Ghost Nets Trap Creatures Small And Great

A white-throated kingfisher, a horseshoe crab, a whale shark and an Asian elephant are some of the species found entangled in ghost nets in India, mostly along the coasts.

An international team has spotted 144 animals belonging to 35 species, 13 of them endangered or vulnerable, entangled in abandoned, lost, or otherwise discarded fishing gear (ALDFG) in the coastal waters and freshwater bodies of India, as part of a social media study.

Such derelict fishing gear includes nets, lines, pots and traps, often made of durable, water-resistant and light plastics. These plastic-made fishing gear float in the ocean for years, trapping or getting eaten by fish and other animals or carrying alien species, scientists said.

The study led by Kannan Gunasekaran, a marine biologist at the Chulalongkorn University, Bangkok, scanned Facebook, Twitter, Instagram, and YouTube posts from 2012 to 2023. The results were published in the journal Biological Conservation in March 2024.

“We looked at entanglement sightings on social media, listed species affected, and identified potential hotspots,” Gunasekaran told Mongabay-India. Most of the reports came from the east coast.

Diverse Species

Gunasekaran and colleagues found 44 sea turtles, including 37 olive ridleys (Lepidochelys olivacea) and 33 fish, mostly whale sharks (Rhincodon typus), the largest living fish. There were five green turtles (Chelonia mydas), a leatherback (Dermochelys coriacea), and a hawksbill (Eretmochelys imbricate).

Among the marine mammals, the researchers found nine spinner dolphins (Stenella longirostris) and a humpback dolphin (Sousa plumbea), a little Indian porpoise (Neophocaena phocaenoides), four sea cows (Dugong dugon), and three whales – a Bryde’s whale (Balaenoptera brydei), a dwarf sperm whale (Kogia sima) and another Balaenoptera. A fifth of all cases of entanglement were marine mammals.

Other animals trapped in ALDFG included crabs, sponges, and, less frequently, seahorses (Hippocampus kuda) and sea snakes (Hydrophis schistosus). Most of the trappings in the freshwater bodies involved birds, including spot-billed pelican (Pelecanus philippensis) and white-throated kingfisher (Halcyon smyrnensis).

More than half of all entangled animals (73) were dead, and the fate of 71 found alive was not known. The elephant was found alive, caught in a net in the Ramganga river that flows through the Corbett National Park, he added.

The Litter Problem 

The spread of ghost nets on the east and west coasts and freshwater bodies and the diversity of the animals they entangled indicate the scale of the litter menace in India, Gunasekaran and colleagues noted in their paper. India is the second-largest contributor to mismanaged plastic in the ocean. Out of 5.6 million tonnes of plastic waste generated annually, 0.6 million tonnes end up in the ocean, the paper noted. Rivers, lakes, and wetlands also receive massive amounts of plastic waste.

A large share of this litter involves ghost nets, a global environmental problem. “The issue poses a severe threat to India’s marine ecosystems. It not only affects endangered species but also impacts the fishing industry’s sustainability and economy,” said P R Jayachandran, a marine ecologist focusing on the Kerala waters. “Over 90% of trapped species are commercially valuable, exacerbating the financial toll.”

A recent study in Kerala revealed that, on average, each year, 11.6% of the total gear used is lost, 7.5% is abandoned, and 2.3% is discarded – that is roughly a fifth of an average of over 500 kg of gear each vessel carries. About 60% of the ALDFG comprised lost gear, as the study noted.

As such, about 5.7% of fishing nets, 8.6% of traps, and 29% of fishing lines get lost in the ocean, annually adding about 1.14 million tonnes of derelict gear to the oceans of the world, studies show.

The reason for abandoning or losing gear differs across types of boats and fishing. Bad weather is a key reason. “Drawing a net can take one or two hours of hard work. When there is high wind, sometimes we have to cut off the net cast in the sea and come ashore quickly,” said Davidson Anthony Adima, a fisherman from Fathimapurm village in Thiruvananthapuram.

Adima and colleagues operate a 34-foot boat with twin outboard engines, and each of their nets can cost Rs. one lakh or more. Discarding them involves huge losses, and the cut-off nets float, trapping fish and other creatures across great distances.

“Sometimes ghost nets get spread over parts of underwear reefs that are rich fishing grounds, scaring fish away,” Adima said. Traditional raft fishers said the best way to fish over reefs involves the hook and line method, an eco-friendly fishing technique. Or nets need to be carefully cast beside or over the reefs without getting too close, the fishers said. However, such precision fishing requires a good knowledge of the underwater structures, an exclusive domain of the local veterans. “Some fishermen cast their nets too close to the rocky reefs, and they get entangled on the jagged reef edges,” Adima said.

There are other underwater obstructions, such as discarded boats and shipwrecks, that eventually become underwater habitats for flora and fauna that attract fish. The Kerala study noted that different kinds of underwater obstruction were the most common reason with regard to trammel nets.

“Trawl and shore seine were abandoned due to bad weather, whereas ring seine was abandoned due to attacks by marine animals,” the Kerala paper notes. “Regarding gill nets and mini trawls, gear conflict was the most common reason for abandonment…Several reasons, such as cetacean attacks, jellyfish blooms, and pufferfish bites, were reported to result in the huge loss of ring seine nets.”

A review and meta-analysis found that while bad weather led to the reasons for gear loss (69%),  gear conflict was the second most common cause (57%), with over a fifth of all studies reporting loss due to conflict between towed and static gears. Hitting against obstructions on the sea bottom was the third most common cause of gear loss reported (31%).

Ghost Nets Galore

Ghost nets are often found covering reefs. “I have found ghost nets on our reefs while diving,” said Kumar Sahayaraju, a fisherman and an ocean scientist from Thiruvananthapuram. Another diver and coordinator of the conservation NGO Friends of  Marine Life, Robert Panipilla, said his team often found ALDFG during their dives off the shores of Thiruvananthapuram. One brief clean-up drive yielded over 400 kg of derelict gear, he said.

In February, remnants of ghost nets washed up on the shores of Puthenthope village in Thiruvananthapuram. Looking at the girth of the ropes, local fishers, mostly raft and shore seine operators who use traditional gear, said they were probably discarded from large vessels that sometimes intrude their coast from elsewhere. As such, marine litter can travel 100s of miles, scientists note.

Puthenthope is a nesting site for sea turtles, including Olive Ridleys. Local observers said turtles sometimes get entangled in discarded nets.

ALDFGs are dangerous as they entangle marine life about four times more than all other marine debris combined. The Kerala study notes that fishers often discard damaged nets onto beaches or in the sea as there is no proper disposal mechanism and it takes too much effort.

Scientists say many countries and regions lack observation, monitoring, surveillance or enforcement systems to address the ALDFG problem. They call for better data and governance frameworks.

“To address this, raising awareness, repurposing old gear, and implementing stricter regulations are essential,” Jayachandran said. “Collaboration among various stakeholders is crucial, including NGOs, researchers, governments, and international bodies like the Global Ghost Gear Initiative, to safeguard India’s coastal communities and marine biodiversity.”

(Originally published under Creative Commons from Mongabay-India. Read the original article here)