By-catch risk for toothed whales in global small-scale fisheries

Fisheries by-catch poses the single greatest threat to cetacean (whales, dolphins and porpoises) populations. Despite this, by-catch of cetaceans does not receive proportionate levels of research or management effort. The contribution of small-scale fisheries to cetacean by-catch is generally overlooked because of the extreme data paucity in these fisheries. Here, we assess the likely geographic distribution of by-catch risk posed to the odontocetes (toothed whales) at the global scale. We combine species’ occurrence and estimates of fisheries susceptibility for all 72 marine toothed whale species with estimates of small-scale fisheries’ gillnet fishing pressure across 163 marine fishing nations. We show that the by-catch risk from small-scale fisheries is likely greatest in low- and middle-income regions, generally in the tropics and sub-tropics. Our findings highlight a “wicked problem”, that the highest by-catch risks primarily occur in regions with lowest fisheries management efficacy. Addressing by-catch in these priority regions is fraught with potentially damaging consequences for the survival of vulnerable human coastal communities. Yet, immediate management and conservation actions are required to prevent species extirpation and extinction through the reduction of small-scale fisheries by-catch. To be successful, these actions will likely require multilateral cooperation and must carefully balance both species and human needs.