Table 33 Releases and returns by months at large for bluefin tuna tagged in the northwestern Atlantic, north of 35°00'N 

 latitude and outside the 100 fathom (183 m) contour (offshore taggmg ceased in 1968) 



able catches (Shingu et al. 1975, 

 Shingu and Hisada 1976) 



If "equatorial" bluefin did leave 

 the Atlantic proper in significant 

 numbers during their northward mi- 

 gration, there is a good chance that 

 they did so through the Windward 

 Passage instead of through the chan- 

 nels between the Lesser Antilles. Evi- 

 dence that giant bluefin migrated 

 from that Passage to the Straits of 

 Flonda by two routes — one through 

 the northwestern Caribbean, the 

 Yucatan Channel, and the Gulf of 

 Mexico, and the other through the 

 Old Bahama and Santaren Channels 

 (Figure 14) has been presented pre- 

 viously in this section. We have found 

 no indications, however, of the route 

 by which the bluefin reached the 

 Windward Passage. 



It will be impossible to even es- 

 timate the percentage of the fish from 

 the equatorial Atlantic which com- 

 plete their northward migration in 

 Atlantic waters, and the percentage 

 which pass through the "American 

 Meditenanean" or the adjacent chan- 

 nels and straits, until significant num- 

 bers of bluefin have been tagged in 

 equatorial waters. 



The return to their spawning ar- 

 eas completes the prodigious migra- 

 tory cycle of the giant "western At- 

 lantic" bluefin, as we now envisage 



it In our opinion, however, this ex- 

 tremely long circuit, extending from 

 latitudes 40°N to 50°N to latitude 

 10°S, or even to 40°S, is the outer 

 perimeter of a very broad pattern 

 Although many fish may follow 

 something resembling this route, oth- 

 ers which winter farther north make 

 correspondingly shorter circuits. 

 Some individuals may not even reach 

 the latitudes of the Bahamas 



c. Medium Fish 



Direct infonnation provided by 

 tag returns from medium .sized (32- 

 122 kg) bluefin tuna, and deductions 

 based on their occurrences in the 

 coastal and oceanic fisheries (Mather 

 1964b) enable us to offer a prelimi- 

 nary hypothesis on their migrations 

 in the western North Atlantic. These 

 fish are the only ones, among the 

 three major size groups, which have 

 been extensively tagged in this re- 

 gion but never recaptured elsewhere. 



The most important tagging in- 

 fonnation resulted from 491 releases 

 in offshore waters, from which nine 

 returns have resulted (I'AO 1972) 

 (Table 33) Seven of the recaptures 

 occurred on the continental shelf from 

 oil Maryland to just north of Cape 

 Cod, one near Yarmouth, Nova 

 Scotia, and finally one at the edge of 

 the continental shelf south of Cape 

 Cod (Figure 80). All of these tags 



were recovered during the normal 

 tuna fishing season, .Tune through Oc- 

 tober. Six of the recaptures near the 

 United States coast, each of which 

 took place after less than four months 

 at large, represented "direct" migra- 

 tions Most of these, and a seventh 

 which could be regarded as repeat- 

 ing its migratory pattern after 13 

 months at large, suggested that me- 

 dium-sized bluefin approached the 

 coast olT Mar\'land and New Jersey 

 in late June or early July from the 

 east, and then worked northeastward 

 toward Cape Cod as the summer ad- 

 \anced The seasonal progression of 

 the recoveries in coastal waters re- 

 sembled that for the larger of the 

 "small" bluefin tagged in those wa- 

 ters. They also coincided with the 

 movements of the medium group 

 through the coastal fishenes (Mather 

 1964b) The other two returns repre- 

 sented much longer times at liberty. 

 31 and 93 months, respectively The 

 former was released in November 

 1 960 off the ea.st end of Georges Bank 

 and recaptured in June 1 963 at Veatch 

 Canyon, .south of Nantucket Island. 

 The recapture location coincides 

 closely with the possible inshore mi- 

 gration route of the five fish tagged 

 al 40°N latitude, 68°W longitude m 

 the same month and eventually re- 

 captured in coastal waters (Figure 



124 



