The range of the Atlantic sea scallop extends from the Gulf of St. Lawrence to Cape Hatteras. Individuals can live up to 20 years and grow in shell height to roughly 9" (22cm) (Hart and Chute, 1994). Sexes are separate, and individuals reach sexual maturity at age 2, although egg and sperm production is fairly low until age 4. Scallops are broadcast spawners, with sperm fertilizing the egg in the water column.
In the Gulf of Maine, spawning occurs generally in July and August, with evidence of semi-annual spawning along at least part of the range (Thompson et al 2014).In Maine, settlement generally peaks during the last two weeks of September and the first week of October.
Larvae undergo several developmental stages before going through metamorphosis and settlement at approximately 45 days post-fertilization. Newly settled larvae are usually smaller than 250 microns(0.25mm) in size, and will grow slowly through the winter, becoming 3–10 mm typically by the following March–May.
Sea scallops are active swimmers, especially when small, and can move 2+m during a single swimming event, although swimming becomes more inefficient over approximately 80mm.
The force for valve contraction during swimming is generated in the single adductor. The muscle itself is comprised of two parts: a larger ‘quick’ muscle that is responsible for the rapid contractions used in swimming and a smaller, slower-acting ‘catch’ muscle that keeps the shell closed for longer periods of time in part to defend against predation. Adductor muscles gain in mass more quickly as the animal passes approximately100mm shell height (Hennen and Hart, 2012),and fisheries usually target larger individuals.
Scallops feed on phytoplankton and detrital matter, similar to other species of filter feeders like oysters and mussels. Flow rate, such as from tides and currents, impacts feeding ability, and rates above 10 –20cm sec2 (0.2 to 0.4 knots) can inhibit feeding.
Scallops are subject to several pests and predators in the natural environment. Principal predators are sea stars (Asterias sp.), crabs (Carcinus maenas, Cancerirroratus, C. borealis) and lobster (Homarus americanus), though much of this predation can be reduced in culture and with proper attention to husbandry.
Pests include fouling organisms like colonial and solitary tunicates, or ‘sea squirts’ (Ciona intestinal is, Botryllus schlosseri, Botrylloides violaceous, Molgulamanhattanensis, Styela clava and Ascidiella adspersa),the hydrozoan Tubellaria, and settling shellfish such as blue mussel (Mya are aria), jingle shells (Anomiasimplex), and barnacles (Balanus sp).
Shell-boringpolychaetes such as Polydora websteri, and boringsponges (Cliona sp) can cause damage to the shell and can reduce condition index—a measure of the overall health of the scallop, by comparing weight of tissues like the meat, roe, and viscera—when infestations become severe.
Fouling by encrusting organisms is likely to be higher in suspension culture, such as ear-hanging, as compared to cages or nets, where the combination of filtration and scallop movement helps to keep the shells somewhat cleaner.