Estimating Space Use of Mobile Fishes in a Large Marine Protected Area With Methodological Considerations in Acoustic Array Design

Marine protected areas (MPAs) have become an increasingly important tool to protect and conserve marine resources. However, there remains much debate about how effective MPAs are, especially in terms of their ability to protect mobile marine species such as teleost and chondrichthyan fishes. We used satellite and acoustic tags to assess the ability of a large oceanic MPA, the British Indian Ocean Territory MPA (BIOT MPA), to protect seven species of pelagic and reef-associated teleost and chondrichthyan fishes. We satellite-tagged 26 animals from six species (Blue Marlin, Reef Mantas, Sailfish, Silky Sharks, Silvertip Sharks, and Yellowfin Tuna), producing 2,735 days of movement data. We also acoustically tagged 121 sharks from two species (Grey Reef and Silvertip Sharks), which were monitored for up to 40 months across a large acoustic receiver array spanning the MPA. We found that the activity spaces of all satellite-tagged animals, including pelagic species, were much smaller than the area of the BIOT MPA, even taking into account errors associated with position estimates. Estimates of space use of acoustically tagged sharks, based on dynamic Brownian Bridge Movement Models (dBBMM), were also much smaller than the size of the MPA. However, we found important limitations when using dBBMM and demonstrate its sensitivity to both study duration and array design. We found that Grey Reef Sharks should be monitored for at least 1 year and Silvertip Sharks for 2 years before their activity space can be effectively estimated. We also demonstrate the potentially important role that intraspecific variability in spatial ecology may play in influencing the ability of MPAs to effectively protect populations of mobile species. Overall, our results suggest that, with effective enforcement, MPAs on the scale of the BIOT MPA potentially offer protection to a variety of pelagic and reef species with a range of spatial ecologies. We suggest that animals need to be tagged across seasons, years, and ontogenetic stages, in order to fully characterize their spatial ecology, which is fundamental to developing and implementing effective MPAs to conserve the full life history of target species

Pop-up archival tags reveal environmental influences on the vertical movements of silvertip sharks (Carcharhinus albimarginatus)

Vertical space use informs the ecology and management of marine species, but studies of reef-associated sharks often focus on horizontal movements. We analysed the vertical movements of silvertip sharks (Carcharhinus albimarginatus) using pop-up archival tags deployed on seven individuals in the Chagos Archipelago, central Indian Ocean. The sharks changed depth predictably with water column thermal structure, moving deeper with seasonal increases in mixed layer depth while occupying a narrow ambient water temperature range around ~27°C. At shorter timescales, higher resolution data from five tags showed that silvertip shark depth varied cyclically with surface light levels, increasing during daylight and on nights around full moon. This matches the diel vertical migrations of many fish species, suggesting the sharks’ light-driven depth changes might relate to foraging. While most vertical movements (>98%) were within the mixed layer, deeper dives to 200-800 m occurred approximately every three days. High-resolution data from one recovered tag showed the shark ascending deep (>200 m) dives in two sharply defined phases, initially fast then slow. Analysis of dive profiles against dissolved oxygen (DO) data suggested that the shark may have ascended rapidly to escape low DO levels at depth, then reduced its ascent rate 50-80% once DO levels increased. While a small sample, the electronic tags deployed in this study revealed the silvertip sharks’ predictable use of mixed layer waters, narrow thermal range and apparent intolerance of hypoxic conditions. These characteristics may exacerbate the species’ vulnerability as oceanic warming and shoaling oxygen minimum zones modify vertical habitat availability

Ethical considerations in natural history film production and the need for industry-wide best practice

Natural history documentary films can be a powerful tool for wildlife conservation, providing an accessible means to increase public knowledge of the natural world. There has been an increasing focus in documentary films on the threats to biodiversity in recent years that has positively aided conservation efforts. However, potential ethical and welfare implications of natural history film making are often overlooked. Here, we consider the design and impact of the narratives used and the filming methods employed in natural history film making and their potential implications for conservation. Although these programmes are often lauded for their cinematography, filming techniques and practices should satisfy high ethical standards and should be evaluated to assess disturbance caused to wildlife and any associated negative behavioural and physiological impacts. This evaluation should include the direct impact of the filming, as well as considering the risk of viewers replicating human-wildlife encounters they see on film. Trends towards the use of highly dramatized storytelling, anthropomorphism and the inclusion of inaccurate information should also be addressed. Although some production companies have filming guidelines in place, this is not standard industry practice. Natural history films are an important means of educating and enthusing people about nature and its conservation; however, it is vital that films are made responsibly. To facilitate this discussion, we propose recommendations, including standardised industry-wide guidelines, codes of conduct and independent ethical reviews, for natural history film makers to mitigate and avoid negative impacts

Understanding Persistent Non-compliance in a Remote, Large-Scale Marine Protected Area

UIDB/04647/2020 UIDP/04647/2020Area coverage of large-scale marine protected areas (MPAs) (LSMPAs, > 100,000 km2) is rapidly increasing globally. Their effectiveness largely depends on successful detection and management of non-compliance. However, for LSMPAs this can be difficult due to their large size, often remote locations and a lack of understanding of the social drivers of non-compliance. Taking a case-study approach, we review current knowledge of illegal fishing within the British Indian Ocean Territory (BIOT) LSMPA. Data stemming from enforcement reports (2010–20), and from fieldwork in fishing communities (2018–19) were combined to explore and characterise drivers of non-compliance. Enforcement data included vessel investigation reports (n = 188), transcripts of arrests (20) and catch seizures (58). Fieldwork data included fisher interviews (95) and focus groups (12), conducted in two communities in Sri Lanka previously associated with non-compliance in BIOT LSMPA. From 2010 to 2020, there were 126 vessels suspected of non-compliance, 76% of which were Sri Lankan. The majority of non-compliant vessels targeted sharks (97%), catching an estimated 14,340 individuals during the study period. Sri Lankan vessels were primarily registered to one district (77%) and 85% operated from just two ports within the fieldwork sites. Social Network Analysis (SNA) showed that 66% of non-compliant vessels were linked by social ties, including sharing crew members, compared with only 34% of compliant vessels. Thematic analysis of qualitative data suggested that perceptions of higher populations of sharks and social ties between vessels may both be important drivers. We discuss our findings within a global context to identify potential solutions for LSMPA management.publishersversionpublishe

Centralized red muscle in Odontaspis ferox and the prevalence of regional endothermy in sharks

The order Lamniformes contains charismatic species such as the white shark Carcharodon carcharias and extinct megatooth shark Otodus megalodon, and is of particular interest given their influence on marine ecosystems, and because some members exhibit regional endothermy. However, there remains significant debate surrounding the prevalence and evolutionary origin of regional endothermy in the order, and therefore the development of phenomena such as gigantism and filter-feeding in sharks generally. Here we show a basal lamniform shark, the smalltooth sand tiger shark Odontaspis ferox, has centralized skeletal red muscle and a thick compact-walled ventricle; anatomical features generally consistent with regionally endothermy. This result, together with the recent discovery of probable red muscle endothermy in filter feeding basking sharks Cetorhinus maximus, suggests that this thermophysiology is more prevalent in the Lamniformes than previously thought, which in turn has implications for understanding the evolution of regional endothermy, gigantism, and extinction risk of warm-bodied shark species both past and present

Detecting Mediterranean White Sharks with Environmental DNA

The white shark (Carcharodon carcharias) is a globally distributed, ecologically important top predator whose biology and population dynamics are challenging to study. Basic biological parameters remain virtually unknown in the Mediterranean Sea due to its historically low population density, dwindling population size, and lack of substantial sightings. White sharks are considered Critically Endangered in the Mediterranean Sea, and recent analyses suggest that the population has declined by 52% to 96% from historical levels in different Mediterranean sectors (Moro et al., 2020). Thus, white shark sightings dating back to 1860 are being used to estimate population trajectories throughout the entire region. Though the population size is unknown, remaining individuals are thought to be primarily restricted to a handful of hotspots deemed important for their reproduction and foraging. One of these hypothesized hotspots is the Sicilian Channel, which accounts for 19% of total historical sightings

Editorial: Coral Reefs in the Anthropocene – Reflecting on 20 Years of Reef Conservation UK

Editorial on the Research Topic Coral Reefs in the Anthropocene – Reflecting on 20 Years of Reef Conservation UK.N

Diving into the vertical dimension of elasmobranch movement ecology

Knowledge of the three-dimensional movement patterns of elasmobranchs is vital to understand their ecological roles and exposure to anthropogenic pressures. To date, comparative studies among species at global scales have mostly focused on horizontal movements. Our study addresses the knowledge gap of vertical movements by compiling the first global synthesis of vertical habitat use by elasmobranchs from data obtained by deployment of 989 biotelemetry tags on 38 elasmobranch species. Elasmobranchs displayed high intra- and interspecific variability in vertical movement patterns. Substantial vertical overlap was observed for many epipelagic elasmobranchs, indicating an increased likelihood to display spatial overlap, biologically interact, and share similar risk to anthropogenic threats that vary on a vertical gradient. We highlight the critical next steps toward incorporating vertical movement into global management and monitoring strategies for elasmobranchs, emphasizing the need to address geographic and taxonomic biases in deployments and to concurrently consider both horizontal and vertical movements

Diving into the vertical dimension of elasmobranch movement ecology

Knowledge of the three-dimensional movement patterns of elasmobranchs is vital to understand their ecological roles and exposure to anthropogenic pressures. To date, comparative studies among species at global scales have mostly focused on horizontal movements. Our study addresses the knowledge gap of vertical movements by compiling the first global synthesis of vertical habitat use by elasmobranchs from data obtained by deployment of 989 biotelemetry tags on 38 elasmobranch species. Elasmobranchs displayed high intra- and interspecific variability in vertical movement patterns. Substantial vertical overlap was observed for many epipelagic elasmobranchs, indicating an increased likelihood to display spatial overlap, biologically interact, and share similar risk to anthropogenic threats that vary on a vertical gradient. We highlight the critical next steps toward incorporating vertical movement into global management and monitoring strategies for elasmobranchs, emphasizing the need to address geographic and taxonomic biases in deployments and to concurrently consider both horizontal and vertical movements