Quatre ans de mesures volumetriques de plancton total dans le Golfe de Gascogne (1964-1967)

This work is about 14 seasonal campaigns carried out by the oceanographic ships Thalassa, La Pélagia and Roselys in the Gulf of Gascony and the Celtic Sea. It aims to highlight the seasonal quantitative variations of planktonic harvests according to the temperature of the waters. In 1964, four campaigns took place: February (98 stations), May (104 stations), August (101 stations) and November (104 stations), which cover an extensive site, from the headlands of Cornouaille to Cape Finisterre. In 1965, the number of stations was fewer: approximately 22 for each campaign. In 1966 (March: 94 stations, May: 99 stations) and 1967 (March: 125 stations, May: 135 stations, August: 140 stations, November: 134 stations) the sector studied does not include the Celtic shelf and only involves the French continental shelf. On the whole, for these four years, 1,190 stations were prospected, which represents more than enough material to authorise a quantitative use of the type we intended. Two sorts of fishing techniques were used: vertical passes using a Hensen net reeled in between 100 metres and the surface at the rate of 1 metre in three seconds (1964, 1965, May 1966,1967); horizontal surface passes for 10 minutes using a standard net, 30 cm opening (March 1966). The volumes of plankton are measured by displacement. The results are provided for 10 cubic metres of filtered seawater in the form of seasonal maps set up in two ways: the areas of concentration are delineated by contour lines for 1964, 1966 and 1967; for 1965, they are represented by squares proportional to the harvests, the network of stations was too restricted to allow the building of large contour lines. In spite of the large differences of station setup, we will compare the results of these four years of prospecting and also try to bring out the big picture of the plankton's geographic, seasonal and nycthemeral distribution and its possible links with the thermal factor.