complex are almost indistinguishable.

The decision also requires Member States to adapt their legislation in order to comply with the specified rules, including the establishment of demarcated areas in cases where the genus Pomacea is found to be present in fields and watercourses. In principle this should be a first step to eradicate the organisms concerned, to raise awareness as appropriate and to ensure intensive monitoring for their presence. Wherever necessary Member States should carry out annual surveys in areas where the specific organisms are likely to be found, e.g. rice fields, and notify the results accordingly (even though the presence of the snail is only suspected). In the meantime in Spain, as reported by EPPO, an action plan was implemented to control and eradicate the apple snail. The main measures included phytosanitary and disinfection treatments, removal of adults and eggs, physical barriers, and surveys.