about 20,000 fish per year from 1 946- 

 1961 (Sakagawa and Coan 1974), 

 took only 388 fish and the company 

 which had operated the Spanish traps 

 since 1929 was dissolved (Rodriguez 

 Roda 1973) Barbate took 1,952 tuna 

 m 1973 (Rodriguez Roda 1974). Two 

 Moroccan traps, the only others set 

 in the Atlantic in that year, caught 12 

 fish (R. Sara, personal com- 

 munication). Two Moroccan traps 

 were also set in 1 974, but took only 

 seven bluefin (M Lambt)euf per- 

 sonal communication). The situation 

 had become such that when Baibate, 

 which had not been set in 1974, took 

 1,842 fish (less than one tenth of the 

 1946-1961 average) in 1975, it was 

 regarded as encouraging (Aioncle et 

 al. 1976)! 



The decline in the Barbate 

 catches was accompanied by a 

 marked increase in the average 

 weight, indicating that poor recruit- 

 ment to the fishen,' was a major cause 

 of the decreased catches Although 

 the annual catch fell from 1 9,000 fish 

 in 1 961 to 2,500 in 1 97 1 , the average 

 weight per fish increased from 145 

 kg to 223 kg. (Sakagawa and Coan 

 1974). Rodriguez-Roda (1964a) had 

 already noted the drastic decrease in 

 the numbers of the smaller bluefin 

 taken in the Spanish traps since 1953, 

 and attributed it to either a high mor- 

 tality on young fish in previous years, 

 or unknown variations in oceano- 

 graphic conditions which might have 

 caused them to go elsewhere 



h. Trends in Eastern Atlantic 

 Fisheries 



The decline in the northeastern 

 Atlantic fisheries for large and me- 

 dium bluefin tuna is illustrated in Fig- 

 ure 51 This trend has been re\ersed 

 to some extent by improved catches 

 off Norway, and more significantly 

 by the entry of the Japanese longline 

 fisher}' into the area in 1971 (Shingu 

 and Hisada 1976) Concern has been 

 expressed o\er hea\y calchcs of \ci\ 

 young bluefin as a possible cause for 

 the decline in the fisheries for larger 

 individuals (Rodriguez-Roda 1964a, 

 1964b, 1969d) 



6. Mediterranean and Black Seas 



The fixed trap has been the prime 

 producer of bluefin tuna in the Medi- 

 terranean Sea (Figures 52 and 53) 



Table 9 Sexes dcteiTnined liom samples of 111 e 1956-1961 catches from the 

 Barbate trap, ;uid the 1 90 1 calchcs of two others 



Trap 



Barbate 



Sancti-Pctri 



Isia Cristina 



Males 

 Females 



403 

 756 



123 

 215 



46 

 66 



for centuries. The most important 

 traps were the large ones in the cen- 

 tral MediteiTanean. Ihe majority of 

 these fished the "anival" run in May 

 and June, the remainder fished the 

 "return" run in July and August Some 

 of the smaller traps also fished these 

 migiatopj' passages and similar runs 

 m the Bosphorus between the Sea of 

 Marmara and the Black Sea The ma- 

 jority of the smaller traps, howeser. 



fished mainh' for bluefin which were 

 too young to spawn, or which were 

 in the feeding, rather than the spawn- 

 ing, phase of their annual cycle. 

 I'herefore the fishing seasons of these 

 traps were not limited to the May- 

 August spawning cycle, and extended 

 through much of the year. These 

 smaller traps for non-spawnmg tuna 

 were widely distributed along the 

 coasts of the Mediterranean, but were 



PERIOD OF REPRODUCTIVE BEHAVIOR 



EMISSION & FERTILIZATION 



ARRIVAL 



IN THE ZONE 

 OF MATURATION 



I 



DEPARTURE 



100 



-SO 



MAY a JUNE 



JULY A AUGUST 



^^NING 



RETURN 



TRAP 



JULY - AUGUST 



Figure 47 Schematic tiiagram of bluefin luna niowmcnts in the vicinity of traps 

 during tlie spawning cvcle 



46 



