Joni Pini‐Fitzsimmons

Commercial gillnet fisheries interact with a wide range of elasmobranch species, many of which are incidentally captured as bycatch. Deterrent technologies have emerged as a potential approach for reducing interactions with threatened elasmobranchs. In this exploratory study, captive Giant Shovelnose Rays ( Glaucostegus typus ) and Brownbanded Bamboo Sharks ( Chiloscyllium punctatum ) were exposed to a static green LED light and a pulsed electrosensory deterrent attached to an experimental gillnet. The light deterrent initially reduced interactions by Giant Shovelnose Rays; however, this response diminished over time. Over a 10‐min period, deterred Giant Shovelnose Rays showed a significantly greater distance of deterrence in both treatments compared to the control. There was also a significant difference in mean eye distance between the control and light treatments, but not in nose distance. In contrast, Brownbanded Bamboo Sharks exhibited no significant response to either deterrent. These contrasting responses may reflect differences in the sensory ecology of the two species, underscoring the importance of species‐specific considerations in developing elasmobranch bycatch mitigation technologies. Given the promising outcomes reported for these deterrents in other studies, and the apparent variability in responses among elasmobranch taxa, further evaluation across a broader range of bycatch species is warranted.

Context: Food provisioning is widely used in elasmobranch tourism to elicit encounters between tourists and these typically elusive species. Wildlife tourism operations usually target a single species, although behavioural responses of these species often differ among provisioning locations. Likewise, provisioned foods are often consumed by multiple non-target species, which may also differ in their behavioural responses despite being exposed to the same provisioning event. Few studies have compared behaviour and movement patterns of multiple species in response to provisioning, particularly of those occupying similar niches. Aims: This study aimed to compare the movement patterns of two sympatric ray species, the smooth stingray (Bathythosia brevicaudata) and the southern eagle ray (Myliobatis tenuicaudatus), around a site where they are fed as part of an unregulated but popular tourist attraction in south-eastern Australia. Methods: Using passive acoustic telemetry, we compared the presence, duration of visits, and space use around the provisioning site for the two ray species. Key results: Both species responded to provisioning at the site, but in different ways, suggesting different temporal use of the provisioning site (i.e. time-sharing). Southern eagle rays exhibited stronger attachment to the site, potentially indicating habituation to regular provisioning and a greater risk of being negatively affected than were smooth stingrays. Conversely, smooth stingrays appeared to focus their use of the site on periods of higher provisioning activity (i.e. daytime and on weekends) and may temporarily displace the smaller eagle rays during these times. Despite their attachment, both species made movements out of the study area, suggesting limited impacts on broader-scale behaviours. Conclusions: Smooth stingrays and southern eagle rays exhibited distinct temporal patterns of site use in response to food provisioning, reflecting differences in their behavioural responses. These patterns suggest that even closely related and co-occurring species may adopt different approaches to accessing the same anthropogenic resource. Implications: This research has highlighted the need for a broader approach to assessing and managing wildlife provisioning activities, that takes into account species-specific responses and interspecific interactions.

Recreational fishing waste, produced from processing catches at shore-based fish cleaning facilities and discarded into adjacent waters, is foraged by various aquatic species. However, the potential alterations to the diet of consumers of these resources are poorly studied. Smooth stingrays (Bathytoshia brevicaudata) are a large demersal mesopredatory ray species and common scavenger of recreational fishing discards around southern Australia. Due to their attraction to fish cleaning sites, they are also common targets of unregulated 'stingray feeding' tourism where they are fed commercially produced baits (e.g., pilchards). This study provides a preliminary assessment of the diet of smooth stingrays provisioned recreational fishing discards and baits at two sites in southern New South Wales, Australia (Discard Site: recreational fishing discards only; Provisioning Site: recreational fishing discards and commercial baits) using stable isotope analysis of carbon (delta C-13) and nitrogen (delta N-15), and Bayesian stable isotope mixing models. Our results indicate that at both sites invertebrates, considered a main part of the natural diet of smooth stingrays, made a limited contribution to the diets of provisioned stingrays, while a benthic teleost fish that is a common recreational catch was the dominant contributor. As the assessed teleost is potentially a natural prey item for smooth stingrays, it remains unclear whether the contribution came from recreational fishing discards or natural foraging. However, due to smooth stingrays' typically opportunistic foraging strategy, we expected a greater mixture of resources from low to high trophic level prey than was observed. These results suggest that smooth stingrays have either lower reliance on invertebrates as a result of utilizing provisioned resources or higher reliance on teleost fishes than previously thought. Commercial bait products fed to stingrays at the Provisioning Site were not a major contributor to the diets of smooth stingrays, suggesting this activity has a low impact on their nutrition.

Context: It is common for recreational anglers to discard waste produced from filleting catches back into the water, which results in a highly spatio-temporally predictable food subsidy for wildlife to scavenge. However, the behavioural responses of these scavengers has received little attention. Aims: We aimed to assess the visitation of a common mesopredatory scavenger in relation to temporal patterns in waste discarding at a boat ramp in south-eastern Australia. Methods: Using passive acoustic telemetry, the movements of 13 adult female smooth stingrays (Bathytoshia brevicaudata) were tracked, and patterns in their acoustic detections and duration of time spent in different sections within the study area were compared. Key results: Use of the study area was strongly focused around the boat ramp, and peaked during periods of increased provisioning activity (i.e. afternoons and weekends). Environmental variables had limited influence on visitation, suggesting that the use of the area was not likely to be linked to natural behaviours. Conclusions: The observed patterns indicated that the movements of smooth stingrays were linked to waste-discard practices by recreational anglers. Implications: This study has implications for the management of discard practices for recreational fishing.

The advent of new technologies and statistical analyses has provided valuable insights into chondrichthyan social behavior. It has become apparent that sharks and rays lead more complex social lives than previously believed. Heterarchy combines hierarchy and social network theory and although it is not a new concept, it is rarely applied to animal social interactions. Here, we applied heterarchy to a case study involving smooth stingrays foraging for fish scraps at boat ramp in Jervis Bay, NSW Australia. We took advantage of their attraction to this site to examine their social behavior during agonistic interactions over the provisioned resource. We observed a stable, relatively linear but shallow dominance hierarchy that was highly transitive dominated by a single individual. Social network analysis revealed a non-random social network centered on the dominant individual. Contrary to previous research, size did not predict dominance, but it was correlated with network centrality. The factors determining dominance of lower ranks were difficult to discern, which is characteristic of despotic societies. This study provides the first heterarchical assessment of stingray sociality, and suggests this species is capable of complex social behavior. Given higher dominance and centrality relate to greater access to the provisioned resource, the observed social structure likely has fitness implications.