What are ghost nets?

HONOLULU — The International Union for Conservation of Nature, or IUCN, describes ghost nets as a silent menace threatening the world's marine species.

Here's what makes them so bad.

Ghost nets as commercial fishing nets that have been abandoned, lost or discarded at sea.

They are made from a strong plastic and can remain in the water for a long time.

Ghost nets float with ocean currents and trap plastic and other debris, as well as fish and crustaceans — a process known as ghost fishing.

Fish caught in the nets often act as bait, luring larger predators like turtles, sharks and dolphins, who eventually become entangled themselves.

When a drifting net becomes too heavy due to its catch, it may eventually sink to the seabed, where smaller ocean dwellers feed on the entangled creatures.

This, along with natural decomposition, reduces the weight of the net so that it floats back up to the surface, where it then restarts its destructive cycle.

In addition to this, ghost nets can also cause damage by smothering reefs and introducing invasive species and parasites into coral reef habitats.

The United Nations Environment Programme estimates that over 600 to 800,000 metric tonnes of ghost gear enters the ocean annually. Some are lost during storms, and some dumped deliberately.

Nick Mallos, director of the Trash Free Seas Program at Ocean Conservancy, says ghost nets are the most deadly form of marine litter.

Efforts being made to lessen their impact include clearing drifting nets and promoting the use of biodegradable fishing gear. But there is no quick-fix solution, and certain practices, such as illegal fishing, remain a block to progress.