LENARZ ET AL.: YIELD PER RECRUIT OF ATLANTIC YELLOWFIN TUNA 



Table 6. — Estimates of average weight of catch (kg) when M = 0.8, initial F = 0.2, and growth curve of 



LeGuen and Sakagawa (1973) is used. — Continued. 



JlrjlK'U" SIZf 



KG 



MUI.TIPLIFP OF FFFOWT 



0.? 



0.6 



1.0 



l.^. 



l.B 



?.0 



2.S 



3. ft 



S.S 



Figure 15. The values of F of large fish are 

 relatively smaller than those estimated with 

 the original growth curve. 



Results of the yield-per-recruit calculations 

 are shown in Table 7. The results indicate that 

 if effort is held constant and size at recruitment 

 is increased to the optimum, less than a 3% 

 increase in yield per recruit would occur. If 

 size at recruitment is constant and effort is 

 doubled, yield per recruit would increase by 

 about 28% which is considerably more than 

 when the original growth curve is used. If size 

 at recruitment is increased to 77.5 cm and ef- 

 fort doubled, a 44% increase in yield per recimit 

 would occur. 



• SMALL PURSE SEINE 

 A LARGE PURSE SEINE 

 A LONGLINE 



80 100 120 140 



FORK LENGTH (cm) 



Figure 15. — Estimates of size-specific F when its initial 

 value is 0.2 and using the modified growth curve. 



Table 7. — Estimates of yield per recruit (kg) for the entire fishery when M = 0.8, initial F = 0.2. and 



hypothetical growth curve is used. 



55 



