of the centrum is ossified on the 17th vertebra. 

 To trace the development of the haemapo- 

 physes on hirger wahoo, two juveniles, 152- and 

 159-mm. SL taken from stomachs, and two 

 adults, 1,066- and 1,252-mm. fork length, were 

 examined. Additional information from an 

 adult 1,468 mm. long (type of length measure- 

 ment not clearly defined) was obtained from 

 Conrad ( 1938) . The vertebra on which the an- 

 teriormost haemapophysis is located, listed in 

 the order of fish size (length in millimeters 

 shown in parentheses), is as follows: 17th 

 (23.7), 12th (152), 13th (159), 14th (1,066), 

 15th (1,252), and 16th (1,468). This sequence 

 suggests first, that after the initial ossification 

 of the anteriormost haemapophysis on the 17th 

 vertebra in the smallest juvenile, other haema- 

 pophyses develop anteriorly until the maximum 

 number has been attained at a length of about 

 152 mm.; second, that as the fish increase in 

 size, the position of the anteriormost haema- 

 pophysis apparently moves posteriorly, prob- 

 ably because of a gradual upward shift in the 

 position of the haemapophysis on the centra as 

 the vertebrae increase in size. 



The development of the anteriormost haemal 

 arch also suggests a shift in position. The po- 

 sition of the initial haemal arch shifts from the 

 23d or 24th vertebra in the juveniles to the 26th 

 or 27th vertebra in the adults. 



OCCURRENCE AND DISTRIBUTION 

 OF WAHOO 



The adult wahoo are generally found in trop- 

 ical and subtropical waters and are taken as 

 incidental catches by surface trolling and long- 

 lining. In both types of fishing, however, the 

 catches are small: in the central Pacific Ocean 

 only 236 wahoo were caught in 8,937 line-hours 

 of trolling (Murphy and Ikehara, 1955) and 58 

 wahoo were taken on 14 POFI (now BCF Bio- 

 logical Laboratory, Honolulu) longline fishing 

 cruises, during which 94,128 hooks had been 

 fished at 45G fishing stations (Murphy and 

 Shomura, 1953a, 1953b, 1955; Shomura and 

 Murphy, 1955). Results of surface trolling 

 within a few kilometers of land in the Line 

 Islands in 1955 have led Iversen and Yoshida 

 (1957) to infer that wahoo prefer shallow 

 depths and are more abundant close to shore. 



318 



To determine whether the wahoo are taken 

 on the longline more commonly in inshore than 

 in offshore areas (areas less than or greater 

 than 110 km. from land), I plotted the locations 

 where wahoo were taken on the longline (fig. 7) 



MOMTH qouAreRiAi 





'^/" .f %, 



^ •? ^eou«To«t|ii. eOUNTflfl curkcn 



SOUTH , BOUATQBIAL CURRENT 



Figure 7. — Location and number of adult wahoo taken 

 during 14 POFI (now Biological Laboratory, Honolulu) 

 longline cruises. Each star represents a single wahoo 

 taken at a fishing station. A star and number show 

 catches of two or more wahoo per station. Broken lines 

 around islands indicate a distance of 110 km. from 

 land. Major currents in the central Pacific Ocean are 

 shown. 



and tested the catch data. The catches in the 

 two areas were not statistically significant. 



Larval wahoo were found also in tropical 

 and subtropical waters of the Pacific Ocean be- 

 tween lat. 30° N. and 25° S., and between long. 

 175° E. and 115° W., the east-west extent of 

 sampling along the Equator. Interestingly, dif- 

 ferences between the catches of wahoo larvae in 

 inshore and offshore areas (areas less than or 

 greater than 110 km. from land) were not 

 significant; 12 larvae were caught in 11 of 566 

 plankton net hauls in inshore areas and 26 lar- 

 vae were caught in 23 of 1,077 net hauls in off- 

 shore areas. The distribution of catches of 

 larvae (fig. 1), moreover, resembled that of 

 the adults taken on the longline. 



Of particular interest to this study are (1) 

 the captures of larvae and adults far from land 

 and (2) the scarcity of larvae in the Equatorial 

 Countercurrent (fig. 1), although adults have 

 been taken there on a number of longline 



U.S. FISH AND WILDLIFE SERVICE 



