[Reading Science] The Ghost Fisherman in the Deep Sea, Its Identity Is 'Discarded Fishing Nets'

Brazil S?o Paulo University Research Team
Global Deep-Sea Coral Reef Survey
Plastic Pollution More Severe Than Coastal Waters

Amid severe plastic pollution in the world's oceans, it has been revealed that the deep-sea seabed is more heavily polluted by abandoned fishing gear than coastal waters, causing fish to die and coral reefs to decay.

▲Coral reefs play an important role in the marine ecosystem by providing shelter for fish and other marine life. [Photo by Bermuda Institute of Ocean Sciences/Stacy Peltier]

A research team from the University of S?o Paulo, Brazil, published a paper on the 12th (local time) in the international journal Nature, reporting the results of a field survey of 84 offshore coral reefs and rocky reefs located in 25 areas across the Pacific, Atlantic, and Indian Oceans. They found large plastic debris over 5cm in size at 77 of these sites. The study also confirmed that 88% of the human-derived waste polluting these coral reef groups consisted of large plastics.

The plastic waste found during the field survey consisted of abandoned fishing gear such as nets, ropes, and hooks. In particular, at some coral reefs, the phenomenon of "ghost fishing," where fish continue to get caught and die in abandoned nets, was observed.

In marine environments without underwater reefs, artificial plastic waste typically accumulates on the sea surface, mostly consisting of everyday items like plastic bags, forming large islands. However, areas with reefs are different. The research team confirmed that deep-sea reefs are more polluted with large plastic debris than shallower areas. This is presumed to be because strong waves and currents push coastal seabed waste into deep reef areas, or because ongoing cleaning efforts have somewhat reduced pollution in coastal seabeds. Another cause is the rapid increase in offshore fishing as coastal fish catches decline due to various pollution in seas worldwide.

The problem is that deep reef groups serve as habitats for many fish. Abandoned nets and fishing gear are severely damaging marine fish and coral reef ecosystems. Moreover, when fishermen pull nets and ropes entangled in coral reefs, the reefs are destroyed. Additionally, bacteria and other microorganisms attached to abandoned fishing gear may also harm the coral reefs.

On the 27th, marine debris such as discarded nets is being collected using an excavator at Dadaepo Port in Geoje.

The research team urged, "The issue of removing pollution from deep reef groups should be included in the international treaty currently being discussed by the United Nations (UN) to end plastic pollution." They also called for "providing incentives to fishermen to reduce the use of plastic tools or mandating the use of biodegradable fishing gear."