Assessment of the abundance and distribution of four species of sawfish
In 2015, Sharks And Rays Australia started an assessment of the current distributions and abundance patterns of four species of sawfishes in Far North Queensland and the Cape York Peninsula.
Sawfishes are the most endangered rays in the world. For example, the freshwater (or largetooth) sawfish Pristis pristis, which we work with, is considered to be amongst the 100 most threatened species in the world.
Northern Australia is the last global stronghold for four species of sawfish. Within this region, the coastline and in the river system of the Cape York Peninsula are most likely to still hold the highest densities of sawfishes.
The last assessment of the distribution and abundance of the four species of sawfish occurring in Queensland’s waters ended in 2008. Since then, sawfish have been declared a no-take species in Queensland’s waters, but it is unclear if this measure is effective.
The ’Vulnerability assessment for the Great Barrier Reef, sawfish’ indicates that:
- “More fishery independent data of sawfish distribution in Far North Queensland is needed, as the data collected to date can only be considered preliminary.
- “There is a paucity of information on the biology and ecology of sawfish in the World Heritage Area and on what is required to maintain their habitats and populations.
- “These concerns present difficulties for informed management of sawfish in the GBR.
Trophic position and ecological roles of euryhaline elasmobranch predators
The key objective of this project is to elucidate the trophic positions and ecological roles of six species of estuarine and euryhaline elasmobranchs within their coastal and riverine habitats on the Cape York Peninsula in Australia. We will involve the public in data collection and thus educate them about these animals and ecosystems.
Why is this important
Globally populations of aquatic apex and mesopredators, including elasmobranchs, are declining at alarming rates. This loss of predators and their regulatory effect on lower trophic species can change ecosystems. Therefore, the assessment of elasmobranch community structures is highly important for the creation of management plans.
The remote habitats of Northern Australia and the Gulf of Carpentaria are home to very rare, globally threatened and little-understood elasmobranchs. Here, the last global stronghold remains for four species of sawfish – the most threatened elasmobranch family. Other endemic and threatened megafauna are speartooth sharks and freshwater whiprays, which were only described in 2008.
Because of its low human population density, Cape York is relative pristine. But as development in these ecosystems progresses, the area might soon be threatened.
This project’s multi-disciplinary scientific approach will allow collection of baseline data on the biology of the study species in a relatively pristine environment. This information is needed to understand the species’ conservation requirements in Cape York and elsewhere around the globe. Meanwhile, the public outreach component of the project aims to put sawfishes on the international eco-tourism map as flagship species in Cape York. This approach will allow us to develop long-term monitoring programmes for these species and also make their existence in Australia common knowledge.
Euryhaline elasmobranchs (that is, elasmobranchs able to adapt to a wide range of salinities) and freshwater elasmobranchs, including the six study species, are particularly vulnerable to habitat modification and destruction, pollution and overfishing because of their restricted habitat and large body sizes. To achieve tailored protection measures, we need to fill the gaps in our knowledge of the biology and community structures of the six study species. This project aims to provide a holistic understanding of the species’ biology through a multi-disciplinary approach. So far, my line of research has focused on the sensory biology and feeding behaviour of these six species, uncovering many of their adaptations, which define their theoretically optimal niche. The proposed project is an expansion of this work to identify where these species fit in food webs and how they use their microhabitats. This will enable us to identify potential impacts of anthropogenic modifications (e.g., sedimentation changes and salinity changes).
Aims & objectives
The aims and objectives of this project are to:
- Assess the ecological niches and microhabitats of the study species. Microhabitats will be identified through analysis of spatial habitat use, activity patterns, predatory behaviour and the species’ relationship with abiotic and biotic habitat factors (e.g., visibility, water temperature, depth, salinity, prey abundance).
- Assess the trophic levels and isotopic niche spaces of the study species within their habitats and in relation to each other and other species. Given their sizes, all could be apex or mesopredators.
- Identify differences and similarities in sensory and neurological adaptations between the study species. Knowledge of these adaptations will shed light on the ‘theoretically optimal niche’ of these species.
This research is part of a larger project that is on-going. Overall it aims to:
- Collect data on the spatial ecology of adult sawfish in North Queensland. Animals will be satellite tagged after they have given birth in estuaries and before they move into the Gulf of Carpentaria. This is vital, as to date virtually nothing is known about sawfish once they become sexually mature
- Involve local schools, the local community, tourism operators and tourists in the proposed research.
Both projects are currently receiving funding from the Save Our Seas Foundation.
As SARA is expanding, we have identified various projects that we would like to pursue together with students. This page serves to provide you with ideas but projects are not limited to what is listed here. Our fieldwork in remote regions of Queensland is very rewarding but also physically demanding. It is important that we work well together and therefore we require all prospective students to join us on at least one expedition. This will allow you to understand our work better and allow us to assess your fieldwork skills, people skills etc. so that we can work out a strategy for your project.
As SARA is not a post-graduate research provider, you will need a primary project supervisor who is based at a University. Dr Wueringer will be your co-supervisor. SARA’s collaborators could also co-supervise your project. SARA will provide you with a platform for you to do your research. As mentioned throughout this page, our field sites are remote and off the beaten track. In order to conduct research in such areas you need a team that plays well together and the necessary infrastructure to conduct the project.
If you want to be involved in any of our projects, we propose the following steps:
- Read through the listed projects and think about them. Do you have skills or interests that match a project?
- Think about the project duration, are you aiming for a one-year honours project or a three-year PhD project?
- Which university would you like to work with? Can you think of supervisors?
- Please also consider visa issues, as SARA will not be able to provide you with a work visa in Australia.
- Can you think of funding that you could apply for?
- You do not need to have answers to all these questions when you get in touch with Dr Wueringer to discuss projects.
GIS desktop assessment of sawfish habitat
There are four species of sawfish found in Queensland waters, each with different habitat requirements and ecologies. The known distributions of these four species are quite broad and/or disjoint, and especially on the east coast of Queensland it is unclear if this reflects incomplete sampling or whether actually distinctive populations exist.
The proposed project is a desktop study and literature review that will identify factors that could affect the distribution of each species and review current knowledge of distribution patterns for four species of sawfish in Queensland’s waters. The study will also identify potentially important habitat for sawfishes within our Queensland study region, for example by expanding the River Disturbance Index. These data can then be used to model and identify key habitat for sawfish under future climate change scenarios.
Distribution patterns of sawfish in Queensland waters
Our sawfish tagging study is ongoing but needs a dedicated student to expand it. We would like to see more stakeholders (commercial and recreational fishermen and Fisheries Queensland) involved in this project. The project also aims to collate information of sawfish captures in Queensland, historic and recent through press releases and working with recreational fishing clubs.
The trophic position and isotopic niche space of sawfishes and other elasmobranchs in riverine communities in tropical Queensland
In 2016 we commenced collecting stable isotope samples of food webs that include elasmobranchs, in a variety of habitats. The aim of this study is to compare the food webs in different river systems that lead into the Gulf of Carpentaria. Each river is quite different, not only in the microhabitat it provides but also in the surrounding terrestrial vegetation. Different approaches could be taken, for example a river with high sawfish abundance could be compared with a river where sawfish are not present (anymore). Moreover, the effects of anthropomorphic degradation of adjacent terrestrial ecosystems (e.g. cattle farming on flood plains, effects of invasive species) on the riverine food webs could also be identified in a comparative study.
Fine tuning of sampling methods for sawfishes
Historically, sawfish are best caught with gill nets compared to lines with hooks (Wueringer, in review). Their saw easily entangles in the monofilament mesh of gill nets, and healthy juvenile sawfish do not often take dead bait. However, sampling with gill nets is a labour intensive, time-consuming method that is also not preferred in the GBRMPA region. Gill nets catch fish by the gills and can quickly kill animals, especially if they require to move in order to ventilate their gills, like sharks. Because of this nets have to be checked regularly (at 15-30 mins intervals). Gillnets can also get entangled in submerged structures and collect debris which creates visual barriers that larger animals will avoid.
Because of this, we want to develop more effective and targeted methods to capture sawfish. These methods could allow us to sample more areas over the course of a sampling session, with the reduction of labour and by-catch.
Students will also be involved in our ongoing projects:
- Collection of genetic samples of all elasmobranchs captured tagged and released from our survey equipment.
- Public awareness campaign for sawfishes, their conservation status and their ecology. We work with Indigenous Ranger groups in the field and also give presentations in local schools during sampling expeditions. We also distribute sawfish ID flyers in the region, and our fieldwork would not be possible without volunteer field assistants. We hope that sawfish will become a flagship species for the region!
- Habitat assessment of rivers and coastal regions in the study region.
- eDNA sampling (to commence in 2017 in collaboration with JCU)
- Detailed terrestrial and aquatic habitat assessment (to commence in 2017). We are already collecting information on the physical parameters of the aquatic habitats that we sample, but we will expand this through the projects mentioned above and in collaboration with Mangrove Watch. We aim to assess the type (mangrove forest, flood plain, grass land) and state (modified by cattle, natural, close to road) of terrestrial habitat surrounding sampling sites.
- Social media outreach. We want to expand this!
Working with wild animals is a privilege that comes with the responsibility of taking care of these animals.
At SARA we are committed to the welfare of everybody involved in our research – including that of animals. All our staff, volunteers and participants are trained to handle animals safely. Our animal capture, handling and release methods are regularly reviewed as part of our Safe Work Procedures.
SARA is registered with Biosecurity Queensland as a user of animals for scientific research. Our research procedures ensure the reduction of stress to the animals during capture, handling and release, under the Australian Code of Practise for the Care and Use of Animals for Scientific Purposes. Before research commences, our research procedures are approved by an Animal Ethic Committee, which also monitors the progress of research projects.
A pump is inserted into the mouth of a juvenile bull shark, to both flush its gills during the work up and also occupy its mouth.