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Mediterranean invasive species factsheet

Similar species with Erythrean spiny oyster, Spondylus spinosus,
The native oyster Chama gryphoides can be another alien oyster. Both species singly or together
distinguished by its smaller size (up to 2.5 cm), can form dense aggregations, producing solid reefs
irregular radial ‘ribs’ arranged in concentric rows and at some sites and completely replacing native
the white colour of its shell. species such as the European thorny oyster,
Spondylus gaederopus, or the smaller oyster, Chama
gryphoides. Competition and reduced plankton
availability caused by decreased water flow can also
slow down the growth of other benthic organisms.

Economic impacts
It is a valuable species for seashell collectors, with a
small trading market. The impact of this invasive
species is unknown.

Chama gryphoides

short and non-striated spines in
irregular radial ribs

Spondylus spinosus. Photo: K. Sangiouloglou

Management options

A suggested prevention action is to conduct public
awareness campaigns combined with monitoring.
Control actions are feasible only in specific
circumstances, such as when individuals are
Chama gryphoides. Photo: J. Ben Souissi
localized in a very confined area. Fouling
communities on recreational boats and ships can be
Brief history of its introduction and removed but larvae can re-establish previous
pathways densities. These bivalves are also strongly attached
Widespread in the Indo-West Pacific, C. pacifica was to the sea bottom and their eradication involves the
recorded for the first time in the Mediterranean Sea removal of part of the local benthic communities and
from Alexandria (Egypt) in 1905. From here, it their substratum. This procedure clearly has a
colonized many areas of the south-eastern basin: considerable impact and must be shown to be
Israel, Lebanon, Cyprus, Turkey, Syria and Greece. justifiable by means of an environmental impact
Its presence in the Mediterranean is due to the assessment, as in the case of the other alien bivalve
opening of the Suez Canal, while it has probably Spondylus spinosus.
been spread further by ships and recreational boats
as part of the hull fouling assemblage.
Further reading
Crocetta, F. & Russo, P., 2012. The alien spreading of
Ecological impacts Chama pacifica Broderip, 1835 (Mollusca: Bivalvia: Drawings: Juan Varela
Chamidae) in the Mediterranean Sea. Turk J Zool 37:1-5.
Chama pacifica has become an important
component of the eastern Mediterranean shallow http://www.ciesm.org/atlas/Chamapacifica.html
benthos, and is occasionally found in association

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