The project proposes to study the influence of abiotic and biotic factors on the ecosystems and demersal resources, as well as the populational dynamics of two species subjected to exploitation on the shelf and slope of the western Mediterranean: the hake and the red shrimp. The study is developed off the island of Majorca (Balearic Islands), which can be considered as an isolated demersal ecosystem, showing large oceanographic spatio-temporal variability. This proposal is an attempt of a multidisciplinary approach towards understanding the dynamics of the exploited demersal ecosystems in the Mediterranean Sea.