Searching For Sawfishes In The World’s Biggest Mangrove System

Source: Anderson Cabot Center for Ocean Life/New England Aquarium

Photo: David Clode/Unsplash

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This post is one of a series on projects supported by the New England Aquarium’s Marine Conservation Action Fund (MCAF). Through MCAF, the New England Aquarium supports researchers, conservationists and grassroots organizations all around the world as they work to address the most challenging problems facing the ocean.

In the blog below, Priyankar Chakraborty, Masters (MSc.) student in Wildlife Conservation Action at BVIEER speaks about his MCAF-supported project to identify remaining populations of endangered sawfish in the Indian Sundarbans. Priyankar’s project is a collaboration with MCAF Fellow, Ruth Leeney, PhD, founder and director of  Protect Africa’s Sawfishes. Ruth has conducted baseline research on sawfishes in nine countries and has significantly improved scientists’ understanding of  the areas where sawfish populations still exist and need urgent conservation action. She also supports the work of several other sawfish researchers in low income countries.  

Pointing towards where he last caught a sawfish, a fisher from the Sundarbans exclaimed how big it was and how much of a struggle it had put up. Sadly, this incident took place almost two decades ago. The fisher, like others in the region whom I spoke to over the course of my study, commented that it is very rare to catch a “Kata Bholi” (the local name for sawfish) nowadays.

The search for sawfishes in the Indian Sundarbans formed the research component of my Masters degree in Wildlife Conservation Action. My interest in sawfishes stemmed in part from having seen a sawfish at a landings site almost a decade ago, as well as a broader fascination with sharks and rays.

Sawfishes are one of the most threatened families of fishes on the planet. Records of sawfishes in this region reach back to the 1800s, and the Sundarbans are the largest mangrove ecosystem in the world —potentially an ideal place for sawfishes to give birth and for young sawfishes to stay protected from predators. Yet up-to-date information on sawfish abundance, distribution and threats in the Indian Sundarbans—essential if we are to develop effective ways to protect them—has been lacking. I decided to fill this gap in our understanding.

The aim of my study was to collect historical and recent information on sawfishes from the Indian Sundarbans, using interviews with fishers. If carefully designed and carried out, interviews can be a cost-effective way to collect both historical and present-day information on rare species. Fishers have a wealth of knowledge on the species present in the areas where they fish, the changes they have seen in where and when those species can be caught, and other changes in aquatic environments, over the years that they have spent fishing—sometimes many decades! By tapping into that knowledge, often referred to as “fishers’ ecological knowledge,” researchers can access information over extensive time frames and large geographical regions.

The same theme recurred again and again during interviews—sawfishes were once common, but now are hardly ever encountered. Most fishers stated that with every passing year, the abundance and diversity of fish in the region is drastically declining.

When asked why they believed that sightings (and catches) of sawfishes were rare in recent years, most of my interviewees blamed the indiscriminate trawling at the mouth of the Ganges River. They believed that the trawlers caught female sawfish that would otherwise have entered the mangroves to give birth to their young. Some also suggested that said that the collection of “meen” (the local name for prawn larvae) is detrimental for sawfishes and other fishes of the region, because it disrupts the food chain.

The many creeks of the Sundarbans were once a refuge for juvenile fishes but have, in recent years, turned into an obstacle course that all aquatic life must navigate. Through many conversations with fishers in the Sundarbans, it seems there is no directed fishery for sharks, rays or sawfishes there, although my interviews and observations suggest that they are often caught as bycatch and once captured, are retained. Fishers here know the value of sawfishes—they sell the meat for local consumption, the liver oil (believed to cure diseases) and the fins—the latter fetching high prices. Most of the individuals I interviewed knew that it is illegal to catch and kill sawfishes, and I was told that those who catch sawfishes hide their catches from the forest rangers who patrol the rivers of Sundarbans.

For most of my field trips to the Sundarbans, I came away disappointed as we found no trace of sawfishes, and I observed concerning levels of stingrays being caught. But finally, in July 2018, I received news from Kakdwip fishing harbour about a sawfish landing. During a visit to the harbour one month earlier, I had left educational materials – posters and identification sheets – with a trawler owner and the harbour master at Kakdwip, and had encouraged them to relay information on any future sawfish catches to me. Aware of the importance of such information, the boat owner reported the landing of an adult largetooth sawfish (Pristis pristis), approximately 1.5 m in length, which had been caught by a trawler operating in the Sundarbans. The trawler owner with whom I left the educational materials photographed the sawfish before it was auctioned off.

My study has confirmed that largetooth sawfish are indeed still present in the Indian Sundarbans, within the largest mangrove ecosystem in the world. This is truly exciting news. However, my work has also revealed that sawfish numbers have plummeted in this region in recent decades, and that small-scale (but widespread) fisheries pose a serious threat to any remaining sawfish.  I hope to publish my findings in a scientific paper so that the plight of the sawfishes in the region is communicated to the concerned authorities effectively. There is still much to do if we are to prevent further declines of this iconic species. I am now collaborating with the Sundarban Tiger Reserve forest department to develop awareness campaigns targeting both fishers and children in the Indian Sundarbans, as the first step towards changing attitudes and eventually, behaviour towards these magnificent and highly threatened inhabitants of our coast.

Article Provided by Anderson Cabot Center For Ocean Life at The New England Aquarium

Photo: David Clode/Unsplash

To view the Creative Commons license for the image, click here.