68 



Fishery Bulletin 98(1) 



Cape .) 



60 



,'»i ■.51 



■t:"^.s50 

 • 31 



Figure 3 



Advanced very high icsolulion infrared radiometer 

 images of sea-surface temperatures ofl' the south- 

 eastern Atlantic coast of the United States; five day 

 composites from National Oceanic and Atmospheric 

 Administration, National Environmental Satellite, 

 Data and Information Ser\ice glohal orbiting satel- 

 lites: (Ai 11 to 15 September; (Bl 16 to 20 September; 

 (C) 21 to 25 Septemberl9H8. Darker to lighter shades 

 denote coolei' to warmer water; squares denote loca- 

 tions of neuston collections; numbers denote .station 

 numbers; and parenthetical numbers within insets 

 denote the number of overlapping stations. 



swordfish retain lai-val characters (lower jaw at least 

 half as long as the rostral cartilage; preorbital, supraor- 

 bital, posttemporal, and preopercular spines; enlarged 

 and spinous dorsal and ventral scales; and a continu- 

 ous and long dorsal fin ) until they are at least 188 mm 

 SL (Ai-ataTl954; Pothoff and Kelley, 1982; McGowan, 

 1988). 



Approximate age of larvae 



The age of swordfish larvae at length was approximated 

 from published accounts of the age and lengths of labora- 

 tory-reared larvae, and fi'om counts of apparent growth 

 increments on otoliths excised fi:'om three specimens col- 

 lected by CH9703. Larvae fi-om the Mediterranean hatch 

 at a length fi'om 4.0 to 4.5 mm TL (measured aUve) after 

 3 d of incubation and deplete their yolk and oil globule at 

 a length of about 5 mm TL after 5 to 7 d at 22.5-25.2°C 

 (Sanzo, 1910; Yasuda et al., 1978). 



Results 



Spatial distribution 



The 1163 MARMAP collections yielded 55 swordfish 

 larvae in 35 collections. Lai'vae were collected in all 

 seasons and at all times of the day. Of the 35 collec- 

 tions that produced lai'vae, 21 were taken in the day, 

 5 at night, and 9 at dawn or dusk. As many as nine lar- 

 vae were taken in a single collection. Between Cape Ca- 

 naveral and Cape Hatteras, larvae were collected more 

 frequently within the fi'ontal zone of the Gulf Stream, 

 than they were in shelf or Gulf Stream waters. Where 

 the Gulf Stream jets through the Florida Straits (25° 

 to 28°N latitude), larvae occuiTed across the narrow 

 body of the Gulf Stream. If these Florida Straits collec- 

 tions are excluded from consideration, along with col- 

 lections from single seasonal or annual surveys that did 

 not produce any larvae, 21 of these 27 collections that 

 yielded larvae were within the probable area of the Gulf 

 Stream frontal zone, i.e. 18.5 km of the assigned position 

 of the Gulf Stream surface frontal axis; one was in shelf 

 water, and five were in Gulf Stream water (Fig. 5; Table 

 1 1. The probability of observing the presence or absence 

 of larvae (calculated as fi-equency of occuirence), among 

 the two water masses and the mixed fi-ontal zone, with 

 at least as much association was 0.000002'X (Fisher's 

 exact test, two-tailed distribution ). 



In June 1984 (CF8406), the frontal zone was de- 

 fined by the 25^ to 27 C sin-face isotherms. North of 

 Florida, the western Gulf Stream front was smooth 

 with no evidence of instabilities in the form of large 

 intrusions (Fig. 2). Twelve of 47 collections of CF8406 

 yielded 16 swordfish lai'vae. Of these, two collections 



