The European eel (Anguilla anguilla L.) has a catadromous life cycle, with a single panmictic population that colonises continental Europe and northern Africa yet migrates 5000 to 9000 km to spawn in...

Juvenile Atlantic salmon (Salmo salar), known as post-smolt as they enter the sea, undergo an arduous migration from their natal rivers to their feeding grounds in the North Atlantic Ocean. It has bec...

Abstract. Monitoring of seabird population size and demography has for decades relied on observer-based methods. While such methods have allowed the accumu

Background There has been ever-growing research fitting movement models to marine mammal satellite tracking data in recent years, yet little focus on methods attempting to go beyond individual restric...

Background Passive acoustic telemetry is a method used to quantify residency within an array of receivers, but this technology has limitations for capturing complex behaviors in sharks: pulse delays…

Background Identifying key areas of animal distribution using individual movement data is fundamental for conservation planning, threat mitigation, and spatial management. Methodologies which define t...

The use of unoccupied aerial vehicles or drones for wildlife research has proliferated in recent years and they have proven to be a valuable tool for collecting data for population surveys, morphomet....

Biologging studies rely on the assumption that equipped animal behaviours are representative of the ones displayed by unequipped individuals. Identifying any tagging effects is therefore necessary to ...

Abstract. The early days of animal tagging and tracking using electronic tags were largely restricted to biologists who were electronics hobbyists capable

Natural mortality can be used as a measure of a species’ resilience and is widely used in the management of fish species. Natural mortality can be calculated using life history parameters, although this is often not possible for data-poor species. Acoustic telemetry provides an accurate alternative to estimate natural mortality based on relocations over time. Northern Australia’s river sharks, the Northern River Shark (Glyphis garricki) and Speartooth Shark (G. glyphis), are two rare and threatened species occurring in rivers, estuaries, and inshore marine waters. This study aimed to use acoustic telemetry to estimate natural mortality across a range of size classes and explore the effect of size class, season, and location on mortality rates. An acoustic receiver array was deployed in rivers of Van Diemen Gulf, Northern Territory, Australia. Detections from 185 sharks between 2013 and 2024 were converted into capture histories, which were used to calculate yearly and monthly estimates of mortality. Data demonstrate that river sharks experience high rates of mortality. Younger individuals had significantly higher rates of mortality, with G. glyphis and G. garricki neonates experiencing average yearly mortality rates of 0.898 and 0.731, respectively, compared with 0.120 and 0.233 in subadults/adults. Although mortality was highly variable temporally, over months and years, there were no significant differences between seasons, years or location, and there was no significant difference between species. Results indicate that river sharks in Van Diemen Gulf likely have very limited capacity to recover from population decline and are therefore vulnerable to environmental change and anthropogenic threats. Population monitoring and habitat management is critical to ensure the persistence of river sharks into the future.

Background Angel sharks (Squatina spp.) are among the most threatened group of sharks worldwide, with half of all recognized species classified as Endangered or Critically Endangered by the IUCN.…