Catch per Unit Effort and Hidden Fleet Dynamic Effects

Fisheries science has shown us many examples where populations “collapse” because sustained periods of decline were not detected quickly enough. Potential biases in fisheries statistics due to non-linear relationships between abundance and catch are  well appreciated. Biases resulting from the nature of fishing itself are less well studied. Traditional fisheries analyses often represent catch in terms of the amount of fishing activity: catch per unit effort (CPUE). However, including effort in the measure of fishing performance can mask disproportionate relationships between catch and nominal fishing effort. I will advocate the separation of catch and effort in fisheries analysis to reveal biases that can result from underlying fisher behavior and common data aggregation. A simple agent based fishery model will be used to illustrate these points and indicate remedial measures for future work.