by Amica Limosani, Jake New, Barbara Wueringer

The Carcharhinidae family, also known as whaler sharks, includes 12 genera and 50 species worldwide, making it one of the largest families of sharks. These sharks are typically found in warm tropical waters, although some species can also be found in brackish and freshwater environments, therefore we encounter these often in the field. Carcharhinids are highly recognizable, often having the classic shark-like shape that many people associate with these animals.

Sicklefin Lemon Shark, Negaprion acudentis   

 Introducing the striking Sicklefin Lemon Shark (Negaprion acutidens)! While most shark enthusiasts are familiar with the Atlantic lemon shark (N. breviostris), widely researched by the Bimini Biological Field Station, the Sicklefin Lemon Shark is equally fascinating. They are easily recognizable by their slender, curved fins, particularly their two equal-sized distinctive sickle-shaped dorsal fins. They often inhabit shallow coastal waters, including mangroves and coral reefs, but are also known to explore farther offshore. With a nocturnal hunting habit, they prey on fish, crustaceans, and cephalopods. Renowned for their relatively docile nature compared to other shark species, encountering them is an unforgettable experience. 

Coates or Australian blackspot shark, Carcharhinus coatesi

Have you ever heard of a Coates or Australian Blackspot Shark, (Carcharhinus coatesi)? Despite recent reclassification and its elusive nature, this species remains largely unstudied. Females give birth to small litters of 1-3 pups, each measuring between 38-40 cm at birth, with adults reaching lengths of up to 88-92 cm.

This species is differentiated from the spot-tail shark as it does not have black markings on the lower caudal fin.

Nervous Shark, Carcharhinus cautus

Have you ever seen a nervous shark, Carcharhinus cautus? Aptly named for its skittish behavior, this shark often darts away when approached by divers or boats, keeping its distance from potential threats. Found in tropical and subtropical waters, primarily in the Indo-Pacific region, they navigate their habitat with caution. Sporting a streamlined body, pointed snout, and large eyes, these features likely contribute to their cautious nature.

Do not confuse the nervous shark with a lemon shark, even though it is slightly greenish in body colour, its dorsal fins are not equal in height.

Blacktip Shark, Carcharhinus limbatus

Introducing the Blacktip Shark, Carcharhinus limbatus! These sharks have black markings on their fins which are not as pronounced as those of blacktip reef Carcharhinus melanopterus. Beware to not confuse the two! Blacktip sharks are common in tropical and subtropical coastal waters worldwide, and they can grow up to 250 cm TL but average around 150cm. They are frequently found nearshore around river mouths, bays, mangrove swamps, and estuaries, though they do not venture far into freshwater. Fun fact their ‘black tips’ fade over time (Compagno et al. 2005). Blacktip sharks are listed as Vulnerable globally (IUCN, 2020) and are targeted by multiple commercial fisheries around the world.

Graceful Shark, Carcharhinus amblyrhynchoides

Named for their smooth swimming style and sleek, streamlined bodies, these sharks are a marvel to watch. With their slender bodies, rounded snouts, and large eyes, graceful sharks have excellent vision in low-light conditions, making them effective nocturnal hunters. Interestingly, graceful sharks are often mistaken for bull sharks because they both have a stocky build. Can you spot the difference?

Learn more about the Mylobatiform rays we encounter here

Learn more about the Rhinopristiform rays we encounter here

Learn more about the Sphyrnid sharks we encounter here

by Amica Limosani, Jake New, and Barbara Wueringer

The Mylobatiformes order includes eight families of stingrays, such as Mylobatidae (eagle rays), Urolophidae (round rays), and Dasyatidae (whiptail rays). Mylobatiformes are incredibly diverse but share the common characteristics of flattened disc or diamond-shaped bodies with tapering tails, often armed with venomous spines. Stingrays from this order are found worldwide in warm coastal waters and can either be bottom dwellers or migratory. They exhibit diverse swimming patterns, either undulating their whole bodies in a wave-like motion or flapping their fins to “fly” through the water column.

Ornate Eagle Ray, Aetomylaeus vespertilio   

Meet the intriguing Ornate Eagle Ray, Aetomylaeus vespertilio. These rays showcase captivating coloration and intricate patterns, featuring dark bands and spots on their dorsal surface. In tropical and subtropical coastal waters, they gracefully roam shallow bays, lagoons, and coral reefs. With a flattened body and broad, wing-like pectoral fins, they move through the ocean depths with elegance. Yet, encountering them in the wild is a rare thrill—there have been fewer than 60 confirmed sightings worldwide. We have been fortunate enough to have four individuals in our dataset over the years!

Cownose Ray, Rhinoptera neglecta

What’s cuter than a Cownose Ray, Rhinoptera neglecta? These rays are as unique as their name suggests, with a forehead resembling the nose of a cow. But don’t let their quirky appearance fool you—they’re highly migratory and can travel long distances in massive schools, sometimes numbering in the thousands. Picture the ocean filled with their graceful gliding as they navigate the waters with their flattened bodies and wing-like pectoral fins. And when it comes to dining, they’re true connoisseurs of the seafloor, using their specialized mouths to crush and feast on shellfish, crustaceans, and other invertebrates. Unfortunately, the Aussie species is much less understood than its Atlantic counterpart, Rhinoptera bonasus. 

Black-spotted Whipray, Maculabatis astra

Say hello to the gorgeous Black-spotted Whipray, Maculabatis astra! With distinctive black and white spots adorning their dorsal surface, these beautiful creatures roam the sandy and muddy bottoms of coastal waters across the Indo-Pacific, often near coral reefs and estuaries. Sporting a diamond-shaped body, a long whip-like tail armed with venomous spines, and a triangular snout, they are truly captivating. Growing up to 80cm in diameter, the Black-spotted Whipray is a true marvel of the marine world! 

Freshwater Whipray, Urogymnus dalyensis

Discover the Urogymnus dalyensis (Freshwater Whipray), a magnificent ray with an apple-shaped body, a prominent snout and a long, whip-like tail armed with venomous spines. These rays call the freshwater rivers and estuaries of New Guinea, northern parts of Australia, including Queensland home. Well-adapted to their environment, freshwater whiprays often bury themselves in sand or mud to ambush prey or evade predators. Sadly, like many freshwater elasmobranchs, they face significant habitat degradation, pollution, and overfishing threats. Advocating for effective management plans is especially difficult because there is so little information on this species in the literature.

Learn more about the Carcharhinid sharks we encounter here

Learn more about the Sphyrnid sharks we encounter here

Learn more about the Rhinopristiform rays we encounter here 

by Amica Limosani, Jake New, Barbara Wueringer

The Rhinopristiformes are an Order of elasmobranchs that comprise shark–like rays. They can be identified by their flattened, either disc– or diamond–shaped heads and shark–like bodies. Common names of this order include guitarfish, sawfish, and shovelnose rays. Rhinopristiformes inhabit warm, shallow waters, making them particularly susceptible to being caught in fishing gear. Unfortunately, global shark–like ray populations are declining due to the combined effect of bycatch in fisheries and targeted fishing for their large fins on the black market. These unique animals need conservation advocacy to restore their populations to healthy levels. SARA’s long-term research and advocacy on sawfish have informed various fisheries’ legislations, leading to increased populations!

Eyebrow Wedgefish, Rhynchobatus palpebratus

Ever heard of a shark with eyebrows? Meet the Rhynchobatus palpebratus also known as the Eyebrow Wedgefish. Named for the prominent ridges above their eyes that resemble eyebrows, these unique creatures grace shallow coastal waters and muddy estuaries. With their distinctive wedge-shaped bodies, broad flattened heads, and elongated pectoral fins, they’re a fascinating sight to behold. Sadly, like many wedgefish species, eyebrow wedgefish are threatened by overfishing and habitat destruction, highlighting the urgent need for conservation efforts. Find out more about the conservation status on the IUCN page. 

Freshwater Sawfish, Pristis pristis

Meet the Freshwater Sawfish, Pristis pristis, also known as the largetooth sawfish. These creatures are among the largest species of sawfish, boasting long, flat rostrums lined with sharp teeth-like structures. They thrive in freshwater and brackish habitats like rivers, estuaries, and coastal lagoons, yet they’re also known to venture into saltwater environments. They journey between freshwater and marine domains for breeding and feeding. Sadly, their populations have plummeted due to overfishing, habitat loss, and bycatch, rendering them critically endangered. 

Narrow Sawfish, Anoxypristis cuspidata

We all recognise this ray, the narrow sawfish (Anoxypristis cuspidata). As the most abundant species of sawfish in Queensland and the only one in its genus, it stands out distinctly. This remarkable species has five canals in its rostrum, compared to the three in the freshwater sawfish. Found in tropical and subtropical coastal waters, these sawfish explore mangrove estuaries, rivers, and shallow bays. When hunting, they are masters, using their rostrum to stun and capture small fish and crustaceans. They are also known to feed on squid! However, these incredible creatures are critically endangered due to overfishing and habitat degradation. They need our help now more than ever.

Learn more about the Carcharhinid sharks we encounter here

Learn more about the Sphyrnid sharks we encounter here

Learn more about the Mylobatiform rays we encounter here

by Amica Limosani, Jake New, and Barbara Wueringer

Great Hammerhead, Sphyrna mokarran

Say hello to the fascinating Great Hammerhead, Sphyrna mokarran! These ocean titans are the largest species of hammerhead shark, instantly recognisable by their “hammer” shaped heads, or cephalofoils. Roaming warm coastal waters worldwide, great hammerheads are master hunters. They use their wide heads to pin down and manipulate prey like stingrays and smaller sharks. They have eyes set wide apart and excellent vision for scoping out the seafloor. In Queensland, they are often seen in shallows as they hunt rays and can sometimes be mistaken for sawfish. However, their dorsal fins can help distinguish between the two. If you are ever in doubt, submit your sighting to www.cytags.com, and we will clarify it for you!

Learn more about the Carcharhinid sharks we encounter here

Learn more about the Mylobatiform rays we encounter here

Learn more about the Rhinopristiform rays we encounter here

Figure 1. Samples, polished, slided and ready for analysis! Image by Nikki Biskis.

By Nikki Biskis

And now the moment of truth! I am currently at the University of Adelaide, working at Adelaide Microscopy, where a spot and/or line along each sawfish tooth is vaporised via a laser and then the chemical composition read in a process called Induction Coupled Plasma Mass Spectrometry (ICPMS).  

Preliminary Findings  

Last year around this time, I ran a pilot study of 40 spot tests, transect analyses, and even complete mapping of individual sawfish teeth. Preliminary results indicated that trace element analysis can resolve the origin at the regional level, potentially narrowing down the capture location by hundreds of kilometres. This precision allows for more accurate incorporation of rostra data into risk maps, highlighting areas where sawfish populations are most vulnerable to ongoing fishing pressures. Now, with further funding from Holsworth and Save Our Seas, we can run the remaining samples and hopefully home in even further. 

Figure 2. Our 2024 run, ready to go. Image by Nikki Biskis.

What’s next? 

As I eagerly await the full results, the question remains: What works, and what still needs investigation? The higher precision spatial data will contribute to the development of targeted conservation strategies, ensuring the long-term survival of sawfish in their northern Australian stronghold. It’s an exciting journey that not only deepens our understanding of these Australian icons but also continues momentum in innovative approaches in conservation. 

Thanks laser – I’m happy to be here too. Image by Nikki Biskis.

And now, the best bit – on to stats. If you’re headed to the Australian Society of Fisheries Biology Conference in November, make sure to come say hello. 

This project is funded by the Holsworth Grant through the Ecological Society of Australia and the Save Our Seas Foundation. We’d like to additionally thank the Queensland Department of Agriculture and Fisheries for their ongoing support of our work. This work would also not be possible without the time and expertise of the team at the Gillanders lab at the University of Adelaide, namely Dr Patrick Reis-Santos and Rhiannon Van Eck, and Dr Paul Olin and Dr Sarah Gilbert at Adelaide Spectroscopy. 

You can read this blog and more on the Save Our Seas Foundation website.

By Nikki Biskis

Sawfishes are iconic species that embody many of the challenges faced in marine conservation. Despite comprehensive protection measures across various levels in Australia, their populations remain under threat from bycatch and illegal fishing for their fins and rostra. Unfortunately, the confiscated or forfeited trophy rostra available for research often come with little to no associated location data. This severely limits their potential for distribution analyses, which are critical for effective conservation strategies. 

The Research Journey 

As a PhD student at the University of the Sunshine Coast (UniSC) and the non-profit organization Sharks And Rays Australia (SARA), one of my research aims is to address this challenge. This project evaluates the use of trace elemental analysis to identify capture locations and origin estuaries for narrow (Anoxypristis cuspidata), green (Pristis zijsron), and freshwater (Pristis pristis) sawfishes along the Queensland coast.  

Methodology 

All the rostra used in this research were received through a collaboration by SARA and the Queensland Department of Agriculture and Fisheries (QDAF). At SARA, over the last two years, I’ve taken teeth from over 200 of these.  

Figure 1. (Left) My first attempts at taking teeth were a bit gruesome and may or may not have given Barbara a heart attack. (Right) We’ve now refined our methods so that sampling scars on saws used for education or that belong to other institutions are more subtle. Image by Nikki Biskis

Figure 2.Our health and safety officer during tooth removal. Image by Nikki Biskis

Trace elements such as strontium, barium, etc. vary in the environment due to salinity, temperature, upwelling, runoff – all these factors give an estuary a unique chemical fingerprint. So, by measuring the quantities of these through just a tiny spot at the base of each tooth, we can use the chemical signatures to assign them to an origin estuary. This is a common technique amongst bony fish but is relatively new amongst sharks and rays. 

If we take a transect, or line along the length of the tooth, we can see fluctuations due to these changes in the environment, allowing us a look into how the animals are moving, how they use their habitat. This is especially meaningful, as sawfishes are now rare, so while it might sound strange, a tooth might provide some of the most in depth insights into the spatial use patterns of these species. 

Figure 3. The teeth were then cleaned, epoxied, sectioned, and polished at UniSC. Image by Nikki Biskis

What’s more, a subset of the samples was taken from an entire animal, meaning we have the vertebrae – the stock standard for aging sharks and rays – as well. This means I have the very exciting side quest of investigating teeth as potential aging structure, through comparison of visual banding and elemental signature across the two sources.  

In other words, the teeth may hold the key to using these trophy rostra for conservation, protecting future populations. 

You can view this blog and more on the Save Our Seas Foundation website.