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Mediterranean invasive species factsheet

Similar species An abundance of bivalves can significantly increase
In the Mediterranean, the Japanese carpet shell sediment erosion and re-suspension rates and over-
Venerupis philippinarum is most likely to be enrich sediments with biodeposits, leading to
confused with the cross-cut carpet shell clam, sediment anoxia which inhibits nitrification and kills
Ruditapes decussatus, whose shell surface has benthic fauna. This species can destabilize the
radiating and concentric ridges that are more widely sediment, and it may also compete for resources
spaced. In Ruditapes decussatus the outline of the with other species and inhibit their population
shell is more elongated than oval, it lacks teeth recruitment by ingesting pelagic larvae, which may
inside the valves near the hinge, and the inside of lead to changes in benthic communities.
the shell is generally completely white.
deep indentation at
the mantle Economic impacts
attachment
The Japanese carpet shell is one of the most
important species in shellfish farming. World
production of this one species accounts for 20% of
the global shellfish market. Italy is the largest
European producer of Venerupis philippinarum with
90% of the market, worth over 100 million euros. The
negative economic impact of the species has not yet
been quantified.

Management options

Suggested prevention actions are to avoid the
establishment of further wild populations by means of
education and public awareness-raising, together
Ruditapes decussatus
with a monitoring programme to monitor parasites
that can infect native bivalves. Monitoring in MPAs
Brief history of its introduction and also facilitates early detection of populations so that
pathways they can be eradicated or contained before they can

Venerupis philippinarum is native to the Indo-Pacific spread further. Aquaculture farms near MPAs should
region. Broodstock was introduced for farming along be encouraged to cultivate other, native species.
the Atlantic coast of France to replace the native Control: eradication of this species from the
clam Ruditapes decussatus in 1972. Since then, environment is unfeasible at the moment due to the
culture has spread to the Mediterranean Sea in Italy, large numbers of individuals forming new
France and Turkey, the first seedlings having been populations. Only in particular conditions, as where a
introduced in the Venice lagoon in 1983. Wild new population is localized in a very restricted area,
populations now thrive in all the lagoons along the can targeted trawling to eradicate the species be
northern Adriatic coast and in other coastal areas. attempted.

Ecological impacts Further reading
Its high potential for dispersal, fast growth and great Sladonja et al, 2011. Manila Clam (Tapes philippinarum
ability to adapt to new environments as an invasive Adams & Reeve, 1852) in the Lagoon of Marano and
Grado (Northern Adriatic Sea, Italy): Socio-Economic and
species can have a major impact on the macro-
Environmental Pathway of a Shell Farm. Aquaculture and
benthic fauna and flora, since it competes for food
the Environment - A Shared Destiny, Dr. Barbara Sladonja
and space with other filter-feeding invertebrates. It (Ed.).
can supplant the indigenous grooved carpet shell, http://www.ciesm.org/atlas/Ruditapesphilippinarum.html Drawings: Juan Varela
Venerupis decussata, and lead to the extinction of
http://www.nobanis.org/MarineIdkey/Bivalvia/RuditapesPhil
other local mollusc populations, as has been ippinarum.htm
observed in the Venice lagoon.

80 Monitoring Marine Invasive Species in Mediterranean MPAs: A strategy and practical guide for managers