FISHERY BULLETIN: VOL. 71, NO. 1 



Table 4. — Observed and estimated size at various ages of yellowfin tuna from the Atlantic and Pacific Oceans. 

 Length (cm) is shown for most ages, and weight (kg) in parentheses for a few ages. Estimated length is based 

 on the von BertalanfFy growth function. 



Source of data 



Age 

 (years) 



Yang et a!., 1969 



Atlantic Ocean 



Le Guen el- a!., 1969 



Present study 



Eastern Atlantic 



Eastern Atlantic 



Davidoff, 1963 



Eastern Pacific 



age fish were similar to those described by Le 

 Guen et al. (1969) and are briefly described as 

 follows. Predorsal length-frequency distribu- 

 tions were tabulated for monthly samples col- 

 lected in 1967-71 off Pointe-Noire in an area from 

 Sao Tome to southern Angola. Modes were se- 

 lected by comparison of successive maxima in 

 the length-frequency distributions and mean pre- 

 dorsal length estimated for each size group by 

 a method described by Gheno and Le Guen 

 (1968). Mean dorsal lengths were then con- 

 verted to fork lengths with the aid of Table 5, 

 which was based on fish measured for both pre- 

 dorsal and fork lengths at Pointe-Noire. The 

 data in Table 5 give a fork length-predorsal 



length relation of log L/ = 0.299 + 1.162 log Ld 

 that is not significantly different from the equa- 

 tion used earlier. 



An estimated age was assigned to each size 

 group (Table 6) based on: (1) date of birth of 

 yellowfin tuna caught off Point-Noire is on the 

 average March 1 and (2) recruitment occurs in 

 the second year of life (Le Guen et al,. 1969). 

 Estimates of parameters of the von Bertalanffy 

 function were then calculated with Psaropolos' 

 (1966) computer program. 



Length at age estimates were converted to 

 weight at age with the weight-length relation 

 of Lenarz (see footnote 4) , which was mentioned 

 earlier. 



Table 5. — Predorsal length and fork length measure- 

 ments of yellowfin tuna landed at Pointe-Noire, 1967-71. 



RESULTS 



Estimates of parameters of the von Bertalan- 

 flfy function were L^ = 175.17 cm (SE = 3.67), 

 K = 0.044 per month (SE = 0.003), and U = 

 9.643 months (SE = 0.815). These estimates 

 are quite similar to those derived by Le Guen 

 et al. (1969) for the Pointe-Noire region based 

 on only data from 1967-68 (Table 7) ; but L« is 

 significantly lower and K significantly higher 

 than our best estimates for yellowfin tuna from 

 a larger area of the eastern Atlantic, even when 

 the difference in range of lengths in the data is 

 taken into account. On the other hand, length 

 at age and weight at age estimates for ages 1-5 

 years are quite similar to those for the entire 

 eastern Atlantic (Table 4). Thus, we conclude 



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