To mitigate anthropogenic impacts such as habitat modification or loss, fishing, and long-term changes to climate, we need to understand how animals use available space and how much space they require. Understanding the spatial and temporal patterns of animal movement is critical to understanding the mechanisms and ecological process that underpin space use. Key parameters of movement include when and for how long animals go to a particular place (residence), how much space they occupy (home range) and the timing, direction, and distance of migrations (Bestley et al. 2013, Kessel et al. 2014, Heupel & Simpfendorfer, 2015). By collecting new data and using an existing dataset collected by CSIRO Oceans and Atmosphere over the past 7 years, this project will address gaps in our understanding of movement and habitat use by several species of sharks along the Ningaloo Coast.
The PhD project will use an existing dataset of 40 satellite tagged whale sharks and ~70 individuals of black tip reef sharks, grey reef sharks, lemon sharks and tiger sharks monitored by an array of 144 Acoustic receivers for 8 years, along with collecting additional data to fill some gaps and address new questions. The research objectives can include the following, noting that not all objectives will be able to be undertaken by a single student.
1) What proportion of the adult population is resident; how much space do individuals utilise and to what extent do animals roam within the ~28 km2 Mangrove Bay array?
2) Are there sex- and size-related patterns in residence, home range, extent of roaming?
3) To what extent does tide, time of day and season influence movement?
4) What are the preferred habitats of adult and juvenile blacktip reef sharks, grey reef sharks, tiger sharks and lemon sharks?
5) Do these species undertake seasonal migrations and if so, is there an annual or biennial cycle to migration what are the potential drivers of movement (environmental or biological).
6) Compare the range and scale of movement and habitat use of different shark species at Ningaloo
7) Using a dataset of 40 satellite tagged whale sharks, examine vertical and horizonal movement of animals during their movements over thousands of kilometres.
This project will use a combination of an existing dataset of ~1.5 million detections of four species of sharks on receivers along the Ningaloo coast. Detections are centered around the tagging site (Mangrove Bay) where ~77 receivers are spaced 400-800 m apart as well detections along the Ningaloo coast by lines of cross shelf receivers. Most sharks tagged are adults and the student may want to tag more juveniles to investigate movement and nursery habitat or explore additional methods such as accelerometer, depth, and temperature tags and/or activity tags to investigate fine scale movement.
In addition to acoustic telemetry data, a dataset of satellite detections of whale sharks tagged at Ningaloo is available for use. This includes satellite detections and depth and temperature profiles. This unique dataset can be used to explore environmental and oceanographic drivers to movement and migration patterns in whale sharks.
Techniques for analysis of movement data has advanced significantly in recent years, however using physical and biological data to better understand the drivers behind movement poses some challenges. Additionally, the analysis of passive acoustic detection data is an area that requires further technical progress to construct useful approaches to quantify spatial usage of marine animals. This PhD would investigate several approaches for quantifying movement, behaviour and habitat/spatial usage including various regression-based approaches (generalized linear and additive models), machine learning methods and state space models (Hidden markov models, Kalman filtering).
A choice of: