Figure 58. Geographic references and movements of bluefin tuna along the 

 Italian Adriatic coast. 



A Yugoslavian purse seine fishery 

 for bluefin tuna was introduced in 

 1929 (Tilic 1954), with seven ves- 

 sels fishing in the period 1936-1940 

 and 1 1 in the period 1 947- 1 95 1 . Like 

 the trap fishery, this occurred mainly 

 off the northern coasts and the adja- 

 cent islands (Morovic 1961). Total 

 yearly bluefin tuna catches in Yugo- 

 slavia averaged 127 tons for 1936- 

 1940 but increased to 468-873 tons 

 in 1947-1951 (Tilic 1954). In 1952- 

 1974, the total yearly catches varied 

 from less than 100 to 700 tons, but 

 have not exceeded 350 tons since 

 1959 (Hamre et al. 1966, Miyake et 

 al. 1976). 



Trap fisheries have long been 

 important in Tunisia (Figure 56). Al- 

 though as many as 1 1 traps have op- 

 erated in some years (Gaudiiliere 

 1954), Roule (1924) recommended 

 that studies of the bluefin tuna stocks 

 in the area be concentrated on the 

 catches of the Sidi Daoud trap on the 

 west side of the Cape Bon peninsula. 

 This trap has been by far the most 

 productive in Tunisia, and has fished 



almost continuously since 1 863 (Fig- 

 ure 59). The other traps have fished 

 intermittently and their catches 

 seemed to follow the same trends as 

 those of Sidi Daoud. Its catches for 

 1863-1923 (excepting 1874 when it 

 was not set) averaged about 8,000 

 bluefin tuna per year (Roule 1924). 

 In the years 1928-1937, regarded as 

 a period of crisis, its annual catches 

 ranged from 1,000 to 3,400 fish 

 (Heldt 1932, 1934, 1937. 1938). In 

 1955 it took 3,600 fish with an aver- 

 age weight of 128 kg (Postel 1956). 

 In the period from 1962 through 

 1976, its approximate average an- 

 nual catches declined from 1 ,500 fish 

 weighing 180 tons in the first five 

 years to about 300 fish weighing 40 

 tons in the last tlve (M. /aouali, per- 

 sonal communication), fhus, the Tu- 

 nisian trap fishery for bluelln has 

 apparently suffered a collapse simi- 

 lar to that of the Italian trap fisheries. 

 Sella (1929a) pointed out that the 

 trends of the Sidi Daoud catches were 

 remarkably similar to those of the 

 important traps off southwestern 



Sardinia. Roule ( 1 924) concluded that 

 the Sidi Daoud catches varied in- 

 versely with the amount of rainfall in 

 the area. He felt that the runoff from 

 the Lake of Bizerte reduced the sa- 

 linity of the waters around the trap, 

 making the area less attractive to the 

 bluefin. 



Total catches of the Tunisian 

 traps in 1 9 1 0- 1 923 ranged from 4,300 

 to 34,400 fish with the larger catches 

 being taken before 1916 (Roule 

 1924). In 1927-1938 catches ranged 

 from 2,200 to 9,000 fish weighing 

 200 to 800 tons with yearly average 

 weights of 7 1 to 1 08 kg (Heldt 1 932, 

 1934, 1937, 1938). The three traps 

 operating in 1955 caught 3,985 blue- 

 fin averaging 1 19 kg (Postel 1956). 

 This constituted only 47 percent of 

 the total catch of the traps, by weight. 

 The annual total catches of all spe- 

 cies by the three Tunisian madragues 

 active in 1 952- 1 958 ranged from 677 

 to 1,013 tons(Belloc 1961). Postel's 

 ( 1 956) data suggest that about half of 

 these tonnages might have been blue- 

 fin. Total Tunisian bluefin catches 

 for 1964-1974 ranged from 200 to 

 900 tons with smaller catches occur- 

 ring since 1970 (Miyake et al. 1976) 

 but no breakdown by gear is avail- 

 able. Heldt (1932. 1934, 1937) re- 

 ported that catches of up to 40 tons a 

 year were taken in the "winter fish- 

 ery", mainly with seines. 



The Tunisian traps all fish in the 

 "arrival" run, except for some ex- 

 perimental fishing of the "return" run 

 by the Cap Zebib trap in 1 924 (Gruvel 

 1926) and an experimental trap at 

 Ras Mustapha (Bellon 1954). For 

 1931-37, the first trap catches were 

 from Ma\ 19 to June 9, and the last 

 from .lune 20 to July 6 (Heldt 1932, 

 1934. 1937, 1938). Heldt(1929)sup- 

 plied average weights of the bluefin 

 caught by the Sidi Daoud and Ras el 

 Ahmar traps and tor all the Tunisian 

 traps for 1904-22. The average for 

 all traps ranged from 50 to 89 kg. 

 The average for Ras el Ahmar (59- 

 126 kg) was higher than that for Sidi 

 Daoud (50-89 kg) in every year but 

 two. Since Ras el Ahmar is situated 

 north of Sidi Daoud, nearer the tip of 

 the Cape Bon peninsula, Heldt con- 

 cluded that the larger bluefin trav- 

 elled farther offshore than the smaller 

 individuals. Heldfs (1932, 1934, 



62 



