Legand summarized his biometrical 

 analysis of yellowfin and albacore taken in the 

 region of New Caledonia. He remarked that 

 insufficient studies havebeenmade on yellowfin 

 to differentiate the sexes by biometric data. 

 There are, nevertheless, indications that the 

 length of the pectoral fin may differ significantly. 

 This possibility should be considered particu- 

 larly in a serious study of the population by mor- 

 phometric characters. Thus in New Caledonia, 

 yellowfin tunas tend to have smaller heads and 

 larger second dorsal and anal fins than fish 

 caught farther east. 



For albacore, it was concluded that re- 

 sults similar to those of Kurogane and Hiyama 

 were obtained from data on the northern Coral 

 Sea, but results were different from those ob- 

 tained in the northwest Pacific. Both phenotypic 

 and genotypic differences have been observed in 

 the number of anal rays and vertebrae in the 

 medaka (Aplocheilus latipes). 



C. Antigens discussed in this section 

 were defined as molecules on the surface of the 

 erythrocyte, or red blood cell, detected by 

 immunological methods. 



Serological comparisons of North Atlan- 

 tic and North Pacific albacore have demonstrated 

 that serological techniques can distinguish repro- 

 ductively isolated tuna populations. 



Two blood group systems in the skipjack 

 are recognized, namely the A and C system. 

 The C system has been found in all tuna species 



thus far investigated. The A system was also 

 present in all the tunas except the yellowfin. 



Systems such as the A and C system in 

 the tunas would be comparable to theA-B-Oand 

 M-N blood groups found in man. 



Students of skipjack population units in 

 the Pacific recognize at least two reproductively 

 isolated units. There is good evidence that the 

 North American and Samoan stocks of albacore 

 are reproductively isolated. 



Discussion of serological studies on Pa- 

 cific, Atlantic, and Indian Ocean albacore dis- 

 closed that the Atlantic forms had a very high 

 percentage of positive reactions with bigeye- 

 antigen-3 . Samples from the eastern Pacific 

 and Indian Ocean had a significantly lower per- 

 cent of positive reactions. It was indicated that 

 further research will be carried out. 



A background study on serology and its 

 implications to tuna research was discussed. It 

 was pointed out that this is just one of the useful 

 tools for identifying population units . Further 

 discussion focused on possible exchange of ma- 

 terial from various parts of the world to help in 

 determining whether similar population units 

 such as those that are now being discovered for 

 some of the tunas can be isolated. 



It was recommended that a working group 

 be formed to attack one particular problem from 

 the standpoint of biochemical, morphological, 

 and serological methods and to present results 

 at the World Tuna Conference in 1962. 



Tuna Oceanography 



Discussion Leader - Thomas S. Austin 

 Rapporteur - Kenneth D. Waldron 



Reference: Papers No. 



V - 1. Rosa, H. , Jr., and T. Laevastu - World distribution of tunas and tuna fisheries 

 in relation to environment 



2. Alverson, D. L. - Ocean temperatures and their relationship to albacore tuna 



( Thunnus germo) distribution in waters off the coast of the States of Oregon, 

 Washington, and the Province of British Columbia 



3. Inoue, M. - Relation of sea condition and ecology of albacore in the northwest 



Pacific Ocean. Parts I and II 



4. Blackburn, M. - Distribution and abundance of eastern tropical Pacific tunas in 



relation to ocean properties and features 



5. Yamanaka, H. , and N. Anraku - Relation between the distribution of tunas and 

 water masses of the North and South Pacific Oceans west of 160° W. 



