FISHERY BULLETIN: VOL. 71, NO. 1 



frequency methods (Table 4). This suggests 

 that the marks on scales of Atlantic yellowfin 

 tuna are indeed layed down at regular intervals 

 and that observed lengths at age rather than esti- 

 mates of parameters of the von Bertalanffy func- 

 tion are more meaningful in comparison of 

 growth of yellowfin tuna. For such a compari- 

 son, the average growth rate of Atlantic yellow- 

 fin tuna is 17 cm/6 months, based on the scale 

 method, and 18 cm/6 months, based on the 

 length-frequency method for ages 1.5-3.5 years. 



The comparison of observed lengths at age 

 also indicates that there is little difference be- 

 tween growth of Atlantic and Pacific yellowfin 

 tuna (Table 4) . Yang et al. (1969) , on the other 

 hand, suggested that growth is faster in the At- 

 lantic than in the Pacific. We analyzed their 

 data with analysis of covariance and found that 

 their Walford curves for the Atlantic and Pacific 

 yellowfin tuna were not significantly different 

 from a common line {F2. 5 = 0.474) nor from 

 parallel lines (Fi, 5 = 0.904). Thus the sug- 

 gestion by Yang et al. was not demonstrated by 

 their data, but in fact, growth of yellowfin tuna 

 appears to be similar in the two oceans. 



Finally, since the parameters of the von Bert- 

 alanffy growth function are sensitive to the 

 method of analysis and range of sizes used to 

 estimate them, we recommend that the observed 

 size at age rather than the estimated size at age 

 from the von Bertalanffy growth function be 

 used in estimating yield per recruitment. The 

 Ricker (1958) model of yield per recruitment, 

 for example, is appropriate for observed values, 



ACKNOWLEDGMENT 



We thank W. H. Bayliff , D. Kramer, and W. H. 

 Lenarz for reading the manuscript and offering 

 helpful suggestions. 



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