Progress in establishing marine protected areas around East Antarctica and in the Ross Sea seems to have stalled, threatening to derail research and conservation in the region. We propose temporary, experimental closures of fisheries to help to disentangle the complex effects of human activities and natural changes on populations of krill predators such as penguins, whales and fish.

The Conservation of Antarctic Marine Living Resources (CAMLR) Convention has been in force since 1982, yet the impact of krill fishing on Antarctic predators is still unclear. In the Western Antarctic Peninsula, confounded variables and the difficulties of obtaining fisheries data at small spatial scales make it hard to evaluate the relative influence of various factors on krill-predator populations. These include climate change and cetacean recovery, as well as fishing effort and other human activities.

Small-scale, temporary experimental closures have been instructive in South Africa; these operate in rotation to focus on the effects of the closure (R. B. Sherley et al. Biol. Lett. 11, 20150237; 2015). Under the convention, the use of such small experimental units has long been considered important for managing scientific study and conservation (A. J. Constable CCAMLR Sci. 9, 233–253; 2002). It mandates that its commission “shall formulate, adopt and revise conservation measures on the basis of the best scientific evidence available”.

Because krill predators in the Western Antarctic Peninsula are well monitored, it makes it a priority area for testing experimental manipulations. We encourage parties to the convention to honour their commitments to Antarctic conservation by putting forward a plan for experimental closures in the region.