The region comprising the Corso-Ligurian Basin and the Gulf of Lion is characterised by very high levels of primary productivity, in contrast to the well-known generalised oligotrophy of the Mediterranean Sea. All cetaceans regularly observed in the Mediterranean can be found in the region, including pelagic species such as the fin whale (Balaenoptera physalus). Results from previous surveys had emphasised that cetaceans in this region are significantly more abundant than in all other seas surrounding Italy, and than in the rest of the western Mediterranean basin.

However, considerable threats exist for cetacean populations living in the region, including, among others: by-catch in driftnet fishing activities; presence of substantial concentrations of toxic xenobiotics in the trophic chain, which accumulate in the cetaceans' fatty tissues, and, last but not least, high levels of maritime traffic, including fast ferries, ships transporting hazardous chemicals to and from the region's commercial harbours, and offshore speedboat competitions.

The research conducted by the Tethys Research Institute has highlighted the need that a conservation structure such as the Sanctuary be created in the area. Fin whales found during summer in the Ligurian Sea were found to be genetically distinct from North Atlantic fin whales, and most likely belonging to a reproductively isolated population, residing year-round in the Mediterranean Sea. At an estimated >4000 individuals, the population in the western Mediterranean is small and potentially vulnerable, particularly since the contribution from the eastern basin to the total Mediterranean population is likely to be negligible.

The Pelagos Project, commissioned in 1990 by the "European Association Rotary for the Environment" to the Tethys Research Institute, envisaged the creation of a Biosphere Reserve in the Corso-Ligurian Basin, and of an international, Monaco-based authority, responsible for the sustainable management of the basin's natural resources.

Three years later (22 March 1993) the Ministers of the Environment of France and Italy, and the Minister of State of the Monaco Principality, signed in Brussels a joint declaration for the institution of a Mediterranean Sanctuary for marine mammals. In the future Sanctuary all direct takes and intentional harassment of marine mammals will be forbidden, potentially invasive research activities and whale-watching will be regulated; large-scale pelagic driftnet fishing will be banned; offshore speedboat competitions will be limited and eventually forbidden; special effort will be devoted to control and curb pollution harmful to cetaceans.

In the following years, several initiatives were taken to implement the above objectives. These include Recommendation 19.92 (Establishment of a marine Sanctuary for large and small cetaceans in the Ligurian Sea, Western Mediterranean) approved by the IUCN General Assembly, January 1994; the mentioning of the Sanctuary in the IUCN Action Plan for the Conservation of Cetaceans; the clear reference to the necessity of creating specially protected areas in the high seas, provided for in the Protocol concerning Specially Protected Area and the Biological Diversity in the Mediterranean of the Barcelona Convention, and in the Agreement for the Conservation of Cetaceans of the Black Sea, Mediterranean Sea and Contiguous Atlantic Area (ACCOBAMS), promoted by the Bonn Convention.