Curve B; Catch-effort 

 relationship in terms of 

 efficiency of period 0, 



Curve A; 

 Catch-effort 

 relationship 

 as observed 



Fi^re 1. — Biased estimate of fishing; effort due to an underestimate of increased efficiency. 



"2 2 



Level of effort required Actual level of 



to obtain the catch of period 2 effort observed 



using vessels of effic. 3. in period 2, 



Effort 

 (ton-trips) 



Figure 2. — Optimal fishing effort based on current efficiency levels. 



59 



