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.