Overview
The Atlantic Sea Scallop (Placopecten magellanicus), celebrated across New England and the Mid-Atlantic as the giant saucer of the continental shelf, is one of the most economically valuable, ecologically vital, and biologically fascinating marine bivalves on Earth. Unlike sedentary clams and cemented oysters, this large, free-living scallop possesses an extraordinary superpower: it can actively swim through the ocean using underwater jet propulsion. Endowed with a perimeter of dozens of tiny, brilliant electric-blue eyes and anchoring the most lucrative commercial fishery in the United States, it is a magnificent titan of cold Atlantic waters.
Biology and Physical Characteristics
Placopecten magellanicus possesses a large, nearly circular, saucer-shaped bivalve shell with two distinct valves: the upper (left) valve is gently convex and colored dirty reddish-pink to chocolate-brown, while the lower (right) valve is flatter and creamy-white, resting against the seafloor. Its interior is dominated by a colossal, cylindrical adductor muscle—the succulent ‘scallop meat’ prized in culinary dining—which can contract with tremendous power to snap the shell shut. Along the outer mantle edge sits an astounding sensory array: a double row of fleshy sensory tentacles and thirty to one hundred tiny, complex, jewel-like electric-blue eyes. Each eye contains a cornea, a lens, a double retina, and a concave guanine crystal mirror that focuses light, allowing the scallop to detect movement and shadows of approaching starfish.
Behavior and Ecology
A free-living filter feeder, the Atlantic Sea Scallop rests unattached on sandy and gravelly continental shelf bottoms like Georges Bank. When a predatory sea star or cod approaches, the scallop activates its emergency escape response: clapping its two shell valves together with rapid, rhythmic contractions of its powerful adductor muscle. This snaps water forcefully out through specialized mantle openings on either side of the hinge, propelling the scallop forward through the water in a graceful, zig-zagging swimming flight that carries it several meters away from danger. During summer, scallops engage in synchronized mass spawning, releasing billions of eggs that drift in offshore currents.
Conservation and Human Impact
The Atlantic Sea Scallop has not been formally assessed by the IUCN Red List, but it is one of the greatest fishery management triumphs in history. Following severe overfishing in the early 1990s, the US National Oceanic and Atmospheric Administration (NOAA) implemented rotating spatial closures, gear restrictions, and strict rotational access areas on Georges Bank and the Mid-Atlantic Bight. The stock rebounded miraculously, making the US Atlantic sea scallop fishery a multi-hundred-million-dollar sustainable industry certified by the Marine Stewardship Council (MSC).
Interesting Factoid
The Atlantic Sea Scallop has up to one hundred bright blue eyes that look like tiny jewels around the edge of its shell, and it can literally fly through the ocean by clapping its shell valves together like castanets to jet away from hungry starfish!