The Aiguillon Bay

Operational action for the Aiguillon Bay

The Aiguillon Bay, located on the border of the Vendée and Charente-Maritime departments, is the outlet for the 600,000 ha of the Marais Poitevin catchment area. The current morphology of the bay is the result of dykes that have been successively built in the marshes over the centuries. Soil and marine influences induce and condition the more important environments found in the Aiguillon Bay, including salt marshes (1,100 ha) and mudflats (3,700 ha).

The Aiguillon Bay landscape – LIFE Baie de l'Aiguillon project

The Aiguillon Bay, the outlet for the 600,000 ha of the Marais Poitevin catchment area

A site used by an important number of migratory birds

ranked as one of the top five sites for ducks and waders

An area of economic importance

for shellfish farming and fishing due to its position at the interface between land and sea.

600,000 hectares of catchment area

drain into the bay and directly condition water quality.


 AN AREA OF HIGH PRIMARY PRODUCTION USEFUL TO BIRDS AND HUMANS

The Aiguillon Bay’s classification as a National Nature Reserve is due to its exceptional ornithological interest. Indeed, the French coast represents an important area on the East Atlantic migration route, and the Aiguillon Bay is a site of primary importance for waterbirds, this is a direct reflection of a rich, quality environment. Birds are undisturbed and find food. Thus, this site of international importance is used by large populations of waders and anatidae for wintering or as a stopover on migration.

Shellfish farming, especially mussel farming, is a traditional activity in the Aiguillon bay. It is practiced in particular on stakes, called locally “bouchots”. However, due to a gradual natural silting-up of the bay this activity tended to decline in the area during the 20th century. This phenomenon was accentuated in particular by the “bouchots” constituting sediment traps, and also by the abandonment of the most upstream concessions: firstly that related to “bouchots” (where mortality was the most important during the Mytilicola crisis in the 1960s) and then the oyster farming that replaced mussel farming in these areas.

These abandoned “bouchot” stakes and oyster tables serve as supports for the development of deposits of wild Pacific oyster Crassostrea gigas with a total weight estimated at 3,400 tons (IFREMER, 2012), spread over an area of about 240 ha, covering the mudflats naturally present in these areas.

Pacific oyster clusters on disused oyster tables © Thomas Jouanneau / PHONIC LIPS


 TOWARDS MORE NATURAL MUDFLATS

The objective of an intervention programme is therefore to experiment over 3 years with a methodology to test the removal of these piles of oysters and abandoned shellfish structures, in consultation with the shell-fishing profession, in order to return to the natural habitat of mudflats. This objective is part of the management plan of the Aiguillon Bay National Nature Reserve.

The aim is to restore at least 140 hectares of mudflats.

The areas of action included in the project are located on the Pointe de l’Aiguillon, around the Canal de Luçon and on the Charron mudflats.

 


SEVERAL PREREQUISITE STAGES

  • Carry out an inventory of the benthic fauna of those areas colonized by wild oysters and highlight the impact of these bivalves on the Baie de l’Aiguillon’s food chains. This work will be carried out through a contract with a research organization and requires the involvement of the reserve management.
  • Conduct a topographic study before and after work to assess its impact, in particular on sedimentary dynamics.
  • To carry out, with the chosen company, a time table of the work in order to fine-tune the areas of intervention, to apprehend the imponderables related to the intervention (accessibility by boat), to determine the phasing of the work (depending above all on the tidal coefficients and the weather).

The difficulties of accessing the mudflats, the age of the concessions and the lack of mapping require a strong investment of time before any work can be started. A preliminary inventory of benthic fauna is also required, as is the completion of the regulatory instructions for the proposed work.

At the end of the works, an assessment of the impact of the work, particularly in the area of sedimentation, will be carried out.

Study of oyster beds – Baie de l’Aiguillon LIFE

Study of oyster beds – Baie de l’Aiguillon LIFE

Oyster beds at the Pointe de Aiguillon

Oyster beds at the Pointe de Aiguillon

A SYMPOSIUM FOR THE RESTITUTUION OF RESULTS

A symposium on the theme “Restoration of coastal environmental functions in a shellfish farming area” took place on 28th and 29th October 2020.

These two days of meetings and exchanges allowed:

  • to review current knowledge of the roles and functions of the coastline within the shellfish farming context
  • to present the results of the restoration work on the Baie de l’ Aiguillon mudflats
  • to present the results of various French, European and American experiments in the restoration of estuarine areas.

All the presentations were filmed and are available on the dedicated page.

More information here, here and here.


BENTHIC WILDLIFE SURVEY AND SEDIMENT ANALYSIS

An inventory of benthic fauna, sediment particle size analyses and measurements of organic matter prior to experiments with “crassat” removals were carried out. Jérôme Jourde, a specialist in the taxonomy of marine macro-invertebrates was in charge of this study. Jérôme Jourde’s report is available for downloading on this site, in the “Studies” section. The same inventory and analyses of sediments have been carried out during spring 2021 and will soon be analysed.

More information can be found in the news section and biological monitoring page..

STUDY OF THE BAIE DE L’AIGIULLON’S TOPOGRAPHY

The company Opsia carried out a study of the Aiguillon Bay’s topography. A digital field model was produced. This public data is available on request from the Marais Poitevin Natural Regional Park.

More information in the news section.

A second topographical survey will be done in autumn 2021 to evaluate the influence of the works on sedimentation.

PROGRESS OF OYSTER BED REMOVAL WORK

Private tendering was launched in July 2017. The chosen company is Trézence TP. The first phase of mudflat restoration began in September 2019 and was completed on 25th February, 2020.

During this first phase of work:

  • 3.1 hectares of tables and oysters have been removed
  • a length of 6704 metres of tables and oysters have been removed
  • about 32 hectares of mudflats have been restored
  • more than 11 tons of scrap metal have been brought ashore

More information here and here.

The second phase of work began in October 2021 until February 2021, during which:

  • 3.8 hectares of tables and oyster shells were removed
  • approximately 80 hectares of mudflats were restored
  • 20 tons of scrap metal were brought ashore

More information here.

 

Sampling mud and Pacific oysters at oyster beds

Sampling mud and Pacific oysters at oyster beds

Ancient oyster tables in the Baie de l’Aiguillon

Ancient oyster tables in the Baie de l’Aiguillon

Oyster bed removal work

Oyster bed removal work


AIGUILLON BAY: MUDFLAT RESTORATION

 

Withdrawal of oyster beds from the Pointe de l’Aiguillon sector at the end of the 2 construction phases.

Removal of oyster beds from the Charron sector at the end of the 2nd phase of the work.