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Sharks and rays are key functional components of coral reef ecosystems, yet many populations of a few species exhibit signs of depletion and local extinctions. The question is whether these declines forewarn of a global extinction crisis. We use IUCN Red List to quantify the status, trajectory, and threats to all coral reef sharks and rays worldwide. Here, we show that nearly two-thirds (59%) of the 134 coral-reef associated shark and ray species are threatened with extinction. Alongside marine mammals, sharks and rays are among the most threatened groups found on coral reefs. Overfishing is the main cause of elevated extinction risk, compounded by climate change and habitat degradation. Risk is greatest for species that are larger-bodied (less resilient and higher trophic level), widely distributed across several national jurisdictions (subject to a patchwork of management), and in nations with greater fishing pressure and weaker governance. Population declines have occurred over more than half a century, with greatest declines prior to 2005. Immediate action through local protections, combined with broad-scale fisheries management and Marine Protected Areas, is required to avoid extinctions and the loss of critical ecosystem function condemning reefs to a loss of shark and ray biodiversity and ecosystem services, limiting livelihoods and food security.

Rhipicephalus sanguineus is a species complex with a challenging diagnosis. There are two main lineages: a temperate lineage—now recognized as R. sanguineus sensu stricto (s.s.)—and a tropical lineage. In the Americas, several studies examined the distribution of both lineages. Meanwhile, in Chile, the distribution of the tropical lineage was reported from 18° to 22° S and R. sanguineus s.s. from 20° to 33° S; the morphological diagnosis located R. sanguineus in south-central Chile. In this study, we assessed the morphological and genetic identity of ticks collected from 47 dogs in southern Chile. Six dogs (12.8%) were parasitized by ticks that were morphologically and genetically assigned to R. sanguineus s.s. This finding would represent the southernmost record of this species in the country, located at over 308 km further south than the previous record, suggesting a latitudinal expansion of its distribution. Experimental studies are further required to understand how this tick survives extreme weather conditions when compared to other R. sanguineus s.s. from lesser latitudes., Centro de Estudios Parasitológicos y de Vectores

Few studies have considered linkages of mobile predators across large spatial scales despite their significant and often critical role in maintaining ecosystem function and health. The bull shark (Carcharhinus leucas) is a large, widespread coastal predator capable of undertaking long-range movement, but there is still limited understanding of intra-regional differences in movement and habitat connectivity across latitudes within the same coastline. This study used acoustic telemetry data and network analyses to investigate long-range movements, residency patterns and seasonal habitat linkages of sub-adult and adult C. leucas along the east coast of Australia. Our results revealed that C. leucas tagged in Sydney Harbour were mainly present within this temperate estuary in summer and autumn; the rest of the year individuals were detected in tropical and subtropical habitats from southern and central Queensland. In contrast, the detection probability of C. leucas tagged in the Townsville Reefs (central Great Barrier Reef) peaked in spring, with a portion of the tagged population migrating south during the summer months. Differences in residency time between tagging locations were also detected, as all C. leucas tagged in Sydney Harbour were absent between June and November, but 35% of the tropical-reef tagged population remained resident year-round. Network analyses complemented these findings by revealing different seasonal habitat use between regions, thus highlighting complex seasonal-habitat linkages of C. leucas along the coast. Our findings support the hypothesis that the timing, duration, and drivers involved in the long-range movements and connectivity of sub-adult and adult C. leucas vary between latitudinal regions, most likely driven by the interaction between seasonal temperature changes, foraging and reproduction.

Understanding how sharks use coral reefs is essential for assessing risk of exposure to fisheries, habitat loss, and climate change. Despite a wide Indo-Pacific distribution, little is known about the spatial ecology of silvertip sharks (Carcharhinus albimarginatus), compromising the ability to effectively manage their populations. We examined the residency and movements of silvertip sharks in the central Great Barrier Reef (GBR). An array of 56 VR2W acoustic receivers was used to monitor shark movements on 17 semi-isolated reefs. Twenty-seven individuals tagged with acoustic transmitters were monitored from 70 to 731 d. Residency index to the study site ranged from 0.05 to 0.97, with a mean residency (±SD) of 0.57 ± 0.26, but most individuals were detected at or near their tagging reef. Clear seasonal patterns were apparent, with fewer individuals detected between September and February. A large proportion of the tagged population (>71 %) moved regularly between reefs. Silvertip sharks were detected less during daytime and exhibited a strong diel pattern in depth use, which may be a strategy for optimizing energetic budgets and foraging opportunities. This study provides the first detailed examination of the spatial ecology and behavior of silvertip sharks on coral reefs. Silvertip sharks remained resident at coral reef habitats over long periods, but our results also suggest this species may have more complex movement patterns and use larger areas of the GBR than common reef shark species. Our findings highlight the need to further understand the movement ecology of silvertip sharks at different spatial and temporal scales, which is critical for developing effective management approaches.

Bays and estuaries are considered essential fish habitat, yet in many parts of the world, these areas have been degraded or destroyed. In southern California, habitat restoration has become a widely used approach for protecting coastal ecosystems; however, there is little information available on the success of these efforts. Monthly abundance surveys were employed to examine spatial and temporal trends in the fish assemblages 3 years after the restoration of the Bolsa Chica Full Tidal Basin (BCFTB). This was used as a short-term success assessment of the BCFTB restoration, as well as an important baseline against which future studies can determine the long-term trajectory of the restoration. Forty-four species of fish were caught inside the BCFTB, at an average density of 116.8 fish 100 m−2 and an average biomass of 4.2 kg 100 m−2. There was a seasonal pattern in fish abundances but no overall increase or decrease in abundances during the entire study period. Marine, estuarine and migrant fish species were found in the BCFTB, each showing different seasonal patterns in abundance, similar to nearby estuaries, with 14 species driving these patterns. Water temperature and season were the most influential factors on the species composition of the fish community in the BCFTB. Therefore, 3 years after restoration the BCFTB is providing habitat for coastal fish species where none existed previously, and shows a community structure similar to natural estuaries in southern California. The BCFTB restoration has been initially successful but needs to be monitored periodically to assess its long-term success.

Shallow intertidal habitats are recognised as critical for larval and juvenile fish, and are often assumed to function as refuge areas where predation risk is reduced. Yet there is growing evidence that suggest these areas may also be regularly inhabited by large bodied fish and be the site of high levels of juvenile fish predation. In the present study we examined the use of an intermittently available surf zone habitat in tropical northern Australia by a diverse community of large-bodied teleosts (mean total length 444 mm), sharks (mean total stretched length 658 mm) and rays (mean total stretched length 1,108 mm). Drawing on the methods and ecological knowledge of a local commercial fishery, gillnets were used to capture fish as they entered the surf zone on the flooding tide. Monthly surveys over a one-year period revealed a dynamic assemblage consisting of 30 species of teleosts (mostly caught as adults) and 14 species of sharks and rays (mostly caught as juveniles or young of the year). Although it is unclear why these fish use this habitat, we conclude that it may support a broad range of biological benefits including spawning for teleosts, parturition for elasmobranchs, as well as foraging and refuge. The unique findings of this study highlight existing knowledge gaps and the need to better understand what fish use the intertidal zone and why. This should be a high priority given the increasing anthropogenic pressures on coastal margins.