Table 19. Bluefin maturity by month from the trap fishery along the southern 

 Atlantic coast of Spain (F. de Buen 1^)27). 



Males 



Females 



Month 



% Not % Fully % 

 Mature Mature Spent 



%Not % Fully % 

 Mature Mature Spent 



two intensive surveys have failed to 

 produce a single identifiable egg or 

 early stage (less than 1 cm long) of the 

 species from the area. 



O. de Buen ( 1 924) and F. de Buen 

 (1924, 1925. 1927) failed to find any 

 eggs or early stages of bluefin tuna 

 during their intensive 1923 survey of 

 the Ibero-Moroccan Bay, west of 

 Gibraltar, and the Alboran Sea, east of 

 it They explained this apparent contra- 

 diction of their theory that the Ibero- 

 Moroccan Bay was a major spawning 

 ground for bluefin tuna, and that the 

 maturing fish did not enter the Medi- 

 terranean to spawn, as follows. The 

 bluefin spawned in this Bay, but the 

 eggs and larvae were carried from it by 

 the surface (Atlantic) current into the 

 Mediterranean before they attained full 

 mobility. There they accumulated off 

 the Moroccan coast between Punta 

 Almina and Cape Tres Forcas, where 

 the rich plankton provided food for the 

 early stages. Roule's (1923) contrary 

 view, that bluefin larvae were abyssal 

 and were passively transported from 

 the Mediterranean into the Atlantic by 

 the deep outflowing (Mediterranean) 

 current will be discussed in Section 

 VE2. More recently, Spanish scientists 

 in the research vessel "Comide de 



Saavedra" conducted an intensive 

 planktonic and hydrographic survey of 

 the waters east and west of Gibraltar in 

 1972. The period of the survey, 19 

 June- 16 July, was chosen because this 

 was regarded as the period of maxi- 

 mum spawning of bluefin tuna in the 

 area (Rodriguez-Roda 1975). During 

 this cruise 66 stations were occupied in 

 the Atlantic, four in the Strait of 

 Gibraltar, and 82 in the Mediterranean 

 (Rodriguez-Roda 1975). No identifi- 

 able larval or juvenile bluefin tuna were 

 collected. 



Until eggs or early stages collected 

 in the Ibero-Moroccan Bay are posi- 

 tively identified as those of bluefin tuna, 

 this area must be regarded as only a 

 hypothetical spawning area forthis spe- 

 cies. 



F. de Buen (1937) proposed a sec- 

 ond spawning area for the eastern At- 

 lantic bluefin in the southeastern cor- 

 ner of the Bay of Biscay. This hypoth- 

 esis was based on reports of bluefin 

 with ripe ovaries being taken there in 

 June. Le Gail (1952) reported similar 

 findings there during the 1 950 and 1 95 1 

 seasons. Creac'h (1952) described the 

 sizes of bluefin tuna landed at Saint- 

 Jean-de-Luz through the 1 95 1 season 

 (April I2-October 26) and the condi- 



tion of their gonads. The ovaries of 

 very few specimens among the bluefin 

 landed in the period June 16-30 were 

 ripe. The fish landed in this period were 

 in the 15-25 kg weight range. Creac'h 

 (1952) noted that a similar situation 

 had been observed for the first time, in 

 about the same period, during the 1 950 

 season. No observations of mature fish 

 during the remainder of the season were 

 reported. 



Cort et al. (1976) and Cort (1977) 

 provided the first detailed information 

 on the gonads of maturing bluefin taken 

 in the Bay of Biscay. These authors 

 examined four bluefin 1 25- 1 49 cm long 

 taken in the Bay of Biscay June 25-26, 

 1976, and seven 111 to 161 cm long 

 taken there on July 15. 1976. On the 

 basis of color (Rodriguez-Roda 1 964a), 

 they estimated that the two males in the 

 first group were fully mature, whereas 

 one female was in pre-spawning con- 

 dition and the other specimen was spent. 

 They classified three females in the 

 second group as pre-spawning and two 

 as spent, and considered one male to be 

 fully mature and the other spent. 



Cort et al. (1976), using the tech- 

 nique ofRodriguez-Roda( 1967), mea- 

 sured the diameters of eggs from two 

 females. 148 and 152 cm long, of the 

 second group. The diameters for the 

 148 cm specimen ranged from 0.10 to 

 0.66 mm, with many from 0.22 to 0.58 

 mm and the highest mode at 0.50 mm 

 Those from the other ranged from 0. 14 

 to 0.58 mm. with most between 0.30 

 and 0.53 mm and a wide mode be- 

 tween 0.40 and 0.46 mm They classi- 

 fied these fish as in stage IV (pre-spawn- 

 ing) or between stage 111 (maturation) 

 and stage IV, since the diameters were 

 greater than those of the ova and oo- 

 cytes of the specimens placed by 

 Rodriguez-Roda (1967) in stage 111. 

 Cort (1977) noted that these observa- 



Table 20. Monthly percentage of the sexual stages (years 1956-1959) of tuna at Barbate (Rodriguez-Roda 1964a). 



Month 



Sexual Stages of Males. Number = 284 



II 



III 



IV 



VI 



Sexual Stages of Females. Number = 495 

 I II III IV V VI 



May — — 100.00 — 



June 0.62 3.09 95.06 — 



July — 1.85 5.55 1.85 



August — — 3.17 — 



1.23 

 90.74 

 96.82 



n.4i 



— 100.00 

 3.26 96.33 



— 9.46 

 1.06 



90.54 

 98.94 



76 



