FISHERY BULLETIN: VOL. 87, NO. 3, 1989 



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Figure 1. — Study area with ichthyoplankton and hydrographic stations plotted, and 

 selected stations numbered. Stations where bluefin tuna larvae were present are 

 indicated by a heavy dot. The dashed line shows the position of the 183 m isobath. 



pendent sets of data, temperature-depth pro- 

 files, and remote sensing images of surface tem- 

 perature, show that the water at these stations 

 when bluefin tuna larvae were caught was the 

 shoreward edge of the Gulf Stream. Tempera- 

 ture profiles of stations 631, 632, and 633 (Fig. 2) 

 show cold water is closer to the surface at the 

 inshore station (633) than at the offshore stations 

 (631, 632). This is typical at the cold edge of the 

 Gulf Stream near the shelf break (e.g. , Atkinson 

 1985). Station 634, where bluefin tuna larvae 

 were present, is a little inshore and north of 

 station 633. Its vertical temperature profile 

 shows warm Gulf Stream water at the surface 



and the cold water of the edge of the stream 

 closer to the surface than at station 633. Station 

 636, where bluefin tuna larvae were present 

 also, has a similar temperature profile. The 

 upper mi.xed layer at stations 634 and 636 is 

 appro.ximately 30 m deep like that at station 633, 

 not 60-80 m deep as at station 631 which was 

 farther offshore. These temperature profiles are 

 typical of the edge of the Gulf Stream at this 

 latitude (Atkinson et al. 1987). 



The third positive station in this group of sta- 

 tions at the shelf edge is station 647. No observa- 

 tions of temperature with depth were obtained 

 at this station but measurements at adjacent 



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