They used the model to test how habitat, fishing pressures and socio-economics affect the population and ranked countries according to the risk of sawfish becoming extinct. The study found that the availability of mangrove habitats coupled with lower pressure from fishing came out as key to healthy populations of all sawfish species.

Colin Simpfendorfer, a sawfish expert at James Cook University in Australia, praised the study, saying, “It’s not just an analysis of where, but also what needs to be done.”

Ms. Yan’s international research was complemented by the American team led by Ms. Graham. This study, published in Endangered Species Research in January, showed that the US Smalltooth Sawfish stronghold is still primarily restricted to Florida, but may be beginning to expand. Her team tracked the fish using passive acoustic tags and a range of receivers and recently spotted them as far as Brunswick, Ga.

Although international trade in sawfish and their parts is prohibited under the Convention on International Trade in Endangered Species of Flora and Fauna, deliberate killing and by-catching still occur. And countries have an incomplete record of enforcing trade bans on the fins and teeth of fish, which are still prized as trophies and used in some cultural settings.

When sawfish are accidentally caught – shrimp trawls are a major threat and mitigation efforts are being studied – they often die unnecessarily because they are so difficult to untangle or release, says John Carlson, a sawfish researcher with the National Oceanic and Atmospheric Administration Fisheries. Your toothy podium will be caught in everything. It’s their Achilles heel, ”he says.

And since mangroves are the most important sites for conservation, Dr. Carlson’s sawfish research to understand why some mangrove fields, although superficially identical, are preferred to others.

After two decades of increasing attention and focused work by scientists and conservationists, “people have a high regard for sawfish,” said Sonja Fordham, co-author of Ms. Yan’s research and president of Shark Advocates International. But she warns: “We still have a long way to go and it really is a race against time.”