The trips took place in June and September during neap tides.

The study area is divided into 15 sampling units, each composed of at least 20 traps set on a line and evenly distributed from north to south of the Flamanville power station. All the lines were positioned by the fisherman the day before the first day of the mission according to the geographical coordinates defined beforehand (same coordinates since 1995).

At each station and during the four days of the mission, biological observations on the fauna caught were noted for the main species of crustaceans (spider, curry, lobster, edible crab), whelks and pagurids. The other species, known as by-catch and represented mainly by fish, are not recorded.

The overall objective of each mission is to carry out a minimum of 800 trap lifts out of a maximum of 2040.

The machine used is a semi-cylindrical trap of the artisanal type, approximately 40 cm high, 50 cm wide and 70 cm long.

A line is made up of 20 or 30 traps spaced about 20 metres apart, forming a unit of about 500 metres with a total weight of 550 kg. The bait used is frozen horse mackerel.

• Sampling plan(s) :

Sampling confined to the same geographical area.

Since 1978 the 15 lines have not always been positioned at the same locations, but it is possible to distinguish at least three periods for which there are stations fairly close to each other. For the first ten years, the positions were defined by landmarks. Following the use of the G.P.S. in 1990, the mooring points of the traps were recorded and since 1995 they have been rigorously identical from one year to the next.

All the lines are systematically surveyed every day during the four days of the campaign, but there is no pre-established order in which the stations are set up. This is a function of the tide, the main component in this region where the current can reach 6 knots in neap.

As far as possible, and depending on the weather conditions, the lines are surveyed every day for four days and re-routed within a radius of 500 metres of the initial point. This is to avoid fishing out individuals caught and released the day before. Thus, except in bad weather conditions, the fishing time does not exceed 24 hours.

• Precision on the type of data:

Each individual of the reference species is identified and kept on board until the various biological parameters are collected on a catch form. The individuals are then returned to the water at the capture site or during the journey to the next point.

The observations are grouped together, taking the line as the main unit.

From 2002, lobsters caught in the reserve are marked before being released in the area. The tag is attached to the joint of a clamp using a polyamide cable tie. The variables are entered on a specific form where each lobster caught is identified by trap and tag number.

Pagurids and whelks are systematically counted despite the fact that the selectivity of the gear used is poorly adapted to their capture.

• Parameter(s) observed or measured :

Biological data observed for crustaceans (except pagurids) concern size, sex, presence of eggs, maturity of spiders and hardness of the carapace of the curry.

Measurements of cephalothoracic, orbital or transverse lengths, depending on the species, are taken to the nearest mm. They are taken with a caliper except for the edible crab, which is measured with a ruler. The biological status codes of the individuals (sex, maturity (Le Foll, 1993), state of the carapace).

No weighing is carried out, but the weight of the lobsters is calculated from a size-weight relationship developed in 1983 by the biologists of the Comité Régional des Pêches et Cultures marines de Bretagne (CORPECUM), the Comité Local des Pêches de Blainville, and the ISTPM stations in Roscoff and Ouistreham, and used since then for the whole of the western Channel.

• Resolution of the parameter(s) :

Quantity, quality

• Format(s):

The data are not yet banked in the HIS database.