Short description of Rapana venosa, Veined rapa whelk

A large, active predatory snail, growing up to 18 cm in length. It has a rounded, knobbly shell, with orange internal coloration. External coloration is grey with dark veins. The shell opening is large, with small teeth on the outer lip and a short, open siphon canal.

Impact summary: Rapana venosa, Veined rapa whelk

The rapa whelk preys voraciously on a range of marine invertebrates, including soft sediment burying bivalves, other snails, and crabs. In large numbers, it has the potential to decimate bivalve fisheries. 

Habitat summary: Rapana venosa, Veined rapa whelk

Usually found on and under soft sediments from 3 – 90m water depth. The species is also occasionally found on hard and mixed substrates. In particular, individuals congregate on hard-surfaces such as rocky outcrops and man-made structures to reproduce in late spring and summer months. 

Overview table

Environment	Marine
Species status	Non-Native
Native range	Taiwan
Functional type	Predator
Status in England	Non-Native
Status in Scotland	Non-Native
Status in Wales	Non-Native
Location of first record	N Sea (wider Thames estuary)
Date of first record	9

Origin

Native to the Sea of Japan, Yellow Sea, Bohai Sea, and the East China Sea to Taiwan.

First Record

Isolated records exist for the southern North Sea, in GB waters approximately 30 km south of the Dogger Bank, the Netherlands coast and in shallow waters off the coast of Brittany. 

Pathway and Method

A major vector for transportation worldwide is through shipping, in particular larval transport in ballast water. It may also be unintentionally transported with aquaculture products; it is thought to have been introduced into the Black Sea in 1947 with oysters imported for culture. Once a founder population is established, natural range extension can occur rapidly through larval dispersal via tidal currents, migration of juvenile or adult whelks, or human-mediated means.

Species Status

There is currently no evidence that the species has established populations, or show active breeding or multiple year classes in GB waters.  A small but stable reproducing population is established in the Bay of Quiberon, Brittany, and recent sightings have been reported from the Dutch coast.  Elsewhere the rapa whelk is invasive in the Chesapeake Bay area of North America, the Aegean and Adriatic Seas, the Black Sea and Uruguay.

Dispersal Mechanisms

A planktonic period occurs ranging from 24 to 80 days, which facilitates a variety of dispersal strategies including natural dispersal by water currents or transport within ballast water.  Juvenile and adult migration also takes place. 

Reproduction

First spawning occurs in the second year when the individual reaches a shell length of 35-78 mm.  Reproduction takes place between 18-26 °C in native Korean waters, with similar results observed in Chesapeake Bay, USA.  In Chesapeake Bay the total number of egg capsules produced annually per whelk ranged from 133 to 2759.  The whelks reach reproductive maturity at 50-70 mm in size and can live to be over ten years old.

Known Predators/Herbivores

Several crab species are known to prey upon small rapa whelk, but it is suggested that the rapa whelk reaches a predator refuge size at several years of age, in part due to its thick, broad shell.

Resistant Stages

None known.

Habitat Occupied in GB

To date the rapa whelk is not established in British waters but there is widespread suitable habitat and prey availability.  Great Britain may be at the edge of the rapa whelk’s temperature tolerance as current literature suggests that water temperatures of 18 °C for extended periods are required for successful reproduction to occur.

Native range includes the Sea of Japan, Yellow Sea, Bohai Sea and the East China Sea to Taiwan.  Non-native distribution includes the Black Sea, the Aegean and Adriatic Seas, Uruguay and the Chesapeake Bay area of eastern USA.  A small but stable reproducing population is established on the Brittany coast.  In GB there is no evidence of established populations but an individual record of several rapa whelks was reported from offshore GB waters in 2005.

Environmental Impact

The rapa whelk is able to rapidly consume large quantities of prey and could become a serious competitor for the native common whelk.  Reduced food availability may also impact other predators of bivalves including crabs, birds, fish and starfish.  A decline in structure forming bivalves may affect local habitat, resulting in reduced refuge for juvenile crustaceans and other organisms. 

The provision of larger shells to hermit crabs may allow increased growth and increased demand by hermit crabs on food resources.

Health and Social Impact

None known. 

Economic Impact

The diet of this voracious predator includes molluscs of commercial interest including oysters, mussels and clams; it has been predicted that successful establishment of this species in Great Britain may threaten the bivalve industry.   A rapa whelk of 14 cm is reported to be capable of consuming an 8 cm hard clam in less than an hour. 

Identification

Biology, ecology, spread, vectors

 Giberto, D.A., Bremec, C.S., Schejter, L., Schiariti, A., Mianzan, H. & Acha, E.M., (2006) The invasive rapa whelk Rapana venosa (Valenciennes 1846): status and potential ecological impacts in the Rio de la Plata Estuary, Argentina-Uruguay. Journal of Shellfish Research, 25, 919-924.

Harding, J.M., Mann, R. & Kilduff, C.W. (2008) Influence of environmental factors and female size on reproductive output in an invasive temperate marine gastropod Rapana venosa (Muricidae). Marine Biology, 155, 571-581 

Kerckhof, F., Vink, R.J., Nieweg, D.C. & Post, J.J.N., (2006)  The veined whelk Rapana venosa has reached the North Sea. Aquatic Invasions, 1, 35-37.

Mann, R. & Harding, J.M., (2000) Invasion of the North American Atlantic Coast by a Large Predatory Asian Mollusc. Biological Invasions, 2, 7-22.

Management and impact

Sewell J., Pearce S., Bishop J. and Evans, J.L. (2008) Investigations to determine the potential risk for certain non-native species to be introduced to North Wales with mussel seed dredged from wild seed beds.  CCW Policy Research Report No. 063. pp 82

General

ICES. (2004)  Alien Species Alert: Rapana venosa (veined whelk). Edited by Roger Mann, Anna Occhipinti, and Juliana M. Harding. ICES Cooperative Research Report No. 264. 14 pp

https://www.cabi.org/isc/datasheet/66682

https://secure.fera.defra.gov.uk/nonnativespecies/downloadDocument.cfm?id=622