Sea surface temperature along the northern coast of the Gulf of Guinea drops abruptly twice a year, with a moderate decrease in boreal winter and a greater one in summer. Several mechanisms have been proposed to explain these coolings: Ekman upwelling due to local wind, remote wind forcing in the western Atlantic, geostrophic adjustment to the Guinea current variations or eddies created by headlands in the current. The resulting seasonally-induced plankton production has led to the development of pelagic fisheries, with dramatic increases in Sardinella aurita catches in Cote d'Ivoire and Ghana during the last decade and new spatial and seasonal distributions. A study to account for these changes was undertaken on the basis of wind and temperature data recorded by merchant ships from 1964 to 1990 and coastal temperature measurements from 1978 to 1990. During the study period, pseudo-wind stress increased by 0.23 (m2/s2)/year and sea surface warming by about 0.03-degrees-C/year. The main changes occurred during the 1980s; in coastal waters, warming was very marked in the western area (0.069-degrees-C/year), even during the cold seasons, and the eastern side experienced a slight cooling (-0.034-degrees-C/year). The latter change is compared to westerly wind intensification (increased speed and slight rotation) which should have enhanced Ekman pumping. These developments are viewed in the context of recent data concerning warming in tropical regions, controversial increased speed of trade winds and changes in oceanic circulation. More frequent Ekman upwelling events in the east of the Ivorian gulf might have favoured an expansion of the S. aurita stock of Ghana towards the Cote d'Ivoire. This possibility does not exclude the hypothesis of a circulation change which has been proposed to explain the settlement of sardinelles up to the western side of the gulf.