Behavioural ecology of provisioned rays in south-eastern Australia

<p dir="ltr">Humans and their activities are ubiquitous in almost all environments and have altered the availability of resources as a result. Many activities result in food subsidies being provisioned to wildlife, either unintentionally (e.g., garbage dumps) or deliberately (e.g., wildlife feeding). These provisioned food subsidies are often highly predictable in time and space – occurring in particular places at particular times. In the terrestrial realm, the effects these subsidies have on the species that exploit them has received considerable attention. In contrast, little has been done to quantify the effects in the marine environment. Fishery discards are a major unintentionally provisioned food source, which, at times has led to the intentional feeding of attracted wildlife and the development of unregulated tourism.</p><p dir="ltr">The smooth stingray (<i>Bathytoshia brevicaudata</i>) is a common scavenger of discarded recreational fishing waste throughout southern Australia, and often the target of unregulated stingray-feeding tourist attractions at these sites. This makes them a key marine species to assess the potential effects of such anthropogenic food subsidies on their movement ecology. The primary aim of this thesis was to assess the use of food provisioning sites by smooth stingrays in south-eastern Australia, with a secondary goal of broadening our understanding of these poorly studied mesopredators. Using passive acoustic telemetry, stingrays were tracked from sites where they (i) scavenge recreational fishing discards (Chapters 2, 3, 5 & 6), (ii) are exposed to unregulated hand-feeding for tourism (Chapters 3 & 4), and (iii) are not provisioned (Chapter 3). Their use of provisioning sites was strongly linked to spatio-temporal patterns in provisioning activity, with no similar patterns detected at the non-provisioned site. Looking at the unregulated hand-feeding context in more detail, Chapter 4 compared the movements of smooth stingrays and another sympatric batoid – the southern eagle ray (<i>Myliobatis tenuicaudatus</i>). The two species showed differing strategies for accessing provisioned food, whereby larger smooth stingrays focussed their efforts on peak feeding times, while smaller southern eagle rays were consistently present, highlighting the value of multi-species approaches to assessing impacts from provisioning. Chapter 5 used stable isotope analyses identified that a common recreationally caught teleost species was the dominant contributor to stingray diets at provisioned sites. This suggests that provisioned stingrays have a lower reliance on invertebrates, which are considered a primary natural prey source. Lastly, Chapter 6 examined the movements of juvenile and adult smooth stingrays, providing novel insights into the movement ecology of this species across ontogenetic phases. This thesis provides the first assessment of the role recreational fishery discards and unregulated feeding play in the movement ecology of a large marine mesopredator, providing a basis upon which monitoring and management programs can be built.</p>