Froese et al. Revisit Population Dynamics Equations to Minimize the Impact of Fishing
How can fisheries science be used to minimize the impact of a given catch? Froese et al. revisited key equations of population dynamics with the explicit purpose of minimizing the impact of fishing in their new paper. The main findings include:
1). For a wide range of realistic cost-of-fishing scenarios, economic yields (= profits) are maximized and impact on stock and ecosystem are minimized when human-induced mortality (= fishing mortality F) is less than mortality caused by predation, diseases, hazards, or old age (= natural mortality M). F = 1/2 M is a reasonable precautionary target with pretty good catches.
2). For every fishing intensity (F/M) there is an optimum length of first capture which maximizes catch and biomass (= stock size). While the length that maximizes catches was known, the length that maximizes catches AND biomass is new.
3). Combining 1) and 2) leads to stock sizes above half of unexploited stock size. This is the area of stock size where most species will be able to fulfill their natural ecosystem roles as prey or predator, the main goal of correctly understood ecosystem-based fisheries management.
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