NOTE Bartoo and Holts Drift gillnet selectivity for Thunnus alalunga 



375 



FORK LENGTH (CM) 



Figure 6 



Linear regressions of observed maximum percent sampling 

 efficiency at 53 cm and 78cmFL against stretch-mesh size for 

 albacore Thunnus alalunga. 



percent efficiency of sampling at the 53 cmFL peak 

 was regressed against mesh size for all mesh sizes 

 (Fig. 6). The estimated percent sampling efficiency at 

 53cmFL for each mesh size is shown in Table 2. 

 Using the same method, the percent sampling effi- 

 ciency was estimated for 78cmFL for each mesh size 

 (Fig. 6, Table 2). 



The family of selectivity curves by mesh size is shown 

 in Fig. 7. These were determined by shifting the mean 

 selectivity-curve limbs to the left or right so that sam- 

 pling efficiencies at 53 and 78cmFL matched the val- 

 ues in Table 2 for each mesh size. Fork lengths 

 between the two limbs were assumed to be sampled 

 with maximum efficiency, consistent with theory asso- 

 ciated with unimodal selectivity curves (Hamley 1975). 



FORK LENGTH (CM) 



Figure 9 



Selectivity curve for albacore Thunnus alalunga for 184mm 

 stretch-mesh size. 



