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Knifetooth sawfish, seen mostly from below.

The knifetooth sawfish (Anoxypristis cuspidata) is one of five sawfish species, all of which are facing extinction. Credit: Norbert Wu/Minden/Nature Picture Library

Conservation biology

Humans push a hulking fish with a chainsaw nose towards oblivion

The strange-looking sawfish, itself a predator, falls prey to overfishing and habitat destruction.

The long-snouted, shark-like predators called sawfish have vanished from nearly 60% of their historical habitat and are nearing extinction, according to a mathematical method of counting marine species.

Sawfish (family Pristidae) are rays that live near seashores and in mangrove areas: habitats that are rapidly disappearing. To study what this means for the five species in the family, Helen Yan at Simon Fraser University in Burnaby, Canada, and her colleagues reviewed sawfish research conducted between 2014 and 2019 in 64 countries. From this, they estimated the distribution patterns of these fishes, which are known for their large size — some species routinely reach 5 metres in length — and their chainsaw-like noses.

The team found the creatures’ distribution patterns had changed in places affected by fishing pressures and habitat loss. These pressures have driven the fishes to extinction in 55 of the 90 countries whose waters they once occupied.

Saving the sawfish, the researchers say, will require countries to protect the creatures’ offshore habitats and to ban fishers from keeping sawfish that are caught in their nets.

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Pulsar wind nebula illustration

Curving purple lines in this artist’s impression represent the magnetic field of a neutron star (white sphere) left over from a brilliant supernova. Credit: Salvatore Orlando/INAF-Osservatorio Astronomico di Palermo

Astronomy and astrophysics

X-rays expose a clue to the mystery of the missing neutron star

Astronomers might have spotted the long-sought debris of a famous stellar explosion.
A bone fragment next to a dime

A bone fragment excavated in Southeast Alaska belonged to one of the earliest known domestic dogs in the Americas. Credit: Douglas Levere/University at Buffalo


An ancient Alaskan dog’s DNA hints at an epic shared journey

To scientists’ surprise, a 10,000-year-old bone found in an Alaskan cave belonged to a domestic dog — one of the earliest known from the Americas.
Emissions billow from smokestacks at a coal-fired power plant as the sun sets, India.

Black carbon emitted by power plants and other sources in Asia wafts to the Arctic, where the pollution accelerates the melting of ice and snow. Credit: Kuni Takahashi/Bloomberg/Getty

Atmospheric science

Soot from Asia travels express on a highway to the high Arctic

Black carbon from fuel combustion in South Asia bolsters the effects of climate change on northern ice and snow.
Prevotella copri bacteria, computer illustration

The gut bacterium Prevotella copri (artist’s impression) has been linked to a reduction in the health benefits of a diet that skimps on red meat in favour of fish and vegetables. Credit: Kateryna Kon/Science Photo Library


Trying a Mediterranean diet? Gut microbes might sway the outcome

The composition of a person’s microbiome could influence the health effects of swapping steak for vegetables and olive oil.
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