Discarded fishing nets are a menace to corals and marine life

2 Juli 2021

Fishermen around the world often discard and abandon their fishing nets and other plastic gear in the seas without giving them a second thought. Out of sight, out of mind.

Yet such plastic waste, which can take decades or even centuries to degrade, adds to the colossal amounts of trash already sloshing around in the oceans and borne far and wide by currents and tides.

Worse, discarded nets can devastate fragile marine ecosystems such as those at coral reefs and decimate vulnerable species such as sea turtles, which can drown if caught in these nets underwater.

Not even pristine tropical isles may be free from the scourge of abandonded fishing nets. Recently, massive nets were discovered over a large area at Koh Losin, a small rocky islet located in the southern region of the Gulf of Thailand. Smothered under the fishing nets were various species of corals and marine species.

Koh Losin, which spreads over an area of around 195 acres, is one of Thailand’s best diving sites. It is located 72km from the nearest coast and its relative isolation means that the islet has been left mostly untouched and marine ecosystems around it have remained largely intact.

Beneath the surface of the azure waters around the islet lie scenic coral reefs, which are home to a large number of marine species. Local waters also support several rare and endangered marine animals, including whale sharks and manta rays.

Yet even in this isolated area the scourge of plastic waste is already taking its toll.

Thailand is one of the world’s worst plastic polluters, dumping as it does some 23 million kilograms of plastic waste into the sea each year. Discarded fishing gear from the country’s lucrative fishing industry accounts for much of the Southeast Asian nation’s plastic pollution.

The abandoned fishing nets at Koh Losin were recovered by a group of divers. Koh Losin’s environs are protected by law, yet the ongoing Covid-19 pandemic has caused most local environmental inspectors to work from home and stop going out to protected sites.

Some fishermen clearly took advantage of this lull in inspections to catch fish in the area illegally before abandoning their nets there.

Their nets damaged fragile corals while also blocking sunlight to reach underwater to corals that contain photosynthetic algae called zooxanthellae in their tissues in a symbiotic relationship. Corals provide the algae with a secure home and compounds required for photosynthesis while the algae return the favor by supplying their hosts with oxygen and helping remove waste.

It took two days to remove the nets covering the coral reefs around Koh Losin during a laborious operation. In all, the recovered nets weighed 800kg.

Yet before the nets were removed, they had already broken pieces off corals over a large area and begun to suffocate them by causing their algae to start growing on the nets.

“If the nets had not been removed, the corals in the area would absolutely have died,” Anchalee Chankong, a marine biologist, stressed.

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