The direct impacts of fishing on chondrichthyans (sharks, rays and chimeras) are well established... more The direct impacts of fishing on chondrichthyans (sharks, rays and chimeras) are well established. Here we review a largely unreported, often misinterpreted and poorly understood indirect impact of fishing on these animals — capture-induced parturition (either premature birth or abortion). Although direct mortality of discarded sharks and rays has been estimated, the prevalence of abortion/premature birth and subsequent generational mortality remains largely unstudied. We synthesize a diffuse body of literature to reveal that a conservative estimate of > 12% of live bearing elasmobranchs (n = 88 species) show capture-induced parturition. For those species with adequate data, we estimate capture-induced parturition events ranging from 2 to 85% of pregnant females (average 24%). To date, capture-induced parturition has only been observed in live-bearing species. We compile data on threat-levels, method of capture, reproductive mode and gestation extent of premature/aborted embryos....
This study aimed to characterize morphological aspects related to abortion through a non-lethal a... more This study aimed to characterize morphological aspects related to abortion through a non-lethal approach in the shortnose guitarfish Zapteryx brevirostris, an endemic and threatened species commonly caught by artisanal fisheries. Two females with signs of abortion and one female exhibiting external signs of pregnancy were purchased alive at a fish market during the period when this species has developing embryos in southern Brazil. Scans were conducted using a portable ultrasound. Females with signs of abortion revealed an absence of embryos despite having a similar morphology of the uterus when compared to the pregnant female. Examination of the pregnant female revealed the presence of two embryos, measuring c. 100 mm, each detected through their midline. This study presents new data on uterine macromorphology following successive abortive events in a viviparous elasmobranch species and validates ultrasonography as a diagnostic tool for the species. Ultrasonography is an effective,...
While aerial shark spotting has been a standard practice for beach safety for decades, new techno... more While aerial shark spotting has been a standard practice for beach safety for decades, new technologies offer enhanced opportunities, ranging from drones/unmanned aerial vehicles (UAVs) that provide new viewing capabilities, to new apps that provide beachgoers with up-to-date risk analysis before entering the water. This report describes the Sharkeye platform, a first-of-its-kind project to demonstrate personal shark alerting for beachgoers in the water and on land, leveraging innovative UAV image collection, cloud-hosted machine learning detection algorithms, and reporting via smart wearables. To execute, our team developed a novel detection algorithm trained via machine learning based on aerial footage of real sharks and rays collected at local beaches, hosted and deployed the algorithm in the cloud, and integrated push alerts to beachgoers in the water via a shark app to run on smartwatches. The project was successfully trialed in the field in Kiama, Australia, with over 350 dete...
Here is presented a list of shark and ray species observed and inferred to exhibit capture-induce... more Here is presented a list of shark and ray species observed and inferred to exhibit capture-induced parturition (birth). This encompasses both premature-birth and abortion of embryos. Also presented are data on species fecundity, International Union for Conservation of Nature (IUCN) threat levels, reproductive mode and fishing methods that induce parturition. If you know of a species that does not appear on the list, please get in contact with Kye Adams via ka738@uowmail.edu.au so that the list may be updated. For analyses and discussion of these data please view the linked article published in Biological Conservation. If you wish to present analyses of these data please reference the dataset DOI and feel free to contact the corresponding author at ka738@uowmail.edu.au with any questions. To cite a single species that exhibits capture-induced parturition please cite the original reference given. For each species the IUCN reference contains a hyperlink to the IUCN threat assessment, with information on taxonomy, geographic range, population, habitat and ecology, use and trade, threats and conservation actions. The reproductive mode for each species is taken from the capture-induced parturition reference, the IUCN threat assessment or from Compagno (1990). General references: Compagno, L.J.V., 1990. Alternative life-history styles of cartilaginous fishes in time and space. Environmental Biology of Fishes 28, 33-75. IUCN 2016. The IUCN Red List of Threatened Species. Version 2016-3. . More specific references are found within the dataset itself.
Stingrays play a key role in the regulation of nearshore ecosystems. However, their movement ecol... more Stingrays play a key role in the regulation of nearshore ecosystems. However, their movement ecology in high-energy surf areas remains largely unknown due to the notorious difficulties in conducting research in these environments. Using a blimp as an aerial platform for video surveillance, we overcame some of the limitations of other tracking methods, such as the use of tags and drones. This novel technology offered near-continuous coverage to characterise the fine-scale movements of stingrays in a surf area in Kiama, Australia, without any invasive procedures. A total of 98 stingray tracks were recorded, providing 6 h 27 min of movement paths. The tracking data suggest that stingrays may use a depth gradient located in the sandflat area of the bay for orientating their movements and transiting between locations within their home range. Our research also indicates that stingray behaviour was influenced by diel periods and tidal states. We observed a higher stingray occurrence during...
Conflict between humans and large predators is a longstanding challenge that can present negative... more Conflict between humans and large predators is a longstanding challenge that can present negative consequences for humans and wildlife. Sharks have a global distribution and are considered to pose a potential threat to humans; concurrently many shark species are themselves threatened. Developing strategies for coexistence between humans and this keystone group is imperative. We assess blimp surveillance as a technique to simply and effectively reduce shark encounters at ocean beaches and determine the social acceptance of this technique as compared to an established mitigation strategy—shark meshing. We demonstrate the suitability of blimps for risk mitigation, with detection probabilities of shark analogues by professional lifeguards of 0.93 in ideal swimming conditions. Social surveys indicate strong social acceptance of blimps and preference for non-lethal shark mitigation. We show that continuous aerial surveillance can provide a measurable reduction in risk from sharks, improvi...
Background Acoustic telemetry has been used with great success to quantify the movements of marin... more Background Acoustic telemetry has been used with great success to quantify the movements of marine fishes in open habitats, however research has begun to focus on patterns of movement and habitat usage within more structurally complex habitats. To date, there has been no detailed assessment of the performance of acoustic telemetry within seagrass, which forms a crucial nursery and foraging habitat for many fish species globally. Information on the detection range of acoustic receivers within seagrass is essential to guide receiver array design, particularly positioning systems. Here, we compare detection ranges for transmitters (Vemco V7) within and above the seagrass to determine impacts on the performance of a Vemco Positioning System (VPS). We also investigate the influence of environmental conditions (i.e. wind, time of day, background noise, atmospheric pressure and depth) on detection probability. Results The performance of the VPS declined dramatically when the transmitters w...
Aerial surveys are a powerful means of collecting ecological data in terrestrial and marine syste... more Aerial surveys are a powerful means of collecting ecological data in terrestrial and marine systems that may otherwise be difficult to acquire. Increasingly aerial observations are made wi...
The direct impacts of fishing on chondrichthyans (sharks, rays and chimeras) are well established... more The direct impacts of fishing on chondrichthyans (sharks, rays and chimeras) are well established. Here we review a largely unreported, often misinterpreted and poorly understood indirect impact of fishing on these animals — capture-induced parturition (either premature birth or abortion). Although direct mortality of discarded sharks and rays has been estimated, the prevalence of abortion/premature birth and subsequent generational mortality remains largely unstudied. We synthesize a diffuse body of literature to reveal that a conservative estimate of > 12% of live bearing elasmobranchs (n = 88 species) show capture-induced parturition. For those species with adequate data, we estimate capture-induced parturition events ranging from 2 to 85% of pregnant females (average 24%). To date, capture-induced parturition has only been observed in live-bearing species. We compile data on threat-levels, method of capture, reproductive mode and gestation extent of premature/aborted embryos....
This study aimed to characterize morphological aspects related to abortion through a non-lethal a... more This study aimed to characterize morphological aspects related to abortion through a non-lethal approach in the shortnose guitarfish Zapteryx brevirostris, an endemic and threatened species commonly caught by artisanal fisheries. Two females with signs of abortion and one female exhibiting external signs of pregnancy were purchased alive at a fish market during the period when this species has developing embryos in southern Brazil. Scans were conducted using a portable ultrasound. Females with signs of abortion revealed an absence of embryos despite having a similar morphology of the uterus when compared to the pregnant female. Examination of the pregnant female revealed the presence of two embryos, measuring c. 100 mm, each detected through their midline. This study presents new data on uterine macromorphology following successive abortive events in a viviparous elasmobranch species and validates ultrasonography as a diagnostic tool for the species. Ultrasonography is an effective,...
While aerial shark spotting has been a standard practice for beach safety for decades, new techno... more While aerial shark spotting has been a standard practice for beach safety for decades, new technologies offer enhanced opportunities, ranging from drones/unmanned aerial vehicles (UAVs) that provide new viewing capabilities, to new apps that provide beachgoers with up-to-date risk analysis before entering the water. This report describes the Sharkeye platform, a first-of-its-kind project to demonstrate personal shark alerting for beachgoers in the water and on land, leveraging innovative UAV image collection, cloud-hosted machine learning detection algorithms, and reporting via smart wearables. To execute, our team developed a novel detection algorithm trained via machine learning based on aerial footage of real sharks and rays collected at local beaches, hosted and deployed the algorithm in the cloud, and integrated push alerts to beachgoers in the water via a shark app to run on smartwatches. The project was successfully trialed in the field in Kiama, Australia, with over 350 dete...
Here is presented a list of shark and ray species observed and inferred to exhibit capture-induce... more Here is presented a list of shark and ray species observed and inferred to exhibit capture-induced parturition (birth). This encompasses both premature-birth and abortion of embryos. Also presented are data on species fecundity, International Union for Conservation of Nature (IUCN) threat levels, reproductive mode and fishing methods that induce parturition. If you know of a species that does not appear on the list, please get in contact with Kye Adams via ka738@uowmail.edu.au so that the list may be updated. For analyses and discussion of these data please view the linked article published in Biological Conservation. If you wish to present analyses of these data please reference the dataset DOI and feel free to contact the corresponding author at ka738@uowmail.edu.au with any questions. To cite a single species that exhibits capture-induced parturition please cite the original reference given. For each species the IUCN reference contains a hyperlink to the IUCN threat assessment, with information on taxonomy, geographic range, population, habitat and ecology, use and trade, threats and conservation actions. The reproductive mode for each species is taken from the capture-induced parturition reference, the IUCN threat assessment or from Compagno (1990). General references: Compagno, L.J.V., 1990. Alternative life-history styles of cartilaginous fishes in time and space. Environmental Biology of Fishes 28, 33-75. IUCN 2016. The IUCN Red List of Threatened Species. Version 2016-3. . More specific references are found within the dataset itself.
Stingrays play a key role in the regulation of nearshore ecosystems. However, their movement ecol... more Stingrays play a key role in the regulation of nearshore ecosystems. However, their movement ecology in high-energy surf areas remains largely unknown due to the notorious difficulties in conducting research in these environments. Using a blimp as an aerial platform for video surveillance, we overcame some of the limitations of other tracking methods, such as the use of tags and drones. This novel technology offered near-continuous coverage to characterise the fine-scale movements of stingrays in a surf area in Kiama, Australia, without any invasive procedures. A total of 98 stingray tracks were recorded, providing 6 h 27 min of movement paths. The tracking data suggest that stingrays may use a depth gradient located in the sandflat area of the bay for orientating their movements and transiting between locations within their home range. Our research also indicates that stingray behaviour was influenced by diel periods and tidal states. We observed a higher stingray occurrence during...
Conflict between humans and large predators is a longstanding challenge that can present negative... more Conflict between humans and large predators is a longstanding challenge that can present negative consequences for humans and wildlife. Sharks have a global distribution and are considered to pose a potential threat to humans; concurrently many shark species are themselves threatened. Developing strategies for coexistence between humans and this keystone group is imperative. We assess blimp surveillance as a technique to simply and effectively reduce shark encounters at ocean beaches and determine the social acceptance of this technique as compared to an established mitigation strategy—shark meshing. We demonstrate the suitability of blimps for risk mitigation, with detection probabilities of shark analogues by professional lifeguards of 0.93 in ideal swimming conditions. Social surveys indicate strong social acceptance of blimps and preference for non-lethal shark mitigation. We show that continuous aerial surveillance can provide a measurable reduction in risk from sharks, improvi...
Background Acoustic telemetry has been used with great success to quantify the movements of marin... more Background Acoustic telemetry has been used with great success to quantify the movements of marine fishes in open habitats, however research has begun to focus on patterns of movement and habitat usage within more structurally complex habitats. To date, there has been no detailed assessment of the performance of acoustic telemetry within seagrass, which forms a crucial nursery and foraging habitat for many fish species globally. Information on the detection range of acoustic receivers within seagrass is essential to guide receiver array design, particularly positioning systems. Here, we compare detection ranges for transmitters (Vemco V7) within and above the seagrass to determine impacts on the performance of a Vemco Positioning System (VPS). We also investigate the influence of environmental conditions (i.e. wind, time of day, background noise, atmospheric pressure and depth) on detection probability. Results The performance of the VPS declined dramatically when the transmitters w...
Aerial surveys are a powerful means of collecting ecological data in terrestrial and marine syste... more Aerial surveys are a powerful means of collecting ecological data in terrestrial and marine systems that may otherwise be difficult to acquire. Increasingly aerial observations are made wi...
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