The few details available on the 

 trap fisheries of Tripolitania, and the 

 ephemeral one in Cyrenaica 

 (Bengasi) may provide clues in re- 

 gard to this important subject. Both 

 Sella (1929a) and Sara (1973) cited 

 the later fishing of the Libyan traps, 

 compared to those in Tunisia, as evi- 

 dence of the eastward "arrival" run 

 of the bluefin from the Atlantic. Sella 

 (1929a) noted, however, that the fish 

 taken in Tripolitanian and Cyrenaican 

 traps were medium and small. In a 

 later work. Sella (1932a) stated that 

 the fish taken by the El Mongar trap 

 near Bengasi, Cyrenaica, although 

 mature, were too small to justify its 

 classification as an arrival trap. 

 Anonymous (1929b) described the 

 fish which it caught in 1928 as very 

 small ("picolissimi"). These data in- 

 dicate that the Libyan traps may have 

 been harvesting the intermediate 

 (Mediterranean) mature fish rather 

 than the large (Atlantic) migratory 

 spawning group. 



Another unsolved question con- 

 cerns the migration between the 

 Mediterranean and the Black Sea. 

 Hovasse (1927), Akyuz and Artiiz 

 (1 957) and lyigUngor ( 1 957) all cited 

 passages of maturing fish through the 

 Bosporus into the Black Sea, and of 

 spent fish in the opposite direction 

 (Section VDl). They differed, how- 

 ever, in regard to the dates of these 

 runs. Hovasse (1927) and lyigungor 

 (1957) set the northward migration 

 in March and April, and the begin- 

 ning of the southward one in July. 

 Akyxiz and Artiiz (1957) postu lated a 

 longer northward passage, starting in 

 April, peaking in July, and extending 

 into September, and a "return" run 

 occurring from late October into No- 

 vember. 



Sella ( 1 929a), on the other hand, 

 cited what he considered to be clear 

 evidence of a massive migration of 

 tuna from the vicinity of Istanbul to 

 spawning grounds off Cyrenaica. 

 Four lures, of special types used only 

 in the Bosporus and its approaches, 

 were retrieved from the few hundred 

 tuna caught during the 1929 season 

 in the EI Mongar trap, the only one 

 set in Cyrenaica. Such a migration 

 would be consistent with Sella's 

 (1929a) hypothesis of spring spawn- 

 ing concentrations in the southern 



parts of the bluefin tuna's range (Sec- 

 tion VIClb). 



These apparently inconsistent 

 findings might be reconciled if it 

 could be shown that the larger fish in 

 the Sea of Marmara entered the Black 

 Sea to spawn, whereas the smaller 

 mature individuals reproduced off the 

 African coast. 



Another probable spawning area 

 for the intermediate bluefin is in the 

 Adriatic Sea, where these fish are 

 much more abundant than giants 

 (Section 1VC6, Section VDI). This 

 would be more in keeping with Sara's 

 (1973) concept of limited spawning 

 migrations, within basins, for the 

 smaller mature fish. 



The configuration of the Medi- 

 terranean and its approaches is such 

 that many important problems could 

 be solved quickly and definitively by 

 tagging, or by tracking with sonic 

 equipment. 



d. Migrations and Stocks in 

 the Eastern Atlantic 



i. Large and Medium Fish 



In addition to the four fish re- 

 captured in the Mediterranean (Sec- 

 tion VIC I b). 1 5 of the 3 1 2 fi.sh tagged 

 in the years 1960-1967 near Cadiz 

 have been recaptured in Atlantic wa- 

 ters (Rodriguez-Roda 1969a). These 

 recaptures provided information on 

 several migrations within the area of 

 the Ibero-Moroccan Bay trap fisher- 

 ies, and one to a more distant locality 

 (Figure 71). 



Since the periodic migratory pas- 

 sages through the trap fisheries ex- 

 tend over only about four months, 

 short-term tag returns are required to 

 study them in detail. All of the six 

 recoveries from 140 fish tagged dur- 

 ing the "arrival" period occurred 

 within 85 days of the releases. As 

 noted in part b of this section, three 

 of these recoveries look place in the 

 Mediterranean, representing a con- 

 tinuation of the expected easterly 

 movement. One of the other recover- 

 ies was irrelevant, since the fish was 

 recaptured almost immediately b>' the 

 trap from which it had been released. 

 The other two recoveries, however, 

 indicated rather rapid "backward" 

 (westward) migrations of 79 miles 

 (146 km) in one day and 100 miles 

 (185 km) in two days, respectively. 



into Portuguese waters. These fish 

 were 170 cm and 133 cm long, re- 

 spectively. Seven of the 13 recap- 

 tures from the 172 fish released dur- 

 ing the "return" run occurred after 

 from three to 23 days at large. One 

 recapture, as noted in part b of this 

 section, had "backed" to the east- 

 ward, well into the Mediterranean. 

 Another, recaptured where it had been 

 released tiiree days previously, pro- 

 vided no information. The remaining 

 five made rather rapid migrations of 

 90 to 100 nautical miles (167-185 

 km) in from four to 1 1 days, travel- 

 ling in the expected direction into, or 

 approaching, the waters south of Por- 

 tugal. Three of these fish weighed 

 from 70 to 90 kg, one weighed 270 

 kg, and the weight of the remaining 

 fish was not reported. These short 

 term recoveries suggested that fish 

 tagged during the "arrival" period 

 were more apt to deviate from their 

 expected migratory pattern than those 

 marked in the "return" period. This 

 is rather surprising, since the "ar- 

 rival" fish are believed to be concen- 

 trating to spawn, whereas the "re- 

 turn" fish are thought to be dispers- 

 ing to feed. 



The approximate times at large 

 for the remaining six recaptures of 

 fish marked in the "return" period 

 were 4 months for one fish, 10 months 

 for three fish and 22 months for the 

 other two fish. The longest Atlantic 

 migration revealed by this set of re- 

 leases near Cadiz, about 370 nautical 

 miles (685 km), was from off Barbate, 

 Spain, in August to off the Moroccan 

 coast between Essaouira and Agadir 

 four months later (Figure 71). This 

 movement supported Aloncie's 

 ( 1 964) hypothesis of seasonal migra- 

 tions of bluefin tuna between waters 

 off southern Morocco and the Ibero- 

 Moroccan Bay. This fish, however, 

 weighed 175 kg, considerably more 

 than the group which Aloncle was 

 discussing. 



All of the long-term (10 months 

 or 22 months at large) recaptures of 

 fish marked during the "return" run 

 were in traps fishing the "arrival" 

 passage Three recaptures occurred 

 near Earache, Morocco, about 40 to 

 60 nautical miles (74-1 12 km) south 

 of the release point, one off Portugal 

 and another at Sancti Petri, about 100 



108 



