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Mediterranean invasive species factsheet

Similar species Tyrrhenian Sea (from Livorno, Elba Island, Sabaudia,
This whelk resembles the native whelk Stramonita Messina and Cagliari). The species was also
haemastoma, but the smaller overall size (up to 7 recorded from Greece (northern Aegean Sea) and
cm), narrower aperture, lack of umbilicus and more Slovenia in the 1990s.
tapered shape of the latter distinguish it from the Larvae are likely to have arrived in ships’ ballast
non-native species. water, while young whelks could also have been
Spire conical with barely
visible suture hidden amongst commercial bivalve seeds and been
transferred to new farm seedling areas.

Ecological impacts
The rapa whelk is a voracious predator of bivalve
molluscs and may also compete with native species
for space; it causes a major decline in local bivalve
populations. In other invasive environments, young
rapa whelks are generalist predators and consume
large numbers of barnacles, mussels, oyster spat,
and small oysters, as well as other whelks.

No umbilicus Economic impacts
Stramonita haemastoma
These whelks can decimate local shellfish
populations and damage the industry that they
support. They also use fishing nets for attaching their
spawn, adding a lot of weight to the nets. Empty
shells may be marketed as tourist souvenirs and the
meat of this species is consumed along the
Romanian Black Sea coast and in Turkey.

Management options

A suggested prevention action is to conduct local
public awareness campaigns combined with
monitoring. There are no proven control methods;
nevertheless, physical hand removal of adults by
MPA technicians, local groups and fishermen could
be explored. Removal of egg cases from any hard
structure present on the bottom can also effectively
address these invasions.

Stramonita haemastoma. Photo: C. Tripodi
Further information
http://www.ciesm.org/atlas/Rapanavenosa.html
Brief history of its introduction and
pathways http://www.nobanis.org/MarineIdkey/Gastropods/RapanaV
enosa.htm
Originally from Sea of Japan, Yellow Sea and East
http://www.europe-aliens.org/pdf/Rapana_venosa.pdf
China Sea, the rapa whelk was first introduced into
ICES. 2004. Alien Species Alert: Rapana venosa (veined
the Black Sea and reported for the first time in the whelk). Edited by Roger Mann, Anna Occhipinti, and
Mediterranean in Italy (Ravenna) in 1973. Juliana M. Harding. ICES Cooperative Research Report
Thereafter, it spread all along the northern Adriatic No. 264. 14 pp. Drawings: Juan Varela
coasts from the Marano lagoon to Ancona. There
are also sporadic records of the rapa whelk in the

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