In West Bengal, marine strandings of endangered horseshoe crabs are increasing

The IUCN has marked all species of horseshoe crabs under the endangered category and India’s Ministry of Environment & Forests has included horseshoe crabs under Schedule-IV of the Wildlife (Protection) Act, 1972. In India, horseshoe crabs are endemic to coastal West Bengal, Odisha and Andhra Pradesh and the stretch of beaches along the West Bengal-Odisha border are home to the largest population of the species in the country.

But marine strandings in this coastal region are on the rise, particularly of horseshoe crabs. “The Purba Medinipur (East Medinipur) coast is the longest continuous coastline in India and the numbers of strandings are more here than other places. Over a ten-year period, these numbers have increased,” says Punyasloke Bhadury, a professor at the Indian Institute of Science Education and Research’s (IISER) Department of Biological Sciences and Center for Climate and Environmental Studies, who is heading the team of scientists.

The IUCN has included all species of horseshoe crabs in the endangered category. Punyasloke Bhadury examines a dead horseshoe crab found on the beaches of East Medinipur, India. Photo credit: Neha Banka

Bhadury has been monitoring strandings of horseshoe crabs for several years, and helps run a community-level network where any horseshoe crab that gets caught in fishing nets is disentangled and released. Prior to the start of this network, fisherfolk would disentangle the horseshoe crab, throw them onto the beaches and leave them to die because they had no use for it.

“We have built a community-level network where whenever any horseshoe crab gets caught in nets, I am informed. I tell them to take a photo and release it. We try to see how we can compensate the fisherfolk and sometimes we pay from our own pockets,” says Bhadury. The horseshoe crab is gently disentangled from the nets tightly bound around its body and released into the water. But for informal systems like this network, it is impossible to track every single horseshoe crabs that get trapped in nets.

Bhadury and his team of researchers walk across the muddy sand stretch, investigating intertidal zones, to look for horseshoe crabs that may be partially burrowed into the ground. A few metres from the water, a dead horseshoe crab is lying on its front, and Swati Das, a researcher in the team, points to an important detail: its tail is missing.

A horseshoe crab entangled in ‘ghost nets’ in West Bengal. Photo credit: Punyasloke Bhadury

According to the IUCN, all four surviving species of horseshoe crabs are at risk because of overfishing for use as food and bait, production of biomedical products derived from their blood, and habitat loss. A Zoological Survey of India report from 2014 states that there are two species of horseshoe crabs reported in India out of the four surviving species: the Tachypleus gigas, mostly recorded along the seashore or in the mouth of rivers in muddy sands, and the Carcinoscorpius rotundicauda, found in areas with extensive mudflats with a prevalence of mangrove vegetation.

The report marks estuaries, along with mangroves and mudflats of eastern West Bengal, Odisha and Andhra Pradesh, as important breeding sites for horseshoe crabs.

Mangroves and mudflats of eastern West Bengal, Odisha and Andhra Pradesh are important breeding sites for horseshoe crabs. Photo credit: Neha Banka

There isn’t enough data available for the status in India, but in the West, particularly in the United States, the horseshoe crab is commercially harvested by biomedical and cosmetic companies for its blood cells to develop a test called Limulus Amebocyte Lysate (LAL), which checks new vaccines for contamination. That means that horseshoe crab blood can detect the presence of toxins, making it indispensable for companies that test to ensure medical equipment, prosthetics and vaccines etc. are sterile.

A horseshoe crab on the beaches of East Medinipur, India. Photo credit: Punyasloke Bhadury

In the West Bengal-Odisha belt, the horseshoe crab goes by several names: ‘bona kankra’, ‘rakkhanpati’ and ‘raj kankra’. “We don’t eat rakkhanpati here. Sometimes it washes ashore during the tides and sometimes we find it dead on the beaches,” says 42-year-old Anadi Maity, a fisherman who has lived in a fishing village near the beaches approximately 40 minutes from Contai, the largest town in the East Medinipur district.

While the meat of the horseshoe crab is not consumed in these parts, the residents of the fishing villages in this belt near the West Bengal-Odisha border have been aware of its medicinal properties for generations. “It has medicinal value and the tail is sold in the local markets. The tail is chopped into smaller pieces and people wear it like amulets tied around the arm or the waist to heal illness and medical problems. I don’t know if it actually works, but people here believe that it does,” Maity says.

“What will the fishermen do keeping the rakkhanpati? They have no use for it. So they just throw it away. People who understand its uses search the beaches and pick it up,” says Maity.

Although locally there is little demand for the species, the horseshoe crab is very much coveted by outside buyers. “It is being sold here on the sly. People come here from elsewhere and purchase it from fisherfolk for a fraction of its price on the black market. The fisherfolk know that it is a threatened species so the sale happens under wraps. Tortoises are sold here in the same way,” says Bidhan Chandra Bera, a masters student in Zoology from Dhauriabar village, located in the outskirts of Contai.

‘Ghost nets’ set up in intertidal zones to catch marine life in East Medinipur. Photo credit: Neha Banka

Scientists categorise the horseshoe crab as a living fossil, pre-dating dinosaurs, that has not changed for 250 million years. Now, the species is threatened because of shrinking breeding grounds due to human activity, particularly fishing trawlers and the shifting of beach sands for construction that damages nesting sites.

Other factors that have contributed to the decline in numbers of the species include the construction of fishing jetties that has resulted in the loss of detritus-rich muddy shores and mangrove vegetation. An increase in anthropogenic activity like sand mining, mechanised fishing close to the shore, illegal prawn farming and the destruction of mangrove habitats and coastal vegetation also pose serious threats to the Indian horseshoe crabs.

At India’s longest continuous coastline, the impact of these anthropogenic activities that are interfering with horseshoe crab populations are clearly visible. “Trawler activities are increasing here. In Purba Medinipur district, the number of trawlers that are operational have gone up in 10 years, because of improvements in mechanised trawling,” says Bhadury. These are not fishing trawlers, he explains, but are essentially large boats which have been customised or manufactured to do small scale fishing activities within one to two kilometres of the fishing coastline.

The East Medinipur coastline is dotted with these boats and Bhadury points to how local fisherfolk have customised them to ensure that they result in larger catches. “The boats have been basically modified, with very powerful engines added. They operate within two to three kilometres away from the coastline,” Bhadury says, because the catch is more within this distance from the shore in the region.

The West Bengal-Odisha coast has two large mangrove populations, which act as nurseries for marine life. Around these shallow waters, fishing can be very profitable. After the outbreak of Covid-19, fishing activity in this region increased because people desperately searched for alternative sources of income. When they turned to fishing, it directly impacted marine life, and in this region, the already threatened population of horseshoe crabs.

‘Ghost nets’ are extremely large plastic nets with a very fine mesh size, which prevents catch, particularly smaller species of marine life like shrimp, from escaping. Photo credit: Neha Banka

The species battles other challenges as well: over the past decade, there has been an increase in the use of ‘ghost nets’ by fisherfolk, in which horseshoe crabs get stranded. These ‘ghost nets’ are extremely large plastic nets with a very fine mesh size, which prevents catch, particularly smaller species of marine life like shrimp, from escaping. Along the East Medinipur coast, indianexpress.com witnessed fishermen put in the nets for the day just before the tide came in.

The wind makes the ‘ghost nets’ blow up into a funnel-like shape, and the water drags all marine animals into the nets. When fisherfolk need to cut off parts of the nets due to operational challenges, they simply leave it in the waters, in which marine life get entangled, resulting in strandings.

Trawler boats operating in the waters off the East Medinipur coastline near the West Bengal-Odisha border. Photo credit: Punyasloke Bhadury

There are environmental violations occurring in this region as well. These trawler boats leak diesel directly into the waters, severely damaging the environment. Although India’s National Green Tribunal and the Supreme Court have intervened several times saying that all coastal fishery states need to look into the impact of diesel leak into coastal waters more seriously, there is no effective monitoring to bring it under control in coastal states, Bhadury says.

The complexities on ground make it necessary to engage with fisherfolk communities to ensure successful conservation, IISER researchers say. “They understand the value of sustainable practices. They have local knowledge of the conservation of the marine environment. But when you want them to practise sustainable technologies, there should be proper incentives or the availability of the technologies for them,” says Bhadury. 

Dead horseshoe crabs on the beaches of East Medinipur, near the West Bengal-Odisha border. The horseshoe crab on the left has its tail intact, while the one of the right is missing a tail. Photo credit: Neha Banka

Researchers in the IISER team whom indianexpress.com interviewed say that criticism against fisherfolk communities claiming that they do not care about the ecosystem are unjustified; on the contrary they have a wealth of local knowledge about the region, the ecosystem and marine life. “But unless you give them a sustainable, viable option with some sort of economic incentives, you can’t expect them to do anything for conservation. They struggle for their daily needs,” Bhadury says.

While researchers admit that when it comes to conserving the species, the challenges are immense, for now, the IISER team is trying to save and rehabilitate the endangered species on the ground level, with the help of fisherfolk communities across the beaches of East Medinipur, one horseshoe crab at a time.