by Barbara | Oct 21, 2019 | Blog |
In Australia, we have a responsibility to look after our four species of sawfish. Sawfish are the most endangered of all sharks and rays globally. Northern Australia is the last global stronghold for four out of five species.
For this year’s International Sawfish Day, some major media outlets became interested in Australian sawfish. These animals are receiving a lot of media attention recently, and with this comes a network of opinions and agendas. Because of these two recent articles on ABC and in the Guardian Australia, which present and also intermingle a lot of different view points, I would like to elucidate the direction of Sharks And Rays Australia in this field.
For the last 5 years, under my lead, SARA has worked with sawfish in Far North Queensland, the Gulf of Carpentaria and the Cape York Peninsula. Our philosophy for sawfish research and conservation is that ‘it takes more than a village’ to bring sawfish numbers back and we need everyone involved. Now, if you are one of the fishers who say that you still see plenty of them, I might ask you to take a look at our species ID flyer. Right now, we are mainly concerned with the three Pristis species, which take 8-10 years to become sexually mature. Anoxypristis (narrow sawfish, slimy’s) mature after 3 years and are thus still found in higher numbers. But even Anoxypristis is in trouble. In 2016 we found fins from this species on a drying rack in the Gulf of Carpentaria, and in 2018 we had a sighting of a sawless individual from the east coast submitted to us. If you regularly see large numbers of the other species, please report them to us!
In Australia, sawfish are federally protected on the EPBC Act and in Queensland they are also protected under the Fisheries Act, which means that from a legislative perspective, they are well covered. But once you spend time in remote regions, talking and working with station managers, Indigenous Rangers and fishermen, a whole different picture emerges. Everyone has a story to tell, of how they used to catch ‘really big ones’, but haven’t seen a single animal in 10-15 years. And everyone has someone else to blame for this.
The reality is that every single person who took a sawfish saw as a trophy contributed to the species’ declines. But while pointing the finger only creates scapegoats, anger and an outlet, it does not help sawfish. These animals continue to fall through the cracks. Instead of judging the past it is more helpful to take responsibility and change the future.
And in this, everyone has a role to play:
- Our regular visits to schools have led to the collaborative development of materials. The Normanton State School has taken the life cycle up in its curriculum, and last time we visited they baked a sawfish shaped cake. Love your work!
- We also work with commercial fishers. So far, I have only collaborated with a handful of fishers, but these guys are now putting tags on sawfish for us and releasing them alive. They are happy to go out of their way to release a 4m sawfish, even when working by themselves. Needless to say, this can be very dangerous as sawfish use their saw to defend themselves and such a large animal can hurt people.
- We are always on the hunt for sawfish sighting submissions from the general public and recreational fishers. The old records that you have at home are important for sawfish conservation. We do not judge people who are in the possession of old saws, it is pretty clear that everyone used to take them as trophies. But it is important that this practise stops, as most animals will not survive this illegal procedure and their saw is much more important then as a dust collector. Your sawfish sighting submissions have already allowed us to show that the historic range of freshwater sawfish was larger than previously assumed, as they occurred near Brisbane.
- Our field assistants are not shy to join us on our field trips and do the hard work. Working in remote regions, without the daily pleasantries of hot showers, air condition and high speed internet, and contributing financially to make those expeditions happen, these young adults are my heros. They might disappear back into a different world after the expedition, but they now understand what’s at stake.
- We also work with Indigenous Land and Sea Ranger groups. With every group we have different agreements, and some are more hands-on in helping us than others. But all of them matter, and sawfish matter to them, as you can see in this blog post.
- We also work with the public aquarium industry, who have sponsored some of our tags and are spreading the word for sawfish through their educational displays.
What about net free zones? Shall we close down all gill net fisheries? I personally think that net-free zones are only a solution in close vicinity of towns with large recreational fishing communities, and active fisheries enforcement. Closing down fisheries is not a solution, as it only exports the problem. Gill nets are used everywhere around the world, and in Australia we can document and invent methods of making these fisheries sustainable when it comes to sawfish by-catch.
In the remote areas that we work in, the displacement of fishers would mean that huge stretches of coastline will receive minimal attention in terms of patrolling and enforcement. The coastline of the Queensland Gulf of Carpentaria alone is about 1200 km long. This could create an open field for foreign fishing vessels, with no quotas or indications of catch and by-catch sizes or management strategies.
The area we work in covers about 2/3 the size of Germany, but it is only inhabited by 28,000 people. Germany, on the other hand, is inhabited by over 82 million people. In such remote areas, it is easy for foreign vessels to enter Australian waters undetected. Remember the vessel full of illegal immigrants that arrived in the Daintree, north of Cairns? This vessel crossed at least 800 km of Australian waters undetected before reaching the coastline.
The Australian fishermen and fisherwomen that I have met have an understanding of how their work changes the environment they work in. They are protective of their industry, that’s for sure, but they are also willing to adopt release practises that are safe and cause minimal harm to the animals. Many of them have developed great methods to release sawfish unharmed, and one of our ongoing projects is to document these methods, with the aim of making them available to every fisher. Without their help, the task of collecting data on Queensland’s sawfish populations is almost impossible. However, individuals who kill sawfish, like the recent deaths in Wujunga or this fisher, who was later found in possession of 63 illegal saws, can give a whole fishery a bad name.
My paper on the sawfish by-catches in the Queensland Shark Control Program indicates that sawfish survive the initial capture in a gill net. Anybody who has caught sawfish in this way, including myself, can confirm that as long as the animals’ gills are not wrapped up they can survive the capture. The key threatening process for sawfish is thus not the capture but the release. It is imperative for the survival of these species, that the animals are released alive, quickly and with minimal damage. Many fishers have adopted methods to avoid catching sawfish (like avoiding certain areas in the ecosystems they work in, or checking their nets very often), and many of them are aware of environmental conditions that will increase sawfish captures. These factors need to be documented in order to create best practise standards across fisheries. Ultimately, I would like to see a Sawfish Sustainability Certification for our Australian fisheries that interact with these animals, but this would require large-scale collaborations between governmental agencies, the conservation sector and fisheries.
Please think about how you fit into sawfish conservation and what you can do to protect these animals, instead of pointing the finger at other people. For example, if you live in an Australian city, you could become a sawfish ambassador and visit schools, hold outreach events and bring the memories of these animals back into people’s minds. This is hard work, but it is also more effective than signing a petition or liking a sawfish conservation post. You could also crochet us a sawfish to give to a remote school, or you could join us in the field. We need more sawfish heros.
by Barbara | Oct 20, 2019 | Blog |
International Sawfish Day in Cairns, October 2019
By Nikki Biskis
In October 2019, SARA and the Cairns Aquarium teamed up for an International Sawfish Day event in Cairns. Our sampling event was hosted by the Cairns Aquarium. The event notice was sent to 6,000 people and we were ecstatic with the response from the Cairns community. Former fishers and their families brought in specimens of all sizes and species to be DNA sampled, all with incredible stories to tell.
Barbara samples a saw at a local fishing store
This engagement with the community is crucial, as it helps SARA to understand genetic diversity amongst sawfish populations, and how the distribution of sawfish species have changed over time.
Barbara is interviewed by Win News!
What came next was even more exciting – many continued to submit information of their old saws to SARA and the aquarium, prompting another round of local visits across Cairns for samples. Our project is ongoing, and submissions are always appreciated!
As of today, Sharks and Rays Australia has received around 420 submissions, sampled over 200 saws including 140 that were received in donation. It is events and partnerships with the community that make this all possible.
Nikki sampels a saw at a local store
A special thank you to Cairns Aquarium and to everyone who made International Sawfish Day a success!
by Barbara | Aug 19, 2019 | Blog |
Once a year, the Cairns Indigenous Art Fair kicks off in Cairns. Indigenous artists from all over Far North Queensland and Cape York come to Cairns to display their arts. The event grows bigger every year and features so many works on sharks and rays that we always try to be in Cairns for CIAF.
This year, Julia, who is our instagram wizard, and myself visited CIAF together. We grabbed some food and sat down in the grass to listen to what was going on at the stage. Various Indigenous leaders from the Cape were talking about how their language and culture was slowly being lost. At some point, one of the elders started to talk about sawfish. He said that they had disappeared from his native waters and that he was from the community of Pormpuraaw. I looked at Julia and said, ‘We need to talk to him!’
After the session we introduced ourselves to Syd Bruce Shortjoe. I told him that we work with sawfish and that we would like to help him protect these animals in the waters of Pormpuraaw. I told him that SARA already works with the Mapoon Land and Sea Rangers as well as the Kowanyama Land and Sea Rangers. As I had heard of recent captures of sawfish from the Pormpuraaw region, I said to him that sawfish still exist in his native waters, but probably in very low numbers. I also gave Syd one of our flyers and a sunnies neoprene strap that has all the information on how people can submit sawfish sightings to us. While Syd was listening, he started stroking the sawfish image on the neoprene strap.
Syd told us that his great grandfathers’ totem is the sawfish. He said that because of this, the sawfish is part of his family and his culture. If the animals go extinct, then not only is the species missing from local ecosystems, but it also means that the totem goes extinct. In his cultural belief, you become your totem animal after your death. His grandfather’s totem is the green sawfish, and Syd described the animals very accurately. In Mugu, the sawfish is called kapainyinh.
Syd is the first person who I have met who had a sawfish totem in his family.
He looked at me and grabbed my arm. He said ‘Sawfish cannot disappear. This means my family’s totem disappears and my culture disappears. And with your help we can stop that.’ I grabbed hold of his arm and said to him that I will help him and I will try my best to teach his community, his people, the school kids and the rangers so that we can all come together to look after sawfish and bring these animals back to his waters.
This moment was highly emotional for Julia and myself. While we often meet people who are very interested in sawfish, and while we both understood the cultural importance of sawfish to Indigenous Australians, we were completely unaware of the cultural impacts of the species’ declines.
When Syd looked at me and asked me for my help I realized that there is too much at stake. We need to look after sawfish and we need to do this together.
At the Cairns Indigenous Art Fair. From left to right Barbara Wueringer (SARA), Eliot Koonutta (Pormpuraaw artist), Julia Constance (SARA) and Syd Bruce Shortjoe (Pormpuraaw Elder)
This blog post was written for the Save Our Seas Foundation. Access the original here.
by Barbara | Mar 9, 2019 | Blog |
Have you received a questionnaire?
In January 2019, SARA teamed up with the Gulf Fisherman Association Inc. to send out questionnaires to fishers regarding accidental sawfish captures. Below we hope to answer some of the questions we have received.
- Please be advised that the questionnaires were sent out by the Gulf Fishermen Association, we do not know who received them!
- These questionnaires were developed specifically for fishers in FNQ. We are using fish measurements in feet as this is what fishers are using (the ones we worked with). Feel free to respond in cm if that’s easier.
- The term ‘freshwater’ can refer to the tidal zone of a river in the wet season. If you feel uncomfortable with this term, replace it with tidal / non-tidal.
- The questionnaire was developed after Barbara spoke with fishers at the Annual Meeting of the Gulf Fishermen Association in October 2017. As explained during the meeting, the lack of SOCI data for sawfish can currently be interpreted in three ways: (1) Fishers are underreporting / fabricating data, (2) Sawfish have disappeared, or (3) Fishers have found ways to prevent sawfish captures. You can use the questionnaire to share your facts and also let us know how management can be improved.
- Many fishers have voiced concerns to Barbara about reporting interactions with endangered species, as they are worried that these reports can close their fishery down. For us, the questionnaire is the first step to a collaboration. We care about fresh caught, local fish (not imported), sustainable fisheries and healthy sawfish populations. The next step will be that we invite you to participate in a sawfish workshop in October 2019. We know that some of you implement good methods to release sawfish, and we want to hear them, so all fishers can use these methods.
If you have not yet received a questionnaire or would like to fill one in now, please get in touch!
by Barbara | Feb 22, 2019 | Blog |
Freshwater (or largetooth) sawfish Pristis pristis
by Gary Ogston
The largetooth sawfish (Pristis pristis) can be found across the globe, and consists of four separate sub populations; the Western Atlantic, Eastern Atlantic, Eastern Pacific, and Indo-West Pacific (including northern Australia – spanning the Kimberley to Cape York Peninsula). The species was once considered common across many of these sub populations but has unfortunately undergone drastic population reductions. The largetooth sawfish is now thought to be locally extinct in many regions, and as such is listed as Critically Endangered under the IUCN Red List. The Kimberley region in north-western Australia represents one of the last intact nurseries for the largetooth sawfish, however even within Australia the species is threatened and listed as Vulnerable under Australia’s EPBC Act.
The species is biologically fascinating, both in appearance, due to its large rostrum (averaging between 17 and 24 teeth per side) which is used for predation and defence, and also in its ability to tolerate a wide range of salinities, from freshwater to saltwater. The largetooth sawfish will spend the first three to four years of its life within freshwater systems growing to a length of approximately 3–4 m, before then migrating into the estuarine and marine environments where they reach over 6m in length as an adult. Within the freshwater systems, the diet of the largetooth sawfish consists primarily of species found in the lower water column or benthic environment, such as the blue-catfish (Neoarius graeffei), and detritus.
Fun Facts!
- Did you know? Largetooth sawfish are ovoviviparous; meaning the young develop inside an egg case but remain within the body of the mother until they are ready to hatch, before then being born as live young!
- Did you know? Unlike bony fish, sawfish have no swim bladders and instead rely on large oil-filled livers to help with buoyancy!
Dwarf sawfish Pristis clavata
by Gemma Bauld
The Dwarf sawfish (Pristis clavata) is a species of sawfish that can reach at least 3.2 m in length. It is greenish-brown above and white underneath with gill opening on its underside. Like other sawfish species it has a toothed rostrum. The Dwarf sawfish is found within sand and mud flats associated with close proximity to mangroves in shallow coastal and estuarine waters of northern Australia in the Northern Territory, Queensland and Western Australia. Dwarf sawfish are viviparous (giving birth to live young), with litter sizes unknown but are assumed to be similar to other Pristis species with an average of approximately seven pups per litter. Juveniles are estimated to be between 60–81 cm at the time of birth, and males of the species reaching maturity at eight years old, and a length of 2.5–2.6 m. It is estimated that the Dwarf sawfish have longevity of up to 34 years. Dwarf sawfish in Western Australian waters have been found to occupy restricted areas of habitat. They move up to 10 km during each tide cycle, staying within inundated mangrove forests during high tide and moving out a few kilometres on the low tide. Individuals were found to return to within 100 m of their previous high tide resting sites demonstrating repeated use of habitat. Even large animals frequently occupy habitats less than 2m deep. Current major threats to the Dwarf sawfish include getting their toothed rostra stuck in fishing nets in shallow waters in which they inhabit. Historically their rostra were also collected and traded. However, from 2009, this species was protected from all commercial and recreational use and trade in Australia. The Dwarf sawfish is currently listed as endangered on the IUCN Red List.
References:
The IUCN Red List of Threatened Species
Fishes of Australia
Green sawfish Pristis zijsron
by Gemma Bauld
The Green sawfish (Pristis zijsron) is a species that can grow to 5–7 m in length and is possibly the largest sawfish. They are greenish-brown or olive above and pale to white underneath, with gill openings on its underside. Like other sawfish species it has a flattened head and an elongated snout with uneven-spaced teeth along each side. The Green sawfish in Australia used to be found as far south as Sydney, however its range is now limited to northern Australia (Queensland, Northern Territory and Western Australia). The Green sawfish is also found in the Indo-West Pacific from southern Africa to the Red Sea, Persian Gulf, southern Asia, Indo-Australian archipelago, east Asia and as far north as Taiwan and southern China. They generally inhabit shallow water in coastal and estuarine areas in close proximity to mangrove shorelines. Green sawfish are viviparous (giving birth to live young), with litters being approximately 12 pups. Juveniles are estimated to be approximately 76 cm at the time of birth, and reaching 3.4–3.8 m at maturity at nine years of age. A maximum age for this species is greater than 50 years. Current major threats to the Green sawfish include getting their toothed rostra stuck in fishing nets in shallow waters in which they inhabit. Historically their rostra, fins and meat were also collected and traded locally and internationally, however, this species is now protected from all commercial and recreational use and trade, although difficult to enforce in some countries. The Green sawfish is currently listed as critically endangered on the IUCN Red List.
References:
Simpfendorfer, C. 2013. Pristis zijsron. The IUCN Red List of Threatened Species 2013: e.T39393A18620401. link
Department of the Environment (2017) Pristis zijsronin Species Profile and Threats Database, Department of the Environment, Canberra. link
Narrow sawfish Anoxypristis cuspidata
by Barbara Wueringer
The Narrow sawfish Anoxypristis cuspidata is the only species in its genus. Amongst commercial fishers the species is often known as ‘Slimys’, as juveniles do not develop dermal denticles until about 1.1 m long. The dermal denticles or skin teeth are what gives the skin of sahrks and rays its sandpaper like appearance. Narrow sawfish are the species of sawfish found most offshore, in clearer waters. They have very large eyes and have been found to feed on fast moving species such as squid.
Narrow sawfish are the fastest reproducing species of sawfish, as they reach sexual maturity at about 2–3 years of age. Because of this, Narrow sawfish are still the most common species of sawfish in Australia, and appear to be still abundant on the east coast of Queensland as well as in the Northern Territory, the Gulf of Carpentaria and Western Australia. They are easily distinguished form the three Pristis species, as Narrow sawfish have flat rostral teeth. It is important to mention that Narrow sawfish do not deal well with being caught and handled so if you catch one be sure to release it as quickly as possible.
Narrow sawfish are listed as Endangered on the IUCN Red List of Endangered Species, and in Australia they are listed as Migratory under the EPBC Act and also protected under various state legislations.
References
D’Anastasi, B., Simpfendorfer, C. & van Herwerden, L. 2013. Anoxypristis cuspidata (errata version published in 2019). The IUCN Red List of Threatened Species 2013: e.T39389A141789456. https://dx.doi.org/10.2305/IUCN.UK.2013-1.RLTS.T39389A141789456.en. Downloaded on 19 February 2020.
Freshwater whipray Urogymnus dalyensis
by Morna McGuire
The freshwater whipray is the only species of Australian stingray to live exclusively in fresh and estuarine waters. It was first discovered in the Daly River, Northern Territory, giving rise to its epithet: dalyensis. Since then, freshwater whiprays have been documented in at least 10 northern Australian rivers, suggesting they are endemic to the region. As bottom-dwelling species, feeding on small fish and shrimps, they are usually distributed at depths of 1–4 m.
What do they look like?
The main body (pectoral fin disc) of freshwater whipray is distinctively apple-shaped, being as wide as it is long. Projecting from this disc is an obtuse snout, which tapers to a pointed tip. The colouration of its dorsal surface is grey-brownish, though darkens towards the tail. Contrastingly, its ventral colouration is banded: brown spots separate the white centre from the brown margins. Its tail is whip-like (long and thin), often measuring double the disc length. The tail bares a single serrated venomous spine, likely used for defence.
Freshwater whiprays are easily confused with two other ray species: giant freshwater stingray (Himantura chaophyraya) of South-East Asia and estuary stingray (Dasyatis fluviorum) of eastern Australia. However, both molecular and morphological comparisons confirm that they are separate species. For example, the tail of freshwater whipray lacks the ventral skin-fold typical of other ray species.
Although freshwater whiprays are regarded of Least Concern (IUCN Red List), very little is actually known about their ecology. How large is the population? At what age are they sexually mature? SARA’s research on this species is therefore integral to its survival, by informing fishing management practices and conservation efforts.
Fun fact!
Freshwater whiprays are fully committed to catching their prey; they may charge up riverbanks so fast that they breach themselves!
References:
Last, P. R., Stevens, J. D. (2009). Sharks and Rays of Australia. Edition 2. CSIRO Publishing.
Last, P. R., & Manjaji-Matsumoto, B. M. (2008). ‘Himantura dalyensissp. nov., a new estuarine whipray (Myliobatoidei: Dasyatidae) from northern Australia’. Descriptions of new Australian Chondrichthyans. CSIRO Marine and Atmospheric Research, 22, 283-291.
Bull shark Carcharinus leucas
by Garry Ogston
The bullshark (Carcharhinus leucas) is found in warm temperate and tropical waters around the globe, including countries such as Australia, India, Ecuador and the United States of America. The species is listed as Near-Threatened under the IUCN Red List and faces several threats including recreational and commercial fisheries with commercial fisheries globally being driven by the demand for shark fins, liver oil and meat, however it is also regularly caught as by-catch. The species is also threatened by habitat modification, particularly of nursery grounds e.g. estuarine and freshwater systems. Within Australia the bullshark is not protected and is able to be caught for both recreational and commercial fisheries. Several regions of Australia however, have imposed size limits to reduce the threat of overfishing mature specimens.
Although common in marine and estuarine waters, it is only one of a few species of shark that can tolerate long periods in freshwater (e.g. also see river sharks Glyphis spp.), allowing it to penetrate large distances upstream. Pregnant females migrate to the estuarine, freshwater regions to give birth, with the juveniles utilising these areas as nursery grounds. When born, the bull sharks measure between 0.5 m and 0.8 m, before maturing at approximately 1.5–2.2 m for males and 1.8–2.3 m for females. A full grown adult bull shark can reach over 3 m in length. As the bull shark matures it also diversifies its diet, consuming a range of prey species from turtles to birds, teleost fishes and elasmobranchs, and even crustaceans.
Fun Facts!
- Did you know? Bull sharks possess organs known as the ampullae of Lorenzini which act as electroreceptors. These organs are “jelly” filled pores that help detect electrical fields within the water
- Did you know? Bull sharks are not always at the top of the food chain and get predated on by other bull sharks, Orca’s, and even crocodiles!
Winghead shark Eusphyrna blochii
by Grace McNicholas
The Winghead Shark (Eusphyra blochii) is found around the Indo-West Pacific continental shelf. Found in shallow coastal waters, wingheads feed on/near the bottom, with a diet consisting of crustaceans, cephalopods and small fish. Growing to a maximum total length of just 186 cm, they are smallest of all hammerhead species. Being the smallest species, their characteristic elongated head or ‘cephalofoil’ also has the highest width to body length ratio of all hammerheads. It can reach nearly 50% of their total body length. Males and females reach maturity at around 108 cm and 120 cm respectively, and both sexes have a distinct seasonal reproductive cycle, breeding once a year. Females give birth to live young in February/March in litters of 6–25 pups, with new-borns measuring approximately 45 cm.
Unfortunately, winghead sharks are impacted by coastal gillnet fisheries, as their slender elongated heads are easily caught in a range of gillnet mesh sizes. They have also been heavily exploited for their fins and meat. Over the last three generations it is estimated the global population has declined by at least 50%. These declines are most pronounced in areas with intense coastal fishing such as Indonesia and other Asian countries, where reports of wingheads in landing surveys have become less and less common. As a result, Eusphyra blochii are now listed as globally Endangered on the IUCN Red List. However, in Australia, winghead populations are still thought to be relatively healthy due to much lower bycatch levels in the better managed Australian gillnet and trawl fisheries. Although the Australian population is currently only listed as Least Concern, they may still be at risk due to their patchy distribution.
References:
Chin, A, et al. (2017). Crossing lines: a multidisciplinary framework for assessing connectivity of hammerhead sharks across jurisdictional boundaries. Nature Publishing Group, (April), Nature Publishing Group., pp.1–14. [Online] Available at: doi:10.1038/srep46061.
Compagno, LJ. (1984). FAO species catalogue. Vol. 4. Sharks of the world. An annotated and illustrated catalogue of shark species known to date. FAO Fisheries Synopsis No. 125, Volume 4, Part 1.
Sainsbury, KJ, Kailola, PJ, and Leyland, GG. (1984). Continental Shelf Fishes of Northern and North-western Australia, an Illustrated Guide. (Clouston and Hall: Canberra.)
Smart, JJ.and Simpfendorfer, CA. (2016). Eusphyra blochii. The IUCN Red List of Threatened Species. [Online]. Available at: doi:org/10.2305/IUCN.UK.2016- 1.RLTS.T41810A68623209.en.
Stevens, JD and Lyle, JM. (1989). Biology of three hammerhead sharks (Eusphyra blochii, Sphyrna mokarran and S. lewini) from Northern Australia. Marine and Freshwater Research, 40, pp.129–146. [Online]. Available at: doi:10.1071/MF9890129.
by Barbara | Feb 18, 2019 | Blog |
By Paddy Burke (Sharks4Kids ambassador & PhD student at Macquarie University, @Patrick_Burke)
The ocean is filled with so many incredible creatures, incredible and bizarre. Many of these fish have evolved under similar pressures which have led them to look quite similar even if they are genetically quite distinct. This similarity in appearance or development of similar structures is what is known as homology. One great example for this can be seen in sawfish and sawsharks!
Now many of you may be saying, wait, aren’t those the same thing? The answer is no! While these two groups of fish are very similar in appearance, they actually have quite a few big differences that can make it easy to tell them apart once you know them! The differences we will cover today are their ‘saws’, general body size and the gills.
The ‘saws’ or elongated toothed rostra are the features that make these fish really quite unique. The saw is thought to be used for predation and defense in both groups. However, the actual structure of the saw is really quite different! Sawfish saws are lined with a number of teeth along both sides of their saw that vary in size and number by species but each one of these teeth are permanent! Meaning that if they happen to lose one it will never grow back. The rostral teeth of sawfish also grow from their base, like a rodent’s tooth, so that the animals can sharpen them regularly in the sand. Sawsharks on the other hand have a very different saw. Teeth can be found along both sides of the saw like in sawfish, however, sawshark teeth are replaceable! The most distinguishable feature to separate a sawfish and a sawshark saw is the presence of what are called ‘barbels’. Barbels are found only on sawshark saws and they look like a little moustache coming off the saw. This moustache is thought to have a tactile function, meaning they use them to feel around in the sand for food.
The size of fish is an easy indicator of species between these groups. Sawfish are very large fish, some reaching over 7 meters in length! While sawsharks are much smaller, averaging around 1 meter for an adult depending on species. In addition to size, it is important to know that sawfish are technically rays while sawsharks are true sharks. What that means is that in sawfish you will find their gills located on the underside of the fish. Where as in sharks they are located on the side of the head.
These fish could be considered ‘cousins’ in a way since they are both chondrichthyans, meaning they both have a skeleton made out of cartilage instead of bone. However, it is important to remember that sawfish are actually rays while sawsharks are true sharks. Sawfish may not follow the typical body plan of their relatives the stingrays, but they are more closely related to them than they are to sawsharks!
A sawshark, Pristiophorus nudipinnis resting on the substrate. See the barbels? Image by Tristan Guttridge.
A freshwater sawfish, Pristis pristis, is disentangled from a gill net in order to be tagged and released. Its teeth are evenly sized and spaced, contrary to those of sawsharks. Image by Dave Nash.
