Recently, Piccinetti (1973), 

 Piccinelti and Piccinetti Man frin ( 1 973 ), 

 and Piccinetti et ai. (1976b) reported 

 on occurrences of larval and juvenile 

 Thunnus thynnus thynnus in the Adriatic 

 Sea, the first positive indication that the 

 species reproduced there. 



Richards ( 1 976) thought that a lar- 

 val specimen collected off Cape 

 Matapan, Greece, on August 26, 1911, 

 and originally identified by Ehrenbaum 

 (1924) as "'Orcynusgermo Lacep. (?)" 

 was probably Thunnus thynnus thynnus. 



Richards agreed with Sella ( 1 929a) 

 that the specimens identified by Ehren- 

 baum (1924) as '"Orcynus thynnus L. 

 (?)" were not of that species. 



Several scientists have reported on 

 eggs and larvae of bluefm tuna col- 

 lected in the Black Sea in mid and late 

 summer. Vodyanitskii and Kazanova 

 (1954) reported that eggs and larvae 

 were encountered there repeatedly in 

 the second half of the summer, but 

 mainly in the beginning of August. 

 Vodyanitskii (1936) and Oven (1959) 

 described eggs found in the latter part 

 of July and in early August, off 

 Sevastopol and Karadag, respectively. 

 Oven hatched some eggs and reared 

 the larvae for up to eight days. 



Many authors have presented in- 

 dices of maturity for bluefin tuna taken 

 in the Mediterranean traps; we cite those 

 of Sara (1964, 1973) because they are 

 among the most recent. He found that 

 the first maturing fish taken in the Si- 

 cilian "arrival" traps in early May had 

 maturity indices of 70-60, whereas those 

 taken toward the end of this fishery in 

 mid Jime had indices of about 25. An 

 index of about 40 was the most fi-e- 

 quent within the entire period. The fe- 

 males were generally in a less advanced 

 state of maturity than the males in this 

 period. During the "return" run of pre- 

 sumably spent fish, the first captures, 

 in eariy July, were of fully mature fish 

 with indices of about 50. By late July, 

 this had increased to 9 1 , and in early 

 August, to 198. This decrease in matu- 

 rity was much more regular than the 

 increase during the "arrival" run. Sella 

 (1929a), as well as Scordia (1932) and 

 Sara (1973), noted that small maturing 

 or ripe fish were sometimes taken in 

 the Sicilian return traps, along with the 

 spent large ones, in July and even in 

 August. Sella and Sara also pointed out 

 that the "arrival" traps in Tripolitania 



took relatively small maturing fish for 

 a considerable period after the conclu- 

 sion of the "arrival" fisheries for larger 

 maturing individuals in the Italian and 

 Tunisian traps. 



Heldt (1938) summarized the re- 

 sults of Frade's histological studies of 

 gonads of bluefin tuna taken in various 

 Tunisian traps. Heldt had collected this 

 material and furnished it to Frade. Frade 

 concluded that, if this small sample 

 was representative, the various groups 

 of tuna which frequent the Mediterra- 

 nean do not mature simultaneously. The 

 fish taken off Tunisia were, in general, 

 less mature than those taken in the east- 

 em Atlantic at the same time. 



Gonad studies related to the spawn- 

 ing of bluefin tuna in tlie Black Sea 

 depended mainly on material collected 

 near Istanbul, Turkey. Hovasse ( 1 927), 

 af^er analyzing statistics of landings at 

 that city in 1915 and 1921-1923, found 

 two significant maxima in the catches, 

 one in the spring (March-April) and 

 one in the summer (July). There was 

 also a minor maximum, whose signifi- 

 cance Hovasse did not understand, in 

 the winter (December). He believed 

 that the spring peak corresponded to a 

 northward migration into the Black Sea 

 and the summer one, to a southward 

 passage back from the Black Sea into 

 the Sea of Marmara. He found that the 

 ovaries of the females taken in the spring 

 were full, whereas those taken in July 

 contained no eggs. Akyiiz and Artuz 

 (1957) stated that bluefin started to run 

 through the Bosphorus into the Black 

 Sea in April, and that this run peaked in 

 July and ended in September. The re- 

 turn migration occurred from late Oc- 

 tober to November. Their studies of 

 gonad condition indicated that spawn- 

 ing occurred in late July, August, and 

 possibly September, ly igiingor ( 1 957), 

 however, listed three periods of pas- 

 sage: November-January, March-April, 

 and July-autumn. Thus there are con- 

 siderable differences in the interpreta- 

 tions of the catch records in regard to 

 migrations and spawning. 



The above research shows clearly 

 that spawning in the Mediterranean by 

 large bluefin tuna starts about mid-June 

 and ends about mid-July. The repro- 

 duction of the smaller (the medium- 

 sized and some of the larger "small" 

 individuals) fish has not been investi- 

 gated as thoroughl) . The a\ ailable evi- 



dence indicates that tiiey begin to spawn 

 later than liie large ones, and that their 

 spawning extends through July well 

 into August, and sometimes even into 

 September. This information is based 

 mainly on observations made in the 

 south-central Mediterranean. The 

 spawning periods in other parts of the 

 Mediterranean and in the Black Sea, 

 are not as clearly defined. Reproduc- 

 tion off the Balearic Islands evidently 

 extends from mid-June at least to late 

 August. Collections of eggs and larvae 

 indicate that spawning in the Black Sea 

 is at its maximum in the second half of 

 July and eariy August, but conclusions 

 based on catch records and gonad con- 

 dition are inconsistent. 



The most completely documented 

 bluefin tuna spawning areas in the 

 Meditertanean are off northeastern and 

 western Sicily, and off the Balearic Is- 

 lands. Another apparently well docu- 

 mented area is in the Black Sea. There 

 are also strong indications of spawning 

 off western Sardinia, northern Tunisia, 

 and Tripolitania. More fi^gmentary data 

 suggest reproduction in the Adriatic 

 Sea, off Algeria and Greece, and in the 

 Aegean Sea. Scaccini et al. ( 1 975) con- 

 cluded that additional intensive research 

 will show that the spawning areas of T. 

 thynnm thynnus cover much more of 

 the Mediterranean than was then be- 

 lieved. 



2. Eastern and Central North 

 Atlantic and the South Atlantic 



a. General Information 



Many experts have assumed that 

 the Ibero-Moroccan Bay (west of 

 Gibraltar) contains the major, or the 

 only, spawning grounds for T thynnus 

 thynnus in the eastern Atlantic. Exten- 

 sive research in this area, dating from 

 the late nineteenth century, has pro- 

 duced much information on the condi- 

 tion of the gonads of the bluefin tuna 

 taken in the once flourishing trap fish- 

 eries in this bay. As noted in Section 

 IV, this fishery was divided into nvo 

 periods, the "arrival" (late April, May 

 and June) and the "return" (July and 

 August). During the "arrival" period, 

 the fish are apparently travelling along 

 both coasts of the bay in the general 

 direction of the Strait of Gibraltar. In 

 the "return" fishery, which occurs only 

 along the Iberian coast, they seem to be 

 travelling westward. The "arrival" traps 



