Scallops are bivalve molluscs living unattached on sandy seabeds. The edge of the mantle shows dozens of tiny blue eyes that serve to detect their natural enemies (crabs, starfish). The shells can swim by powerfully opening and
closing their valves. Scallops are hermaphrodites. The edible meat consists for ¾ of the adductor meat (the creamywhite part) and ¼ of the coral (roe) which usually has 2 colors: cream = seed; red = eggs.
The Peruvian scallop (Argopecten purpuratus) is farmed in a completely natural way, in the open sea. The shells merely feed on the plankton they filter out of the seawater. The largest production area is Sechura Bay, in the north of the country. There are about a hundred zones (concessions) in this area, recognized by the EU and monitored by the Peruvian government. The ocean water here is pure and has a lot of current so there are many nutrients in the water. However, production suffers strongly from the natural phenomenon El Niño that occurs every 3 to 7 years. It causes an unusual, strong warming of the ocean water. The negative effect of El Niño on production lasts 2 to 3 years. In Peru two different types of farming are practiced.
Bottom farming, which accounts for 80% of production, requires little investment and it’s rather a passive system. The larvae or 'spat' (<1 cm) are 'sown’ up to 20 m deep in rectangular zones which are delineated with buoys and nets.
The growth is strongly determined by the condition of the water, the natural food availability, currents, diseases and natural enemies. The scallops are ready for harvest after about 1 year. They are hand‐harvested by divers who gather the shells from the bottom of the ocean.
Another method is lantern farming. This technique uses lantern nets consisting of 10 compartments. The nets are attached to longlines with buoys, They are lowered to an ideal breeding depth. This method is more expensive than bottom farming but has many advantages: the concession is used optimally, growth is better and there is less risk of natural enemies. The shells also contain less sand. The nets are removed from the water every 3‐4 months for cleaning. On a floating platform, the shells are then sorted by hand and again stored in the nets according to size. Here the harvest is done by boat and crane.
After the harvest the shells are loaded alive into refrigerated trucks and taken to the factory where they are cleaned and processed. Depending on the desired end product, one shell is removed (half shell) or only the meat is shucked (with or without roe). There is no significant difference between the end product of bottom or lantern farming.