The possibility of loss of pigment spots 

 from exposure to ultraviolet rays or from the 

 preservatives was mentioned, and care in han- 

 dling and storage of samples was stressed. 



One character which might be useful for 

 larval tuna identification and, therefore, worthy 

 of study was the position of the eye relative to 

 the horizontal axis through the tip of the snout. 



Identification of Juveniles 



Ocean. Unfortunately, all the larvae died soon 

 after hatching. The failure to keep the larvae 

 alive was attributed to inadequate preparation, 

 as the opportunity to do this work was entirely 

 unexpected. Because such opportunities appear 

 unpredictably, it was suggested that adequate 

 preparations to do this type of work be made on 

 all future cruises. In order to ensure greater 

 success in keeping the larvae alive after hatch- 

 ing, it was suggested that antibiotics be added 

 to the water to keep bacterial counts at a low 

 level. 



Results of preliminary trials with soft 

 X-rays indicate that this technique is a promis- 

 ing tool for identifying juveniles and adults of 

 certain tunas, particularly the smaller species 

 such as T. atlanticus. For the yellowfin, big - 

 eye, albacore, and bluefin, species determina- 

 tion was made by the position of the first ventrally 

 directed parapophysis . The position of the first 

 parapophysis in the juveniles, however, agreed 

 with that of the adults only in the bluefin. In 

 yellowfin this structure was on the seventh ver- 

 tebra in the juvenile and on the ninth vertebra in 

 the adult, as illustrated by Godsil and Byers 

 (1944)1/ and Kishinouye (192 3) .U In albacore it 

 was on the 9th vertebra in the juvenile and on 

 the 10th in the adult (Godsil; Kishinouye). Since 

 the total vertebral count of both species shown 

 by the X-rays was identical with counts obtained 

 from Kishinouye and Godsil, it was suggested 

 that perhaps the difference in the position of the 

 first parapophysis in these two species could be 

 due to growth. It was therefore suggested that 

 a wider range of sizes be X-rayed for each of 

 these species . 



Realizing that identifications obtained 

 with the X-ray method would not be helpful to 

 other larval tuna researchers unless they were 

 interpreted in terms of external appearance of 

 the fish, it was recommended that descriptions 

 of external appearnace be supplied with X-ray 

 data. 



In view of the preliminary status of lar- 

 val and juvenile studies and the fact that the re- 

 sults obtained are only tentative, it was agreed 

 that it was premature to arrive at any conclu- 

 sions concerning the positive identity of all the 

 species. It was therefore recommended that the 

 various investigators continue with their work 

 until more definite results are obtained. 



Hiroshi Nakamura presented figures and 

 results of embryonic development of thebigeye, 

 which personnel of the Nankai Laboratory had 

 fertilized artificially aboard ship in the Indian 



Methods and Gear 



While it was agreed that standardization 

 of gear was desirable, there were contrasting 

 opinions as to whether this should be done at 

 the present time. Some felt that for the present 

 the collecting of larvae in large numbers was 

 still important and should be continued until 

 positive species identifications were attained. 



Gear modifications were suggested for 

 sampling larvae. It was reported that attach- 

 ment of a light to the 6-foot Isaacs -Kidd trawl 

 and towing the net at slow speeds resulted in 

 large catches of forage organisms. It was also 

 reported that a plankton net attached to the float 

 line of the last basket of longline gear resulted 

 in large catches of larval fish. Finally, 

 Nakamura suggested a possible method of col- 

 lecting larvae and keeping them alive by attach- 

 ing a piece of bamboo, which was open at one 

 end and slit along the sides, to the cod-end of a 

 plankton net, with the entire cod-end enclosed 

 with netting. The larvae are less likely to be 

 injured when taken in this device. 



Recognizing that more effective gear for 

 collecting juveniles is necessary, the Working 

 Group recommends increased effort toward this 

 end. 



— Godsil, H. C. and R. D. Byers. 1944. 

 A systematic study of the Pacific tunas . Califor- 

 nia Dept. of Fish and Game, Fish Bulletin No. 

 60, 131 p. 



Al 



Kishinouye, Kamakichi. 1923. Contri- 

 butions to the comparative study of the s o -called 

 scombroid fishes. Journal of the College of 

 Agriculture, Tokyo Imperial University, Vol. 8, 

 No. 3, p. 293-475. 



17 



