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Scientists deploy satellite tags on rarely studied sawsharks for the first time

An Australian research expedition has successfully deployed three satellite telemetry tags on sawsharks for the first time! These rarely-seen sharks have a toothy rostrum similar to a sawfish, but are true sharks while sawfish are rays. Sawshark rostrums also have sensory barbels, unlike the rostrums of sawfish. “This is actually a good example of convergent evolution where two distantly related species have adaptations that have converged to be very similar in looks and (purportedly) function,”said professor Jane Williamson, the head of the Marine Ecology Group at Macquarie University and the leader of this expedition. “Sawsharks probably use their rostrum in a similar manner to sawfish: as a tool for sensing and capturing prey, and possibly for self-defense.”

Temporarily-held sawsharks P. cirratus on the R/V Bluefin. Photo credit: Jane Williamson

 

Professor Williamson’s research focuses on two of Australia’s three endemic sawshark species: the common sawshark Pristophorus cirratus and the southern sawshark P. nudipinnis“Sawsharks are very difficult to study as they occur in waters 500m+ depth,” she said. “We don’t have much idea how far these animals travel, and thus not much clarity as to whether there are particular pupping grounds, seasonal movement, or how animals utilize particular habitats.”

While satellite telemetry tags are an important and commonly-used tool in marine ecology, the biology and behavior of sawsharks makes their use challenging in this case. “These animals don’t ever come to the surface, so we are unable to glean regular pings of data as you would in other species of sharks,” Professor Williamson said. “The tags were also difficult to build as our sawsharks are slender and weigh, on average, only 2-3 kg.”

Satellite tags attached to the sawsharks. Photo credit: Jane Williamson

So far, the research team has received data from one of the three tagged sawsharks. It moved approximately 300 kilometers from its tagging location over the course of about a month. The popped-off satellite tag also contains lots of other data, which the team has not yet analyzed. If the results of this pilot study show that satellite tags can successfully be deployed on sawsharks, Professor Williamson hopes to expand it to a much larger scale. To our knowledge this is the first time that satellite tagging has been tried on any sawshark species, and information gained will be extremely valuable to the conservation and management of these species,” she said.

Tagging location (green) and detection location 33 days later (blue).

Other recent research published by this team includes a look at identifying sawshark species once fishermen remove their heads and a look at the trophic ecology of these species. Professor Williamson is looking for a Ph.D. student to help research these amazing animals, and invites candidates to contact her directly. You can follow Professor Williamson and her research on twitter here.