stations (fig. 7). One site of larval capture, 

 lat. 8°42' S. and long. 115°39' W., was 2,057 

 km. from the nearest land mass, Ducie Island. 

 This distance is only 181 km. less than the 

 greatest distance from land where an adult 

 wahoo has been taken. Six other capture sites 

 were farther than 900 km. from land. Although 

 adults frequent the Equatorial Countercurrent, 

 they may not spawn there in appreciable num- 

 bers. Only one wahoo larva was taken there, 

 representing a catch rate of 0.14 larva per tow. 

 More adult wahoo are taken around the Ha- 

 waiian Islands in summer (April through Au- 

 gust) than in other seasons (Welsh, 1949). 

 Seasonal trends are absent, however, near the 

 Equator and around the Line Islands (Iversen 

 and Yoshida, 1957), as they also were in the 

 longline catches made on the 14 POFI cruises 



Table 9.— Adult wahoo caught on U POFI longline cruises 

 in the central Pacific Ocean between lat. 14° N. and 14° S. 



Montli 



Wahoo 

 caught 



Catch ot 



wahoo/ 



1,000 hooks 



January 



February... 



March 



April 



May 



June 



July 



-Vugust 



September. 



October 



November., 

 December.. 



Number 

 1 

 8 





 2 

 4 



B 

 H 

 6 

 3 



4 I 

 4 



Number 



0.29 



.96 



1.33 



.00 



.29 



.72 



2.70 



.69 



.40 



.30 



.37 



.56 



T.\BLE 10. — Catch rate of wahoo larvae and number of plankton 

 samples collected by months in three areas ' of the central 

 Pacific Ocean, 1950-63 



' Area I from lat. 30° to 15° N.; Area II from lat. 14° N. to 14° S.; Area III 

 from lat. 15° to 25° S. 



(table 9) between lat. 14° N. and 14° S. Most 

 of the fishing on these cruises was done between 

 lat. 9° N. and 8° S. 



Monthly catches of larval wahoo show similar 

 trends (table 10). In the area near the Ha- 

 waiian Islands (Area I) larvae were taken only 

 in the summer and early fall (May through 

 September) , but in the equatorial region (Area 

 II) they were taken in nearly all months of the 

 year. 



SUMMARY 



Thirty-eight wahoo larvae were taken in a 

 1-m. plankton net during 32 cruises of the Bu- 

 reau of Commercial Fisheries research vessels, 

 Hugh M. Smith and Charles H. Gilbert, in the 

 central Pacific from May 1950 to July 1962. 

 The standard lengths of these specimens ranged 

 from 2.8 to 17.8 mm. In addition, six adults 

 and four juveniles from other sources were ex- 

 amined. 



Published accounts of adult wahoo give a 

 vertebral formula, 23 to 33 precaudal +31 to 34 

 caudal = 54 to 66 total vertebrae, which is an 

 extremely wide range of variation for a fish be- 

 longing to the Scombridae. All studies based on 

 examination of specimens indicate only minor 

 variation (31 to 33) in the number of pre- 

 caudals. Consequently, I conclude that the wide 

 range of precaudal vertebrae first credited to 

 Kishinouye (1923) is incorrect and that the 

 lower figure of 23 precaudals must be a typo- 

 graphical error — a transposition of digits from 

 32 to 23. 



The number of first dorsal spines is constant 

 at 27 in both juveniles and adults. The number 

 of finlets in juveniles is greater than that in 

 adults by one, owing to the fusion of the last 

 two finlets in adults. 



Body pigmentation is relatively sparse in 

 larvae smaller than 3.4 mm.; a few melano- 

 phores occur on the tip of each jaw, one in each 

 primordial nasal cavity, one on the ventral 

 margin of the caudal peduncle, and a series of 

 about nine evenly spaced along the dorsal sur- 

 face of the digestive tract. The most noticeable 

 change in pigmentation occurs in larvae above 

 5.8 mm., when the melanophore at the caudal 

 peduncle migrates to the base of the anal fin 



MORPHOLOGY AND DISTRIBUTION OP LARVAL WAHOO 



319 



