Which characteristics define the prey species constituting the diet of a given predator? Answering this question would help predict a predator's diet and improve our understanding of how an ecosystem functions. The aim of this study was to test if the diet of common dolphins, Delphinus delphis, in the oceanic Bay of Biscay reflected prey availability or a selection shaped by prey energy densities (ED). To do this, the community of potential prey species, described both in terms of relative abundance and energy densities, was compared to the common dolphin diet in this area. This analysis of a predator's diet and its prey field revealed that the common dolphin selected its diet on the basis of prey energy densities (significant values of Chesson's index for ED > 5 kJ g − 1 ). High-energy prey were positively selected in the diet [e.g. Notoscopelus kroeyeri, ED = 7.9 kJ g − 1 , 9% of relative abundance in the environment (%Ne); 62% of relative abundance in the diet (%Nd)] and low-energy prey disregarded (Xenodermichthys copei, ED = 2.1 kJ g −1 , 20%Ne, 0%Nd). These results supported the hypothesis that common dolphins selected high energy density prey species to meet their energetically expensive life style and disregard prey organisms of poor energy content even when abundant in the environment.

The records of tropical fishes and the warming of the European Atlantic waters. A recapitulation of the records of tropical fishes from European Atlantic waters shows that 67.6 % were fishes caught from the upper slope, between approximately 200 and 600 m; 19.8 % were fishes caught from the continental shelf; and 13.5 % were specimens caught from the middle slope, between 700 and 1 300 m. Since 1963, the upper slope species have made regular northward range extensions off of south Portugal to northwestern Ireland (about 55" 30' N), more and less rapidly, about 30 years for Cyttopsis roseus and only 6 years for Sphoeroides pachygaster. The continental shelf species, observed from 1969 but mostly from 198 1, have a northward range to southeastern Ireland (about 52" N), but 65.2 % of them have been caught off the south of the Bay of Biscay. The middle slope species, recorded only from 1991 according to the development of the deep fishery, were caught between 48" N and 60" N. The northward range extension of upper slope species and the higher frequency of records of continental shelf species from the southern part of the Bay of Biscay coincide with the investigations on the warming of the south-north current in the upper slope of northern Spain and of the south French Atlantic continental shelf. 0 Elsevier, Paris biodiversity I tropical fishes I warming I European Atlantic

Studies of actual ichtyological biodiversity in the European Atlantic Ocean and estimation of changes in the relative abundance of fish species in catches off Arcachon, on the shelf and in the Bassin d'Arcachon, from 1727 to the present day are made. These show that some previously dominant species are now rare. Several disappeared to the south of the Bay of Biscay, such as the bottom-living elasmobranchs with low reproduction rates (Echinorhi- nus brucus, Squatina squatina, Raja batis, R. brachyura, R. clavata, Dasyatis pastinaca, Myliobatis aquila, Galeorhinus galeus, Mustelus asterias), and teleostean fishes Trigla lyra andEutrigla gurnardus. Overfishing with most fishing gears, but especially bottom trawls is responsible for their reduction. An additional study was made on tropical species which were not recorded before 1950 to the north of Portugal. The species include

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