Madagascar May Be Stronghold for Ancient Fish With 420-Million-Year History

In the 1980s, when demand in Asia for shark fins increased, fishermen in southwestern Madagascar began to cast mesh gillnets in deeper waters. However, instead of just sharks, the retrieved walls of netting brought up various Indian Ocean coelacanths. Unintentionally, the fisherman had discovered a previously unknown population of a fish that can be traced back 420 million years. Now, in a March study published in the South African Journal of Science, researchers write that Madagascar may be an epicenter for the critically endangered fish and a source for other populations, reports Tony Carnie for Mongabay.

Coelacanths are striking in appearance with distinctive white spots, arranged in unique patterns on each fish, according to Mongabay. Previously, the fish, often called a "living fossil," was thought to be extinct until one resurfaced in 1938 off the coast of South Africa. Since then, fishermen have caught coelacanths off the shores of Tanzania and the Comoros Islands off Africa's east coast.

Underwater, coelacanths inhabit undersea canyons at depths between 300 and 1600 feet. High tech gillnets can easily reach those depths and, unlike trawl nets, can be used near rocky environments the fish prefer, Mongabay reports. Coelacanths have poor eyesight and likely can't detect the nets using electroreception—so they often get trapped inside, reports Stephanie Pappas for Live Science.

When researchers reviewed the data of bycaught coelacanths, they found 34 confirmed catches off the western coast of Madagascar between 1987 and 2019. Experts say the catch is likely much higher based on anecdotal reports from local fishermen, per Mongabay. Fishermen caught the largest number of fish in Onilahy Canyon, a marine area located off the island's southwest coast, Live Science reports. The researchers hypothesize that the fossil fish originated in Madagascar and eventually spread to the Comoros Islands.

While a complete picture of the fish's population size is unknown, Mongabay reports, researchers and conservationists are calling for the protection of the ancient species. Because the fish takes a while to reach maturity and rarely reproduces, the estimated bycatch is likely detrimental to the species. Scientists recommend setting up a coelacanth sanctuary in Onilahy Canyon, adding the fish to Madagascar's protected species list and negotiating gillnet management where coelacanth can be found, per Live Science.

Elizabeth Gamillo | | READ MORE

Elizabeth Gamillo is a daily correspondent for Smithsonian and a science journalist based in Milwaukee, Wisconsin. She has written for Science magazine as their 2018 AAAS Diverse Voices in Science Journalism Intern.