Portuguese EEZ - Ecology

The waters of continental Portugal can be classified as being a subtropical sub-province of the Lusitanian province. Nevertheless, boreal species are also found in the ecosystem, at the southern most extreme of their distribution, meaning that species diversity is high in this region.
The environmental conditions of the ecosystem shape the trophic structure, in particular upwelling. Thus, a large proportion of the biomass and production is pelagic. Phytoplankton grazing is low, so detritivorous species are important. Suspension and deposit feeders constitute a high percentage of the biomass. Abundant suprabenthic zooplankton is also available to pelagic and small demersal fish species. Decapod crustaceans are important prey items for benthic fish species. Blue whiting (Micromesistius poutassou) is one of the main prey items for many demersal piscivorous fishes.
The main fish species in the West Iberian Sea pelagic ecosystem are: sardine (Sardina pilchardus), anchovy (Engraulis encrasicolus), mackerel (Scomber scombrus), horse mackerel (Trachurus trachurus) and blue whiting. Other mackerels and horse mackerels such as chub mackerel (Scomber japonicus), Mediterranean horse mackerel (Trachurus mediterraneus) and blue jack mackerel (Trachurus picturatus) are also common.
The most important fish species in the demersal community are hake (Merluccius merluccius), megrims (Lepidorhombus boscii and L. whiffiagonis), monkfish (Lophius spp.) and sole (Solea solea). There are many elasmosbranch species in the region, including rays (Raja clavata, R. montagui, and R. miraletus) and catsharks, (Scyliorhinus canicula and Galeus melastomus) near the coast and on the slope and several deepwater sharks and chimaeroids. Wide-ranging migratory sharks such as blue shark (Prionace glauca), shortfin mako (Isurus oxyrnchus), porbeagle (Lamna nasus), tope (Galeorhinus galeus) and spurdog (Squalus acanthias), also occur in the region. Some are taken in mixed demersal and pelagic (especially for tuna and swordfish) fisheries.
Several studies have been carried out to determine the distribution and seasonal variability of demersal fish assemblages in the area . These have shown that species are organised according to depth, bottom topography and latitude and are stable over time, despite variations in species abundances.