At the end of September 2014, S.E.A. Aquarium welcomed our resident Largetooth Sawfish (Pristis pristis) to the Open Ocean Habitat. This species spends its younger years in freshwater water and moves into a salty, marine environment in its adult years.
What is a Largetooth Sawfish?
The Largetooth Sawfish is listed as Critically Endangered on the International Union for Conservation of Nature’s (IUCN) red list of threatened species.
The species previously had widespread tropical distribution with four subpopulations in the Eastern Atlantic, Western Atlantic, Eastern Pacific and Indo-West Pacific. Now the population has dwindled, due to overharvesting and entanglement in fishing gear.
The Largetooth Sawfish is ovoviviparous. Young Sawfish grow in eggs contained within the mother. After the embryos are fully developed, the mother Sawfish gives live birth with a litter size of one to 13 pups.
This species can grow to 6.5 metres long. It reaches reproductive at 10 years and usually lives to 25 or 30 years.
How the Sawfish use its “saw”
Sawfish are rays, despite looking similar to sharks. Its unique feature is its long, narrow, flattened rostrum (nose extension) which is lined with sharp transverse “teeth” that makes the rostrum look like a saw. These aren’t actual teeth but are modified tooth-like structures called denticles.
The rostrum is covered with electrosensitive pores so the Sawfish can detect slight movements of prey hiding in the muddy sea floor. The rostrum is also used to dig for buried crustaceans.
If suitable prey swims past, the normally lethargic Sawfish springs from the bottom of the sea and slashes at the prey with its saw. This usually stuns or impales the prey enough for the Sawfish to devour it. Sawfish also defend themselves with their rostrum against intruding divers and predators such as sharks.
Three interesting observations about Sienna the Sawfish
The female Largetooth Sawfish at S.E.A. Aquarium, which the aquarist team named Sienna, has been at the Aquarium for more than a year. James Hong, Aquarist at S.E.A. Aquarium, shares some of her quirks.
1. Sienna knows when feeding time happens.
Sienna eats a varied diet including her seemingly favourite food; tuna and mackerel.
At S.E.A. Aquarium, Sienna eats multiple times each week. She knows exactly when it is feeding time, as the aquarists have created an underwater “dinner bell”.
2. Sienna likes to spend her time resting at the bottom of Open Ocean Habitat.
If you’re wondering where Sienna the Sawfish is in the Open Ocean Habitat, look at the bottom of the habitat.
Like other bottom dwelling (benthic) animals, the Sawfish spend much of their time resting on the sea floor. This allows them to save energy.
They can still breathe even while stationery, unlike some sharks and rays which need to keep swimming to breathe.
3. Sienna tends to shy away from divers.
Sawfish are reclusive, and only attack when they feel threatened. All species of sawfish are listed on Appendix I of the Convention on International Trade of Endangered Species (CITES), which effectively bans commercial international trade in sawfish or their parts.
In contrast, some marine creatures in the Open Ocean Habitat such as the Manta Ray and Eagle Ray follow divers around.