Nearly 100 Baby Hammerhead Sharks Found Dead in Hawaii, Fishing Gear Suspected

A La Mariana Sailing Club worker made a sad discovery on a beach in Hawaii near the club. Nearly a 100 endangered hammerhead shark bodies are rotting on the shore—all of them newborn pups.

Scalloped hammerhead sharks are relatively common around Oahu's Keehi Lagoon in Hawaii, where the carcasses ended up. However, they are an endangered species, and it is illegal to kill them in most circumstances. A Hawaii bill that would impose a $500 fine per shark on anyone whose net kills a hammerhead shark is pending.

A hammerhead shark swims. PABLO COZZAGLIO/AFP/Getty Images

Unlike many species of fish, hammerhead sharks give live birth instead of laying eggs. They often swim closer to the shore during birthing season in the summer. Each mother gives birth to 13-56 pups at a time, meaning these deaths represent the destruction of at least a few litters. An investigation into whether someone killed these animals intentionally and in an illegal way is pending.

The cause of death is unknown, but according to Hawaiian news station KHON 2, which reported the story, experts have some ideas.

Andrew Rossiter, director of the Waikiki Aquarium, told KHON 2 the cause of death was most likely a gill net, a type of net hung vertically through the water and designed to catch animals by their gills. It's possible that someone hung these nets in order to catch species that are legal to harvest, but the pups were caught accidentally as bycatch.

Hammerhead sharks need to keep swimming in order to flush water through their gills so that they can breathe. When they're caught in a net, they'll die within minutes.

Fishing gear is notorious for catching non-target species. For example, scientists have identified discarded fishing gear as a major threat to the endangered North Atlantic right whale. The whales become entangled in the gear, become injured, and have trouble migrating, or die.

Undercover footage has discovered drift nets kill dolphins and sea turtles. Sixty percent of animals caught in drift nets are accidental catches, although sometimes those catches make it to the fish market anyway. Other times, such as in the case of species that are illegal to kill and sell for food, they are simply thrown overboard.