An encounter with sawfish

As this one slid over my head I couldn’t help but think there is something especially  intriguing about Sawfish. What is the go with the saw? Do they need it in case they encounter an underwater forest or was it a simply a hiccup in evolution that resulted in them having to carry around this cumbersome appendage?

Sawfish from below at the Sydney Aquarium
Sawfish from below at the Sydney Aquarium

When you look at where sawfish live it gives us some clues as to why they sport such a vicsious bit of hardware upfront. There are five species found in Australia and they all occur in tropical waters. They generally prefer muddy water and one species, the Freshwater Sawfish, has been found upto 100km inland. The saw, or rostrum, is made of cartilage and contains sensitive fish detecting equipment (Lowrance take note) that can detect the movement of a crab, shrimp or fish in dirty water. Once a detection is made it can lash out with the rostrum and impale its prey. It’s tropical habitat means it has to share its living room with crocs and sharks so the extra defence offered by the rostrum would be a useful disincentive for uninvited dinner guests. The spikes on the saw are painfully sharp and I was suprised to learn they are actually modified scales. The real teeth reside on bony plates inside the mouth.

Can you imagine giving birth to one of these creatures? The whole birds and the bees scenario only happens once every two years for these rays – that’s right, they aren’t really fish. Don’t worry, I’m confused too… Anyway, mother sawfish aren’t stupid and they only equip developing pups with a soft rostrum which is coated in a mucus membrane. After being born the mucus washes away and the rostrum hardens in preparation for some serious fish terrorising.

Evan nearly had his head slashed off while trying to release this Sawfish back into the Keep River
Evan nearly had his head slashed off while trying to release this Sawfish back into the Keep River

Sadly, all species of sawfish are listed as Critically Endangered by the IUCN. This is probably due to their pathetic libido! That said, there seems to be a healthy population in the Northern Territory and Kimberley where we often encounter these beauties when livebaiting for barra. We’ve even seen packs of them hunting mullet at the mouth of the Ord River. Spectacular stuff that you wouldn’t even want to put a line into because handling these guys is like wrestling with a rosebush and they get massive – up to seven meters!!

Netting and rostrums aren’t a pretty combo so many of these rays end up being accidently caught by other fisheries as bycatch. NT Fisheries has done a good job of reducing by catch by having all inshore netters (eg barra pros) use only nets that don’t touch the bottom. Simple stuff really but it has given these prickly bottom feeders a better chance of survival.

Good luck to all the sawfish out there – I will continue to respect you, from a distance…

2 thoughts on “An encounter with sawfish

  • May 25, 2013 at 1:31 pm
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