Catch-per-unit-effort (CPUE) has been central to fisheries stock assessment for over 60 years, yet its reliability depends on catchability remaining constant. This assumption is increasingly challenged by evidence that fish-fisheries interactions, fish physiology, behaviour, and environmental variability can alter vulnerability to capture. When catchability shifts, CPUE decouples from true abundance, with serious consequences for stock assessment and management. For example, following the 2016 Great Barrier Reef marine heatwave, CPUE of coral trout (Plectropomus leopardus) increased despite declining biomass. This illustrates how acute environmental events can drive catchability changes that undermine the very metrics managers rely on.
Here, we draw on the literature to reframe catchability as a dynamic, emergent property of coupled fish-fisher systems embedded in broader socio-ecological contexts. We examine how fish internal states, fisher behaviour, and environmental variability interact to shape individual-level vulnerability to fishing gears in hook-and-line fisheries and assess how this scales to population-level catchability. We thereby elevate catchability from a nuisance parameter to a central concept linking individual fish behaviour, population dynamics, and human fishing processes. This framing invites discussion toward more adaptive, trait- and environment-based approaches to stock assessment that reflect the dynamic state of fish and fisheries under rapid environmental change.