The reproduction of the plaice has been studied in the North Sea (Wimpenny, 1949; Barr, 1963), in the eastern and western English Channel (Houghton & Harding, 1976) as well as in the bay of Douarnenez (Deniel, 1981). In 1972, Lahaye described the sexual cycle of the plaice caught in the Portsall area.
After the wreck of the ‘Amoco Cadiz’ off Brittany in March 1978, more diversified studies of this species were made to assess the effects of the oil spill on the plaice stocks in the contaminated area. In Lannion and Morlaix Bays, these fishes exhibited a clear decrease of growth, fin necrosis and an absence of recruitment in the population in 1978 (Desaunay, 1981; Maurin, 1984). In the Abers Wrac'h and Benoit, estuaries of the north-west coast of Brittany (Fig. 1) which were gravely affected by the oil spill, Haensly & Neff (1979) and Miossec (1981, 1984) noted a big change in reproduction. Conan & Friha (1981) observed abnormally low growth for plaice in Aber Benoit.