The bowmouth guitarfish (Rhina ancylostoma) is one of the most visually striking and endangered rays in the ocean, an animal whose flattened, shark-like body and broad, rounded snout make it look like an evolutionary experiment that couldn’t decide between shark and ray. Found across the tropical and subtropical Indo-Pacific, it sits in a taxonomic gray zone that has puzzled scientists for decades, and its critically endangered status has made it a high priority for marine conservation. Despite its size and charisma, much of its basic biology remained poorly understood until recently, and what researchers have uncovered paints a picture of a slow-reproducing animal facing threats from multiple directions.
A Ray That Looks Like a Shark
The bowmouth guitarfish gets its common name from the shape of its head: a wide, rounded snout that curves into a mouth on the underside, vaguely resembling the body of a guitar. Adults can reach about 2.7 meters (roughly 9 feet) in length, making this one of the larger ray species. Its body is thicker and more muscular than a typical flat ray, which is why divers sometimes mistake it for a shark at first glance. The coloring is distinctive too, with a bluish-grey dorsal surface marked by white spots and dark bands, especially vivid in juveniles, that fade somewhat with age.
What really sets the bowmouth guitarfish apart are the prominent bony ridges and thorns running along its head, above the eyes, and down the back. These calcified structures give the animal an armored, prehistoric look. They also, unfortunately, are the reason this species has become a target in a wildlife trade that most people have never heard of.
Where It Lives
The bowmouth guitarfish ranges across the Indo-West Pacific, from the coast of East Africa through the Arabian Sea, around India and Southeast Asia, and into the western Pacific as far as Australia and Japan. It is a bottom-dwelling species, typically found on sandy or muddy substrates near coral reefs, at depths that range from very shallow water to around 90 meters.
A study in Djibouti waters found that bowmouth guitarfish showed strong site fidelity, returning to the same dive locations year after year. Over half of the sightings occurred at a site called The Dome, at depths of 30 to 40 meters, and the species was consistently associated with sandy seabeds adjacent to coral formations at around 35 meters depth. Dive sites characterized by strong currents or rocky habitats had no sightings, suggesting the species selects its habitat carefully.1PubMed Central. Annual Recurrence of the Critically Endangered Bowmouth Guitarfish (Rhina ancylostomus) in Djibouti Waters
Local knowledge from fishers in Goa, India, adds another layer. Communities there report that nearshore habitats around river mouths serve as nursery grounds for rhino rays, including the bowmouth guitarfish, with seasonal patterns of occurrence tied to breeding activity.2People and Nature. Drawing on local knowledge and attitudes for the conservation of critically endangered rhino rays in Goa, India These river-mouth nurseries are ecologically important and also highly vulnerable to coastal development and fishing pressure, a combination that makes protecting them both urgent and complicated.
Taxonomic Identity
Classifying the bowmouth guitarfish has been a long-running headache. It is currently the sole member of the genus Rhina within the family Rhinidae (wedgefishes), but its placement has shifted over the years. It has been grouped at various times with guitarfishes, wedgefishes, and even placed closer to skates depending on which characteristics taxonomists prioritized. Molecular work has clarified things somewhat. Analysis of its complete mitochondrial genome placed it in a cluster with Rhinobatos, the guitarfish genus, supporting the idea that despite its unusual appearance, the bowmouth guitarfish’s closest relatives are other guitarfish-like rays rather than true sharks.3PubMed Central. Complete mitochondrial genome and the phylogenetic position of the Bowmouth guitarfish Rhina ancylostoma (Rajiformes, Rhinobatidae)
This matters beyond academic tidiness. Conservation resources for rays and sharks are allocated partly by taxonomic grouping, and knowing where the bowmouth guitarfish sits on the family tree helps researchers understand its life history, predict its vulnerability, and prioritize it alongside related species that face similar threats.
What It Eats and Where It Fits in the Food Web
The bowmouth guitarfish is a predator, but not a top-tier one. A dietary study based on stomach contents from specimens caught in the eastern Arabian Sea found that bony fish (teleosts) made up the bulk of the diet at about 73%, followed by crustaceans at roughly 21% and mollusks at about 6%.4Indian Journal of Fisheries. Catch composition, reproductive biology and diet of the bowmouth guitarfish Rhina ancylostomus Bloch and Shneider, 1801 (Batoidea: Rhinidae) in the eastern Arabian Sea, India Its mouth, positioned on the underside of its head, is equipped with rows of rounded, plate-like teeth well-suited for crushing hard-shelled prey, even though fish dominate the diet overall.
Stable isotope analysis of elasmobranchs caught off Gujarat, India, placed the bowmouth guitarfish at a trophic level of about 3.2, which is relatively low for a predatory ray of its size. Its nitrogen isotope values were close to those of a planktonic-feeding deep-sea shark, suggesting a diet heavy in crustaceans and zooplankton-feeding fish.5ICES Journal of Marine Science. Trophic ecology of elasmobranchs caught off Gujarat, India, as inferred from stable isotopes This is consistent with the stomach content findings and paints a picture of a mesopredator: an animal that eats smaller organisms but is itself potential prey for larger sharks, and one whose feeding role in the ecosystem is more about processing mid-level prey than controlling populations at the top of the food chain.
Reproduction in Captivity
Almost everything known about bowmouth guitarfish reproduction comes from a single aquarium program. At Newport Aquarium in Kentucky, researchers documented five confirmed pregnancies in two mature females, three of which resulted in live births. The 2014 birth produced three pups, the 2016 birth produced nine, and the 2017 birth produced a single pup. Survival rates varied dramatically: only one of the three pups in 2014 survived past 30 days, eight of nine survived in 2016, and the lone 2017 pup did not survive. Paternity analysis confirmed that all litters were sired by the same male.6Endangered Species Research. Observations of reproductive behaviors in the Critically Endangered bowmouth guitarfish Rhina ancylostoma
These numbers illustrate a challenge common to large rays and sharks: small litter sizes, long gestation periods, and high variability in pup survival. Even in the controlled, predator-free environment of an aquarium, survival was not guaranteed. In the wild, where pups face predation, habitat degradation, and accidental capture, the reproductive math is even worse. Species that produce few offspring and mature slowly are inherently less able to bounce back from population declines, which is a central reason why the bowmouth guitarfish is so vulnerable to overfishing.
The Newport breeding program also provided rare behavioral observations. Reproductive interactions were documented using diagnostic ultrasound to track pregnancies, something nearly impossible to do with wild populations. These captive-breeding efforts are not just scientifically valuable; they represent a potential insurance population if wild numbers continue to fall.
Why It Is Critically Endangered
The International Union for Conservation of Nature (IUCN) lists the bowmouth guitarfish as Critically Endangered, the highest threat category before extinction in the wild. The primary driver is incidental capture in fisheries. A global review of fishing interactions with rhino rays (the group that includes wedgefishes and giant guitarfishes) found that trawlers and gillnets together accounted for 59% of all reported interactions across the scientific literature. The bowmouth guitarfish was the single most reported species, appearing in nearly 10% of all documented interactions.7Reviews in Fish Biology and Fisheries. A tangled web: global review of fishing interactions with rhino rays
Being caught as bycatch is especially damaging for a species like this because it cannot easily absorb additional mortality. The combination of slow reproduction and widespread overlap with coastal fishing grounds means that even modest levels of bycatch can push population trajectories downward. And unlike some bycatch species that are simply discarded, bowmouth guitarfish have high market value when caught. Their fins are prized in the international fin trade, and their meat is sold in local markets across parts of Asia and the Indian Ocean.
In 2019, the bowmouth guitarfish and related wedgefish species were listed under Appendix II of CITES (the Convention on International Trade in Endangered Species), which requires that international trade be regulated and sustainable. Yet enforcement remains uneven. Research has confirmed ongoing trade in fins from critically endangered rays, including wedgefishes and the bowmouth guitarfish, despite the regulations. Scientists have developed a PCR-based genetic test capable of identifying ray fins among products labeled as “shark” fins, a step toward better enforcement at trade checkpoints.8Conservation Genetics. Ongoing trade of fins from critically endangered rays (wedgefish and giant guitarfish) despite international regulations and a novel PCR test to detect rays among ‘shark’ fins
The Hidden Trade in Thorns
The fin trade gets most of the conservation attention, but there is another market for bowmouth guitarfish parts that flew under the radar until researchers went looking for it. A systematic search of online marketplaces uncovered nearly a thousand bowmouth guitarfish products for sale, the vast majority of which were the bony thorns from the animal’s head and back. Roughly 97% of these listings originated from Thailand, despite the fact that trade in this species should be regulated. Prices ranged from around $3 to $300, and the thorns were marketed alongside high-profile wildlife products from other CITES-listed species, such as tiger claws.9Conservation Science and Practice. Internet trade of a previously unknown wildlife product from a critically endangered marine fish
The advertisements dated back to at least 2012, meaning this trade had been running for years before anyone formally documented it. The thorns appear to be sold as curios and spiritual or talismanic items, similar to the way shark teeth or ray stingers are marketed in some cultures. What makes this trade particularly concerning is that it represents additional demand on top of the already serious pressure from the fin and meat trades. A fisherman who catches a bowmouth guitarfish can sell the fins, the meat, and the thorns, making each animal economically valuable from multiple angles and reducing the incentive to release one alive.
This online marketplace also highlights a blind spot in elasmobranch conservation research. Fin trade has been studied for decades, but the trade in non-fin body parts from rays and sharks has received far less attention. The discovery of such a large online market for bowmouth guitarfish thorns suggests that similar trades in other species may exist undetected.
The Enforcement Problem
Even when regulations exist on paper, enforcing them for a species like the bowmouth guitarfish is enormously difficult. Several factors conspire against effective protection. First, much of the animal’s range falls within developing nations where fisheries enforcement capacity is limited and coastlines are vast. Second, once a bowmouth guitarfish has been processed, its fins are nearly indistinguishable from those of other large rays and even some sharks without genetic testing. The fins enter a supply chain that is global, complex, and often deliberately opaque. The development of genetic tools to identify ray fins in mixed shipments of “shark” fins is a meaningful step, but deploying those tools at scale across dozens of countries and thousands of ports is a different problem entirely.
Third, the CITES Appendix II listing requires countries to issue export permits confirming that trade is sustainable, but “sustainable” is hard to define when basic population data is scarce. Nobody knows how many bowmouth guitarfish remain in the wild. Range-wide population estimates simply do not exist, and the species’ wide distribution across the Indo-Pacific means that no single country’s monitoring program can capture the full picture. What data does exist comes mostly from fisheries landings and bycatch records, which tell you about catch trends but not about how many animals remain uncaught.
Aquarium Programs and Public Awareness
The bowmouth guitarfish has become something of a flagship species in aquariums that focus on elasmobranch conservation. Its unusual appearance makes it immediately compelling to visitors, and facilities that house it can use the animal as a gateway to broader conversations about ray conservation, bycatch, and the fin trade. The captive breeding successes at Newport Aquarium are among the very few documented cases of live reproduction for this species and have provided data that would be virtually impossible to collect in the wild.
Several aquariums across Asia, Europe, and North America now maintain bowmouth guitarfish in their collections. These captive populations serve dual roles: they educate the public about a species most people have never heard of, and they provide a genetic reservoir. If wild populations collapse to the point where recovery becomes necessary, captive individuals could theoretically contribute to restocking efforts, though the logistics of reintroducing a large marine ray into degraded tropical habitats are daunting and have never been attempted for this species.
The challenge for awareness campaigns is that the bowmouth guitarfish lacks the cultural profile of a whale, dolphin, or even a great white shark. “Rhino rays” as a group have been called the most threatened yet least known family of marine fish, and the bowmouth guitarfish fits that description perfectly. It is critically endangered, it faces threats from multiple independent markets, and most people who live within its range have never seen one, let alone know what it is.
River Mouths and Coastal Nurseries
Protecting a wide-ranging species often comes down to identifying the specific places where it is most vulnerable. For the bowmouth guitarfish, those places appear to include the shallow, nearshore waters around river mouths. Fisher communities along the coast of Goa have long recognized that juvenile rays congregate in these habitats seasonally, using them as nursery grounds where young animals can feed and grow in relatively sheltered conditions.10People and Nature. Drawing on local knowledge and attitudes for the conservation of critically endangered rhino rays in Goa, India
River mouths are productive ecosystems, rich in nutrients flushed downstream and in the small fish and invertebrates that juvenile rays depend on. They are also among the most heavily impacted coastal habitats worldwide, subject to pollution, sand mining, shrimp farming, port construction, and artisanal fishing. A juvenile bowmouth guitarfish sheltering in a river estuary may face gillnets set for completely different species. The combination of habitat degradation and fishing pressure in nursery areas could be quietly suppressing recruitment into the adult population, even if adults in deeper offshore waters face somewhat lower direct risk.
Integrating local ecological knowledge with scientific survey data is one of the more promising approaches for identifying and protecting these nursery habitats. Fisher communities often have observations spanning decades that no scientific study has the time or budget to replicate, and their buy-in is essential for any local management measures to succeed. In Goa and elsewhere along the Indian coast, researchers have found that engaging with fishers reveals both the ecological details and the social dynamics needed to design realistic conservation strategies for species like the bowmouth guitarfish.