thermophiles and sought surface wa- 

 ters of at least 18°C. The migrations 

 were probably provoked by the 

 "transgressions" of Atlantic water, 

 which controlled their period and vol- 

 ume, and were independent of gonad 

 condition (Scordia 1932). 



The biometric studies of Arico 

 and Genovese (1953) and Genovese 

 (1957, 1958) supported Scordia's 

 hypothesis of a distinct and separate 

 Tyrrhenian-Ionian stock of bluefm 

 tuna. 



Sella ( 1 929a) maintained that the 

 Mediterranean bluefin could not be 

 separated into autochthonous stocks 

 corresponding to the various basins, 

 as proposed by Roule (1917) and 

 Ninni (1922). In addition to his 

 Atlantic-Mediterranean results, 

 Sella's (1927, 1929a) hook recover- 

 ies indicated that bluefin tuna were 

 constantly moving from one place to 

 another within the Mediterranean (see 

 Heldt 1930a, his unlabeled figure). 

 These findings will be considered in 

 terms of three general areas of ori- 

 gin: the western Mediterranean, cen- 

 tral Mediterranean, and the 

 Bosphorus (Istanbul, Turkey). Hook 

 items of Atlantic origin which were 

 retrieved in the Mediterranean will 

 be considered with those of the west- 

 em Mediterranean, since the fish in 

 which they were found could only 

 have entered the Mediterranean 

 through the Strait of Gibraltar. 



Hook recoveries indicated exten- 

 sive eastward migrations within the 

 Mediterranean. Numbers in paren- 

 theses following deduced migrations 

 show the number of such migrations 

 revealed, if more than one. Items from 

 Malaga were recovered at Arzeu, Al- 

 geria, and near Tripoli, Libya. One 

 from Arzeu was found off southwest- 

 ern Sardinia. Another, from 

 Philippeville, Algeria, was retrieved 

 at Sidi Daoud, Tunisia. More numer- 

 ous and extensive eastward migra- 

 tions were deduced from recoveries 

 of fish with Atlantic hooks, whose 

 Mediterranean movements must be 

 considered to have begun at Gibraltar. 

 These retrievals occurred off Sardinia 

 (10 + 1 probable), Sicily (5), 

 Gallipoli, Italy southeast of Taranto 

 (1)), Tunisia (4 + 1 probable) and 

 Tripolitania (3). Thus movements 

 from Gibraltar as far east as the heel 



of the Italian boot on the north coast 

 (longitude IS^E) and nearly to Cape 

 Misurata on the south coast (longi- 

 tude 1 5°E) are indicated. 



Recoveries of single hooks or 

 lures of central Mediterranean origin 

 suggested that bluefin moved freely 

 between the various fishing centers: 

 Sardinia to Tunisia, Messina to 

 Sardinia, and Palermo. Sicily, to the 

 Aegades Islands. More numerous re- 

 ported findings showed movements 

 from the Strait of Messina to the "re- 

 turn" traps along the southern part of 

 the east coast of Sicily, which cap- 

 tured fish travelling southward along 

 the coast. The only movements to 

 other regions were a westward one 

 from Messina to Arzeu, Algeria, and 

 a longer migration to the east and 

 north, from Sicily or Tunisia to the 

 upper Adriatic near Trieste, Italy. 



More dramatic findings resulted 

 from six recoveries of very distinc- 

 tive and easily recognized lures used 

 only in the vicinity of Istanbul, Tur- 

 key. Two of these recoveries indi- 

 cated migrations to eastern Tunisia 

 and southwestern Sardinia. Sella 

 ( 1 929a) considered the finding of four 

 lures, each in a different individual 

 caught in the same season and in the 

 only trap operating in the area around 

 Bengazi, Libya, as proof of the ar- 

 rival of several schools coming di- 

 rectly from the Sea of Marmara and 

 the Bosphorus. Despite these impres- 

 sive findings, the tendency to split 

 the Mediterranean bluefin into sepa- 

 rate stocks continued for another 30 

 years. 



The taggings of bluefin in the 

 Mediterranean have not been suffi- 

 ciently numerous to answer the ques- 

 tions which have been raised by de- 

 ductive research. Arena and his col- 

 leagues marked 288 bluefin tuna off 

 Sicily and the Aeolian Islands in the 

 years 1963-1968 (Arena and Sara 

 1967, Arena and Li Greci 1970, 

 Arena 1 97 1 ). Most of these were very 

 small individuals (age 0, lengths 28- 

 42 cm), but eight were adults weigh- 

 ing 28 to 60 kg (ages 4-5). Returns 

 from four small fish and one adult 

 have been recorded. The recapture of 

 another small fish was reported but 

 the tag was not returned. 



The returns for small fish were 

 from releases in October 1967. The 



recaptures occurred after periods at 

 liberty of 65 days or less and within 

 distances of 150 km from the release 

 points. One had passed through the 

 Strait of Messina into the Ionian Sea, 

 but the others had remained in the 

 southeastern comer of the Tyrrhenian 

 Sea. The unconfirmed recovery from 

 a small tuna reportedly occurred 

 within the general release area after a 

 time at large of about 18 months. 

 The adult tuna had made a longer 

 migration, from off Punta Raisi near 

 Palermo at the end of May 1968, to 

 off Castellon, Spain, in mid-October 

 1969 (Figure 71). Its weight was es- 

 timated as 28-30 kg when released, 

 and reported as 45 kg when recap- 

 tured 17 months later. 



The returns from small fish sug- 

 gest that their movements are quite 

 limited, but the times at liberty were 

 not sufficient, except in the case of 

 the one unconfirmed recapture, to 

 establish this as a definite tendency. 

 The migration from Sicily to Spain 

 by the larger fish, which was prob- 

 ably age 4 when released and age 5 

 when recaptured, supports Sella's 

 (1929a) view that the mature bluefin 

 travel freely about the Mediterranean, 

 and refutes the concept of a distinct 

 Tyrrhenian stock (Ninni 1922, 

 Scordia 1938, Arico and Genovese 

 1953, Genovese 1957. 1958). Obvi- 

 ously, much more tagging in various 

 parts of the Mediterranean is needed 

 to solve the complex problems of the 

 migrations and stock structures in that 

 sea. 



Sara (1964. 1973) studied the 

 behavior of bluefin tuna in the 

 Mediterranean extensively. He be- 

 lieved that age bluefin made only 

 very limited local movements in the 

 area where they were spawned. As 

 they grew larger, they migrated far- 

 ther, but always within the same ba- 

 sin, until they attained a weight of 

 about 100 kg and joined in the Atlan- 

 tic-Mediterranean migration. The re- 

 sults of tagging in the Mediterranean 

 cast doubt on the hypothesis of a 

 separate Tyrrhenian-Ionian stock 

 (Scordia 1938, Arico and Genovese 

 1953, Genovese 1957, 1958). 



Sara (1973) described the mi- 

 gratory and distributional patterns of 

 bluefin in the Mediterranean in terms 

 of the size groups. He used size 



106 



