Making Harvest Control Rules Robust towards Environmental Variation and Perturbations

Harvested populations are under strong pressure by a number of forces. Fishing has lead to age truncated spawning stock biomass (SSB), at the same time, climate change can affect ecological processes as recruitment and individual growth. Overall, this may make the populations less resilient, and more susceptible to larger perturbations, such as an oil spill. Some exploited fish stocks are managed through a harvest control rule (HCR), which delivers a total allowable catch for a given level of SSB. Such HCRs typically serve multiple objectives as ensuring economic profitability, maintaining stable employment over time, and keeping the stocks above precautionary limits. Here, we use a bio-economic model on the Northeast Arctic cod fishery that is currently managed with a HCR. We compare this rule with alternative control rules being optimized for different objectives as maximum sustainable yield or fleet profits. We examine their robustness towards increasing stress factors in terms of stock persistence and productivity. This study sheds light on the interactions between fishing, environmental variability, population robustness and stability. Our aim is to provide knowledge on how an HCR framework can meet specific management objectives, while avoiding a loss of resilience of the population, which may largely go unnoticed.