Invasive Species in Cape Breton

The Atlantic Bay Scallop (Argopecten irradians) is an invasive species to Cape Breton. This species can be recognized by its nearly identical, deeply ribbed fan-shaped shells with a distinctive wing-like hinge. The shell color has quite a range from blue-black to orange, white or reddish brown. The shell we found in Dominion Beach had a blue-gray color that was almost purple. Their shells grow to approximately 2.5-3 inches in length.

http://www.projectufo.ca/drupal/Atlantic_Bay_Scallop

There are 4 sub-species of the Atlantic Bay Scallop - A. irradians irradians has 17-18 ribs and can be found the North shore of Cape Cod to New Jersey, A. irradians concentricus has 19-20 ribs and can be found from Maryland to Georgia and Louisiana to Tampa. It is also rarely found in Jersey. A. irradians amplicostatus has 12-17 ribs and can be found from central Texas to Mexico and Colombia. A. irradians sablensis has 18-21 ribs and is an extinct species. Valves can be found on Sable Island dating to times of warmer waters (1800 years ago).

Scallops feed by filter-feeding. They trap, absorb and ingest floating dead and decomposing plant and animal matter. Since what they feed on doesn’t negatively impact any particular species it is more important to observe what feed on this scallop. I’m sure many of us, including myself, were first introduced to scallops when they were served up on a plate. That is, humans are predators of this species along with starfish, wading birds, seagulls, pinfish, lightning whelks, cow-nosed rays, and crabs are among its numerous predators.

The habitat of the Atlantic Bay Scallop is usually eelgrass beds (Zostera marina) on sandy and sandy-mud bottoms. They prefer areas where the salt content is high and the water is calm. The range of this species extends from the Gulf of Mexico all the way to Cape Cod and now, more recently, in Nova Scotia. Their shells have been found at Dominion Beach and Big Glace Bay beach over the past few years. In Cape Breton, there have been live sighting along the coast near Cheticamp and Lingan Bay along with shells found at Dominion Beach and Glace Bay Beach. “It is possible that the introduction of the Atlantic Bay Scallop into Cape Breton waters is a result of the aquaculture of this species. Several areas in Nova Scotia (unlike Cape Breton) have water temperatures warm enough to support the development of juvenile Atlantic Bay Scallops. It is possible that adult scallops have escaped from aquaculture captivity and have entered our waters.” (Project UFO, 2008). While on a field trip to Dominion Beach we found evidence of this invasive species when we found the blue-gray shell that was either washed ashore or leftovers from some bird’s meal.