Moules de Bouchot (Rope grown mussel)

From Cookipedia

Moules de Bouchot


STG 'Moules de bouchot' are French, cultivated mussels produced exclusively on stakes on the foreshore from larvae caught in their natural habitat. It does not cover mussels that are fished or cultivated in other ways. To qualify as ‘Moules de bouchot’ STG, the mussels must be fresh, live and intact. Two species are cultivated to produce ‘Moules de bouchot’: Mytilus edulis and Mytilus galloprovincialis (or crosses between the two). These species are selected for their ability to thrive:

— in the cultivation conditions on the foreshore set out in this specification

— with methods and a period of cultivation that ensure the products’ specificity and consistency

The anatomical and organoleptic characteristics of ‘Moules de bouchot’ are due both to the species itself and also to the particular production method.

Physical characteristics:

The shell consists of two smooth, regular-shaped halves which are dark brown to slate blue and have concentric striations showing their growth. The minimum shell thickness is 12 mm. The mussels are characterised by two specific organs: a ‘foot’, enabling movement of the mussel, and a gland producing byssus (threads whereby it fixes itself to a surface). Producing the mussels on stakes on foreshores regularly exposed by the outgoing tide means that:

— they develop strong adductor muscles to keep the shell closed when the tide is out

— the shell is more resistant and solid when the mussels are harvested because it is hardened by frequent exposure to the open air and the sun

A distinctive feature of mussels produced on stakes is the flesh-to-shell ratio, consistently high among mussels belonging to the same batch. This ratio is measured on the Lawrence and Scott indicator scale, with ‘Moules de bouchot’ scoring 100 or more. Also, ‘Moules de bouchot’ contain no foreign bodies (such as crabs or grains of sand) and have clean shells (no algae, slime or sand), because a gap of at least 30 cm is left between the ground and the bottom of the ropes or net coils on the stakes.

Organoleptic characteristics:

When cooked, the mussel flesh is a cream to yellow colour, more or less orangey depending on the mussels’ diet (the presence of carotene and vitamin A in the phytoplankton) and physiological (reproductive) stage. The mussel flesh is smooth, silky and not floury; this is due to the production method making the mussels more resistant to air exposure (when packaged, transported, stored and put up for sale). The production method also means that the mussels are not in contact with the ground and are therefore not affected by unpleasant tastes or smells (e.g. from slime).

Production method:

Fixing the stakes:

The mussels are bred in plots or parts of plots in cultivation areas on the foreshore. These are parts of the shoreline affected by wave movements and consisting of the section between the high tide and low tide marks, the width of which is proportional to the gradient of the shoreline when the tide is at its highest. The stakes are arranged in a series of rows running down from the top of the foreshore. The rows at the top form a storage area for mussels that are big enough for human consumption. Each plot contains parallel lines of vertical stakes at right angles to the coastline.

Catching and transporting the larvae:

The mussels go through the following stages of development:

larva: still small enough to move about. Larvae caught on collectors (hemp and/or coconut fibre ropes) can still detach themselves, either by sliding along using their foot or by letting themselves float in the water column

spat: firmly fixed to a collector prior to being transferred to the stakes

juvenile: surplus spat removed and put into net tubing that is then wound around a stake (a process known as boudinage)

young mussel: the mussel after the spat or juvenile has been definitively fixed to the stake

Catching mussel larvae on collectors:

This, a preliminary stage to the actual cultivation of the ‘Moules de bouchot’, involves getting the mussel larvae to gather on collectors (specially adapted natural supports made of natural biodegradable fibres). Catching takes place in suitable areas along the coast that are designated and recognised by the competent authorities of the country in question and precisely delineated in a maritime cadastre. The sites have high natural concentrations of mussel larvae brought in by sea currents. The larvae can also be caught directly on the stakes.

Transporting mussel larvae on collectors:

Many cultivation areas have no catching grounds in the immediate vicinity. In these cases, the collector ropes have to be brought in from the catching grounds. Once firmly in place, the larvae develop into spat, growing either on the ropes in holding areas in the cultivation area or directly on the stakes.

Cultivation and harvesting:


Seeding involves coiling the spat ropes and fixing them to the stakes. It can also refer to the coiling around the stakes of net tubing (boudins) containing the spat. The juveniles grow from spat cultivated on the site and taken from the surplus from other stakes seeded in the same production year. If, exceptionally, there is a shortage of larvae on the ropes, the competent authorities of the country in question may authorise that the juveniles (to be put into the net tubing) be caught from natural grounds subject to the health supervision rules applied by that country to production sites. Under no circumstances may hatchery or nursery products be used. The mussels are cultivated on stakes in plots or parts of plots on the foreshore. ‘Moules de bouchot’ are cultivated on vertical stakes of a maximum height of 6 metres (part of which is in the ground), which cannot be moved once the spat is secured. The height of the seeded part of the stake is restricted to 3,5 metres. A minimum 30 cm gap is left between the ground and the bottom of the ropes or net coils when they are fixed to the stakes.

Cultivation: This stage — from when the mussels are put onto the stakes to the start of preparations for sale — takes from a minimum 6 to as many as 24 months. Cultivation first involves placing the right number of individual mussels on the stakes. The mussels in the outer layer grow more quickly than those near the stake. The mussels may be transferred to new stakes during the growth period: the outer layer of mussels is collected and put into net tubing, which is then coiled around a new stake. This is known as boudinage. This can take place several times in the course of the mussels’ growth. The resultant coils are generally fixed to the stakes towards the top of the foreshore.


Harvesting takes place after the cultivation process. It involves removing clumps of mussels from the stakes and may be done by hand or by machine. Picking up fallen mussels from the foot of the stake is not allowed.

The tradition of cultivating mussels on stakes goes back to 1235. The story has it that an Irishman, Patrick Walton, was shipwrecked that year in the Bay of Aiguillon; ‘... the only person saved, he settled in Esnandes and lived off birds he would snare in a special (allouret) net stretched above the water between two large poles embedded in the seabed. He soon noticed that mussels gathering on the poles grew bigger and were of a superior quality to wild mussels. He then decided to try to cultivate the molluscs.’ (Marteil, 1979). To this end, he set up lines of stakes on which the mussels could gather and grow. He called the stakes bouchots, ‘a word of Celtic origin stemming from bout (closure) and choat/chot (wooden stake)’. (Marteil, 1979). This form of cultivation is still practised today on the same principles. The equipment has evolved a little thanks to certain technical developments.

Over the centuries since, the handful of writers who have taken an interest in mussel farming have emphasised that Patrick Walton’s techniques have altered very little. For example, Coste wrote in 1855 that ‘the techniques that he [Walton] instituted were so well suited to the ongoing needs of the new industry that almost eight centuries later they are still common practice for the communities whose heritage they have become.’ After 1930, the traditional poles were replaced by stakes (more solid lengths of tree trunk that are thicker than the poles, which also did not last very long).

Changes were made to the cultivation areas after 1950 as a consequence of the first decrees regulating mussel farming. They came under the ownership of the state, which issued licences for their use and supervised them; stakes could no longer be arranged in a ‘V’ shape as this leads to a build-up of slime. Since then, the stakes have been arranged in parallel lines at right angles to the coastline. Setting up stakes is regulated; the rules vary from one region to another depending on local conditions — the immediate surroundings, the type of beach, sea currents, presence of nutritional elements, etc.

The mussels are cultivated strictly in their natural surroundings. They are still fertilised naturally in the sea without human involvement, feed exclusively on natural, living phytoplankton and no chemical treatment is used in their marine environment during their growth.

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