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Sawn Off

Over recent decades the general public have become ever-more aware of how climate change, pollution, habitat degradation and over-fishing are pushing sharks and rays to the very brink of extinction. And not only are people aware, but they also care! The change in attitude towards sharks - once considered mindless killing machines - has meant that enormous campaigns championing their rights have spread all over the world. This has lead to the ban on finning in many different countries and the control of trade in shark and ray products. All fin-tastic improvements... But did you know there are still situations where these animals experience terrible cruelty at the hands of man... Threatening some of the most endangered animals on the planet...


Sawfish are amongst the most threatened fish in the world (Image Credit: Ryhor M Zasinets / Shutterstock)

Fin to Finning?

Anyone who has any interest in shark and ray conservation will undoubtedly cite finning as one of the major threats that has lead to precipitous declines in chondrichthyan populations. With an enormous value on the global market, in the past shark fins have been harvested via very cruel, inhuman practices - fishing a shark or ray from the water and cutting the fins off while the animal is still alive and throwing the carcass back overboard.


The movement against shark finning is growing all around the world (Image Credit: Socheid / WikimediaCommons)

After becoming the subject of wide-spread public disgust at how cruel and wasteful the practice was, many nations now impose legislation that bans finning in their waters. In some places animals must now be landed with their fins intact. Other countries demand that fins and carcass ratios must tally. Some countries have also banned the import and export of fins completely. It is not perfect, but it seems we may be well on the way to winning the battle against finning... but this doesn't mean that sharks and rays are protected from all human cruelty.


SawfIshes use their rostrum both to detect and to manipulate their prey (Image Credit: Andrea Izzotti / Shutterstock)

See Saw

One group of shark relatives that has suffered great cruelty at human hands are the sawfishes. Whilst these wonderfully bizarre animals might look more like their shark cousins, sawfishes are actually a type of ray (aka a "batoid"). As a part of a group known as the Rhinopristiformes, the sawfishes (family Pristidae) are closely related to wedgefishes and guitarfishes (Morgan et al, 2016).


All five species of sawfish use their toothed rostrum for foraging (Image credit: Flavio Ferrari / WikimediaCommons)

Whilst it may be misleading, it is no surprise that these creatures are also commonly known as 'carpenter sharks' because all five species of sawfishes possess a magnificent saw (called a "rostrum") that projects out of the front of their faces (Wueringer et al, 2012; Morgan et al, 2016).


The rostrum on a sawfish is an extension of the cartilage that projects from their head. Whilst it is made of cartilage and armed with "rostral teeth", the saw is very much living tissue. In fact, the brain cavity actually extends into the rostrum (Wueringer et al, 2012; Morgan et al, 2016).


Each of the five species of sawfish has subtle difference in the size, shape and rostral teeth of their saw (Image Credit: Bonnie Taylor Barry / Shutterstock)

Desawing

Sadly, this magnificent feature has contributed massively to the decline of sawfishes all over the globe. As it is easily entangled in all different kinds of fishing gear, sawfishes are all too catchable and their mortality as bycatch in fisheries is high. But an even more alarming issue is that of "desawing"...


Akin to the trade in elephant and rhinoceros ivory, for centuries it was commonplace to take sawfish rostra as trophies or curios. Despite being strictly controlled by listing of sawfishes on the Convention of International Trade in Endangered Species of Flora and Fauna (CITES Appendix I), international trade in sawfish rostra still goes on today (Morgan et al, 2016).


Like elephants for their ivory, sawfish are hunted for their rostra (Image Credit: ShaunWilkinson / Shutterstock)

Absolutely Ne-saw-ssary

The rostrum is absolutely vital to a sawfish's survival because they use it when hunting their prey. As it is packed full of electrosensory organs called "ampullae of Lorenzini", sawfishes use their saw to track down and dig up any little critters that are hiding under the sand. They also use the saw to pin down prey and slash the rostrum through the water to chop their meal into bite-sized pieces (Wueringer et al, 2012; Morgan et al, 2016).

Incomprehensibly some people value sawfish rostra as home decor (Image Credit: Auge=mit, / Wikimedia Commons)

Scientists have had the unhappy opportunity to study what happens to a sawfish after it's saw has been amputated, after coming across them in the wild. They have learned that it is very common for sawfish to die after losing their saw because they bleed to death or they are not able to hunt for food food (Wueringer et al, 2012; ).


For example, one team discovered a recently desawed male green sawfish (P. zijsron) in northern Australia. After fitting the animal with a tag, they learned that, whilst the sawfish was miraculously able to survive for at least several months, the way that it moved around and used its habitat changed, indicating that it was having to forage very differently. This animal also became increasingly emaciated, suggesting it was struggling to catch enough prey. The scientists lost track of the sawfish after 75 days and whether it left the study site or finally perished, is not known (Wueringer et al, 2012; ).




Save a Saw

After extreme fishing pressure and habitat degradation sawfishes are classified as some of the most seriously threatened of all animals on our planet today. To learn more, you can check out Extinction of the Rhino-Saws.


"The sawfishes (Pristidae) are the most threatened of all of the world’s shark and ray families"

- Dulvy et al, 2016


The desawing of sawfishes for the sale of curios is contributing to their continued declines, but in addition, its cruelty makes this practice simply unacceptable. It is not only a conservation concern, but an animal rights issue (Wueringer et al, 2012; Dulvy et al, 2016; Morgan et al, 2016; Kyne et al, 2020).


We must raise awareness that desawing occurs and demand that these threatened fishes be offered stricter protections throughout their range. You don't have to love the animal itself to know that poaching any creature - be it elephant, rhinoceros or sawfish - just for their body parts is a barbaric practice that has absolutely no place in our modern society.



References

Dulvy NK, Davidson LNK, Kyne PM, Simpfendorfer CA, Harrison LR, Carlson JK & Fordham SV (2016). Ghosts of the coast: global extinction risk and conservation of sawfishes. Aquatic Conservation: Marine & Freshwater Ecosystems, 26: 134–153. Access online.


Kyne PM, Jabado RW, Rigby CL, Dharmadi, Gore MA, Pollock CM, Herman KB, Cheok J, Ebert DA, Simpfendorfer CA & Dulvy, N. K. (2020). The thin edge of the wedge: Extremely high extinction risk in wedgefishes and giant guitarfishes. Aquatic Conservation: Marine and Freshwater Ecosystems, 30(7), 1337-1361. Access online.


Morgan DL, Wueringer BE, Allen MG, Ebner BC, Whitty JM, Gleiss AC & Beatty JC (2016). What is the fate of amputee sawfish? Fisheries, 41:2, 71-73. Access online.


Wueringer BE, Squire L, Kajiura SM, Hart NS & Collin SP (2012). The function of the sawfish’s saw. Current Biology, 22:R150–R151. Access online.


By Sophie A Maycock for SharkSpeak


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