The oceanography in this ecoregion is characterized by marked seasonal mixing and stratification of water masses typical of temperate seas. This general pattern is modified over the shelf by wind-driven upwelling, river outflow, and tidal-related processes, increasing the productivity of the system with large variation across the region. Habitats further offshore are shaped by the influence of Atlantic waters in the Bay of Biscay and western Iberia.
The ecoregion includes waters from Brittany to the Gulf of Cadiz; four key areas constitute the ecoregion (Figure 1):
- the Bay of Biscay, characterized by a wide shelf extending west of France. Upwelling events occur in summer, off southern Brittany, and low-salinity water lenses are associated with the river outflows of the Landes coastline;
- the Cantabrian Sea (northern Iberian shelf), characterized by a narrow shelf with intermittent summer upwelling events west of Cape Peñes and a winter slope undercurrent, the Iberian Poleward Current;
- the western Iberian Shelf, characterized by a narrow shelf with upwelling events in summer and the Iberian Poleward Current in winter. Off Galicia (at its northern limit) the input of freshwater from rivers and estuaries form the Western Iberian Buoyant Plume, which is an important shaping event under downwelling-favourable winds; and
- the Gulf of Cadiz, characterized by a wide shelf strongly influenced by river inputs, zonal currents, wind patterns, and the deep inflow of Mediterranean water.
The ecoregion includes parts of three Exclusive Economic Zones (EEZs) of EU Member States (France, Spain, and Portugal) and a small portion of high seas; it strongly overlaps with the administrative region of the South West Waters Advisory Council (SWWAC). Fisheries in the Bay of Biscay and the Iberian Coast ecoregion are managed through national administrations under the Common Fisheries Policy (CFP), with some fisheries managed by the North East Atlantic Fisheries Commission (NEAFC) and by coastal states. Responsibility for salmon fishery management lies with the North Atlantic Salmon Conservation Organization (NASCO) and for large pelagic fish with the International Commission for the Conservation of Atlantic Tunas (ICCAT). Fisheries advice is provided by the International Council for the Exploration of the Sea (ICES), the European Commission's Scientific Technical and Economic Committee for Fisheries (STECF), and the SWWAC. The EU's marine conservation policy is coordinated by the Habitats Directive and the Marine Strategy Framework Directive (MSFD). In coordination with the Birds Directive, the Habitats Directive has established the EU Natura 2000 ecological network of protected areas, which includes some vulnerable marine ecosystems (VMEs). Environmental policy is guided by national agencies and OSPAR, with advice being provided by both of these as well as the European Environment Agency (EEA) and ICES. International shipping is managed under the International Maritime Organization (IMO).
