A contribution to the study of surface and subsurface zooplankton in the Strait of Sicily

Abstract

Analysis of 71 hauls of plankton in the Strait of Sicily, from 2 February to 16 March 1966, enabled us to make a systematic, quantitative and ecological study of all zooplankton systems present. A synthesis was made, from the point of view of hydrology and of the study of currents, of all the work performed by the Bureau d'Etudes Oc~anographiques. This showed that in the Strait of Sicily species of Atlantic origin are fished in greater numbers i n those places where the influence of the Atlantic water is most felt. Among these species, twclYe Copepoda and one Mollusc were the first ever to be fished in the Strait, while, for two o f the Copepoda, it was even the first time they were found in the Mediterranean. It was established that the bathygeography of the Strait, as well as the local circulation within the water mass, causes bathythermal inversion both for the surface and for the deep zooplankton. The stenothermia of certain species, particularly Copepoda, Chaetognatha, Euphau@ids andThaliacea was demonstrated and confirmed. Though the continental shelf is quite extensive, neritic species are scarce, however, their percentages as compared to oceanic species is not unimportant.