FISHERY BULLETIN: VOL. 70, NO. 1 



at hand a complete series of larvae of more than 

 two to four species. 



In an attempt to resolve the conflicting views 

 on T. alalunga and to review the identification 

 of larvae of other species of tunas, a Larval Tuna 

 Identification Workshop was held at the Bureau 

 of Commercial Fisheries (BCF) Biological Lab- 

 oratory (now the National Marine Fisheries 

 Service, Southwest Fisheries Center) , Honolulu, 

 Hawaii, on March 2-6, 1970. The workshop also 

 afforded an opportunity to workers specializing 

 on larval tuna identification to assemble speci- 

 mens of the various species of tunas and to ex- 

 amine these together. The procedure followed 

 at the workshop was (1) to summarize the 

 status of larval tuna identification to date by 

 species and (2) to evaluate the identifying char- 

 acters by examining larval specimens. As time 

 permitted, the status of juvenile tuna identifi- 

 cation was also examined. 

 The participants included: 



Mr. Walter M. Matsumoto, Convenor 



Dr. Elbert H. Ahlstrom, Advisor 



Dr. Santhappan Jones 



Mr. Witold L. Klawe 



Dr. William J. Richards 



Dr. Shoji Ueyanagi 

 Dr. Jean-Yves Le Gall of the Centre Ocean- 

 ologique de Bretagne, Brest, France, attended 

 the workshop as an observer. 



The sessions were conducted informally with 

 a summary of the present status of larval tuna 

 identification, including recent developments, 

 followed by evaluation of the various characters 

 that could be relied upon for positive identifica- 

 tion. Most of the sessions were devoted to direct 

 examination of larval specimens of the various 

 species and discussions of unpublished data of- 

 fered by participants. 



This report summarizes the proceedings and 

 results of the workshop. 



RECENT DEVELOPMENTS IN THE 

 IDENTITY OF Thunnus alalunga 



Two diff'ering versions of the identity and de- 

 scription of T. alalunga had arisen from reliance 

 on black pigmentation in diff"erent parts of the 

 body. Matsumoto (1962) relied upon black pig- 



mentation on the dorsal and ventral edges of 

 the trunk forward of the caudal fin base, where- 

 as Yabe and Ueyanagi (1962) relied upon black 

 pigmentation on the tips of the upper and lower 

 jaws and the absence of pigmentation on the 

 trunk. 



The lack of sufficient larvae fitting Matsu- 

 moto's description from areas presumed to be 

 spawning grounds on the basis of gonad studies 

 casts some doubt on his identification. On the 

 other hand, good correspondence in the occur- 

 rence of larvae fitting Yabe and Ueyanagi's de- 

 scription with catches of adult T. alalunga in 

 various areas in the Pacific seemed to support 

 the latter identification. A study of red pigment 

 patterns in larvae prior to preservation (Ueya- 

 nagi, 1966) reinforced Yabe and Ueyanagi's 

 identification and description. Additional ob- 

 servations on red pigmentation by Matsumoto 

 (see later discussion) confirmed Ueyanagi's re- 

 sults and also provided more data to enhance 

 the reliability of red pigmentation as a supple- 

 mentary character for identifying T. alalunga. 



IDENTIFICATION OF TUNA LARVAE 



With the problem of differences in the identity 

 and description of T. alalunga larvae fairly well 

 settled at the outset, there remained the tasks of 

 evaluating the various identifying characters, 

 not only for this species but for other tunas as 

 well, and of describing the species at various 

 size categories. 



DEFINITION OF LARVA 



In tunas, as in many other fish, it is difficult 

 to clearly separate the larval from the juvenile 

 stages because there is no marked metamor- 

 phosis and the usual adult characters used for 

 species identification develop gradually and sep- 

 arately. It is generally accepted among workers 

 in larval tunas that the larval stage ends when 

 the larva has developed the full complement of 

 spines and rays in all the fins, all the vertebrae 

 have ossified, and the anal opening has moved 

 back near the origin of the anal fin. For nearly 

 all tuna species, these developments occur when 

 the larva has attained 10 to 13 mm SL. We use 

 this as our definition, also. 



