Seafood of the Week - Mussels

A bed of blue mussels

Mussel is the common name used for members of several families of clams or bivalvia mollusca, from saltwater and freshwater habitats. These groups have in common a shell whose outline is elongated and asymmetrical compared with other edible clams, which are often more or less rounded or oval.
The word "mussel" is most frequently used to mean the edible bivalves of the marine family Mytilidae, most of which live on exposed shores in the intertidal zone, attached by means of their strong byssal threads ("beard") to a firm substrate. A few species (in the genus Bathymodiolus) have colonised hydrothermal vents associated with deep ocean ridges.
In most marine mussels the shell is longer than it is wide, being wedge-shaped or asymmetrical. The external colour of the shell is often dark blue, blackish, or brown, while the interior is silvery and somewhat nacreous.
The common name "mussel" is also used for many freshwater bivalves, including the freshwater pearl mussels. Freshwater mussel species inhabit lakes, ponds, rivers, creeks, canals, and they are classified in a different subclass of bivalves, despite some very superficial similarities in appearance.
Freshwater Zebra mussels and their relatives in the family Dreissenidae are not related to previously mentioned groups, even though they resemble many Mytilus species in shape, and live attached to rocks and other hard surfaces in a similar manner, using a byssus. They are classified with the Heterodonta, the taxonomic group which includes most of the bivalves commonly referred to as "clams".





The mussel's external shell is composed of two hinged halves or "valves". The valves are joined together on the outside by a ligament, and are closed when necessary by strong internal muscles. Mussel shells carry out a variety of functions, including support for soft tissues, protection from predators and protection against desiccation.

The Asian green mussel

The shell has three layers. In the pearly mussels there is an inner iridescent layer of nacre (mother-of-pearl) composed of calcium carbonate, which is continuously secreted by the mantle; the prismatic layer, a middle layer of chalky white crystals of calcium carbonate in a protein matrix; and the periostracum, an outer pigmented layer resembling a skin. The periostracum is composed of a protein called conchin, and its function is to protect the prismatic layer from abrasion and dissolution by acids (especially important in freshwater forms where the decay of leaf materials produces acids).
Like most bivalves, mussels have a large organ called a foot. In freshwater mussels, the foot is large, muscular, and generally hatchet-shaped. It is used to pull the animal through the substrate (typically sand, gravel, or silt) in which it lies partially buried. It does this by repeatedly advancing the foot through the substrate, expanding the end so it serves as an anchor, and then pulling the rest of the animal with its shell forward. It also serves as a fleshy anchor when the animal is stationary.
In marine mussels, the foot is smaller, tongue-like in shape, with a groove on the ventral surface which is continuous with the byssus pit. In this pit, a viscous secretion is exuded, entering the groove and hardening gradually upon contact with sea water. This forms extremely tough, strong, elastic, byssus threads that secure the mussel to its substrate. The byssus thread is also sometimes used by mussels as a defensive measure, to tether predatory molluscs, such as dog whelks, that invade mussel beds, immobilising them and thus starving them to death.
In cooking, the byssus of the mussel is known as the "beard" and is removed before the mussels are prepared.






Marine mussels are abundant in the low and mid intertidal zone in temperate seas globally. Other species of marine mussel live in tropical intertidal areas, but not in the same huge numbers as in temperate zones.

Bouchots are marine pilings for growing mussels

Certain species of marine mussels prefer salt marshes or quiet bays, while others thrive in pounding surf, completely covering wave-washed rocks. Some species have colonized abyssal depths near hydrothermal vents. The South African white mussel exceptionally doesn't bind itself to rocks but burrows into sandy beaches extending two tubes above the sand surface for ingestion of food and water and exhausting wastes.
Freshwater mussels inhabit permanent lakes, rivers, canals and streams throughout the world except in the polar regions. They require a constant source of cool, clean water. They prefer water with a substantial mineral content, using calcium carbonate to build their shells.






 Freshwater mussels are used as host animals for the cultivation of freshwater pearls. Some species of marine mussel, including the Blue Mussel (Mytilus edulis) and the New Zealand green-lipped mussel (Perna canaliculus), are also cultivated as a source of food.
In some areas of the world, mussel farmers collect naturally occurring marine mussel seed for transfer to more appropriate growing areas, however, most North American mussel farmers rely on hatchery-produced seed. Growers typically purchase seed after it has set (about 1mm in size) or after it has been nursed in upwellers for 3-6 additional weeks and is 2-3mm. The seed is then typically reared in a nursery environment, where it is transferred to a material with a suitable surface for later relocation to the growing area. After about three months in the nursery, mussel seed is “socked” (placed in a tube-like mesh material) and hung on longlines or rafts for grow-out. Within a few days, the mussels migrate to the outside of the sock for better access food sources in the water column. Mussels grow quickly and are usually ready for harvest in less than two years. Unlike other cultured bivalves, mussels use byssus threads (beard) to attach themselves to any firm substrate, which makes them suitable for a number of culture methods. There are a variety of techniques for growing mussels.

 In roughly 12-15 months, mussels reach marketable size (40mm) and are ready for harvest (FAO). Harvesting methods depend on the grow-out area and the rearing method being used. Dredges are currently used for on-bottom culture. Mussels grown on wooden poles can be harvested by hand or with a hydraulic powered system (FAO). For raft and longline culture, a platform is typically lowered under the mussel lines, which are then cut from the system and brought to the surface and dumped into containers on a nearby vessel. After harvest, mussels are typically placed in seawater tanks for depuration before marketing.






Humans have used mussels as food for thousands of years and continue to do so. About 17 species are edible, of which the most commonly eaten are Mytilus edulis, M. galloprovincialis, M. trossellus and Perna canaliculus.

Mussel Stew

Freshwater mussels nowadays are generally considered to be unpalatable, though the native peoples in North America ate them extensively. During the second World War in the United States, mussels were commonly served in diners. This was due to the unavailability of red meat related to wartime rationing.
In Belgium, the Netherlands, and France, mussels are consumed with french fries ("mosselen met friet" or "moules-frites") or bread. In Belgium, mussels are sometimes served with fresh herbs and flavorful vegetables in a stock of butter and white wine. Frites/Frieten and Belgian beer sometimes are accompaniments. In the Netherlands, mussels are sometimes served fried in batter or breadcrumbs, particularly at take-out food outlets or informal settings. In France, the Éclade des Moules is a mussel bake that can be found along the beaches of the Bay of Biscay.
In Italy, mussels are mixed with other sea food, they are consumed often steam cooked (most popular), sometimes with white wine, herbs, and served with the remaining water and some lemon. In Spain, they are consumed mostly steam cooked, sometimes boiling white wine, onion and herbs, and served with the remaining water and some lemon. They can also be eaten as "tigres", a sort of croquette using the mussel meat, shrimps and other pieces of fish in a thick bechamel then breaded and fried in the clean mussel shell. They are used in other sort of dishes such as rices or soups or commonly eaten canned in a pickling brine made of oil, vinegar, peppercorns, bay leaves and paprika. In Turkey, mussels are either covered with flour and fried on shishs ('midye tava'), or filled with rice and served cold ('midye dolma') and are usually consumed after alcohol (mostly raki or beer). They are used in Ireland boiled and seasoned with vinegar, with the "bray" or boiling water as a supplementary hot drink. In Cantonese cuisine, mussels are cooked in a broth of garlic and fermented black bean. In New Zealand, they are served in a chili or garlic-based vinaigrette, processed into fritters and fried, or used as the base for a chowder. In India, mussels are popular in Kerala, Maharashtra, Karnataka-Bhatkal, and Goa. They are either prepared with drumsticks, breadfruit or other vegetables, or filled with rice and coconut paste with spices and served hot. Fried mussels ('Kadukka' in Malayalam) of north Kerala are a spicy, favored delicacy.

Mussel Dish

Mussels can be smoked, boiled, steamed, roasted, barbecued or fried in butter or vegetable oil. As with all shellfish, except shrimp, mussels should be checked to ensure they are still alive just before they are cooked; enzymes quickly break down the meat and make them unpalatable or poisonous after dying or un cooked.[citation needed]Some mussels might contain toxins. A simple criterion is that live mussels, when in the air, will shut tightly when disturbed. Open, unresponsive mussels are dead, and must be discarded. Unusually heavy, wild caught, closed mussels may be discarded as they may contain only mud or sand. (They can be tested by slightly opening the shell halves.) A thorough rinse in water and removal of "the beard" is suggested. Mussel shells usually open when cooked, revealing the cooked soft parts.
Although mussels are valued as food, mussel poisoning due to toxic planktonic organisms can be a danger along some coastlines. For instance, mussels should be avoided along the west coast of the United States during the warmer months. This poisoning is usually due to a bloom of dinoflagellates (red tides), which contain toxins. The dinoflagellates and their toxin are harmless to mussels, even when concentrated by the mussel's filter feeding, but if the mussels are consumed by humans, the concentrated toxins cause serious illness, such as paralytic shellfish poisoning.