Govoni et al.: Early life history o\ Xiphias gladius in the western North Atlantic 



785 



20 



D 



2()r 



15 

 10 

 5 



20|- 



15 

 10 



Winter spawning 



ai 



tru 



20 



40 



no larvae 



20 



40 



60 



60 



40 



20- 



15^ 



loi- 



60 20| 



Spring/summer spawning 



20r 

 10k 



5^ 



20 40 



no larvae 



no larvae 



no larvae 



Estimated age from spawning (days) 

 Figure 5 (continued) 



c 



CO 



en 



o 



Pz 





60 



O 0) 

 IT) 



S 3 



0) m 

 cr u> 



different diets, even when occupying the same space (e.g. 

 Govoni et al., 1983; 1986b). Larvae of the related istiophorids 

 have limited diets, but these are not as exclusive or abruptly 

 changing as that of swordfish. Diets of larvae examined in 

 our study showed no evidence of cannibalism. 



The diet of larval swordfish helps to resolve their vertical 

 distribution. Most larvae have been collected at the surface 

 in neuston or dip nets (Taning, 1955; Yabe et al., 1959; Gor- 

 bunova, 1969; Nishikawa and Ueyanagi, 1975), although 

 some have been collected in plankton nets that fished 

 principally below the surface (Grail et al., 1983; Govoni et 

 al., 2000). The diet of swordfish larvae indicates that larvae 

 <11 mm PSL may live in the near surface water, whereas 

 larvae >11 mm are neustonic. Corycaeus is a common ne- 



ritic copepod of the Caribbean, the Florida Current, and 

 the continental shelf off the southeast coast of the United 

 States; Corycaeus is not neustonic (Owre and Foyo, 1967; 

 1972; Paffenhofer, 1983; 1985). That Corycaeus is eaten 

 almost exclusively by young swordfish larvae implies that 

 these larvae occupy the near-surface pelagia. Istiophorid 

 larvae undertake dietary shifts (Voss, 1953; Gorbunova 

 and Lipskaya, 1975; Lipskaya and Gorbunova, 1977) and 

 changes in vertical distribution (Bartlett and Haedrich, 

 1968; Leis et al., 1987) that are similar to those of sword- 

 fish larvae, but conflicting evidence exists for vertical dis- 

 tribution of larval istiophorids. Gorbunova and Lipskaya 

 (1975) implied that istiophorid larvae accumulate in sur- 

 face waters during the day and disperse below the surface 



