by the discontinuous north-south distribution of lar- 

 vae in the western Pacific, compared with the con- 

 tinuous distribution across the equator of blue marhn 

 larvae. 



Seasonal Distribution. — The seasonal occur- 

 rence of shortbill spearfish larvae in the Hawaiian 

 Islands (Fig. 4) resembles that of blue marlin in 

 certain respects, the northern edge of distribution 

 being parallel to the chain of islands and the move- 

 ment across the islands being from southwest to 

 northeast. The differences, though small, are 

 nevertheless evident. In the first quarter shortbill 

 spearfish larvae were found approximately 500 km 

 southwest of the islands, as compared to about 950 

 km for blue marlin larvae. The northern edge of the 

 larval distribution shifted northeastward to about 

 320 km past the islands in the second quarter, re- 

 treated to the islands in the third quarter, and con- 

 tinued southwestward past the islands in the fourth 

 quarter. This north-south movement of larval short- 

 bill spearfish distribution seemed to precede that of 

 larval blue marlin distribution by a full quarter. 



One reason for these differences could be that the 

 shortbill spearfish may be able to spawn in colder 

 water than the blue marlin. The temperature data 

 seem to suggest this. Shortbill spearfish larvae were 

 found in waters with temperatures as low as 22.3°C, 

 with most catches having been made in 25° to 26°C 

 water. Both minimum and best catch temperatures 

 for shortbill spearfish larvae were at least TC lower 

 than for blue marlin larvae. 



DISTRIBUTION OF 

 XIPHIID LARVAE 



Larvae of the Xiphiidae, the second of two 

 families that make up the billfishes, were taken only 

 occasionally. Only 20 specimens ranging in sizes 

 from 5.8 to 23.0 mm were found in plankton samples 

 taken from 1950 through 1971 (Table 1 and Appendix 

 Table 2). 



Larval and juvenile stages of swordfish from the 

 Atlantic and Pacific Oceans have been described by 

 a number of workers (Arata, 1954; Nakamuraet al.. 



Figure 4. — Localities of captures of young shortbill 

 spearfish by quarters. Solid lines represent mean surface 

 temperature for last month of quarter. Dashed lines rep- 

 resent surface temperature at time of sampling. Small 

 dots represent sampling with plankton nets in 1° square 

 area; large dots represent capture sites. 



243 



