Shout from the rostrum:
‘Poor Carpenters in the soup!’
Such dentistry snared.
Tracking declining animal populations can be tricky enough on land, but in the ocean it’s an even harder proposition. Yet without knowledge of marine animal populations, conservation efforts can’t be directed effectively. One way to solve this issue is to examine drivers of site occupancy – what causes some populations to thrive or decline in an area. Understanding these drivers can allow researchers to predict population declines and gain insight into the probability of local population extinctions.
Sawfish are a family of rays with distinctive long, flat snouts which have horizontal teeth running along the length to resemble saws. Known as rostrums (an alternative definition to the more common meaning of a raised platform for speaking or performing from) they are packed with electroreceptors that allow them to detect prey, whilst the teeth are thought to be used in a swiping motion to incapacitate fish.
Sadly, three of the five sawfish species are Critically Endangered and the other two are Endangered. Since sawfish aren’t commonly sighted keeping track of their populations is hard and there’s little systematic monitoring. To address this Yan et al. (2021) combined data from occurrence surveys with indices of ecological carrying capacity, fishing pressure and management capacity to predict local population extinctions and identify regions where conservation efforts might be most effective.
Overfishing of sawfish is a particular threat: their fins are prized for shark fin soup (whilst sawfish are known as Carpenter sharks, they aren’t actually sharks), their teeth are used as spurs for cockfighting, their rostrum are frequently sold as novelties or trophies, and parts of them are used in traditional medicines in countries including China, Mexico, Brazil, India, Kenya and Iran.
Accidental overfishing is an issue too: their iconic rostrum and teeth are easily tangled in fishing nets and lines. What’s more, untangling sawfish from nets can be difficult and dangerous so some fishermen will kill them before bringing them aboard.
By understanding issues like overfishing and habitat loss Yan et al. were able to show that sawfish are likely to be extinct off the coasts of 55 of the 90 countries where they previously existed. Their findings also suggest that if eight nations prioritise sawfish conservation (Cube, Tanzania, Colombia, Madagascar, Panama, Brazil, Mexico and Sri Lanka), then up to 71.5% of the sawfish family’s historical global distribution would be protected.
Original research: https://doi.org/10.1126/sciadv.abb6026