More than 300 olive ridley sea turtles were found dead in August 2018 off Mexico's southern coast, an alarming loss for a species classified as vulnerable to extinction by the International Union for Conservation of Nature. The turtles were floating together in a cluster near Oaxaca, National Geographic reports, apparently all killed by the same wayward fishing net.

These turtles are just the latest victims of a growing problem that's decimating marine animals around the world. The killers are known as "ghost nets" — abandoned or lost fishing lines, nets and traps that drift in the water or snag on reefs or rocks along shorelines, trapping and killing animals for years, even decades.

"Literally hundreds of kilometers of nets get lost every year," according to Mission Blue, "and due to the nature of the materials used to produce these nets they can and will keep fishing for multiple decades, possibly even for several centuries."

Ghost nets kill indiscriminately, entangling everything from sea turtles and seals to manta rays, sharks and whales, often causing a slow and painful death. As animals are caught, they sometimes attract predators that end up becoming trapped themselves.

According to the Marine Mammal Center, "It is estimated that ghost nets account for approximately 10 percent of all marine debris. Birds, fish, crabs, turtles, dolphins and thousands of marine mammals get caught in this deadly, silent floating debris in what is called 'ghost fishing.' And every year over 100,000 marine mammals die from the harmful effects of plastic, fishing nets, and trash in our oceans."

A team of researchers from SINTEF, Norway's largest research institute, believe they have found a solution. They've developed small cards that attach to nets and send out sonar signals of their location. The cards don't use any energy and can operate much longer than the traditional transponders used to locate nets.

We have heard many stories about the rescue efforts of good citizens or professional divers cutting away the nets entangling whales. Most of these have a happy ending — sometimes with the rescued victim even seeming to celebrate and thank the rescuers. Below is a video of just how intense and difficult it is to rescue a single entangled whale, not to mention how dangerous it is to those trying to help.

This whale was freed and had a very happy ending to her situation. However, tens of thousands of animals every year can't be saved. Ghost Fishing is a nonprofit organization of experienced divers who clean up ghost nets and abandoned fishing gear, and help bring attention to the issue. They are part of a coalition of organizations promoting healthy seas. Their help, and the help of similar organizations, is invaluable.

If you would like to find out more about how you can help reduce the danger of ghost nets to wildlife, check out NOAA's Ocean Today, Project AWARE and Waste Free Oceans and similar organizations and see how you can lend a hand.