McGOWAN and RICHARDS: BLUEFIN TUNA LARVAE 



Table 1. — Stations where bluefln larvae were present on Oregon II Cruise 152, 



April and May 1985. 





 20 

 40 



60 

 80 

 100 

 120 

 140 

 160 

 180 



200 



5 10 15 20 25 5 10 15 20 25 5 10 15 20 25 5 10 15 20 25 30 



TEMPERATURE (°C) 



Figure 2. — Temperature-depth profiles of selected stations in the southern part of the study area. 

 Stations 631, 632, and 633 are along an east to west transect at the edge of the shelf (see Figure 1). The 

 edge of the Gulf Stream is indicated by colder water near the surface inshore at station 633. Bluefin 

 larvae were collected at stations 634 and 636 where the profile is similar to that at 633. 



stations are useful as proxies. Station 646, which 

 was south and a little offshore from 647, shows a 

 vertical temperature profile (Fig. 3) typical of 

 the Gulf Stream, similar to that at 631 (Fig. 2). 

 Station 650, at a similar isobath and distance 

 from the shore, also shows a temperature profile 

 similar to 631 and 632. Therefore station 647 

 would reasonably be expected to be more similar 

 to 646 and 650 than stations 648, 645, and 649, 

 which are farther inshore. These temperature 

 profiles indicate that Gulf Stream water was 

 present at stations 634, 636, and 647 when blue- 

 fin tuna larvae were collected there. 



This conclusion is supported further by charts 

 of satellite data showing the position of the edge 

 of the Gulf Stream. The edge of the stream was 

 just offshore of the 183 m isobath on 26 April, the 

 day before the bluefin tuna larvae were collected 

 at stations 634 and 636 (Fig. 4). The edge was 

 inside the 183 m isobath and inshore of the three 

 stations three days later on 29 April, when blue- 

 fin tuna larvae were collected at station 647 (Fig. 

 5). The satellite-detected temperature fi'ont 

 associated with the inshore edge of the Gulf 

 Stream is known to be in accord with the classi- 

 cal definition of the stream path (Olson et al. 



619 



