Look at this crazy fish: it’s going extinct

Apparently it’s weird fish week here. Meet the sawfish!

The sawfish is a extant species of shark, notable for its elongated, flattened rostrum (nose extension) lined with sharp teeth, which uncannily resembles a saw. There are several species of sawfish, but it is not studied very much, so little is known about them. The rostrum is used for digging to unearth crustaceans, but it is also covered in electro-sensitive pores which allow it to sense microscopic movements of prey on the sea floor; they also use it to defend against predators (and unlucky divers…). Their mouth, like with rays, is located on the bottom of their body. Sawfish range in size from the not-so-mini 1.4 m dwarf sawfish to the gargantuan large-tooth sawfish (P. microdon), the Leichhardt’s sawfish (P. perotteti), and the common sawfish (P. pristis), which can all reach about 7 m (23 ft) in length.

They are also, however, one of the most threatened species of fish on the planet, and researchers from Simon Fraser University, BC, Canada are investigating the causes and effects of this. The biggest threats to sawfish are low population growth, habitat destruction and fishing. Sawfish are large and live in shallow water areas, so are easily caught by fishing boats- they are sources of shark fin soup, and their rostrum make popular souvenirs. Their survival is also often linked to mangrove and seagrass habitats, which are under threat, mostly by human encroachment and development (more on that another time). The figure below shows how the distribution of the sawfish is shrinking across the world.

Shrinking distribution of the sawfish. Image credit: N. Dulvy et al.,  Aquatic Conservation, DOI: 10.1002/aqc.2525
Shrinking distribution of the sawfish. Image credit: N. Dulvy et al., Aquatic Conservation, DOI: 10.1002/aqc.2525

There is some protection for sawfish, and a Global Sawfish Conservation Strategy is being developed. This is just an example of how human action affects the marine ecosystem, and is a symptom of a much larger problem. Hopefully by taking action to conserve specific species like the sawfish will have positive knock-on effects for other plants and animals.

Read more at Aquatic Conservation or at Dr. Nick Dulvy’s research website.

Image credit: “Sawfish genova2” by Flavia Brandi from Roma, Italy – Genova – sonno. Licenced under CC BY-SA 2.0 via Wikimedia Commons

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