Fleet Behaviour Under Economic Uncertainty: Multi‐Species Policy Scenarios for the Purse‐Seine Fishery

ABSTRACT Managing fishing effort remains a central challenge in achieving sustainability in many fisheries, particularly where high‐value species attract intense competition. In the Indian Ocean tropical tuna fishery, understanding how fishers respond to changing bio‐economic conditions is essential for developing effective management. This study evaluates the influence of effort‐based management measures on the size and investment behaviour of the purse‐seine fleet targeting skipjack ( Katsuwonus pelamis ) and yellowfin tuna ( Thunnus albacares ). Using Random Utility Models (RUMs), we identify the key economic drivers of strategic decision‐making, validate them through model evaluation, and integrate them with age‐structured operating models (OMs). The RUM achieves 93% predictive accuracy, offering a robust basis for exploring policy options that balance conservation and economic objectives. Scenario testing under different cost and price conditions illustrates how economic pressures shape entry and exit decisions within the fleet.