Great Scallop

The shell of Pecten maximus is quite robust and is characterised by having "ears" of equal size on either side of the apex. The right, or lower, valve is convex and slightly overlaps the flat left, or upper, valve. Larger specimens have a nearly circular outline and the largest may measure 21 cm in length. The "ears" are prominent and are a minimum of half the width of the shell, with the byssal notch situated in the right anterior ear being slight and not serrated. The sculpture of the valves is distinctive and consists of 12 to 17 wide radiating ribs and numerous concentric lines, which clearly show the scallop's growth history, while the "ears" show a few thin ribs, which radiate from the beaks. The radiating ribs reach the margins of the valves and this creates a crenulated form.

Pecten maximus occurs in the eastern Atlantic along the European coast from northern Norway, south to the Iberian Peninsula, it has also been reported off West Africa, off the Macaronesian Islands. In Great Britain and Ireland it is distributed all round the coast but it is uncommon and localised on the eastern North Sea coast. It prefers offshore waters down to 100 metres (330 feet; 55 fathoms) depth.

As well as the starfish species Asterias rubens and Astropecten irregularis, major predators of Pecten maximus are crabs such as Cancer pagurus, Carcinus maenas, Liocarcinus depurator and Necora puber, which will prey on the scallops as they grow. The anemone Anthopleura ballii was found preying on young specimens of P.maximus in south-western Ireland.

The larvae of Pecten maximus are attacked by the bacterium Vibrio pectenicida, which was described in 1998 as a new species after incidents of mortality among cultured scallops in France in the early 1990s. Other strains of pathogenic bacteria were detected in Norway following mass mortality of larvae in culture.

In 1999 the total catch reported by the United Nations Food and Agriculture Organisation was 35,411 tonnes with the two biggest catches being reported from the United Kingdom and France which landed 19,108 tonnes and 12,745 tonnes respectively. It is believed that some natural stocks are showing indications of over exploitation resulting in strict enforcement of fisheries legislation and by the development of stock enhancement practices. Great scallops are fished for using Newhaven scallop dredges, and less than 5% is gathered by hand by divers. In total the scallop fisheries for P. maximus and for the Queen scallop Aequipecten opercularis are one of the top five fisheries by value in United Kingdom waters. However, the use of towed gear to harvest scallops causes damage to the wider ecosystem.