King Scallop- Pecten Maximus
King Scallops are one of the most iconic and well known bivalve species found in Scottish waters. Scallops have huge commercial worth and are the second most valuable shellfish species landed in Scotland. In 2013, 12,448 tonnes of scallops were landed with a value of £23.3 million.
King scallops are also known as great scallops or St James Shell, due to the fact that in ancient times, pilgrims to the shrine of St James in Santiago de Compostela, Spain carried a scallop shell with them. They could expect to receive as much food as they could gather from one scoop of the shell at households along their journey.
Scallops are commonly found in hollows on the seabed in gravel or sandy habitats. They are opportunistic filter feeders, gathering particles of organic matter and phytoplankton in through their filtering structure found along the mantle of their shell. Predators of scallops include starfish, crabs and cephalopods. They are very adept at jetting away from harm by rapidly opening and closing their two shells together. Scallops open and close their shell using the adductor muscle, which is the part most commonly consumed.
Their ability to sense harm is facilitated by tiny blue light sensors embedded around the edge of their shell. Scallops are thought to have the most complex retina of any bivalve. Their ‘eyes’ (which can only detect light and not movement) are actually made up of two different types of retina, one which detects light and another which detects sudden darkness- like the shadow of an approaching predator. The commercial scallop fishery originated in Scotland in the Clyde during the early 1930s and rapidly developed in the 1960s and 1970s. Around Scotland, 95 % of King Scallops are caught by dredgers. A dredge is a type of fishing gear which targets bottom-dwelling species. Scallop dredges consist of a steel frame with rake like teeth at the front, attached at the back there is a chain mesh which acts as a net. Dredges are normally towed along the side of the vessel, ploughing up the seabed as they go to capture buried scallops. They operate in both inshore and offshore waters. The other 5 % of scallops landed in Scotland are caught by hand by commercial divers. King Scallops are hermaphroditic. Eggs and sperm are fertilised externally, and tiny free-living larvae are formed. After around 30 day’s growth, the larvae will settle on suitable substrate and attach themselves using byssal threads (like those found in mussels). They will remain in this state till they are about 13 mm in length, when they detach and settle on the seabed. Scallops can live for up to 20 years, and become reproductively active at 3-5 years, or when they are at least 60 mm in length. King scallops commonly grow to a size of 150-210 mm width.
COAST are against the use of scallop dredgers in inshore waters due to the habitat damage sustained to the seabed and to important marine plants and animals, such as maerl. Maerl is a very slow growing seaweed, which has an unusual coral like structure. It provides a great nursery habitat for juvenile species and bivalves, urchins, sea cucumbers and other species love to burrow underneath it. Maerl is destroyed by dredgers. When buying scallops, hand dived are the most sustainable option.
Latin name: Pecten Maximus
Habitat: Benthic species, living in gravel or sand. Can live up to depths of 100m.
Distribution: Western Europe
Size: 150-210 mm width