Such a strange looking lumberjack undersea. Might seem hard to see prey with a snout like that.... so the story gets stranger
"Tiny pores called ampullae of Lorenzini allow sharks and rays to detect the minute electric fields produced by their prey. These ampullae are especially common on the heads of sawfish" — Ed Yong's An Immense World: How Animal Senses Reveal the Hidden Realms Around Us, p.303.
Some "can detect an electric field of just one nanovolt — a billionth of a volt (as faint as a AA battery with electrodes on opposite sides of the Atlantic ocean) — across a centimeter of water. It's electric sense only enters the fray at the close of the hunt, to pinpoint the exact position of its prey and guide its strike. That's why the ampullae of Lorenzini are usually concentrated around the mouth." (p.292)
The saw "is packed with ampullae, top and bottom. It greatly extends the sawfish's electrical awareness into the space ahead of it — a useful trait in turbid water. 'We find them in rivers where we can't even see our boat's propeller,' says Barbara Wueringer, who studies these animals. She showed that the saw doubles as both a sensor and a weapon. When fish swim above the saw, the sawfish slashes at them, using its sideways teeth to impale, stun, and bisect. When the wounded fish fall to the bottom, the sawfish uses the underside of it saw to find and pin them. 'Whenever I see them, I think: how is this a thing?'" (p.293)
