EDITOR’S NOTE: Call to Earth is a CNN editorial series committed to reporting on the environmental challenges facing our planet, together with the solutions. Rolex’s Perpetual Planet Initiative has partnered with CNN to drive awareness and education around key sustainability issues and to inspire positive action.

In the rough waters of western Ghana, a fisherman lifts a strange-looking, flat creature — half-shark, half-ray — out of his net.

It’s a guitarfish, a “living fossil” whose ancestors swam the same Jurassic oceans as dinosaurs. Today, it’s among the most threatened fish in the ocean — its fins sold for hundreds of dollars in Asian markets to make luxury soup, a trade pushing them toward extinction.

The fisherman measures the animal, notes where he caught it, and slides it back into the waves, unharmed.

Behind that small act is a decade of work by marine biologist Dr. Issah Seidu, whose research is responsible for much of what Ghana knows about its sharks and rays.