groupings recommended at the "Re- 

 union sur ie Developpement et la 

 Coordination de Programmes de 

 Recherches sur Ie Thon en 

 Mediterranee, Palermo 22-24/5/ 

 1967" (Anonymous 1968). These size 

 ranges, which are quite similar to 

 those we have used, were as follows: 

 large spawning tuna of over 150 kg, 



medium spawning and feeding tuna 

 of 15 to 60-70 kg, 



very small tuna and small tuna of up 

 to 15 kg which have not yet at- 

 tained their first maturity. 

 Sara believed that most of the 

 large spawners which were observed 

 from the end of April through all of 

 August, were of the same stock, of 

 which a portion, greater or smaller in 

 relation to certain oceanographic con- 

 ditions, entered the Mediterranean to 

 spawn and, having accomplished this, 

 returned to the Atlantic to reconsti- 

 tute their biological reserves (Sec- 

 tion VIC lb). The numbers of tuna 

 "hesitating" in the Ibero-Moroccan 

 Bay and the volume of water enter- 

 ing the Mediterranean determine how 

 many of these tuna enter in a given 

 year. These "arrival" tuna swim in 

 the surface layers, following the 

 branches of the Atlantic currents or 

 its counter currents. These usually 

 follow routes quite similar to the 

 much-criticized ones proposed by 

 Cetti (1777). Displacements of these 

 branches of the currents by the winds, 

 toward or away from the traps, has a 

 critical effect on their catches. 



These currents were illustrated 

 by Sara (1964, his Figure 1). The 

 main current generally followed the 

 African coast, bringing the tuna 

 within range of the traps of Tunisia 

 and Tripolitania. A west-flowing 

 counter current brought the "arrival" 

 tuna into the traps along the north 

 coast of Sicily from the east, rather 

 than from the usual westerly direc- 

 tion. 



According to Sara (1973), the 

 "return" tuna swim in deeper layers, 

 following the westward flow of the 

 Mediterranean water. This current 

 flows southward and westward along 

 the east and south costs of Sicily, 

 where "return" traps were set until 

 recent years. Sara (1973) found evi- 

 dence of this in the new night fishery 



practiced in waters from south to 

 southwest of the western end of Sic- 

 ily. Dead bait was thrown into the 

 water (chumming) to attract the tuna 

 to the surface. There they fed on small 

 live fish which had previously been 

 drawn to the boat by powerful lights. 

 The tuna were then vulnerable to cap- 

 ture by seining. These catches took 

 place from late July until mid Sep- 

 tember. 



Some large tuna remain in the 

 Mediterranean through the fall and 

 winter in areas of rich and available 

 food, such as the islands of the Tuscan 

 Archipelago, the area between the 

 Aeolian Islands and the Strait of 

 Messina, the Dardanelles, and Port 

 de Bouc in the Gulf of Lion. The 

 numbers of these fish are in- 

 consequential in comparison with the 

 great mass of migrating fish which 

 occur in the period of reproduction. 

 The schools of large "Atlantic" 

 tuna remain separate, according to 

 size offish, during the period of matu- 

 ration. During the time of actual 

 spawning, however, they mix tem- 

 porarily with each other, and with 

 younger Mediterranean fish of ages 

 4-7. The latter at other times remain 

 altogether aloof from the larger fish, 

 and, even during the reproductive 

 processes, occupy other layers and 

 areas when constrained together with 

 them. 



Medium and small fish weigh- 

 ing from 20 to 50 kg, with fringes of 

 larger and smaller individuals, are 

 seen and captured along the coasts of 

 the Mediterranean countries through- 

 out the year (Sar^ 1973). These fish 

 school very strictly according to size, 

 They are seen closer to the coast in 

 late summer and autunm, often on 

 the surface in constant and furious 

 pursuit of prey. They are present all 

 year in certain locations near the coast 

 where they can be observed and 

 fished, even in bad weather, and the 

 currents and geomorpholog) of the 

 bottom are favorable, as at the Straits 

 of Bonifacio, in the Adriatic, at the 

 Aeolian Islands, at the Strait of 

 Messina, at the Kerkennahs, and at 

 the Dardanelles. 



These fish have a different mi- 

 gratory pattern from the large ones 

 and make limited spawning and tro- 

 phic (feeding) migrations, within the 



limits of each basin. Apparently it 

 was their contemporaneous presence 

 in several localities, and their habit 

 of remaining off this coast or that 

 one, that, years ago, led to the con- 

 cept of various populations differing 

 at the racial level. In the spawning 

 period, they approach the coasts, ag- 

 gregating with the schools of large 

 Atlantic tuna with which they can 

 mix only during the limited period of 

 reproduction. 



Sara (1973) considers the small 

 and very small tuna next. In the 

 months from August through all of 

 November, almost all of the Medi- 

 terranean Basin is occupied by great 

 schools of young of the year. Re- 

 maining for a few months along any 

 coast, one can see them grow day by 

 day until in November they attain 

 about 2 kg. After this, probably more 

 because of bad weather than because 

 of their departure, they are rarely cap- 

 tured. With the return of good 

 weather, ihey are found again in the 

 late winter months in almost the same 

 places where they had been seen ear- 

 lier, but now weigh 4-5 kg. The young 

 tuna stay in the same areas, making 

 small movements in response to 

 meteoro-hydrological conditions and 

 in search of food. They remain sed- 

 entary until they attain their first 

 sexual maturity, when they begin 

 their first migrations about the Medi- 

 terranean. 



Sara's (1973) concept of the mi- 

 gratory and distributional patterns of 

 bluefin tuna in the Mediterranean is 

 very similar to Sella's (1929a) in re- 

 gard to the large bluefin, which both 

 consider to be essentially migratory, 

 and the immature fish, which both 

 consider to be relatively sedentary. 

 They differ somewhat concerning the 

 behavior of the intermediate (me- 

 dium) fish. Sella (1929a) felt that 

 these were constantly moving, and 

 could not be separated into groups in 

 the various basins, whereas Sara 

 (1973) believed that their aggrega- 

 tions tended to remain stationary for 

 considerable periods, and migrated 

 only within the basin which they oc- 

 cupied. Both scientists agreed that 

 knowledge of the spawning behavior 

 of these intermediate bluefin was in- 

 adequate. 



107 



