research Archives - Sharks And Rays Australia

A rare insight into the habitat requirements of large Aussie sawfish

by Barbara | Jan 21, 2020 | Blog | 0 comments

By Barbara Wueringer

Sawfish are very unique creatures, which sometimes poses problems when working with them. The saw of a large sawfish can easily be one the biggest safety hazard you will face during fieldwork. But these animals have another adaptation that has made it difficult to attach tags to them. As the animals often come into shallow waters they have the ability to loosen up their dorsal fins, allowing the fins to fall on the side.

When I worked with captive largetooth sawfish (locally in Australia known as freshwater sawfish) Pristis pristisa decade ago, I realized that in situations that I interpreted as likely stressful for the animals, their two dorsal fins would not stay upright anymore. In captivity these situations included water changes where the water levels in the tanks were first dropped and again raised.

In the wild, when juvenile sawfish venture into shallow waters of 20 cm depth or less, they could easily fall prey to terrestrial predators such as wedgetail eagles, which can reach a wingspan of 2.8m and are commonly encountered in the outback, and near rivers in Northern Australia. This means that it might not be stress, but the low water levels that caused the fins to drop!

The floppy fins pose some difficulties to attaching satellite tags to the dorsal fins of sawfish. The last time that sawfish in Australia, according to our knowledge, were tagged with satellite tags was in 2008 (Stevens et al. 2008). The authors tagged 7 sawfish (5 P. clavataand 2 P. zijsron) with SPOT tags that were bolted to the tip of the dorsal fins of sawfish. These tags are commonly used on sharks, and they can only connect to a satellite and send a location point when the dorsal fin breaks the surface. Additionally one pop-up satellite archival tag was put on another P. clavata. While the PAT tag provided depth data and popped off from the animal after 49 days within a few km of the tagging location, the SPOT tags only provided a handful of locations each (Stevens et al. 2008).

Dr Wueringer holds a towed SPOT-253 tag from Wildlife computers that has been attached to a sawfish. Note the first dorsal fin of the animal falling to the side.

The dwarf sawfish that has been tagged is ready to be released.

Since then, satellite tagging of sawfish has come a long way, and thankfully with the information provided by our American colleagues, our tagging has been more successful. They successfully trialled the methods of attaching towed tags to large smalltooth sawfish Pristis pectinata (for more info see Carlson et al. 2014, Guttridge et al. 2015, Papastamatiou et al. 2015) and shared their set up with us.

The next challenge for us was to find sawfish that were healthy (i.e. did not have their saws amputated) and large enough to tow the tags. In March 2019 it finally all came together and we were able to deploy two of our towed SPOT (smart position and temperature) tags! The first one was deployed on a 280cm long, and likely sexually mature female, Dwarf sawfish Pristis clavata and within 24 hrs the second tag was deployed on a 300cm long juvenile green sawfish Pristis zijsron.

One tag detached after about 3 months while the other one stopped sending location data 10 months after deployment. However, while the analysis and project is still ongoing, we can already see that the data we have received is amazing.

One of the most important outcomes of the tag deployments is that we were working with a commercial fisher on this expedition, who now knows how to deploy tags for us and is excited to do so. So we hope that the next tags won’t have to wait another 3 years to be deployed, as we all work together to find large sawfish.

This image shows a subset of the raw location fixes that we received from our tagged green sawfish. Each dot represents a location fix. Location fixes can have errors (including land based locations), especially when a tag does not surface long enough to send its data to the satellite.

This project has received funding by the Save Our Seas Foundation, the Seaworld Research and Rescue Foundation Inc., the Shark Conservation Fund and the Sydney Aquarium.

This blog post was originally written for the Save Our Seas Foundation. you can access the original here.

References

Carlson, J. K., Gulak, S. J. B., Simpfendorfer, C. A., Grubbs, R. D., Romine, J. G. and Burgess, G. H. (2014). Movement patterns and habitat use of smalltooth sawfish,Pristis pectinata, determined using pop-up satellite archival tags. Aquatic Conserv. Mar. Freshw. Ecosyst.24, 104-117.

Guttridge, T. L., Gulak, S. J., Franks, B. R., Carlson, J. K., Gruber, S. H., Gledhill, K. S., Bond, M. E., Johnson, G. and Grubbs, R. D. (2015). Occurrence and habitat use of the critically endangered smalltooth sawfish Pristis pectinata in the Bahamas. J Fish Biol87, 1322-1341.

Papastamatiou, Y. P., Dean Grubbs, R., Imhoff, J. L., Gulak, S. J. B., Carlson, J. K. and Burgess, G. H. (2015). A subtropical embayment serves as essential habitat for sub-adults and adults of the critically endangered smalltooth sawfish. Global Ecology and Conservation3, 764-775.

Stevens, J. D., McAuley, R. B., Simpfendorfer, C. A. and Pillans, R. D. (2008). Spatial distribution and habitat utilisation of sawfish (Pristis spp) in relation to fishing in northern Australia. 26.

Outreach, outreach, outreach

by Barbara | Dec 15, 2017 | Blog | 0 comments

By Barbara Wueringer

Even if your research is extremely meaningful, there is a high chance that most people outside of your field have never heard of it. Even if your study species is extremely endangered, unless it is a cute flagship species (think panda, elephant, rhino), there is a chance that many people including local stakeholders do not know much about it.

The second most important pillar of your work as a scientist, right after producing good quality science, is to communicate your science with those who need to know about it. Social media is important, but in many cases you are ‘preaching to the converted’ as even on twitter someone will have to search #EndangeredSpecies or #Shark in order to find your post within the short period of its lifetime.

Whenever we want to affect a status quo, we have two options: the top down approach and the bottom up approach. Both are equally important! For example, if we want to reduce the number of single use plastic bags in the system, we need to convince companies and governments to ban the bags (top-down), but we also need to work with consumers (bottom-up) who might otherwise unknowingly undermine a ban on bags by asking for single use plastic bags at the supermarket counter, thus creating consumer demand.

One of the most effective, fun and rewarding ways of conducting outreach is to work with local schools. In the last year, which is also our second year of working with volunteers, Sharks And Rays Australia has finally commenced its outreach program in local schools. In an area the size of Germany, that is only inhabited by 28,000 people, a handful of visits in local schools mean that we were able to speak to almost 1% of the population during these school visits, and 4% of all inhabitants under the age of 14.

During our school visits in Aboriginal communities, we do not ask children about the traditional uses of sawfish. Under Native Title law, Indigenous Australians are allowed to capture and eat sawfish for personal consumption only. Many Indigenous Australians are protective of their customs and we respect that. But already the simple question of “Hands up if you’ve ever seen a sawfish!” can provide quantitative insights into current abundances of these animals. In one of the schools, around 90% of the kids had seen a live sawfish before!

After we have explained to the kids what sharks, stingrays and sawfish are and why they are in trouble around the world, we play a game with them, the Food Web Game (download it for free here https://www.sharksandraysaustralia.com/SARAFWG1-4.pdf). The game uses local food webs of species that the children know. While the kids colour in the sheets, we explain some of the cool facts about each species to them. Afterwards the big question is who eats whom and once that is established, we pick an animal out of our food chain and ask the kids what happens if this species is overfished, thus teaching them about the importance of maintaining a natural balance.

So far, the feedback has been incredible. The volunteers are stoked to meet the locals, the kids love it, and so do the teachers, as our visits provide the kids with a real world insight into the classroom science they are taught. I personally hope that the presence of female scientists in their classroom will also help some of the girls to realize that STEM science is not for boys only.

This blog post was written for the Save Our Seas Foundation. Access the original post here

It was also published in ‘Inside Ecology’ magazine, which can be found here