Simple solutions to complex problems in fisheries

Abstract

Fisheries science faces a challenging combination of complexity and data limitation that places opposing pressures on theoretical research - which seeks to describe the complexity - and empirical research - which is constrained to simplicity by the limitations of available data. In this volume, I present studies aiming to reconcile theoretical and empirical approaches to assessing the current status of fished populations and designing management plans in two ways: i) by using concise mechanistic theories rooted in measurable parameters to develop new predictive assessment tools; and ii) by using ecological and economic theory to develop insights whose applications are not data-dependent or system specific. My research provides several important insights for assessment and management in fisheries: 1) Combinations of biological and socioeconomic conditions that eventually lead to extinction or overfishing can often be empirically identified decades before high harvest rates and large population declines occur, allowing for preventative management. 2) Though there is concern that harvest value, which rises as a harvested species is depleted, can allow profits to be maintained it is driven extinct, this threat most often also requires catch-rates to be substantially robust to declining abundance. Because range contraction often buffers population densities against abundance declines, habitat destruction may exacerbate threats of overharvesting. 3) Assessments based on single-species population models in multispecies fisheries can often provide reliable estimates of sustainable yields and harvest rates in populations with high vulnerability to overfishing, but often significantly overestimate sustainable yields and harvest rates in populations with lower vulnerability. However, single-species assessment frameworks can nonetheless be used to identify conditions leading to such bias, and estimate bounds on its magnitude. 4) Diversifying technologies and efficiencies within fishing fleets often leads to fewer population collapses in both managed and unmanaged fisheries; and increases the positive impact management can make on fishery yields and profits. The studies in this volume provide new perspectives on theoretical-empirical synergies in fisheries research, and maximizing the information value of fisheries data through theoretical concision and ecological abstraction.