BLUE MUSSEL

The common mussel, scientifically known as “Mytilus edulis” and commonly referred to as the blue mussel due to its coloration is mainly found in the waters of the Atlantic Ocean. Let’s explore its main features and how it differs from the Mediterranean mussel.

Morphological characteristics of the Blue mussel

The Blue mussel, which can grow up to 9 cm in length, is characterized by a smooth, solid and inequilateral shell, with beaks at the anterior end, giving it an apparently triangular profile. The pallial line is broad; the upper margin is not particularly curved and appears almost straight and parallel to the lower margin, which has a rounded posterior edge and a lunule-shaped anterior edge.

The umbo is terminal, slightly pointed and curved.

The valves have:

• The sign of the posterior adductor muscle on the internal surface, which merges with that of the posterior retractor muscle, while the sign of the anterior adductor muscle is small and not very distinct;
• The ventral surface is not flattened behind the umbo;
• The outer surface shows concentric growth lines, covered by a shiny, thin periostracum.

The hinge line has no teeth but is made up of small crenulations, with 3 or 4 tiny teeth.

The most distinctive trait of this mollusk is its color polymorphism: in young specimens, the blue tones are less intense, whereas adult mussels can display a deep violet-blue color. The inside of the shell, on the other hand, is pearly white.

The history of the Blue Mussel

Mytilus edulis is one of the oldest known mollusk species. Just think that its origins date back to around 6000 BCE and, since then, it has been a staple in many traditional dishes.

Initially, mussels were used not only as food but also as bait for fishing and as natural fertilizers. They were harvested using traditional “bouchots”, vertical wooden stakes used for mussel and shellfish farming, a method that originated in the 13th century in France.

This technique spread widely along the entire French Atlantic coast, while countries in Northern Europe developed subtidal farming methods.

In the 1970s, traditional farming gradually gave way to the more innovative suspended culture system, known as “ropes,” which is still used today.

Blue mussel’s distribution and origin

The Blue mussel is primarily found along the coasts of the Atlantic Ocean, including:

• North America;
• Europe;
• The Northern Palearctic.

It can also be found from the White Sea in Russia down to southern France, as well as throughout the British Isles.

In the western Atlantic, it is present from the southern Canadian maritime provinces down to North Carolina.

Habitat, biology and fishing of the Atlantic Mussel

Atlantic mussels, like other mussel species, are highly resistant to various climatic and environmental conditions. Their ideal temperature range is between 5°C and 20°C, with a tolerance limit around 29°C.

They inhabit subtidal and intertidal beds on rocky coastlines, where they remain permanently attached.

Regarding reproduction, once the egg is fertilized, it develops into a larva, specifically into a veliger (a larval form typical of mollusks), which persists for about one to one and a half months.

It then enters the juvenile phase, during which it finds a settlement area, typically in crevices of rocky substrates, away from mature mussels. After a few weeks, it doubles in size and detaches from its initial location to find a new surface to permanently attach to.

The best time for spawning? Spring, as the larvae can benefit from phytoplankton blooms.

Additional Information, fun facts and data on Blue mussels

A very interesting fact is that each female mussel can produce up to 8 million eggs!

As for their lifespan, it varies depending on several factors. The primary one is the settlement location: mussels along coastal areas are more exposed to potential predators. Another key factor is the quality and stability of the surface they attach to. The most vulnerable life stages are the larval and juvenile phases (where the highest mortality rates occur).

How do they protect themselves? By forming clusters: this creates a protective barrier against predators through sheer numbers. Their shell also acts as a defense mechanism, even if some predators are capable of crushing it, causing the mussel’s death.

Predator attacks follow a very basic logic: they wait for the mussel to open its valves to breathe, then strike at the right moment.

The main difference between this species and the Mediterranean mussel is that the Blue one tends to be larger and has paler flesh.