hauled obliquely from 140 m. to the surface. 

 On a few cruises the net was hauled obliquely 

 from a depth of 60 m. and horizontally near the 

 surface. Each haul lasted 30 minutes. 



Of the 1,643 plankton .samples obtained, 600 

 were taken near the Hawaiian Islands (lat. 15 

 to 30° N., long. 150° to 165° W.) and most of 

 the others in the equatorial region (lat. 10' N. 

 to 10^ S.. long. 110 to 170 W.). The 38 

 wahoo larvae were found in 34 plankton 

 samples; 2 larvae were found in two samples 

 and 3 larvae in one (fig. 1 and table 1). All 



'r.\BLK 1. — Record of Itnval and juvenile wahoo captured in 

 plankton net hauls in the central Pacific Ocean, 1950-62 



Figure 1. — Locations at which wahoo larvae were taken 

 in plankton net hauls. Each star represents a single 

 larva. A star and number show catches of two or 

 more larvae. Broken lines indicate a distance of 110 

 kilometers from land. Major currents of the central 

 Pacific Ocean arc shown. 



the larvae were preserved in a 10 percent solu- 

 tion of Formalin.' The wahoo larvae ranged 

 from 2.8 to 17.8 mm. SL. The size i-ange was 

 extended to 23.7 mm. by the inclusion of a juve- 

 nile (collected in a midwater trawl) described 

 by Stra.sburg (1964). 



Of the 38 larvae, 21 were cleared in a weak 

 (1-2 percent) solution of potassium hydroxide 

 and stained with alizarin in the technique de- 

 scribed by Lipman (1935). Standard length 

 and various body parts were measured, and 

 counts of fin rays and spines, myomeres, teeth. 

 and branchiostegal rays were made before 

 clearing and rechecked after staining. Verte- 



' Trade rianifs reftrrcd to in thi^ iiublic-utiuti do not iinijly endorse- 

 iiicni of coinmereiai products. 



1 Bureau of Commercial Fislicrics research vessels, Ilugti M. Smith (IIMS) 

 and Charlta H. Oilhrrt (CHG). 

 -Length nr7.9.nnn, and fi.O.mm. specimens estimated, 



brae were counted after the specimens had 

 been stained. In a few instances where the 

 body was slightly bent, a small piece of glass 

 slide was placed over the specimen to straighten 

 it before measuring. The following measure- 

 m.ents were made on each specimen : 



Standard length : The distance from anter- 

 iormost tip of snout to posterior end of noto- 

 chord ; after the notochord had flexed dorsad, 

 the distance from tip of snout to posterior edge 

 of hypural complex was measured. 



Head length : The distance from anterior- 

 most tip of snout to dorsal end of gill cover. 



Snout length : The distance from anter- 

 iormost tip of premaxillary to anterior edge of 

 orbit. 



Orbit diameter : The greatest distance meas- 

 ured along the longitudinal axis of the body. 



300 



U.S. FISH AND WILDLIFE SERVICE 



