northwestern Bahamas in May 1971. 

 The inshore location of its recapture 

 suggests that it might have eventu- 

 ally entered New England or Cana- 

 dian coastal waters. Its recapture date, 

 April 4, however, indicates that, if it 

 had come from the Straits of Florida, 

 it must have left there in March, well 

 ahead of the usual May-June pas- 

 sage. The other two recaptures oc- 

 curred in offshore waters, from 40 to 

 65 nautical miles (74 to 120 km) out- 

 side the 2,000 m contour. One fish, 

 which was recaptured 135 nautical 

 miles (250 km) southeast of Nan- 

 tucket Island, Massachusetts, in June 

 1970 had been released four years 

 previously, in May 1966, in the Cat 

 Cay-Bimini area. The fourth tuna had 

 been released in the same locality in 

 early June 1970, and was recaptured 

 just 30 days later 100 nautical miles 

 (185 km) southeast of Sable Island, 

 off Nova Scotia. Thus it had trav- 

 elled at least 1,500 nautical miles 

 (2,800 km) in a maximum of 30 days, 

 requiring a minimum average speed 

 of 2.1 knots (3.9 km per hr). It is 

 uncertain whether these fish, had their 

 journeys not been terminated, would 

 have proceeded to the feeding 

 grounds off the American coasts, 

 completing the hypothetical migra- 

 tion, or continued across the ocean to 

 Norwegian waters, as so many other 

 bluefin released off the Bahamas have 

 done. It is widely believed, however, 

 that these animals have a strong ten- 

 dency to follow favoring currents 

 when migrating (Sella 1929a, Rivas 

 1955, Lozano Cabo 1958, 1959b; 

 Sara 1964, 1973; Rodewald 1967). 

 Since both of these fish were recap- 

 tured far north of the Gulf Stream, 

 which would have favored a migra- 

 tion to Norway, it seems more prob- 

 able that they would have proceeded 

 to the nearby American feeding 

 grounds than that they would have 

 wandered out into the less produc- 

 tive waters of the open ocean. 



Two giant bluefin tagged off the 

 northwestern Bahamas have been re- 

 captured in the South Atlantic (Table 

 28 , Figure 75) (Mather 1974). One 

 fish was marked in May 1963 and 

 recaptured southeast of Recife, Bra- 

 zil, in March 1965. The other fish, 

 released in June 1969, was recap- 

 tured off Argentina in February 1973. 



This migration of at least 6,600 nau- 

 tical miles (12,250 km) is the longest 

 ever recorded for an Atlantic bluefin. 

 These surprising recoveries pro- 

 vided the first clues to the relation- 

 ships between the bluefin tuna stocks 

 of the North and South Atlantic. 

 Catch records of the Japanese 

 longline fishery (Fisheries Agency 

 of Japan 1965, 1966, 1967a, 1967b. 

 1968, 1969, 1970, 1971, 1972, 1973) 

 show that, in some years, an area of 

 intensive bluefin fishing develops in 

 March and April off easternmost Bra- 

 zil, moves northwestward toward the 

 Bahamas and then northward to off 



Cape Hatteras in May and June. In 

 Jul), the longline catches of large 

 fish diminishes. The capture off 

 Recife of a giant bluefin which had 

 been tagged off the Bahamas in- 

 creases the probability that a group 

 of large fish does actually migrate 

 from off the Bahamas in May-June 

 to off Cape Hatteras by early July, 

 thence to various summering areas 

 farther north (Figure 75), and south- 

 ward in the fall to wintering areas 

 around the Antilles and off South 

 America. It had been generally be- 

 lieved (Wise and Davis 1973) that 

 bluefin tuna concentrations north of 



Table 28. Releases and returns for giant bluefin tuna (over 120 kg) tagged off the 

 Bahamas by year of release, months at large, and area* of recapture. Also shown 

 is the estimated percentage of German North Sea bluefin tuna catches in late 

 season (September 15 - October 3 1 ) recruited from the western Atlantic (Tiews 

 1964). 



Year Releases 



Returns by Month at Large 



% 



114 



