Gourmet Art – Bay Scallops

Three Bay Scallops Washed Up on Indian Neck, Wellfleet

As the Turtle Journal team combed the tidal flats of Indian Neck just south of the boat entrance to Wellfleet Harbor, we discovered a large number of bay scallops that had been deposited in the shallows by a previous high tide.  They appeared around, maybe just below, legal harvesting size, and had somehow been dislocated from their deeper locations in Wellfleet Bay between Indian Neck to the east and Great Island to the west.  Seagulls were having a feast, prying open the shells and stripping out the meat.  [ASIDE:  You may have gotten the impression from this and previous posts that seagulls on the Outer Cape enjoy a fairly easy life and a luxuriant palate.  They don’t seem to be bothered by the moral dilemma of shellfish sizing rules.] 

Bay Scallop Opens and Snaps Shut Again

Bay scallops (Pecten irradians) should not be confused with much larger deep sea scallops (Placopecten megallancius) that are harvested off the coast in areas such as Georges Bank.  Bay scallops are sweeter, more tender and much more flavorful.  They are also rare and very difficult to obtain, having been harvested to near exhaustion in pressured coastal habitats.  Today, sea scallops account for the overwhelming bulk of the commercial scallop fisheries and are likely to be the menu item sitting on your plate.  If and when you can order bay scallops, do so.  You will savor the difference.


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Bay Scallop (Pecten irradians)

The shell-clapping behavior illustrated in the video is used by bay scallops to drive jets of water for propulsion to evade predators and to move toward sources of food.  Movement is created by contraction of the yummy adductor muscle.  The process doesn’t quite work as well when being held in mid-air by a human hand, but it gives us an opportunity to examine this artistically exquisite culinary delight.

Two Hinged Shells Held Together by Edible Adductor Muscle

Scallops consist of two hinged shells (hence: bivalve) connected together by an adductor muscle.  This thick white fleshy muscle, the adductor, is the “scallop” that we actually eat; all the rest of the animal is scraped out and tossed back out to sea to re-enter the food chain.  (The entire scallop is actually edible, but U.S. preference is to eat only the adductor muscle.)


Colorful Multihued Shells & Beautiful Blue Eyes

Bay scallop habitat is the subtidal zone in five to twenty-five feet of water.  Scallops spend the first week or so of life as free-floating plankton.  After seven to ten days a juvenile scallop develops byssal threads projecting from its foot and attaches itself to a substrate.  The preferred substrate is eelgrass (Zoestera marina) where juvenile scallops are protected from voracious predators.  They can detach themselves at any time, and after a year or so, the mature scallop breaks free of the eelgrass and settles on sandy and muddy bottoms of harbors and estuaries.  This behavior is unlike their clam relatives such as quahogs and soft-shelled clams that prefer to burrow into sandy, silty bottoms.  Bay scallops reach reproductive maturity around 12 months and will spawn only once in its lifetime.

Coastal development adversely impacts scallop habitat primarily through silt runoff that smothers eelgrass beds.  In estuaries that permit dense boat moorings, such as Sippican Harbor, the constant swinging of boats on mooring lines mows eelgrass beds, while added silting and shading thwart growth of new plants.  Overfishing of bay scallops has been a big problem for sustainable populations, as has the decrease in water quality and clarity, and obviously the drastic reduction in viable eelgrass beds.

“Ol’ Blue Eyes” Himself Would Be Jealous

Scallops are unusual among shellfish in that they frequently rest with their shells open, creating a one-quater inch gap between shells.  Nestled along the mantel are rows of brilliantly colored blue eyes and fleshy tentacles.  Both eyes and tentacles funtion as sensory organs.  Those beautiful blue eyes would have made Frank Sinatra jealous because each animal has 30 to 40 of them.  Scallop eyes are similar to human eyes in that each one contains a lens, a blue iris, a retina & a cornea, and each eye is attached to an optic nerve.  Eyes are sensitive to movement and to shadows, enabling the scallop to detect and thereby to avoid predators.

Blue Eyes along Perimeter; Chemosensory Tentacles Below

Blue scallop eyes are scattered along the outer circumference.  Inside the eyes the mantel is ringed by fleshy, chemosensory protuberances called tentacles that are sensitive to odors and to changes in water temperature.

Chemosensory Tentacles Above; Gills Below

Bay scallops, like other bivalves, are filter feeders and their primary prey are diatoms (phytoplankton).  With its two shells partially open, a scallop can pass large volumes of diatoms across its gills (orange ring below chemosensory tentacles above).  Rows of cilia sweep diatoms across the gill surface, where mucus traps and concentrates diatoms for the palps.  Palps are fleshy tissue on the gills that move diatoms toward the stomach where they are consumed as nutrients and transported throughout the scallop via an open circulatory system.

Edible Adductor Muscle Holds Shells Together

The delicious adductor muscle makes humans the principal predators of bay scallops.  In the plankton stage, scallops are easy prey for fish and other marine animals.  As they grow scallops become prey for crabs and sea birds.  Seastars and oyster drills prey on adult scallops, as do ubiquitous seagulls when they get a chance.  Humans, though, create the greatest impact on scallop populations.  Overfishing has driven bay scallops into extirpation in many estuaries.  Habitat destruction and reduced water quality have exacerbated population declines.

Bay Scallop:  A Gourmet Work of Art

Sue Wieber Nourse led a bay scallop research and restoration project in Sippican Harbor with her Tabor Academy advanced marine science students during the early 2000s.  In collaboration with the Marion shellfish officer, Kevin Snow, Sue and her students spread seed scallops in protective cages in various substrates throughout the bottom of Sippican Harbor.  Besides allowing students to engage in hands-on science with real world impact, Sue’s project increased bay scallop productivity in Sippican for several years.  Unfortunately, the project was discontinued.  You can read about this successful research and education program in a November 2001 article, “Tabor Students Keep Close Watch on Tiny Scallops,” in the New Bedford Standard Times.

Fun Facts:  Life span – 20 to 26 months.  Maximum size in Massachusetts – 3.5 inches.  Reproductively mature in one year; spawns only once in a lifetime.  Spawning time – June 15th to August 15th.  Average number of eggs – 2 million.  Shallow water habitat: prefer 5 to 25 feet depth.  Minimum water coverage at low tide – 1 to 2 feet.

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