enter their feeding area in late June or 

 July. In recent years, they have tended 

 to enter the coastal waters in the south- 

 em part of this area, off Virginia, Mary- 

 land, or southern New Jersey. Again, 

 this is basically an east-west migratory 

 pattern, in contrast to the generally ac- 

 cepted concept of northerly and south- 

 erly movements. At least 500 medium 

 bluefin have been tagged in the north- 

 western Atlantic; all of the returns were 

 consistent with the above pattern and 

 not one tag was returned from any other 

 area. 



d. Large Fish 



The distribution and migratory pat- 

 terns of the large (more than 185 cm, 

 usually more than 7 years old) bluefin 

 in the western Atlantic are much more 

 extensive than those of the smaller fish. 

 The main warm season habitat of this 

 group includes much of the coast from 

 Cape Cod to the east coast of New- 

 foundland, including the southwestern 

 Gulf of St. Lawrence, but usually ex- 

 cluding most of the Bay of Fundy. Sec- 

 ondary concentrations, usually of brief 

 duration, occur in the Cape Hatteras- 

 Cape Cod area. In the 1930s, the late 

 1940s, and the 1950s, however, giant 

 fish were often quite abundant in parts 

 of that area. The large fish usually ar- 

 rive in their southern feeding grounds 

 between early June and early July, and 

 in their northern ones in late July Tlie 

 movements of fish within this large 

 area are not well known, except that 

 some fish released in St. Margaret's 

 Bay, near Halifax in June or July have 

 been recaptured in the Gulf of St. 

 Lawrence in August or September. 



The giant fish usually leave this 

 feeding area in October and migrate to 

 their very extensive wintering areas. 

 Routes of this migration can only be 

 surmised. They probably spread over a 

 very wide front, with some fish travel- 

 ling eastward and then southward with 

 the currents, while others follow more 

 direct routes south. Since bluefin, most 

 of which are large individuals, are dis- 

 tributed almost all over the Atlantic 

 between latitudes 35°N and 10°S dur- 

 ing the northern cold season, the limits 

 of this wintering area cannot be deter- 

 mined with certainty. There are indica- 

 tions, however, that it extends east- 

 ward to longitude 40°W and south- 

 ward, in some cases, to latitude 40°S. 

 These fish are dispersed; the relative 



abundance is usually highest off east- 

 ernmost Brazil in late winter and early 

 spring, and around the Antilles. ITiere 

 are indications of an important 

 northeastward migration along the 

 South American coast from the former 

 area to the latter in April. Iliis would 

 be a spawning migration, since the 

 prime known reproductive area in the 

 western Atlantic is in the Gulf of 

 Mexico. There is evidence that spawn- 

 ing also occurs in the enclosed waters 

 adjacent to the Gulf and in the ocean 

 east of the Bahamas and the southeast- 

 ern United States. These spawning 

 grounds are actually a part of the much 

 more extensive wintering area. Thus 

 the giant bluefin may move from their 

 wintering areas to their spawning 

 ground by m igrations of various lengths 

 and directions; some may not have to 

 move at all. 



The spawning season in the west- 

 em Atlantic area extends from late April 

 through June, with the maximum emis- 

 sion probably occurring in May and 

 early June. When spawning is com- 

 pleted, the spent fish migrate north- 

 ward toward their feeding grounds. This 

 is most dramatically illustrated by the 

 northward passage of spent bluefin 

 through the Straits of Florida, close to 

 the northwestern Bahamas. The dura- 

 tion of this run, which usually occurs in 

 strength from early May to mid June, is 

 consistent with the period of maximum 

 spawning stated above. Soon after it 

 leaves the Straits of Florida, this north- 

 ward migration is joined by a similar, 

 but less concentrated one which fol- 

 lows the Antilles Current along the oce- 

 anic side of tlie West Indies and the 

 Bahamas. The combined contingents 

 of giant fish tend to concenti'ate along 

 the eastern edge of the Florida Current 

 and follow it to beyond Cape Hatteras, 

 where it becomes the Gulf Stream and 

 gradually turns eastward. Contingents 

 probably cross the Gulf Stream at vari- 

 ous distances east of the American coast 

 and resume their northward course. 

 These groups of fish follow various 

 routes to different parts of their feeding 

 grounds. Tlieir arrival there completes 

 a prodigious circuit where distance may 

 vary for different groups of fish. This 

 is, for most of the fish at least, a three 

 phase migration. 



In some years, substantial contin- 

 gents offish remain in the Gulf Stream 



and its continuation, the North Atlantic 

 Current, until they reach the Norwe- 

 gian coast in late summer or early fall. 

 We believe that this is unusual behav- 

 ior, rather than part of an annual pat- 

 tern, for reasons enumerated in Section 

 VIC. These migrations will be discussed 

 later in the context of stock identifica- 

 tion. 



3. Eastern Atlantic and 

 Mediterranean 



a. Very Small Fish 



Very small (less than 50 cm long, 

 less than 1 year old) bluefin are very 

 widely distributed in the Mediterranean, 

 but are known from only a very small 

 part of the eastem Atlantic. Larvae and 

 very small (less than 10 cm long) juve- 

 niles have been collected in many parts 

 of the central and western Mediterra- 

 nean, and in the Black Sea. In amazing 

 contrast, not one has been captured in 

 the supposed reproductive areas in the 

 eastem Atlantic, despite prolonged and 

 sometimes intensive efforts. The Ibero- 

 Moroccan Bay has long been regarded 

 as the prime or only bluefin tuna spawn- 

 ing ground in the region on the strength 

 of the massive catches of maturing and 

 spent fish which were formerly taken 

 by numerous traps along its coasts. 



Age bluefin are observable in 

 great numbers over much of the Medi- 

 teirancan, and are often available to 

 fisheries, from August through Novem- 

 ber. Then they usually disappear, prob- 

 ably by simply remaining below the 

 surface during the cold season. In April 

 they reappear, supposedly in or near 

 the same localities, and finish out their 

 first year of life without having moved 

 extensively. 



These fish, along with older im- 

 mature bluefin in the Mediterranean 

 are believed to be sedentary, remaining 

 near their birthplace until they attain 

 maturity. Their distribution, however, 

 is even more extensive than that of the 

 known and supposed spawning areas. 

 Reproduction is known or supposed to 

 occur off most of the western, northem 

 and eastem coast of Sicily and in much 

 of the south Tyrrhenian Sea; off west- 

 em Sardinia; around the Balearic Is- 

 lands; off western Libya, Tunisia and 

 Algeria; and in the Adriatic and Black 

 Seas. The distribution of age bluefin, 

 however, extends into the Ligurian and 

 Aegean Seas, and the northeastern 



135 



