The direct assessment consists of taking sediment samples from the entire classified deposit with a specific device following a standardised sampling protocol, applied since 1997 (Berthou et al., 1998), modified in 2003 (Péronnet et al., 2003) by eliminating replicates.

The methodology is standardised. Sampling is carried out with a Hamon bucket, the bucket of which can trap 0.25 m2 of sediment.

Sampling was carried out from the 17 m long oyster farming vessel "Le Corto", equipped with a powerful hydraulic crane to manoeuvre the bucket and with a draught of less than 1 m. This barge was chartered by the CLPMEM for the duration of the campaign. The campaign took place with coefficients between 44 and 88, and the samples were taken over a period of six hours (three hours before and three hours after high tide).

Once collected, the clams were washed and sieved on three sieves with a square mesh of 20, 10 and 5 mm. The clams are measured individually in the direction of the largest dimension. They are weighed in batches corresponding to the harvesting conditions (commercial >35mm/non-commercial <35mm).

Currently only data from the 1996, 1997 and 2001 to 2012 seasons are available.

Cruise reports are available at https://archimer.ifremer.fr/.