The certainty of uncertainty in marine conservation and what to do about it

The confounding effects of difficult sampling and dynamic systems make uncertainty the norm for managers of marine ecosystems. Thus managers need approaches that use relatively small amounts of information and account for a wide suite of biological and physical influences. Here we use a case study approach to review the use of several possible techniques for making decisions about marine ecosystems despite uncertainty. We describe the use of expert judgment in the rebuilding plans for data-poor US fisheries, models to manage the krill fishery in the Southern Ocean to account for both the impacts of climate change and the resource needs of krill predators, an integrated risk assessment framework to prioritize shark management in the Atlantic Ocean despite severe data limitations, and models to account for climate impacts on salmonid populations in California. Through this review, we show that with limited information, managers can use models to explore how highly variable systems might respond to management options under different scenarios. Expert judgment can help shape the assumptions that form the basis for those models and propose sensible boundaries within which management options can be developed. A weight of evidence approach can take advantage of small amounts of information from multiple sources, including models and expert judgment. Although none of these approaches is perfect, they can help provide a logical starting point for conservation and management, despite the certainty of uncertainty.