782 



Fishery Bulletin 101(4) 



B 



■-«»Si,~, 



<5 5 to 10 10 to IS 



Standard lengtti (mm) 



>1S 



Figure 3 



Diet composition of larval swordfish from the western North Atlantic: (A) a 3.9-mm-PSL larva and cyclopoid copepods 

 (genus Corycaeus) that were removed from the gut; (B) a 12.7-mm larva with a larval fish in its gut; and (C) the frequency 

 of occurrence of copepods and larval fishes in the guts of larval swordfish. 



gnaths. Larvae > 1 1 .0 mm PSL ate almost exclusively larval 

 and juvenile fishes (Fig. 3, B and C). Remnant jaws and 

 heavy pigmentation of many of the fishes eaten, indicated 

 that most were neustonic. One exocoetid was identified by 

 intact pectoral fins and counts of vertebrae. 



Jaw and alimentary canal structure 



The structure of the alimentary canal and jaws changed 

 concomitantly. The alimentary canal began to change from 

 three segments (foregut, midgut and hindgut), typical of 

 larval fishes (Govoni et al., 1986a), to four segments (esoph- 

 agus, stomach, anterior intestine, and posterior intestine) 

 between 9.0 and 12.0 mm PSL. Jaws change during this 

 period from the beak-like jaws to the elongate rostral bill 

 of the istiophorids (Fig. 3, A and B). Gastric glands were 

 evident in the fundic region of the stomach (ventricili-gas- 

 tric cecum), close to the junction with the esophagus in the 

 30.0-mm-PSL larva (Fig. 4, A and B). The pyloric region of 

 the stomach (pars pylorica) was evident in the 21.5-mm- 

 PSL larva and the 30.0-mm larva. 



Time and location of spawning 



Back-calculated spawning dates demonstrated year-round 

 spawning and peaks in three seasons and five regions 

 (Fig. 5, A-C). Larvae collected in the eastern Caribbean 

 were spawned in the winter (northern hemisphere) only. 

 Larvae collected in the western Gulf of Mexico were 

 spawned in spring. In the north-central Gulf of Mexico, 

 larvae were spawned in all seasons, but spawning peaked 

 in spring. Off south Florida, larvae were spawned in 

 all seasons, and spawning peaked peaked in spring. Lar- 

 vae collected off the southeastern United States were 

 spawned throughout the year whereas larvae collected in 

 the north-central Gulf of Mexico and in southern Florida 

 waters were spawned mostly in spring and early summer. 

 Modes of the number of larvae collected and their esti- 

 mated DFF advanced slightly in day of the year from the 

 north-central Gulf of Mexico to off the southeastern United 

 States. Larvae <10 DFF were collected both in the north- 

 central Gulf of Mexico and off the southeastern United 

 States (Fig. 5D), but not off South Florida. 



