A collection of scallops and one clam found on a plastic toy boat washed up on the Co Clare coast over five years ago represent the first such specimens recorded in Irish waters, marine biologist Declan Quigley says.
The eight Calico scallops Argopecten gibbus found on Fanore beach, Co Clare also represent the first records from European and north-east Atlantic waters, he says.
One Transverse Ark clam Anadara transversa found with the scallops inside the toy boat’s hull is the most northerly European Atlantic record of this species to date, he says.
In a paper for the Irish Biogeographical Society, also published by Afloat below, Quigley notes the discovery was made by Liam MacNamara on Fanore on July 18th, 2016.
Plastic toy boat (deck view)
Argopecten gibbus and Anadara transversa shells
Although all of the specimens were dead, the shells were intact and each contained the remains of desiccated muscle tissue which suggests that they were all probably still alive when stranded, Quigley says.
The Calico scallop is native to the western North Atlantic, ranging from Delaware Bay, U.S.A. (39 degrees N) southwards to the Gulf of Mexico (20 degrees N), where it commonly occurs at depths of 10 to 400 metres, Quigley writes.
He says records indicate that the species is not uncommon further southwards, particularly in the Caribbean Sea (Cuba, Puerto Rico, Virgin Islands and Guadeloupe), and along the northern coast of South America (Columbia, Venezuela, Guyana, Suriname and French Guiana).
The Transverse Ark clam is native to the western North Atlantic where it commonly occurs in coastal waters from Cape Cod, Massachusetts in the US southwards to the Yucatan, Mexico.
The specimens were donated to the National Museum of Ireland – Natural History Division
Argopecten gibbus (external view of shells)
Quigley says it is unlikely that either species could establish self-sustaining populations in Irish waters based on their relatively high sea water temperature requirements for spawning (>20oC).
Although surface sea water temperatures around Ireland are about 7-8°C warmer than the global average at equivalent latitudes, primarily due to the North-Atlantic drift which transports warm water from the Gulf of Mexico to north-west Europe, they are still too low to support the survival of A. gibbus and A. Transversa, he says.
However, if current and predicted future increases in climatic warming continue, it is possible that some passively rafting non-native warm-water species may eventually become established in Irish and other north-west European waters, he says.
Quigley’s full paper is downloadable below as PDF file
