While fisheries scientists are still struggling with uncertainties in stock assessments for single species (Nature 494, 282; 2013), a giant leap towards a whole-ecosystem approach is being embedded into international policies for fisheries management. However, underwater monitoring of a huge and complex range of environmental and biological processes will be difficult and costly.

The unsustainable use of a resource can have knock-on effects within an ecosystem, as well as socioeconomic repercussions. If budget constraints limit the monitoring of whole communities, however, population estimates and predictions could be compromised, possibly masking a species decline and leading to misguided policy decisions. Governments should not be tempted to find inexpensive solutions to fulfil policy requirements and to meet deadlines.

There are tools available to help countries pinpoint problems, direct research efforts, quantify acceptable limits for degradation, calculate the monitoring effort needed to detect a meaningful change, and gather resources for implementing a useful strategy (see B. S. Halpern et al. Nature 488, 615–620; 2012).