Small ray of hope for Sri Lanka’s sawfish, now feared ‘functionally extinct’

Known for its saw-shaped snout or rostrum, the sawfish is now feared “functionally extinct” in Sri Lankan waters, with the last record dating back to 2017.
Three critically endangered sawfish have historically been reported in Sri Lanka — the narrow sawfish (Anoxypristis cuspidata), largetooth sawfish (Pristis pristis), and green sawfish (P. zijsron) — but they are listed as either endangered or critically endangered due to overfishing, habitat loss and bycatch.
Researchers say small populations may still be surviving and call for more surveys to identify potential habitats toward conservation.
The sawfish’s rostrum serves as both a weapon and a sensory organ, helping it to hunt prey in murky waters, and in Sri Lanka, these are traditionally offered to churches as a sign of goodwill.

COLOMBO — The sawfish, a large ray, is easily recognized by its long, flattened snout edged with sharp, tooth-like projections that form a distinctive “saw,” technically known as a rostrum. Despite being one of the ocean’s most extraordinary creatures, very little research has been carried out on sawfish in Sri Lanka.

This gap in knowledge prompted researchers at the Colombo-based Blue Resources Trust (BRT) to investigate a pressing question: Where have all Sri Lanka’s sawfish gone? Their islandwide survey, interviewing 300 fishers from 21 fishing harbors scattered along Sri Lanka’s coastline led to some alarming findings. None of the fishers under the age of 30 could identify a sawfish from photographs. Among those who had seen one, about half had not encountered a sawfish since 1992, and only 32 reported ever catching one, says Akshay Tanna, a researcher at the Blue Resources Trust.

This juvenile sawfish was captured at an estuary in southern Balapitiya, exactly a decade ago, suggesting that refuges still exist where sawfish survive and require protection. Image courtesy of Blue Resources Trust.

Older fishers, however, had very different recollections. Many over the age of 50 had encountered sawfish in Sri Lankan waters, suggesting that populations were once far more abundant. Some even remembered using sawfish rostra to construct fences to keep stray dogs away from drying fish, Tanna tells Mongabay.

Fishers are often the most reliable source of such historical information, Tanna explains. Even if they had not personally caught a sawfish, news of unusual catches would quickly spread within fishing communities, allowing others to see such species. This collective memory made fishers a key source of data for the study.

This sawfish, caught off Sri Lanka’s eastern coast in March 2017, represents the last known record of the species in the country. Image courtesy of the Blue Resources Trust.

Fishers’ collective memory

Available records show that the last confirmed sawfish catch in Sri Lankan waters dates back to 2017, to Kuchchaveli in Sri Lanka’s eastern district of Trincomalee. “This was a chance encounter,” says Buddhi Pathirana, a researcher who traced the fisher. “Struck by its unusual appearance, the fisher had photographed the animal and even framed the image,” Pathirana tells Mongabay.

Globally, sawfish are among the most threatened marine fishes, notes Rima Jabado, chair of the IUCN Species Survival Commission’s Shark Specialist Group. Jabado says all five living species are now classified as either endangered or critically endangered on the IUCN Red List. Once abundant across many parts of the world, their populations have declined drastically due to overfishing and habitat loss.

Their biology makes recovery especially difficult, as sawfish grow slowly, mature late and produce relatively few offspring. As a result, even small increases in mortality rates can have long-lasting impacts, and depleted populations may take decades to recover, if they recover at all, Jabado adds.

The absence of sawfish records in Sri Lankan waters for nearly a decade raises serious concerns as Jabado warns that the species may now be “functionally extinct” in the island, meaning that even if a few individuals remain, their numbers are too low to sustain a viable breeding population, making long-term survival unlikely.

The fisher who caught the last recorded sawfish later enlarged and preserved the photograph as a cherished memory. This image was discovered during fieldwork by researcher Buddhi Pathirana. Image courtesy of Sahan Thilakaratna.

Functionally extinct

Sawfish have been recorded in various Sri Lankan species checklists since 1889, and of the five species known globally, three — the narrow sawfish (Anoxypristis cuspidata), largetooth sawfish (Pristis pristis), and green sawfish (P. zijsron) — have historically been listed, says Sahan Thilakaratna, a marine biologist at Ocean Rosy, a research organization that participated in the BRT survey. All sawfish species are protected under Appendix I of the Convention on International Trade in Endangered Species (CITES), which prohibits their international trade, Thilakaratna notes.

The decline of sawfish is largely driven by fisheries interactions and the degradation of critical habitats. Shallow coastal waters, estuaries and river mouths serve as important breeding and nursery grounds. However, these habitats are increasingly threatened by coastal development, pollution and destructive fishing practices. Their toothed rostra easily become entangled in fishing gear, making them particularly vulnerable, Thilakaratna adds.

There are five species of sawfish in the world but all of them are either endangered or critically endangered due to overfishing and slow breeding. Image courtesy of Sawfish Conservation Society.

Despite the bleak outlook, researchers say there is still a ray of hope for recovery. Thilakaratna, who participated in the field surveys, documented a fisher who had caught a sawfish in brackish waters in Balapitiya in southern Sri Lanka. “Sawfish do use brackish habitats as breeding and nursery grounds, and these environments are critical for their survival,” he says.

In an effort to better understand historical interactions, Thilakaratna also visited churches in coastal fishing communities, where he made an intriguing discovery: numerous sawfish rostra preserved as offerings. “Fishers offer the sawfish rostra to churches as acts of gratitude or for protection at sea,” he explains.

Such cultural practices indicate that sawfish were once more commonly encountered and even held symbolic value among coastal communities. These insights highlight the potential for community-based conservation efforts.

In some predominantly Christian coastal fishing communities, sawfish rostra are offered to churches in gratitude and for protection at sea, where this collection of old rostra was found in a church storeroom in Sri Lanka. Image courtesy of Blue Resources Trust.

A cultural symbol

Targeted conservation measures, including protecting key habitats, reducing accidental capture in fisheries, strengthening community awareness and reporting, could help support any remaining populations. Expanding research efforts and safeguarding breeding grounds are especially urgent, Thilakaratna adds.

The sawfish’s most striking feature, its rostrum, is more than just a weapon. Made of cartilage and reinforced with hard denticles, it also functions as a sophisticated sensory organ. It is lined with electroreceptors known as ampullae of Lorenzini, which detect faint electric fields produced by prey, Pathirana says. Using this ability, sawfish can locate fish, crustaceans and mollusks buried in sediment, even in murky waters, and strike with swift, slashing movements to stun or injure them, which is a remarkable adoption, she notes.

A 2021 study interviewing 300 fishers found that none of the fishers under the age of 30 could identify a sawfish from photographs, and among those who had seen one, most had not encountered a sawfish since 1992. Infographic courtesy of the Blue Resources Trust.

Effective conservation of threatened marine species requires coordinated action — strong legislation, awareness among fishers and incentives such as compensating those who release accidentally caught animals. A similar approach in Sri Lanka could aid the recovery of sawfishes while also protecting other highly threatened groups, especially guitarfishes and wedgefishes, which are similarly important ray species, Jabado says.

Sri Lanka’s rich diversity of sharks and rays underpins both ecosystem health and coastal livelihoods. While steps such as banning bottom trawling and increasing marine protection are encouraging, stronger science-based policies and implementation are urgently needed to halt declines and support recovery of both sharks and ray species, Jabado stresses.

Banner Image: The sawfish is a large ray, easily recognized by its long, flattened snout edged with sharp, tooth-like projections that form a distinctive “saw,” known as a rostrum. Image via Pixabay.

Citation:

Tanna, A., Fernando, D., Gobiraj, R., Pathirana, B. M., Thilakaratna, S., & Jabado, R. W. (2021). Where have all the sawfishes gone? Perspectives on declines of these critically endangered species in Sri Lanka. Aquatic Conservation: Marine and Freshwater Ecosystems, 31(8), 2149-2163. doi:10.1002/aqc.3617