Most baleen whales use a strategy called lunge feeding: They swim rapidly toward a swarm of krill, opening their enormous mouths at the exact right moment. Then they close their jaws and force the seawater out through the bristly baleen plates in their mouths, filtering the krill from the water.

This behavior consumes a lot of energy, so the whales target large, dense swarms of krill, and so do fishing boats. From 2021 through 2023, four humpback whales died after becoming entangled in krill fishing nets.

The Commission for the Conservation of Antarctic Marine Living Resources, an international organization that manages use of the Southern Ocean, is required to ensure that whales and other krill-dependent populations are not harmed due to fishing. However, the commission operates by consensus, so if one member state opposes an action, nothing changes.

Member states have stalled proposals to create marine protected areas in the Southern Ocean and regulate krill fishing more tightly. A U.S.-led coalition is pressing for stricter limits, but Russia and China have resisted. Our work shows that if Antarctic krill fishing expands without strict guardrails to protect wildlife, the fragile comeback of baleen whales could be halted or even reversed.