FISHERY BULLETIN: VOL. 71, NO. 1 



Table 7. — Estimates of parameters of the von Bertalanffy growth 

 function for yellowfin tuna from the Atlantic and Pacific Oceans. Es- 

 timates are based on data reported in various studies, and were calcu- 

 lated by Fabens' (1965) procedure, except those of Le Guen et al. (1969). 



1 Estimates were based on weighed average length 

 et al. (1960). Sample size of each sex wos used as 



for each scale mark reported by Yabuta 

 the weighing factor. 



smaller. Possiblj^ this smaller K is caused by 

 error in the interpretation of scale marks and 

 the paucity of large fish in their data. The max- 

 imum number of marks observed by Yang et al. 

 was five, with a corresponding mean length of 

 132.9 cm at time of fifth mark formation, but 

 fish as large as 180 cm long were reportedly 

 sampled. For our study, fish as large as mean 

 length 166 cm were used in the calculations. 



ESTIMATES FROM MODAL PROGRESSION 



Davidoff (1963) examined modal progressions 

 of length-frequency distributions of eastern Pa- 

 cific yellowfin tuna caught by baitboats and purse 

 seiners and calculated with the Walford pro- 

 cedure L«, = 167 cm and K = 0.05, on a monthly 

 basis, which he noted were similar to earlier esti- 

 mates reported by Hennemuth (1961). David- 

 oflF's estimates were based on average modal 

 length at each age of all year classes combined. 

 Equal weight was therefore given to each datum 

 point in his calculation. 



Using the Fabens' procedure and data for each 

 year class reported by Davidoff (his Table 6), 

 we recalculated the growth estimates. The re- 

 sults, L„ = 200.3 and K = 0.030, are consider- 

 ably larger for L„ and smaller for K than 

 Davidofl["'s estimates but similar to our estimates 

 for Atlantic yellowfin tuna (Table 7). 



Hennemuth (1961) reported that fish 70 cm 

 long in the eastern Pacific were about 20 months 

 old. Entered into the von Bertalanflfy equation, 

 this gives a ^o of 5.67 months with L« = 200.3 

 and K — 0.030, and a means of estimating length 

 at age for eastern Pacific yellowfin tuna. The 

 results are shown in Table 4. They compared 

 favorably with our estimates for Atlantic yellow- 

 fin tuna, although apparent growth in the east- 

 ern Atlantic is 0.9 to 2.8 "^f faster than that in the 

 eastern Pacific for ages 2 through 5 years. 



Moore (1951) based his estimates of growth 

 on length-frequency distributions of yellowfin 

 tuna caught primarily by longline gear in the 

 central Pacific. He used the Walford procedure 

 and calculated L« = 190.0 cm and K = 0.037 

 per month. Because of a limitation of Walford's 



184 



