SYSTEMATICS AND MORPHOLOGY OF THE BONITOS (SARD A) AND 

 THEIR RELATIVES (SCOMBRIDAE, SARDINI)^ 



Bruce B. Collette^ and Labbish N. Chao^ 



ABSTRACT 



The bonitos constitute the scombrid tribe Sardini, consisting of eight species placed in five genera. They 

 differ from the more primitive mackerels and Spanish mackerels in lacking a notch in the hypural plate 

 and in having a bony lateral keel on the posterior caudal vertebrae. From the higher tunas, they differ 

 in having the bony keel only incompletely developed and in lacking a specialized subcutaneous vascular 

 system. The monotypic Australian endemic Cybiosarda elegans shares several characters with the 

 monotypic eastern Atlantic endemic Orcynopsis unicolor (structure of the bony caudal keel; relative 

 lengths of liver lobes; position and size of spleen) that distinguish them from Gymnosarda unicolor and 

 the species of Sarda. Sarda contains four allopatric species, which differ from each other in such 

 characters as numbers of fin rays, gill rakers, vertebrae, and teeth: the Atlantic S. sarda; the 

 southeastern Australian S. australis; the tropical Indo-Pacific S. orientalis; and the eastern temperate 

 Pacific S. chiliensis. The monotypic Indo-West Pacific reef species Gymnosarda unicolor is the only 

 member of the Sardini that has a swim bladder and lacks intermuscular bones on the back of the skull. 

 The monotypic Southern Ocean Allothunnus fallai differs from all other scombrids in having laterally 

 extended prootic wings. It is more closely related to the bonitos than to any other scombrids. 

 Allothunnus resembles the higher tunas in having a prootic pit but lacks the subcutaneous vascular 

 system. Tables of meristic characters, diagrams of the soft anatomy, and drawings of most bones are 

 included in the first part of the paper. The second part of the paper includes sections on synonymy, 

 comparative diagnosis, types of nominal species, and distribution for each species. 



The purpose of this paper is to clarify the rela- 

 tionships of the Sardini at the generic and specific 

 level. This work is part of a continuing study of the 

 systematics of the Scombridae. The methods used 

 are similar to those used by Gibbs and Collette 

 (1967) in a revision of Thunnus and rely heavily on 

 the classic work of Kishinouye (1923) and Godsil 

 (1954, 1955). 



The bonitos (Sarda) and their relatives form a 

 tribe (Sardini) of the subfamily Scombrinae inter- 

 mediate between the primitive mackerels (Scom- 

 brini) and Spanish mackerels (Scomberomorini), 

 and the more advanced tunas (Thunnini) (see 

 Collette and Gibbs 1963a; Gibbs and Collette 1967). 

 Five genera are treated in this paper. The status 

 of the related monotypic genera Orcynopsis, 

 Cybiosarda, and Gymnosarda has been unclear; 

 for example, Fraser-Brunner (1950) placed 

 Cybiosarda in the synonymy of Gymnosarda. The 



■Contribution No. 529, Virginia Institute of Marine Science, 

 Gloucester Point, VA 23062. 



^vstematics Laboratory, National Marine Fisheries Service, 

 NOAA, National Museum of Natural History, Washington, DC 

 20560. 



'Virginia Institute of Marine Science, Gloucester Point, VA 

 23062. 



systematic position of the monotypic Allothunnus 

 has been still more confused-whether it is closer 

 to Thunnus (Fraser-Brunner 1950), to Sarda (Fitch 

 and Craig 1964), or strikingly different from all 

 other scombrids (Nakamura and Mori 1966). There 

 has been no agreement on the number of species of 

 Sarda. Fraser-Brunner (1950) recognized three 

 species: chiliensis, orientalis, and sarda. Godsil 

 (1955) believed that there were two basic groups of 

 species— sarda-chiliensis and orientalis-velox. 

 Some authors have considered S. australis as a 

 valid species, others as a subspecies of S. chilien- 

 sis. 



This project was initiated at the request of the 

 FAO (Food and Agriculture Organization of the 

 United Nations) panel of Experts for the Facili- 

 tation of Tuna Research at its Fourth Session in 

 La Jolla, Calif, in November 1971, and should be 

 considered as a report from the Working Party on 

 Tuna and Billfish Taxonomy. Bonitos, as a group, 

 are one of the few underexploited groups of 

 tunalike fishes; therefore, research on their 

 systematics is a necessary predecessor of success- 

 ful management. 



According to the FAO Yearbook of Fishery 

 Statistics for 1972 (Food and Agriculture Or- 



Manuscript acx:epted January 1975. 

 FISHERY BULLETIN: VOL. 73, NO. 3, 1975. 



516 



