In the remote corners of north-western Australia, where the azure waters teem with marine life, a significant discovery has come to light. Recognized as a haven for numerous marine and terrestrial species, this pristine region has long been the subject of scientific intrigue. While sharks are a common topic for research here, the lesser-known, large-bodied rays that inhabit these waters have remained elusive to scientists, their secrets hidden beneath the waves.
Until now.
Western Australia Murdoch University’s Rebecca Bateman and her colleagues have unveiled the region’s role as a sanctuary for these mysterious creatures. The study, recently published in Aquatic Conservation: Marine and Freshwater Ecosystems journal meticulously documented 2,343 records of globally threatened rays belonging to the orders Rhinopristiformes and Pristiformes. The region was inhabited by all of Australia’s Pristidae (four sawfish species), all of Australia’s Rhinidae (three wedgefish species) and the sole Australian representative of the Glaucostegidae (giant shovelnose ray). Of the 2,343 records, ~49% were sawfishes, while giant guitarfish and wedgefishes contributed to ~33% and 18% of records, respectively. The Exmouth Gulf, in particular, stood out as a global stronghold for the green sawfish (Pristis zijsron), emerging as the most frequently encountered sawfish species; this of significance because the green sawfish holds the status of a globally threatened species, making the newly discovered stronghold a beacon of hope for its survival. Stretching its azure arms into the Indian Ocean, the Exmouth Gulf is a marine jewel, captivating the hearts of scientists, conservationists, and nature enthusiasts alike. Encompassing approximately 2,500 square kilometers, it provides a diverse array of habitats, from mangroves and tidal flats to seagrass meadows and coral reefs. The region’s various ecosystems serve as vital nurseries, spawning grounds, and habitats for a myriad of marine species, contributing to the overall biodiversity of the Indian Ocean.
Also known as the lombcomb or narrowsnout sawfish, they have a shark-like physique despite being a species of ray. Characterized by a flattened head and an elongated snout, commonly referred to as a rostrum, which adorned with 24–28 pairs of meticulously arranged rostral teeth on this ‘saw.’ Achieving an impressive length of 16.4 feet (5 meters) in Australian waters, they have greenish-brown or olive hues on its upper body which seamlessly transitions to pale or white tones on its ventral side. This camouflage is not just an aesthetic evolutionary choice, but a strategic adaptation for survival in the varied aquatic environments it inhabits.
It isn’t only the green sawfish making this gulf home. The Bottlenose wedgefish (Rhynchobatus australiae) took center stage as the most commonly encountered rhinid in the region, with less frequent encounters of shark rays (Rhina ancylostoma) and eyebrow wedgefish (Rhynchobatus palpebratus). Also called the white-spotted guitarfish or white-spotted wedgefish, it occurs in tropical and subtropical waters of the Indo-West Pacific and across northern Australia. Distinguished by its flattened body and a distinctive wedge-shaped head, its upper body often sports a mottled pattern of browns and grays, providing effective camouflage against the sandy seafloor, while its ventral side tends towards lighter tones. One of the defining features of the Bottlenose Wedgefish is its ‘bottlenose’ – a rounded, bulbous tip at the front of its rostrum. This adaptation is believed to aid in its foraging behavior and sensory exploration of the seafloor. The Bottlenose wedgefish is targeted and taken incidentally across the Indo-West Pacific in a variety of fishing gears and is retained for its meat and highly-valued fins (except in Australia).
The Ningaloo Coast World Heritage Area and adjacent Exmouth Gulf were also found to host all life stages of giant shovelnose ray (Glaucostegus typus). Designated as a World Heritage Site, the Ningaloo Coast has earned its esteemed status for its unique blend of terrestrial and marine ecosystems, showcasing the extraordinary biodiversity and rich cultural heritage of the region. The giant shovelnose ray is observed in the tropical and subtropical waters of the Indo-Pacific, where its dark dorsal coloration (ranging from brown to gray with a lighter ventral side) make it this larger guitarfish species a sight to behold. True to its name, adults can reach lengths of up to approximately 10 ft (3 m), making them a formidable presence in their coastal and estuarine habitats. These rays are commonly found in shallow, sandy environments, often venturing into bays, estuaries, and nearshore waters.
Rhinopristiformes and Pristiformes are among the most threatened chondrichthyans, which refers to cartilaginous fish species. Wedgefish, shovelnose rays, and sawfish face severe conservation challenges primarily due to overfishing, habitat degradation and incidental capture in fisheries. That the Exmouth Gulf and Pilbara coast have a newfound status as a global refuge for these large-bodied animals underscores the critical need for conservation efforts in these pristine marine environments. As anthropogenic pressures on oceans continue to escalate, understanding and protecting these havens becomes paramount in ensuring the survival of these creatures. The Exmouth Gulf and Pilbara coast are not just regional treasures now; they are global lifelines for some of the ocean’s most extraordinary inhabitants.
