Biodiversity threats from ghost fishing gear in the Ganga

The endangered Ganges river dolphin and species of threatened freshwater turtle and otter are wildlife “most at risk” from getting tangled up in waste fishing gear adrift in the transboundary Ganges river system, research has said.

Scientists associated with the Sea to Source expedition carried out a biodiversity threat assessment of Gangetic wildlife species most at risk from entanglement in abandoned, lost, or otherwise discarded fishing gear (ALDFG) in nine sampling sites along the river in Bangladesh coast in the Bay of Bengal to upstream in the Himalayas in Rishikesh, India.

“Waste and active fishing gear impact aquatic wildlife in similar ways, but what we know about them differs quite significantly. Generally, we know more about how entanglement in active gear (called ‘by-catch’) affects species because fishers encounter the animals more frequently while checking their nets, etc.,” study author Sarah Nelms, University of Exeter, Cornwall, told Mongabay-India.

Although ingestion of debris can pose a risk to fauna, the threat assessment focused on entanglement because entanglement in plastic pollution, such as waste fishing gear, is known to cause mortality and injury in various aquatic vertebrate species. “This has clear welfare implications for the individual animals but may also cause declines in populations of species that are of conservation concern,” observed Nelms.

Twenty-one species of conservation concern, as identified by the Wildlife Institute of India, with ranges that overlap with the sampling locations, were investigated during river bank surveys in Bhola, Chandpur, Rajbari (in Bangladesh) and Sahibganj, Patna, Varanasi, Kannau, Anupshahr, Rishikesh (in India).

Three-striped roofed turtle (Batagur dhongoka), Ganges river dolphin (Platanista gangetica gangetica), black-spotted turtle (Geoclemys hamiltonii), northern river terrapin (Batagur baska) and smooth-coated otter (Lutrogale perspicilata) were found to be most vulnerable to entanglement with, and impacts from, waste fishing gear.

Nelms underscored that since waste gear is not monitored and can move over large distances, humans don’t necessarily observe how it interacts with wildlife. This could lead us to underestimate the harm it causes, she said.

The Ganges river system (known as the Ganga in India and Padma and Meghna in Bangladesh) has been identified as one of the 14 continental rivers in the world into which over a quarter of global waste is discarded; it is considered the second-largest plastic pollution-contributing catchment in the world (0.12 million tonnes of plastic discharged per year).

The expedition researchers recorded the abundance, distribution and characteristics of waste fishing gear such as nets, ropes, string, floats and line along the river, complementing their surveys by speaking to fishers to understand the behavioural drivers that lead to waste fishing gear entering the environment.

Led by women scientists, this expedition is the world’s first ground-truthing effort to verify the quantum of plastic load that a freshwater body carries to the sea and substantiate theory as well as models proposed in research.

They found higher levels of waste fishing gear in sampling sites near the sea: likely due to the high prevalence of fishing activity at these sites combined with the downstream accumulation of waste gear from further up the river.

The study comes amid an increasing awareness on understanding what impacts plastic is having on species living in and around rivers. The United Nations Environment Programme (UNEP) Regional Office for Asia and the Pacific is implementing the Promotion of Action against Marine Plastic Litter in Asia and the Pacific (CounterMEASURE II) project that aims to generate, share and disseminate scientific knowledge on plastic pollution in the Mekong, Ganges and selected rivers in Sri Lanka and Myanmar to inform policy and decision-making processes at the local, national, regional and global level.

Parties to the Convention on Migratory Species (CMS) adopted Decisions 13.122 – 13.125 and called for further research on this issue at COP13 of the Convention on Migratory Species, held in earlier this year in India, according to the CMS.

There is emerging evidence demonstrating that ‘ghost gear’ is not only a marine issue but can pollute freshwater habitats too (Spirkovski et al., 2019). For example, Kappenman and Parker (2007) recovered 33 lost gill nets from the Columbia River (USA) and found 126 white sturgeon (Acipenser transmontanus), which had been ‘fished’ by this ghost gear. Additionally, Spirkovski et al. (2019) reported 116 fish and four birds entangled in ghost nets retrieved from Lake Ohrid (Macedonia and Albania).

The 2,525 km-long Ganga binds five Indian states along its main stem and 11 in her entire basin that is home to 625 million people. Despite its cultural and religious importance, the river has rapidly degraded since the 20th century due to human activities.

The Ganges River catchment supports some of the world’s largest inland fisheries but no research has yet been conducted to examine the input of debris from this industry.

Additionally, no studies have investigated the potential movement of ALDFG from rivers into the sea. By highlighting the most at-risk species, focused interventions, such as monitoring programs, can be developed to better understand the impacts and potential solutions, the authors emphasise.

Recycling waste fishing gear

Interviews with fishers revealed that many replace their nets every 1-6 months, and it is common for people to discard their old gear into the river. This was most common in Sahibganj in India and Rajbari and Chandpur in Bangladesh.

This high turn-over rate and disposal method is bad news for the river and its wildlife because most of the gear is made from plastic and does not biodegrade, meaning that it will continue to capture animals for a long time. “The good news is that our study found that over 50 percent of the nets were made from Nylon 6, which is a type of plastic that has high value and can be recycled into many new products. We are currently looking into setting up a net recycling project, particularly at the sites where this discarding behaviour is prevalent,” said Nelms.

The project is called Net-Works and has proved so successful in reducing waste gear in coastal areas in the Philippines and Cameroon that it has now spun out into the new social enterprise Coast-4C. The idea is that members of the local community collect nets from the environment, which are then turned into products, such as carpet tiles. “This reduces plastic pollution in the environment and provides a source of income for fishers and their communities,” said Nelms.

Indian biologist Ravindra Kumar Sinha, who has worked extensively on the Gangetic dolphins and was not involved in the research, commended the study for spotlighting the understudied biodiversity threats associated with discarded fishing gear. “Earlier, the fisher community used handspun cotton nets that could be torn off by the animal if they got entangled in it. But with the introduction of sturdier plastic nets, animals can’t wriggle free. So we have to think of reducing, reusing, and recycling waste plastic fishing gear,” Sinha told Mongabay-India.

Shailendra Singh, Director of Turtle Survival Alliance, India, adds that the easy availability of nylon gill nets also adds to the complexity of the challenge. “Even if you confiscate the gill nets it doesn’t impact the fishers financially; they know its easily available and cheap, compared to the cotton nets,” said Singh. Eco-friendly substitutes for plastic could be tried as an alternative material for fashioning nets, “but they have to meet their purpose: it should be wildlife-friendly, any animal should not get entangled and the fishers should be able to get the volume of catch they require. Most of the time the fisher community is not interested in catching animals; the fish catch matters,” Singh, who was not associated with the study, told Mongabay-India.

Plastic waste fishing gear beyond protected areas

Singh also stressed that forest management/enforcement needs to go beyond the protected stretches in riverine systems. “We always tell management and enforcement officials to look out for gill nets. These nets are particularly detrimental to fauna in a linear system such as riverine areas. In core of protected areas the rules are enforced but we encourage management officials to also look out for such practices beyond the protected areas. The habitats are contiguous and the wildlife doesn’t have boundaries,” said Singh.

Nelms adds that plastic pollution in rivers and the ocean does not respect protected area boundaries, so such areas are likely to be exposed to the same levels of waste gear as unprotected sites. However, the presence of sensitive species and habitats in protected areas may mean that protected areas are more vulnerable.

There are 15 protected areas along the Ganga, including the Turtle Wildlife Sanctuary and Vikramshila Gangetic Dolphin Wildlife Sanctuary. A recent study that sampled 55 sites along the Ganga’s 2500 km stretch for microplastics found microplastics in 72 percent of the sediment samples.

Gawsia Wahidunnessa Chowdhury of Department of Zoology, University of Dhaka, study co-author and member of the Sea to Source expedition, said some areas directly or indirectly get conservation attention through different steps such as ban on fishing and angling. The extent, and enforcement, of fisheries management restrictions, differ among the various regions of Bangladesh and India and likely influence the temporal trends and spatial patterns of waste fishing gear and types of equipment found, according to the researchers.

Monofilament fixed gill nets (current jal) and mosquito nets are illegal or restricted in Bangladesh and India, but their presence as observed during the riverbank surveys suggest that fishers are not adhering to the restrictions.

Ravindra Kumar Sinha adds that government policies such as the National Mission for Clean Ganga do seek to reduce plastic pollution in rivers but their execution needs to be strengthened on the ground which shows the need for improved awareness of the significance of biodiversity around river systems and how their conservation is connected to human well-being. “There was negligible awareness of the Gangetic river dolphin in the 1980s when I began working on the species. Most people would say it was a fish (susuk fish),” noted Sinha. Ganga river dolphins also have to deal with chronic noise pollution. A recent study found that increased ship traffic and dredging are stressing the dolphins and changing how they communicate. This is concerning, researchers say, since the Indian government has plans to expand the Ganga waterway, increasing the number and frequency of the ships that ply the river.

Replicating strategies

Chowdhury adds that the shared problems reinforce the importance of replicating strategies in the transboundary region.“In India, WII has initiated Ganga Prahari – guardians of the Ganges. I feel in Bangladesh, we may replicate this idea to empower fishers and the key stakeholders who entirely depend on the rivers of Bangladesh. Similarly, India may also adopt some strategic directions from Bangladesh that bring success in our hilsa conservation,” said Chowdhury.

The expedition leveraged support of the praharis for the socio-economic and education component of the project. They are a cadre of about 1000 local community members from Ganga states who are actively involved in conservation.

Ruchi Badola of Wildlife Institute of India who leads the praharis said the guardians who lead conservation efforts in their communities will contribute to empowering communities to tackle plastic pollution and change behaviours, especially in the management of plastic waste.

“Raising awareness among the people to reduce plastic pollution (that mainly originate from the mismanaged plastic wastes) is essential. We also feel like more collaborative solution-oriented research works between Bangladesh and India should be designed and implemented as both countries are connected with the aquatic system,” signed-off Chowdhury.

Banner image: Higher levels of waste fishing gear were reported in sampling sites near the sea. It is likely due to the high prevalence of fishing activity at these sites combined with the downstream accumulation of waste gear from further up the river. Photo by Heather Koldeway.