Maryland Fish Facts

Shellfish - Bay Scallop
Shellfish - Bay Scallop

Shellfish - Bay Scallop
Argopecten irradians

Key Distinguishing Markings:
  • Shell lightweight, thin, but strong.
  • 13 to 22 symmetrically radial ribs originating from central point (umbo) of shell.
  • The marginal wings or ears at the umbo are slightly different in size and shape.
  • Bottom valve more convex than top valve.
  • Color highly variable in this species:
    • Top (left) valve – drab; dark grey, black, or brown; occasionally with yellow, orange, or red highlights; ribs sometimes mottled or concentrically banded.
    • Bottom (right) valve – usually lighter in color than top valve, sometimes pale yellow or white.​

  • Bay scallops are primarily found from Massachusetts to Texas.
  • In Maryland, they only occur in the coastal bays behind Ocean City and Assateague Island.​

  • Adults can grow as large as 90 mm (3 ½ in).
  • Scallops reach sexual maturity at about 55 mm (2 ¼ in), although age actually determines this.​

  • Bay scallops inhabit the higher salinity (>15-20 ppt) shallows of bays and estuaries along the coast.
  • This species is intimately associated with eelgrass beds.
  • When a blight wiped out the grass beds in the 1930's, scallop populations plummeted and completely disappeared in some areas.
  • Young scallops attach to blades of eelgrass with thin byssal threads.
  • By suspending themselves above the substrate, they are removed from suffocating silt and bottom-marauding predators such as crabs.
  • Adult scallops live on the bottom, unlike many other bivalves such as clams which live buried in the sediment.
  • Because scallops do not burrow into the bay bottom, adults only have a non-functional foot and do not have siphons.
  • They can also be found occasionally on shelly areas such as the remnant oyster shell bars in Chincoteague Bay.​

  • Scallops are hermaphrodites, simultaneously having both male and female sex organs.
  • Spawning in Maryland occurs during May/June, with a second spawning in September.
  • Eggs are released into the water column, where they are fertilized.
  • During its spawning period, a one-year old scallop produces an average of 16 million eggs.
  • The fertilized eggs develop into swimming larvae, complete with tiny shells.
  • Water currents distribute the larvae around the estuary. Mortality is very high during this stage of their life history.
  • After about 2 weeks, the larvae drop out of the water column and change into juvenile scallops, a process called metamorphosis.
  • During metamorphosis, a foot and gills develop, the swimming organ disappears, and the tiny scallops attach to seagrasses or other objects.
  • The foot, along with byssal threads, allows the juveniles to crawl up the grass blades.
  • The juveniles will remain attached until they reach a size of 20 – 30 mm (¾ – 1 ¼ in), when they drop to the bottom.
  • The foot fails to develop further, becoming a vestigial organ in the adults.
  • This is a short-lived species, with a life span of only 12 to 26 months.​

Fishing Tips:

Scalloping Tips:

  • The recreational season for catching black drum is an intense four to six week fishery from late April to early June and is usually concentrated on and around the spawning grounds west of Cape Charles.
  • The majority of black drum caught as part of the commercial or recreational fishery in the Bay are older, larger fish, with an average age in the Virginia fishery of over 20-years (CBP, 1994).
  • Because age distribution of this species varies greatly along the East Coast, southern fisheries mainly target younger, smaller fish, while northern fisheries target older, and larger fish.
  • For current recreational size and creel limits, see Maryland's updated regulation page.​

Fun Fact:
  • Unlike other species which are bound to some substrate either by burrowing or attachment, adult bay scallops are free-living and extremely motile.
  • They are capable swimmers for short distances, which they accomplish by jetting water through their valves, generally in response to predators.
  • Bay scallops have 18 pairs of blue eyes set in the mantle along the margin of the shell.
  • The eyes can detect shadows and movement, which brings about an escape response.
  • In an attempt to re-establish a population in Chincoteague Bay, MDNR Shellfish Program planted 1.2 million juvenile bay scallops in protective pens and raised them to reproductive age during1997 and 1998.
  • By 2002, live scallops were recorded north of the Ocean City Inlet, possibly for the first time in well over a century.
  • Although low densities suggest that the long-term viability of this scallop population is still in doubt, the extraordinarily rapid range expansion is a major step towards their establishment in Maryland.​

Phylum: Mollusca​

Family: Pectinidae
Order: Ostreoida
Class: Bivalvia

For more information on bay scallops, please contact Mitchell Tarnowski.