Implementation of alternative CPUE/abundance dynamics for purse seine fisheries within MULTIFAN-CL with application to effort-based projections for skipjack tuna

A common assumption in most stock assessment models is that catch per unit of effort (CPUE) scales in strict proportion to stock abundance. However, for purse seine fi sheries in particular, this assumption may not hold. As a stock is depleted, catches can remain high as abundance decreases. This is known as hyperstability in CPUE and can impact the conclusions of analyses undertaken to inform management decisions.