According to marine biologist Declan Quigley, a collection of scallops and a clam found on a plastic toy boat washed up on the Co Clare coast more than five years ago represent the first such specimens recorded in Irish waters.
The eight Calico Argopecten gibbus scallops found on Fanore Beach, Co Clare also represent the earliest records from European and northeast Atlantic waters, he says.
A cross-arch clam Anadara transversa found with the scallops inside the hull of the toy boat is the most northerly European Atlantic record of this species to date, he says.
In an article for the Irish Biogeographical Society, also published by Afloat below, Quigley notes that the discovery was made by Liam MacNamara on Fanore on July 18, 2016.
Although all of the specimens died, the shells were intact and each contained remnants of desiccated muscle tissue, suggesting they were likely all still alive when they washed ashore, Quigley says.
The Calico scallop is native to the western North Atlantic, ranging from Delaware Bay, USA (39 degrees N) south to the Gulf of Mexico (20 degrees N), where it occurs typically at depths of 10 to 400 meters, writes Quigley.
He says records indicate the species is not uncommon farther south, particularly in the Caribbean Sea (Cuba, Puerto Rico, Virgin Islands and Guadeloupe) and along the northern coast of South America. (Colombia, Venezuela, Guyana, Suriname and French Guyana) .
The Transverse Ark clam is native to the western North Atlantic where it commonly occurs in coastal waters from Cape Cod, Massachusetts in the United States south to Yucatan, Mexico.
The specimens were donated to the National Museum of Ireland – Natural History Division
Quigley says it is unlikely that either species will be able to establish self-sustaining populations in Irish waters due to their relatively high seawater temperature requirements for spawning (>20oC ).
Although sea surface temperatures around Ireland are around 7-8°C warmer than the global average at equivalent latitudes, mainly due to the North Atlantic Drift carrying warm water from the Gulf of Mexico to northwestern Europe, they are still too high. low to support the survival of A. gibbus and A. transversa, he says.
However, if current and projected future increases in global warming continue, it is possible that some passively floating non-native warm water species may eventually become established in Irish waters and other waters of northwestern Ireland. Europe, he says.
Quigley’s full article can be downloaded below as a PDF file