50' 



45' 



40" 



35' 



30' 



25* 



20" 



15» 



95° 



— T— 



85" 



1^ 



LEGEND 



o RELEASE LOCALITY 

 • RECAPTURE LOCALITY 

 O RETURN NUMBER 



i®,,S^,^^:,,_ 



& 



Figure 79. Geographic distribution of bluefin tag release and recapture data from 

 northeastern North America tagging studies with recovery sites in the Gulf of 

 Mexico and Caribbean Sea 



maturing ovaries (Table 25), have 

 been caught there by longlme in April 

 1955, April 1960, and May 1951 

 (Bullis and Mather 1956, Anonymous 

 1960, 1962). There are three major 

 routes along which tuna might mi- 

 grate from the Windward Passage 

 through the spawning areas and north- 

 ward toward their summer feeding 

 grounds (Figure 31) 



The best documented of these 

 routes, although it is the longest, is 

 through the northwestern Caribbean, 

 the Gulf of Mexico, and the Straits of 

 Florida This pattern is indicated by 

 the distribution of longline catches 

 of bluefm during cruise 30 of M/V 

 "Oregon" in the spnng of 1 955 (Bullis 

 and Mather 1 956). Bluefin were taken 

 in the Windward Passage, at stations 

 south of the eastern end of Cuba and 

 near the Cayman Islands and 

 Cozumel Island m the northwestern 

 comer of the Caribbean, but not one 

 was taken at several stations m the 

 Caribbean east of the Windward Pas- 

 sage A migration between eastern 

 Cuba and Jamaica was also indicated 

 by the existence of a Cuban-based 

 sprmg longline fishery for giant blue- 

 fin in this area (Ubeda 1974). Schools 



of large bluefin have been observed 

 occasionally during this same season 

 in several consecutive years on the 

 surface between Cozumel Island and 

 the Yucatan Peninsula. Many of these 

 fish have been hooked, but verj' few 

 landed, by biUfish anglers (personal 

 communications). Similar occur- 

 rences off the Mississippi River delta 

 have been reported (Nakamura and 

 Rivas 1972) The catch rate distribu- 

 tion charts of Wise and Davis (1973) 

 (Figure 32) and l.e Gall (1974) indi- 

 cate that the winter concentration 

 around the Greater Antilles and in 

 the southeastern Gulf of Mexico 

 moves westward and northward in 

 the spring, occupying the northern 

 Gulf as well as waters north of Cuba, 

 Hispaniola and Puerto Rico The 

 abundance of bluefin tuna larvae in 

 the Gulf of Mexico in April, May 

 and June also implies the presence of 

 large numbers of adults (Richards 

 1976, Montolio and Juarez 1977) 

 The connection between the disap- 

 pearance of this concentration of 

 adults from the Gulf by the end of 

 June (Shingu et al 1975) and the 

 northward migration of large num- 

 bers (Tyler el al. 1979) of giant blue- 



fin through the Straits of Florida in 

 May and June seems obvious. It is 

 also indicated by occasional catches 

 of deep swimming bluefin off Ha- 

 vana (Rivas 1955) and by the 

 sightings of schools off Cay Sal, at 

 the southwestern comer of the Cay 

 Sal Bank (P. Pierce, T. Sanchez, per- 

 sonal communications). 



There are also strong indications 

 that many bluefin follow the north 

 coast of Cuba westward from the 

 Windward Passage, through the Old 

 Bahama and the Santaren Channels 

 to the "tuna alley" in the Cat Cay 

 area. We have received reports of 

 sightings of schools moving through 

 the Old Bahama Channel from per- 

 sons who operated aircraft there, but 

 were unable to obtain precise details. 

 During cruise 62 of R/V Crawford in 

 April-June 1961, which had been 

 planned to study these migrations, 

 additional evidence of such a migra- 

 tion was obtained Giant bluefin were 

 taken by longline in the Windward 

 Passage (sample 10, Table 25, Fig- 

 ure 70), near Cay S Domingo off 

 the eastem end of the Old Bahama 

 Channel, and at the edge of the Great 

 Bahama Bank on the eastem side of 

 the Santaren Channel (sample 15, 

 Table 25, Figure 70) (Anonymous 

 1962, unpublished data). Sample 14 

 was taken about 60 nautical miles 

 (110 km) northwest of the western 

 end of the Old Bahama Channel and 

 about 1 1 nautical miles (204 km) 

 south by cast of the center of the Cat 

 Cay spcirt fishery for giant tuna. The 

 capture of eight giant bluefin and the 

 loss of many hooks, leaders and 

 branch lines, all at the inshore end of 

 the line, indicated a heaw concen- 

 tration of the fish close to the steep 

 drop-off at the edge of the bank at 

 this station. Radio telephone reports 

 from participants in a tuna tourna- 

 ment al Cat Cay bewailed a prolonged 

 dearth of fish. Two days later, they 

 reported one of the best catches in 

 many years The distribution of these 

 four catches and the subsequent catch 

 off Cat Cay strongly suggests that 

 contingents of bluefin migrate from 

 the Windward Passage through the 

 Old Bahama and Santaren Channels 

 and continue northward through the 

 Straits of Florida. Because of the mp- 

 ture of diplomatic relations between 



120 



