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Simple Summary: Northern Australia represents an important region for the conservation of globally threatened sharks and rays; however, much of the region has been understudied. We aimed to survey the Roper River system of the Northern Territory of Australia for sharks and rays and compile records from other sources. Five shark and ray species were recorded, including four euryhaline species which can occur in any level of salinity, and one Critically Endangered marine species. This study found that the Roper River is a reproductive area for the observed euryhaline species and is used extensively, with some species extending almost 400 km upstream. Further research is required to understand the abundance and biology of sharks and rays in the Roper River, and how they may respond to human-driven threats. Northern Australia is considered a 'lifeboat' region for globally threatened shark and ray species (elasmobranchs), although much of the region is understudied. The Roper River in the Northern Territory's Gulf of Carpentaria has been inadequately surveyed, with most elasmobranch data gained opportunistically through freshwater fish surveys. This study aimed to report the occurrence of elasmobranch species in the Roper River through targeted field surveys conducted between 2016 and 2024 and to review data from other sources. Four euryhaline species were recorded, comprising two sharks, a sawfish, and a stingray. Records of the globally Vulnerable speartooth shark (Glyphis glyphis) represented a significant range extension and the documentation of a new reproductive population. Records of the Critically Endangered largetooth sawfish (Pristis pristis) extended almost 400 km upstream, highlighting extensive use of the river system. A predominantly marine species, the Critically Endangered giant guitarfish (Glaucostegus typus) was observed in brackish estuarine waters, approximately 15 km upstream from the river mouth. Further research is required to develop a more thorough understanding of abundance, life history, and population connectivity for these species in this river system. Given the documentation of threatened species, the potential impacts of fisheries, water allocations, and climate change require assessment. [ABSTRACT FROM AUTHOR]

Here, we summarise the extinction risk of the sharks and rays endemic to coastal, shelf, and slope waters of the southwest Indian Ocean and adjacent waters (SWIO+, Namibia to Kenya, including SWIO islands). This region is a hotspot of endemic and evolutionarily distinct sharks and rays. Nearly one-fifth (n = 13 of 70, 18.6%) of endemic sharks and rays are threatened, of these: one is Critically Endangered, five are Endangered, and seven are Vulnerable. A further seven (10.0%) are Near Threatened, 33 (47.1%) are Least Concern, and 17 (24.3%) are Data Deficient. While the primary threat is overfishing, there are the first signs that climate change is contributing to elevated extinction risk through habitat reduction and inshore distributional shifts. By backcasting their status, few endemic species were threatened in 1980, but this changed soon after the emergence of targeted shark and ray fisheries. South Africa has the highest national conservation responsibility, followed by Mozambique and Madagascar. Yet, while fisheries management and enforcement have improved in South Africa over recent decades, substantial improvements are urgently needed elsewhere. To avoid extinction and ensure robust populations of the region's endemic sharks and rays and maintain ecosystem functionality, there is an urgent need for the strict protection of Critically Endangered and Endangered species and sustainable management of Vulnerable, Near Threatened, and Least Concern species, underpinned by species-level data collection and reduction of incidental catch. [ABSTRACT FROM AUTHOR]

Overfishing is the primary cause of marine defaunation, yet declines in and increasing extinction risks of individual species are difficult to measure, particularly for the largest predators found in the high seas.sup.1-3. Here we calculate two well-established indicators to track progress towards Aichi Biodiversity Targets and Sustainable Development Goals.sup.4,5: the Living Planet Index (a measure of changes in abundance aggregated from 57 abundance time-series datasets for 18 oceanic shark and ray species) and the Red List Index (a measure of change in extinction risk calculated for all 31 oceanic species of sharks and rays). We find that, since 1970, the global abundance of oceanic sharks and rays has declined by 71% owing to an 18-fold increase in relative fishing pressure. This depletion has increased the global extinction risk to the point at which three-quarters of the species comprising this functionally important assemblage are threatened with extinction. Strict prohibitions and precautionary science-based catch limits are urgently needed to avert population collapse.sup.6,7, avoid the disruption of ecological functions and promote species recovery.sup.8,9. The global abundance of oceanic sharks and rays has decreased by 71% since 1970 and 24 species are threatened with extinction owing to a concomitant increase in fishing pressure., Author(s): Nathan Pacoureau [sup.1] , Cassandra L. Rigby [sup.2] , Peter M. Kyne [sup.3] , Richard B. Sherley [sup.4] , Henning Winker [sup.5] [sup.6] , John K. Carlson [sup.7] , [...]