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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]

Connectivity--movements of animals between and among numerous habitats--and the factors (rhythmic cycles and environmental variables) influencing connectivity of juvenile Lichia amia (Teleostei: Carangidae) were assessed in complementary acoustic telemetry studies in two geographically separated estuaries (620 km apart) in South Africa. The studies were conducted within a nationwide array of acoustic receivers moored in estuaries and coastal waters. Tagged fish in both the Kowie (n = 21) and Goukou (n = 17) estuaries displayed high levels of multiple habitat connectivity, with 81% and 76% visiting nearby marine and estuarine environments, respectively. The presence of tagged L. amia within the tagging estuaries was significantly influenced by river and sea temperature (Kowie) and river inflow and moon phase (Goukou). Tidal phase, time of day, and season were found to significantly influence marine excursions undertaken by Kowie- and Goukou-tagged fish. Our study provides an assessment of connectivity among multiple estuarine, port, and marine habitats, relating those movements to rhythmic cycles and environmental variables, and highlights the benefits of tracking animals using an extensive acoustic receiver array that spans multiple habitats. La connectivity, soit les deplacements d'animaux entre differents habitats et au sein de ceux-ci, et les facteurs (cycles rythmiques et variables environnementales) qui influencent la connectivity des Lichia amia (teleosteens : carangides) juveniles ont ete evalues dans le cadre d'etudes de telemetrie acoustique complementaires dans deux estuaires separes dans l'espace (distants de 620 km) en Afrique du Sud. Les etudes ont ete menees au sein d'un reseau pannational de recepteurs acoustiques installes dans des estuaires et des eaux littorales. Des poissons etiquetes dans les estuaires des rivieres Kowie (n = 21) et Goukou (n = 17) presentaient des degres eleves de connectivite a des habitats multiples, 81% et 76 % d'entre eux visitant des milieux marins et estuariens a proximite, respectivement. La presence de L. amia etiquetes dans les estuaires ou a eu lieu l'etiquetage etait significativement influencee par la temperature de la riviere et de la mer (Kowie) et par l'apport de la riviere et la phase de la lune (Goukou). La phase de la maree, l'heure du jour et la saison s'averent influencer significativement les excursions en mer effectuees par les poissons etiquetes dans les estuaires des rivieres Kowie et Goukou. L'etude fournit une evaluation de la connectivite entre habitats estuariens, portuaires et marins, reliant les deplacements a des cycles rythmiques et des variables environnementales, et elle souligne les avantages de suivre des animaux a l'aide d'un vaste reseau de recepteurs acoustiques couvrant differents habitats. [Traduit par la Redaction], Introduction Differences in distribution, dispersal, growth, abundance, and survival of a species generally depends on, among other factors, the quantity, quality, distribution, and composition of habitats and resources (Bekkby et [...]

The white‐spotted wedgefish (Rhynchobatus djiddensis) is a Critically Endangered shark‐like ray in the family Rhinidae. Throughout its Western Indian Ocean distribution, it is targeted for its valuable meat and fins and is reported to have undergone major population declines. However, there remains a need for species specific time‐series data to accurately assess localized population declines.This study used two independent long‐term (37 and 40 years) time‐series catch data from competitive shore angling and shark nets to investigate the size composition and catch per unit effort (CPUE) and conduct a risk assessment for the population on the east coast of South Africa.From 1977 to 2017 the competitive shore fishery captured 7,703 individual R. djiddensis, whilst shark nets in the same region captured 2,856 individuals from 1981 to 2017. Individuals captured in the nets had a sex ratio of 1.8:1 females to males, and were larger than those caught by the anglers. Although the mean annual sizes of net‐caught individuals were above the size of reported sexual maturity, there was little evidence to suggest that any individuals captured were reproductively active.Both the competitive shore fishery and shark net catches exhibited strong seasonal trends with the majority of R. djiddensis catches occurring from October to May peaking in austral summer. Standardized CPUE from the competitive shore fishery declined substantially between 1977 and 2017 and shark net catches exhibited a significant (p < 0.05) fourfold decline in annual nominal CPUE from 1981 to 2017.Ultimately, a risk assessment showed a 65.1% decline in abundance over a period of three generation lengths, which indicates that the sampled population of R. djiddensis in South Africa should be classified as Endangered according to the IUCN Red List using criterion A2b. The conservation implications of this are discussed. [ABSTRACT FROM AUTHOR]

The megamouth shark Megachasma pelagios (Lamniformes: Megachasmidae) was described in 1976 from a specimen caught off Hawaii (Taylor et al. 1983) and is the only extant member of its family and genus (Diez et al. 2022). From 1976 to 2010 M. pelagios was considered rare, with only 50 individuals recorded globally during that time (Nakaya 2010). In recent years it is apparent that it is more common and widespread than previously thought, with 273 confirmed records to date across 16 countries in the Atlantic, Indian and Pacific Oceans (Yu et al. 2021; Diez et al. 2022; Skelton et al. 2023). This species is classified as Least Concern on the IUCN Red List of Threatened Species, as it is globally distributed and does not appear to be heavily impacted by fisheries (Kyne et al. 2019).