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clams. Green crabs have also had long-term impacts on shell shape and morphology
of herbivorous snails in New England (Grosholz, 2011).
The Chinese mitten crab Eriocheir sinensis is another species for which
impacts have been quantified fairly extensively. In Europe during the early twentieth
century, population explosions resulted in extensive efforts to mitigate their impacts
in rivers, canals, and associated municipal facilities (Grosholz, 2011). It caused
damages to river banks by burrowing and considerable damage to fisheries by
consuming netted fish and by cutting nets (CIESM, 2014). In the San Francisco Bay
following population outbreaks in the late 1990s, substantial investments by state
and federal agencies were required to prevent clogging of water pumps and
associated fish salvage facilities. Major losses were experienced by commercial and
sport fishing interests as well in central California.
Among the regions that could potentially provide the source for introduced
crabs, the most common source region is overwhelmingly the Indo-Pacific region.
Every introduction is strongly influenced by the level of taxonomic effort in addition
to characteristics of propagule pressure habitat matching between source and
recipient communities, and other general processes known to influence species
introductions have clearly influenced patterns of crab introductions (Grosholz, 2011).
Particular recipient regions in warm temperate and subtropical areas such as the
Mediterranean region have the greatest number of established introduced crab
species.
Newcomers (whether natural or introduced) can trigger major changes in
ecosystem functioning. Τhe same ecosystems are increasingly exposed to pollution,
overfishing, and to alterations in the normal patterns of temperature and several
other physical–chemical factors associated with temperature, such as sea level
changes and acidification. If pollution, mass mortalities and biological invasions are
also taken into account, the effects on ecosystem functioning are likely to be
dramatic. Only a multidisciplinary approach can tackle such a complex problem:
linking functional ecology with invasion biology and macrophysiology.

Legislation in EE
Although the European states have a comprehensive regulatory framework to
protect economic interests against diseases and pests, these are often inadequate to
safeguard against species that threaten native biodiversity. Moreover, the regulatory
system pertains to pathogens while large sized species that may have considerable
impact on health or the economy are not considered to date.
Changes in European reference regulations testify this growing concern: in
the Water Framework Directive (WFD; 2000/60/EC) alien species were not included
among the ecological quality indicators for coastal habitats (EU, 2000); conversely, in
the Marine Strategy Framework Directive (MSFD; 2008/56/EC), and, more recently,
in the Biodiversity Strategy to 2020 [2011/2307(INI)] IAS have been explicitly
recognized as a biological pressure (MSFD descriptor D2), whose magnitude and
functional effects need to be estimated for an integrated assessment of the
ecological status of marine ecosystems (EU, 2010; Borja et al., 2010).
The ‘‘Jakarta Mandate on Marine and Coastal Biological Diversity’’, adopted
by the Parties to the ‘‘Convention on Biological Diversity’’ (CBD), cites ‘‘invasion of
exotic species’’ as one of the five main categories of the anthropogenic impact on