Highly migratory species are referred to in Article 64 of the UN Convention on the Law of the Sea which provides for the rights and obligations of coastal and other states whose nationals fish for these species. Although no operational definition of "highly migratory" is given in the Convention, an agreed list of species considered highly migratory during elaboration of the Convention was attached to it as Annex 1.

The list includes species with wide geographic distribution, both inside and outside the 200-mile zone, and which undertake migrations on significant but variable distances across oceans for feeding or reproduction. They are pelagic species with neritic and oceanic phases in their life cycle. The list includes 11 tuna, 12 billfish species, pomfrets, 4 species of sauries, dolphinfish (Coryphaena spp.), oceanic sharks and cetaceans (both small and large). Mammals are treated separately in the Convention (under Article 65).

Article 64 reflects the view that the management of highly migratory species requires cooperation between the coastal State and other states fishing for resource. A trend is developing in which fishing agreements are signed between coastal and distant-water fishing nations (DWFNs). The DWFNs accept to pay for the access to tunas in the EEZs and where the coastal State unilaterally fixes (or negotiates) the quotas or the number of licences such as in the South Pacific area, Seychelles, Mauritius, Morocco and Senegal.

Some species that make large-scale migrations are not in the list. For example, Euthynnus lineatus, which is probably more oceanic than the other two Euthynnus species listed in Annex 1 is not included. Another three tuna-like species (Acanthocybium solandri, Allothunnus fallai, and Gasterochisma melampus), classified as oceanic in the FAO SPECIESDAB, are not included in the list. Many other tuna-like species migrate long distances but remain close to the coast and, from a purely biological point of view, may be considered as highly migratory or straddling. In addition, some scientific names have changed in the meantime and the list, as it presently stands, is not satisfactory from a taxonomic point of view.