farther. Also, side swimming would place both pelvic 

 fins in a position where they could facilitate rapid 

 left (now ventral) turns while possibly adding lift. 



Acknowledgments 



This study benefited from funds provided by the 

 Foundation for Ocean Research at SIO, and by 

 University of California, San Diego, Biomedical and 

 Academic Senate research grants. We thank Cap- 

 tain Jesus Yamamoto for saving the specimen for 

 study and W. Bayliff for providing it to us. We also 

 thank W Klawe, W Bayliff, and A. Dizon for com- 

 menting on the manuscript. 



Literature Cited 



FlERSTINE, H. L., AND V. WALTERS. 



1968. Studies in locomotion and anatomy of scombroid fishes. 

 Mem. South. Calif. Acad. Sci. 6:1-29. 

 GIBBS, R. H., AND B. B. COLLETTE. 



1967. Comparative anatomy and systematics of the tunas, 

 genus Thunnus. Fish. Bull., U.S. 66:65-130. 

 Graham, J. B., F. J. Koehrn, and K. A. Dickson. 



1983. Distribution and relative proportions of red muscle in 

 scombrid fishes: consequences of body size and relationships 

 to locomotion and endothermy Can. J. Zool. 61:2087-2096. 

 Magnuson, J. J. 



1973. Comparative study of adaptations for continuous swim- 

 ming and hydrostatic equilibrium of scombroid and xiphoid 

 fishes. Fish. Bull., U.S. 71:337-356. 

 1978. Locomotion by scombrid fishes. In W. S. Hoar and D 

 J. Randall (editors), Fish physiology, Vol. 7, p. 239-313. 

 Acad. Press, N.Y. 

 Magnuson, J. J., and D. Weininger. 



1978. Estimation of minimum sustained speed and associated 

 body drag of scombrids. In G. D. Sharp and A. E. Dizon 

 (editors), The physiological ecology of tunas, p. 

 293-311. Acad. Press, N.Y. 



UCHIYAMA, J. H., AND P. STRUHSAKER. 



1981. Age and growth of skipjack tuna, Katsuwonus pelamis, 

 and yellowfin tuna, Thunnus albacares, as indicated by daily 

 growth increments of sagittae Fish. Bull., U.S. 79:151-162. 



Jeffrey B. Graham 



Richard H. Rosenblatt 



Darcy L. Gibson 



Physiological Research Laboratory and 



Marine Biology Research Division 

 Scripps Institution of Oceanography 

 La Jolla, CA 92093 



CHROMOSOMAL ANALYSIS OF ALBACORE, 



THUNNUS ALALUNGA, AND YELLOWFIN, 



THUNNUS ALABACARES, AND SKIPJACK, 



KATSUWONUS PELAMIS, TUNA 



Chromosomal analysis is being used as part of an 

 investigation of the population stock structure of the 

 North Pacific albacore, Thunnus alalunga. There is 

 a growing body of evidence (Brock 1943; Laurs and 

 Lynn 1977; Laurs and Wetherall 1981; Laurs 1983) 

 that North Pacific albacore are not as homogeneous 

 as usually assumed (Clemens 1961; Otsu and Uchida 

 1963). Results from recent tagging studies suggest 

 that northern and southern substocks constitute the 

 North Pacific albacore population and that these 

 proposed substocks have different migratory pat- 

 terns (Laurs and Nishimoto 1979 1 ; Laurs 1983). 

 Laurs and Wetherall (1981) also found that the 

 growth rates were significantly different in the two 

 proposed substocks. In addition, the differences in 

 growth rate are consistent with differences in length 

 frequencies of albacore caught in commercial fish- 

 eries off North America (Brock 1943; Laurs and 

 Lynn 1977). 



In this paper we report results from chromosomal 

 analysis using C-banding for albacore (from the pro- 

 posed North Pacific southern substock) and compare 

 them with similar results obtained for yellowfin, 

 Thunnus alabacares, and skipjack, Katsuwonus pela- 

 mis, tuna. We demonstrate that there is a chromo- 

 somal basis for placing the albacore and the yellow- 

 fin tuna in the genus Thunnus and that recognizable 

 chromosomal differences exist between the genera 

 Thunnus and Katsuwonus. These findings corrobo- 

 rate the taxonomy of the albacore and the yellowfin 

 and skipjack tuna based on comparative anatomy 

 (Gibbs and Collette 1967; Collette 1978). 



The results reported here are from part of a larger 

 study, which is helping us to evaluate if genetic 

 heterogeneity exists in the North Pacific albacore 

 population. Information on chromosome character- 

 istics is scarce for fishes, and to our knowledge this 

 is the first time chromosome analyses have been 

 reported for scombrid fishes. 



Materials and Methods 



All blood samples were collected from freshly 

 caught fish either aboard the NOAA RV David 

 Starr Jordan (August 1983) or aboard fishing boats 



»Laurs, R. M., and R. N. Nishimoto. 1979. Results from North 

 Pacific albacore tagging studies. U.S. Dep. Commer., Natl. Mar. 

 Fish. Serv., SWFC Admin. Rep. LJ-79-17, 9 p. 



FISHERY BULLETIN: VOL. 84, NO. 2, 1986. 



469 



