Originally published in [2002] International Fisheries Bulletin, Focus, No. 5

One fin, two fins, red fins, bluefins - some problems of nomenclature and taxonomy affecting legal instruments governing tuna and other highly migratory species

Andrew Serdy†

ABSTRACT

In the light of recent recognition by the FAO that what were thought to be separate Atlantic and Pacific stocks of the species Thunnus thynnus (northern bluefin tuna) are in fact two distinct species, this paper examines and finds considerable variation in how tunas are named and classified in the UN Convention on the Law of the Sea and other fisheries treaties.  He highlights two consequences related to the superimposition on this variation of the entry into force of the UN Fish Stocks Agreement – an end to the mixing of northern and southern bluefin tuna for quota management purposes and a potential legal problem that may arise from the lack of taxonomic specificity with regard to species coverage in the International Convention for the Conservation of Atlantic Tunas.  Calling for the wider use of FAO species names, he concludes that, until this occurs, it is the Latin scientific names rather than the common names in the “authentic” vernacular treaty texts on which reliance should be placed for legal purposes.
    

According to the Food and Agriculture Organization of the United Nations (hereinafter FAO), the tunas, making up the tribe Thunnini in the family Scombridae, are sub-classified into four genera (Thunnus, Euthynnus, Katsuwonus and Auxis) containing thirteen species altogether.[1]  Recent scientific findings suggest that one of these – northern bluefin tuna (NBT), of which the Atlantic and Pacific stocks were hitherto thought to be subspecies – is actually two species, bringing the total to fourteen.

Six or seven of these species (depending on how one counts NBT), all but one of them belonging to the genus Thunnus, are considered by the FAO as principal market tuna species because of their global economic importance and the international trade in them for canning and sashimi, raw fish being regarded as a delicacy in Japan and more recently also in other countries.  The principal market tunas are albacore (Thunnus alalunga), bigeye tuna (T. obesus), NBT (T. thynnus in the Atlantic and T. orientalis in the Pacific), southern bluefin tuna (SBT) (T. maccoyii) and yellowfin tuna (T. albacares).  Skipjack tuna (Katsuwonus pelamis) is the remaining principal market tuna species. They are all oceanic, capable of long migrations or movements, and constitute one or two stocks in each ocean.  Longtail tuna (Thunnus tonggol) is another species of tuna that is becoming increasingly important for canning and in which substantial international trade takes place.[2]

The other six species are more neritic (that is, they live in the water column superjacent to the continental shelf).  They are blackfin tuna (Thunnus atlanticus), bullet tuna (Auxis rochei), frigate tuna (A. thazard), black skipjack (Euthynnus lineatus), kawakawa (E. affinis) and little tunny (E. alletteratus).[3]

Six species of Thunnus, along with both of the Auxis species, two of the three species of the genus Euthynnus and Katsuwonus pelamis (the only species in its genus), are listed in Annex I to the United Nations Convention on the Law of the Sea[4] (hereinafter UNCLOS[5]) as highly migratory species, collectively accounting for the first nine items of the Annex, viz.

1. Albacore tuna: Thunnus alalunga.
2. Bluefin tuna: Thunnus thynnus.
3. Bigeye tuna: Thunnus obesus.
4. Skipjack tuna: Katsuwonus pelamis.
5. Yellowfin tuna: Thunnus albacares.
6. Blackfin tuna: Thunnus atlanticus.
7. Little tuna: Euthynnus alletteratus; Euthynnus affinis.
8. Southern bluefin tuna: Thunnus maccoyii.
9. Frigate mackerel: Auxis thazard; Auxis rochei.

Two observations may be made.  First, five of the tuna species listed in Annex I are among those regarded by the FAO as neritic and not truly highly migratory (items 6, 7 and 9); conversely, the omission of both longtail tuna and black skipjack from Annex I might also be questioned on the same basis.  With numerous other species known to undertake large-scale migrations also not included in Annex I, it is not surprising that in the FAO’s view the list of species is unsatisfactory from a scientific perspective.[6]  Secondly, as shown in Table 1 below, the names by which the species are referred to in UNCLOS does not in all cases match those used by the FAO.  

Table 1 - FAO names of highly migratory tunas in the respective texts of UNCLOS[7]

The reason for the first of these discrepancies lies in the negotiating history of Annex I at the Third United Nations Conference on the Law of the Sea[8] and need not trouble us unduly.  Like the outer limit of the continental shelf, the line between highly migratory and other marine species is a legal rather than a scientific one.   A recent illustration of this can be seen in Articles 1(f) and 3(3) of the Convention on the Conservation and Management of Highly Migratory Fish Stocks in the Western and Central Pacific Ocean, which incorporate Annex I of UNCLOS by reference rather than listing the species to which this Convention applies – with the omission of sauries (item 14 of Annex I), reflecting a Japanese view that these are not highly migratory species.

The second discrepancy is more curious, and the reasons for it more complex.  It has a parallel in the French and Spanish texts of Annex I when compared against the corresponding lines of the table in Annex B to the Agreement Establishing the Indian Ocean Tuna Commission (IOTC Agreement), which lists the “FAO English name”, “FAO French name”, “FAO Spanish name” and scientific name of nine species of tuna, as shown in Table 1 above and Table 2 below.[9] 

Table 2 – Current FAO species names of fishes of the tribe Thunnini[10]

* In 1983 the first letter of Sud/Sur was written in lower case.                                           

First, as is evident from a comparison of the FAO names in the three languages with their UNCLOS counterparts, the same species may be known by different names even within the same language as used by countries in different parts of the world.[11]  Thus, for English:  

Secondly, from Table 2 it is evident that not all tunas are recognisable as such by their FAO names, and in particular that the list of species whose FAO English name contains “tuna” is different from the equivalent French list, which in turn is different from the Spanish.  Indeed only for four tunas is there consistency across all three languages: blackfin tuna, NBT, SBT and longtail tuna.  This inconsistency is even greater in the UNCLOS nomenclature shown in Table 1.

Conversely, several species commonly known by a name of which “tuna” is an element do not fall within the tribe Thunnini.  As shown in Table 3, a few are even outside the family Scombridae:  

Table 3 - FAO and scientific names of other “tunas”[13]