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Global marine biodiversity declines require bold and ambitious plans to safeguard ecosystem services. Overfishing, habitat loss and projected climate impacts have yielded deleterious effects on marine predators, in particular, driving increasing threat of extinction for many shark species with implications for ecosystem health. Identifying and protecting critical habitat areas for sharks is fundamental to their protection, and may allow for species recovery. Here we use baited remote underwater video stations to investigate spatial and temporal patterns of habitat use by sharks in a Special Area of Conservation (SAC) that is centrally important to the regional blue economy in the UK, the Cardigan Bay SAC. Our results show heterogeneous spatial habitat use and temporal trends in habitat sharing between smallspotted catsharks Scyliorhinus canicula and nursehounds S. stellaris. Nearshore reef habitats are substantially more important than non-reef habitats for both species. The relative abundance of each species, however, is roughly inversely seasonally proportional, with S. canicula and S. stellaris relative abundance highest in March and September, respectively. Temporal niche partitioning may be an important mechanism in marine systems, but has not been widely investigated in sympatric shark communities. These findings are directly relevant for ongoing development of the Welsh Marine Evidence Strategy (2019-2025) and the Welsh National Marine Plan, particularly to inform spatial planning to strengthen the role of SAC management design in protecting important shark areas. [ABSTRACT FROM AUTHOR]

Venom represents a key adaptation of many venomous predators, allowing them to immobilise prey quickly through chemical rather than physical warfare. Evolutionary arms races between prey and a predator are believed to be the main factor influencing the potency and composition of predatory venoms. Predators with narrowly restricted diets are expected to evolve specifically potent venom towards their focal prey, with lower efficacy on alternative prey. Here, we evaluate hypotheses on the evolution of prey-specific venom, focusing on the effect of restricted diet, prey defences, and prey resistance. Prey specificity as a potential evolutionary dead end is also discussed. We then provide an overview of the current knowledge on venom prey specificity, with emphasis on snakes, cone snails, and spiders. As the current evidence for venom prey specificity is still quite limited, we also overview the best approaches and methods for its investigation and provide a brief summary of potential model groups. Finally, possible applications of prey-specific toxins are discussed., (© 2024 The Author(s). Biological Reviews published by John Wiley & Sons Ltd on behalf of Cambridge Philosophical Society.)

New approaches to abundance surveying utilizing unoccupied aerial vehicles (UAVs) are proving to be effective tools in marine and terrestrial environments. We explored UAV efficacy for surveys in the Galapagos Marine Reserve (GMR), where relative abundance patterns of juvenile sharks and subsequent classifications of putative nursery areas based on environmental drivers are lacking. The UAV method allowed greater temporal and spatial coverage. We expanded classification of shark nursery habitat through monthly drone surveys and environmental data collection at 14 sites around San Cristobal Island (GMR) from November 2018 to July 2019. In the period of surveying, 56 flights identified 453 juvenile Carcharhinus limbatus (blacktip shark). Classification of nurseries followed three criteria, necessitating higher density, short-term residency, and annual site fidelity in target locations. We developed preliminary generalized linear models to elucidate potential environmental parameters influencing the perceived abundance and habitat preference of juveniles. Four sites were identified as either potential nurseries or nursery areas for the target species based on previous excursions. An averaged model was subsequently created from the models found to best explain deviance patterns (R 2  = 0.10-0.44) in perceived shark abundance and habitat preference. Relative variable importance (RVI) values further clarified the parameters most associated with higher juvenile presence. This approach provides a systematic method of abundance surveying while simultaneously beginning the process of defining when and where we expect to find higher abundance through environmental modelling of most influential parameters to perceived abundance in this environment., (© 2024 Fisheries Society of the British Isles.)

Research Highlight: Shiratsuru, S., & Pauli, J. N. (2024). Food-safety trade-offs drive dynamic behavioural antipredator responses among snowshoe hares. Journal of Animal Ecology, DOI: 10.1111/1365-2656.14183. Predation-risk effects are known to be context dependent, with impacts of perceived predation threat on individual antipredator responses, prey population demography, species interactions and community organization hinging on traits of the prey, the predator(s) and setting of the interaction. Yet, few empirical studies to date have simultaneously explored how these three drivers shape contingency in antipredator behaviour, the key first step in the process by which predation-risk effects play out, especially in free-living vertebrates. In a new study, Shiratsuru & Pauli (2024) address this knowledge deficit by showing that snowshoe hares (Lepus americanus) trade foraging for anti-predator vigilance dynamically as a function of winter food availability (a proxy for individual energetic state), the timing and intensity of predator activity, and environmental properties associated with elevated vulnerability to predator-induced mortality, notably including coat colour mismatch caused by variation in snow cover. These results offer new insight into the complexity of predation-risk effects and should serve as a guide for research aiming to better understand the expression of these effects under varying circumstances., (© 2024 The Author(s). Journal of Animal Ecology © 2024 British Ecological Society.)

Silky shark (Carcharhinus falciformis) populations in the South Atlantic Ocean are listed as vulnerable under the IUCN. In fact, this species is classified as critically endangered in Brazil under the Ministry of the Environment. The present study reports the first opportunistic sighting of an aggregation of 250-300 silky sharks in the Alcatrazes Archipelago Wildlife Refuge. Aggregation sites are important in the life cycle of silky sharks, and identifying these sites is essential for conservation efforts., (© 2024 Fisheries Society of the British Isles.)

Prey adopt various antipredator responses to minimize the risk of predation, and the fitness costs of antipredator responses can have emergent effects on the population dynamics of prey species. While the trade-off between food acquisition and predation avoidance has long been recognized in predicting antipredator responses, less attention has been paid to the dynamics of the food-safety trade-off driven by temporal variation in multiple risk factors under changing seasonal conditions. Here, we monitored foraging and vigilance behaviour of a central prey species, snowshoe hares (Lepus americanus), at fine temporal scales over the winter with various types of predation risk, while also experimentally manipulating predation risk by attracting predators to foraging patches. Hares increased foraging and decreased vigilance over the winter, but hares under chronic risk decreased their antipredator efforts to a lesser degree, indicating that those individuals prioritized risk avoidance over food acquisition. Hares also decreased foraging and increased antipredator efforts in response to the temporal activity of predators and environmental cues of predation risk. However, the magnitude of the responses to the environmental cues was mediated by time of winter. While we did not detect a reactive response of hares to acute risk, we did find that hares exhibiting camouflage mismatch proactively increased vigilance. Overall, our results highlight the importance of species-specific traits and changing seasonal conditions in addition to temporal variation in multiple risk factors in predicting antipredator responses and the context dependence of risk effects., (© 2024 The Author(s). Journal of Animal Ecology published by John Wiley & Sons Ltd on behalf of British Ecological Society.)

Patterns of mother-embryo fractionation of 13 C and 15 N were assessed for their predictability across three species of batoids caught as by-catch in south-eastern Australia. Stable isotope analysis of 24 mothers and their litters revealed that isotope ratios of embryos were significantly different from their corresponding mothers and that the scale and direction of the difference varied within and across species. The range of variation across species was 3.5‰ for δ 13 C and 4‰ for δ 15 N, equivalent to a difference in trophic level. In one species (Urolophus paucimaculatus) litters could be significantly enriched or depleted in 13 C and 15 N relative to their mothers' isotope signatures. These results suggest that patterns of mother-embryo isotope fractionation vary within and between species and that these patterns may not be explained only by developmental mode. Contrasting patterns of fractionation between and within species make it difficult to adjust mother-embryo fractionation with broad-scale correction factors., (© 2022 The Authors. Journal of Fish Biology published by John Wiley & Sons Ltd on behalf of Fisheries Society of the British Isles.)

Stomach contents of 175 Brazilian sharpnose sharks, Rhizoprionodon lalandii, were examined to assess their feeding habits. Caught by artisanal fishers between June 2006 and July of 2007 at Ipanema Beach, on the central coast of the state of Paraná, southern Brazil, R. lalandii appears to be piscivorous (89.7% IRI), feeding mainly on families of Clupeidae (5.1% IRI) and Sciaenidae (3.7% IRI) and secondarily on squid Lolliguncula brevis (8.6% IRI). Diets were similar between sexes and seasons. However, there were ontogenetic changes in their diets. The major items for neonates were Penaeidae crustaceans (%IRI = 56.4) and Engraulidae fishes (%IRI = 29.3); for the juveniles, Sciaenidae (%IRI = 62.5) and Clupeidae (%IRI = 19.7), and for adults Clupeidae (%IRI = 45.8) and Sciaenidae (%IRI = 15.9). Only neonate sharks consumed crustaceans, whereas all size classes consumed cephalopods and teleosts. Neonates had the lowest trophic level (TR = 3.8), with the diet of juveniles and adults the highest (TR = 4.2). Given its abundance and diet, R. lalandii may be an important predator of demersal and pelagic prey in coastal waters of Brazil. [ABSTRACT FROM AUTHOR]

Seasonal variability in environmental conditions is a strong determinant of animal migrations, but warming temperatures associated with climate change are anticipated to alter this phenomenon with unknown consequences. We used a 40-year fishery-independent survey to assess how a changing climate has altered the migration timing, duration and first-year survival of juvenile bull sharks (Carcharhinus leucas). From 1982 to 2021, estuaries in the western Gulf of Mexico (Texas) experienced a mean increase of 1.55°C in autumn water temperatures, and delays in autumn cold fronts by ca. 0.5 days per year. Bull shark migrations in more northern estuaries concomitantly changed, with departures 25-36 days later in 2021 than in 1982. Later, migrations resulted in reduced overwintering durations by up to 81 days, and the relative abundance of post-overwintering age 0-1 sharks increased by >50% during the 40-year study period. Yet, reductions in prey availability were the most influential factor delaying migrations. Juvenile sharks remained in natal estuaries longer when prey were less abundant. Long-term declines in prey reportedly occurred due to reduced spawning success associated with climate change based on published reports. Consequently, warming waters likely enabled and indirectly caused the observed changes in shark migratory behaviour. As water temperatures continue to rise, bull sharks in the north-western Gulf of Mexico could forgo their winter migrations in the next 50-100 years based on current trends and physiological limits, thereby altering their ecological roles in estuarine ecosystems and recruitment into the adult population. It is unclear if estuarine food webs will be able to support changing residency patterns as climate change affects the spawning success of forage species. We expect these trends are not unique to the western Gulf of Mexico or bull sharks, and migratory patterns of predators in subtropical latitudes are similarly changing at a global scale., (© 2024 The Author(s). Journal of Animal Ecology published by John Wiley & Sons Ltd on behalf of British Ecological Society.)

Freshwater megafauna, such as sturgeons, giant catfishes, river dolphins, hippopotami, crocodylians, large turtles, and giant salamanders, have experienced severe population declines and range contractions worldwide. Although there is an increasing number of studies investigating the causes of megafauna losses in fresh waters, little attention has been paid to synthesising the impacts of megafauna on the abiotic environment and other organisms in freshwater ecosystems, and hence the consequences of losing these species. This limited understanding may impede the development of policies and actions for their conservation and restoration. In this review, we synthesise how megafauna shape ecological processes in freshwater ecosystems and discuss their potential for enhancing ecosystem restoration. Through activities such as movement, burrowing, and dam and nest building, megafauna have a profound influence on the extent of water bodies, flow dynamics, and the physical structure of shorelines and substrata, increasing habitat heterogeneity. They enhance nutrient cycling within fresh waters, and cross-ecosystem flows of material, through foraging and reproduction activities. Freshwater megafauna are highly connected to other freshwater organisms via direct consumption of species at different trophic levels, indirect trophic cascades, and through their influence on habitat structure. The literature documenting the ecological impacts of freshwater megafauna is not evenly distributed among species, regions, and types of ecological impacts, with a lack of quantitative evidence for large fish, crocodylians, and turtles in the Global South and their impacts on nutrient flows and food-web structure. In addition, population decline, range contraction, and the loss of large individuals have reduced the extent and magnitude of megafaunal impacts in freshwater ecosystems, rendering a posteriori evaluation more difficult. We propose that reinstating freshwater megafauna populations holds the potential for restoring key ecological processes such as disturbances, trophic cascades, and species dispersal, which will, in turn, promote overall biodiversity and enhance nature's contributions to people. Challenges for restoration actions include the shifting baseline syndrome, potential human-megafauna competition for habitats and resources, damage to property, and risk to human life. The current lack of historical baselines for natural distributions and population sizes of freshwater megafauna, their life history, trophic interactions with other freshwater species, and interactions with humans necessitates further investigation. Addressing these knowledge gaps will improve our understanding of the ecological roles of freshwater megafauna and support their full potential for facilitating the development of effective conservation and restoration strategies to achieve the coexistence of humans and megafauna., (© 2024 The Authors. Biological Reviews published by John Wiley & Sons Ltd on behalf of Cambridge Philosophical Society.)

Levels of dissolved oxygen in open ocean and coastal waters are decreasing (ocean deoxygenation), with poorly understood effects on marine megafauna. All of the more than 1000 species of elasmobranchs (sharks, skates, and rays) are obligate water breathers, with a variety of life-history strategies and oxygen requirements. This review demonstrates that although many elasmobranchs typically avoid hypoxic water, they also appear capable of withstanding mild to moderate hypoxia with changes in activity, ventilatory responses, alterations to circulatory and hematological parameters, and morphological alterations to gill structures. However, such strategies may be insufficient to withstand severe, progressive, or prolonged hypoxia or anoxia where anaerobic metabolic pathways may be used for limited periods. As water temperatures increase with climate warming, ectothermic elasmobranchs will exhibit elevated metabolic rates and are likely to be less able to tolerate the effects of even mild hypoxia associated with deoxygenation. As a result, sustained hypoxic conditions in warmer coastal or surface-pelagic waters are likely to lead to shifts in elasmobranch distributions. Mass mortalities of elasmobranchs linked directly to deoxygenation have only rarely been observed but are likely underreported. One key concern is how reductions in habitat volume as a result of expanding hypoxia resulting from deoxygenation will influence interactions between elasmobranchs and industrial fisheries. Catch per unit of effort of threatened pelagic sharks by longline fisheries, for instance, has been shown to be higher above oxygen minimum zones compared to adjacent, normoxic regions, and attributed to vertical habitat compression of sharks overlapping with increased fishing effort. How a compound stressor such as marine heatwaves alters vulnerability to deoxygenation remains an open question. With over a third of elasmobranch species listed as endangered, a priority for conservation and management now lies in understanding and mitigating ocean deoxygenation effects in addition to population declines already occurring from overfishing., (© 2024 The Author(s). Journal of Fish Biology published by John Wiley & Sons Ltd on behalf of Fisheries Society of the British Isles.)

Killer whales (Orcinus orca) occur seasonally in the eastern Canadian Arctic (ECA), where their range expansion associated with declining sea ice have raised questions about the impacts of increasing killer whale predation pressure on Arctic-endemic prey. We assessed diet and distribution of ECA killer whales using bulk and compound-specific stable isotope analysis (CSIA) of amino acids (AA) of 54 skin biopsies collected from 2009 to 2020 around Baffin Island, Canada. Bulk ECA killer whale skin δ 15 N and δ 13 C values did not overlap with potential Arctic prey after adjustment for trophic discrimination, and instead reflected foraging history in the North Atlantic prior to their arrival in the ECA. Adjusted killer whale stable isotope (SI) values primarily overlapped with several species of North Atlantic baleen whales or tuna. Amino acid (AA)-specific δ 15 N values indicated the ECA killer whales fed primarily on marine mammals, having similar glutamic acid δ 15 N-phenylalanine δ 15 N (δ 15 N Glx-Phe ) and threonine δ 15 N (δ 15 N Thr ) as mammal-eating killer whales from the eastern North Pacific (ENP) that served as a comparative framework. However, one ECA whale grouped with the fish-eating ENP ecotype based δ 15 N Thr . Distinctive essential AA δ 13 C of ECA killer whale groups, along with bulk SI similarity to killer whales from different regions of the North Atlantic, indicates different populations converge in Arctic waters from a broad source area. Generalist diet and long-distance dispersal capacity favour range expansions, and integration of these insights will be critical for assessing ecological impacts of increasing killer whale predation pressure on Arctic-endemic species., (© 2024 The Author(s). Journal of Animal Ecology published by John Wiley & Sons Ltd on behalf of British Ecological Society.)

Remoras are a highly specialised group of fishes known to associate with a range of marine megafauna, including elasmobranchs, cetaceans and marine reptiles. Remoras appear to benefit from these interspecific interactions through consumption of host dermal parasites or reduced cost of transport. Shark-remora associations are widely documented, yet our understanding of the costs and benefits involved in these interactions is poor. Studies frequently make claims about mutualistic, commensalistic or parasitic relationships without providing the necessary quantitative information necessary to make these claims. Here I explain why this approach is problematic, and proceed to examine shark-remora interactions in a rigorous eco-evolutionary framework. These interactions cannot be properly classified without considering net evolutionary fitness and context dependence. In reality, shark-remora interactions are best defined by a multidimensional spectrum of fitness consequences, with net fitness outcomes shifting between mutualism and parasitism (and vice versa) through space and time., (© 2024 Fisheries Society of the British Isles.)

Climate change is an environmental emergency threatening species and ecosystems globally. Oceans have absorbed about 90% of anthropogenic heat and 20%-30% of the carbon emissions, resulting in ocean warming, acidification, deoxygenation, changes in ocean stratification and nutrient availability, and more severe extreme events. Given predictions of further changes, there is a critical need to understand how marine species will be affected. Here, we used an integrated risk assessment framework to evaluate the vulnerability of 132 chondrichthyans in the Eastern Tropical Pacific (ETP) to the impacts of climate change. Taking a precautionary view, we found that almost a quarter (23%) of the ETP chondrichthyan species evaluated were highly vulnerable to climate change, and much of the rest (76%) were moderately vulnerable. Most of the highly vulnerable species are batoids (77%), and a large proportion (90%) are coastal or pelagic species that use coastal habitats as nurseries. Six species of batoids were highly vulnerable in all three components of the assessment (exposure, sensitivity and adaptive capacity). This assessment indicates that coastal species, particularly those relying on inshore nursery areas are the most vulnerable to climate change. Ocean warming, in combination with acidification and potential deoxygenation, will likely have widespread effects on ETP chondrichthyan species, but coastal species may also contend with changes in freshwater inputs, salinity, and sea level rise. This climate-related vulnerability is compounded by other anthropogenic factors, such as overfishing and habitat degradation already occurring in the region. Mitigating the impacts of climate change on ETP chondrichthyans involves a range of approaches that include addressing habitat degradation, sustainability of exploitation, and species-specific actions may be required for species at higher risk. The assessment also highlighted the need to further understand climate change's impacts on key ETP habitats and processes and identified knowledge gaps on ETP chondrichthyan species., (© 2024 The Author(s). Global Change Biology published by John Wiley & Sons Ltd.)

Interspecific interactions, including predator-prey, intraguild predation (IGP) and competition, may drive distribution and habitat use of predator communities. However, elucidating the relative importance of these interactions in shaping predator distributions is challenging, especially in marine communities comprising highly mobile species. We used individual-based models (IBMs) to predict the habitat distributions of apex predators, intraguild (IG) prey and prey. We then used passive acoustic telemetry to test these predictions in a subtropical marine predator community consisting of eight elasmobranch (i.e. shark and ray) species in Bimini, The Bahamas. IBMs predicted that prey and IG prey will preferentially select habitats based on safety over resources (food), with stronger selection for safe habitat by smaller prey. Elasmobranch space-use patterns matched these predictions. Species with predator-prey and asymmetrical IGP (between apex and small mesopredators) interactions showed the clearest spatial separation, followed by asymmetrical IGP among apex and large mesopredators. Competitors showed greater spatial overlap although with finer-scale differences in microhabitat use. Our study suggests space-use patterns in elasmobranchs are at least partially driven by interspecific interactions, with stronger spatial separation occurring where interactions include predator-prey relationships or IGP., (© 2024 The Authors. Journal of Animal Ecology © 2024 British Ecological Society.)

Predators display rhythms in behavior and habitat use, often with the goal of maximizing foraging success. The underlying mechanisms behind these rhythms are generally linked to abiotic conditions related to diel, lunar, or seasonal cycles. To understand their effects on the space use, activity, and swimming depth of gray reef sharks (Carcharhinus amblyrhynchos), we tagged 38 individuals with depth and accelerometer sensors in a French Polynesian atoll channel exposed to strong tidal flow, and monitored them over a year. C. amblyrhynchos used a larger space during nighttime and were more active at night and during outgoing currents. Shark activity also peaked during the full and new moons. The swimming depth of sharks was mostly influenced by diel cycles, with sharks swimming deeper during the day compared to nighttime. The dynamic energyscape may promote the emergence of discrete behavioral strategies in reef sharks that use the south channel of Fakarava for resting and foraging purposes. Turbulence imposed by outgoing tides induces additional foraging cost on sharks, shifting their hunting areas to the southern part of the channel, where turbulence is less pronounced. Understanding when and where sharks are active and foraging is important for our understanding of predator-prey dynamics and ecosystem dynamics. This study highlights how abiotic rhythms in a highly dynamic environment likely generate spatiotemporal heterogeneity in the distribution of predation pressure., (© 2024 The Author(s). Journal of Fish Biology published by John Wiley & Sons Ltd on behalf of Fisheries Society of the British Isles.)

Marine predators are vital to the healthy functioning of coastal ecosystems, but to understand their roles, it is necessary to elucidate their movement ecology, particularly in relation to one another. A decade's worth of acoustic telemetry data (2011-2020) from Algoa Bay, South Africa, was investigated to determine how two mesopredatory species (teleosts: dusky kob Argyrosomus japonicus, n = 11, and leervis Lichia amia, n = 16) and two top predatory species (sharks: ragged-tooth sharks Carcharias taurus, n = 45, and white sharks Carcharodon carcharias, n = 31) used and shared this bay ecosystem. Multi-annual seasonal fidelity to the bay was exhibited by all species, but differences in residency were observed among species. Similarly, species used space in the bay differently-the teleosts moved less and had movements restricted to the central and western inshore regions of the bay. Conversely, the sharks roamed more, but detections were concentrated in the western part of the bay for C. taurus and in the eastern part of the bay for C. carcharias. Social network analysis showed that species segregated in space and time on a fine scale. However, there was some interaction observed between C. taurus, L. amia, and A. japonicus, but to varying degrees. This is likely because of strong habitat preferences exhibited by each species and predator-prey relationships between these predatory guilds. Results highlight that the sheltered marine Algoa Bay is a resource-rich environment, supporting multiple predators with different hunting strategies albeit similar prey preferences. Finally, these species are likely afforded some protection by the current Greater Addo Elephant National Park Marine Protected Area in the bay but are vulnerable to fishing pressure when they leave this ecosystem., (© 2024 The Authors. Journal of Fish Biology published by John Wiley & Sons Ltd on behalf of Fisheries Society of the British Isles.)

In dynamic fission-fusion societies, following specific individuals consistently would not be expected in the absence of benefits to followers. Followers in groups may benefit if leaders have greater knowledge about habitats that are available for foraging and how to access these areas efficiently. A small residential population of bottlenose dolphins (Tursiops truncatus) in the Lower Florida Keys (LFK) demonstrates such specific individual leadership, but why others choose to follow is unknown. To determine whether consistent leaders demonstrated greater knowledge of resources and habitat we (1) compared habitat use patterns across areas that varied in prey abundance for groups led by consistent leaders and groups led by individuals that did not consistently lead, (2) compared directness of travel along with number of lead animal switches when traveling for these same two group types and (3) compared home range size and home range complexity between animals that consistently led and those that did not. Foraging groups led by consistent leaders were sighted more frequently over habitat with higher fish biomass, while those led by non-consistent leaders were sighted most often over habitat with lower fish biomass. Groups with consistent leaders had less frequent lead animal switches and took more direct paths when traveling than groups led by those that did not consistently lead. Home ranges of consistent leaders did not differ in size from other individuals, but were more complex. Our results indicate that followers in LFK dolphin groups could potentially benefit from those that consistently lead due to use of profitable habitat, ability to navigate efficiently and potentially the number of areas consistent leaders are familiar with. [ABSTRACT FROM AUTHOR]

Predation risk is a function of spatiotemporal overlap between predator and prey, as well as behavioural responses during encounters. Dynamic factors (e.g. group size, prey availability and animal movement or state) affect risk, but rarely are integrated in risk assessments. Our work targets a system where predation risk is fundamentally linked to temporal patterns in prey abundance and behaviour. For neonatal ungulate prey, risk is defined within a short temporal window during which the pulse in parturition, increasing movement capacity with age and antipredation tactics have the potential to mediate risk. In our coyote-mule deer (Canis latrans-Odocoileus hemionus) system, leveraging GPS data collected from both predator and prey, we tested expectations of shared enemy and reproductive risk hypotheses. We asked two questions regarding risk: (A) How does primary and alternative prey habitat, predator and prey activity, and reproductive tactics (e.g. birth synchrony and maternal defence) influence the vulnerability of a neonate encountering a predator? (B) How do the same factors affect behaviour by predators relative to the time before and after an encounter? Despite increased selection for mule deer and intensified search behaviour by coyotes during the peak in mule deer parturition, mule deer were afforded protection from predation via predator swamping, experiencing reduced per-capita encounter risk when most neonates were born. Mule deer occupying rabbit habitat (Sylvilagus spp.; coyote's primary prey) experienced the greatest risk of encounter but the availability of rabbit habitat did not affect predator behaviour during encounters. Encounter risk increased in areas with greater availability of mule deer habitat: coyotes shifted their behaviour relative to deer habitat, and the pulse in mule deer parturition and movement of neonatal deer during encounters elicited increased speed and tortuosity by coyotes. In addition to the spatial distribution of prey, temporal patterns in prey availability and animal behavioural state were fundamental in defining risk. Our work reveals the nuanced consequences of pulsed availability on predation risk for alternative prey, whereby responses by predators to sudden resource availability, the lasting effects of diversionary prey and inherent antipredation tactics ultimately dictate risk., (© 2024 The Authors. Journal of Animal Ecology © 2024 British Ecological Society.)

Migration is a critical aspect of ocean ecosystems, and understanding this phenomenon answers ecological and management questions. Given the difficulty in tracking ocean animals across large distances, the extent to which different ray species perform long-distance movements, such as migrations, remains unknown. This study used passive acoustic telemetry to track the movements of endemic diamond Gymnura natalensis and critically endangered duckbill Aetomylaeus bovinus rays along the South African coastline using a collaborative nationwide network of coastal acoustic receivers for up to 7 years. Duckbill rays were detected significantly more frequently than diamond rays, but both species moved between the south and east coasts of South Africa (traveling up to 1167 km). Tagged individuals were detected significantly more often in their tagging locations during summer months but traveled significantly further distances during winter months. Furthermore, movement models fitted to individual duckbill rays' annual net-squared displacement identified most individual annual movements as migratory. This evidence suggests that both diamond and duckbill rays make eastward winter migrations and return to specific areas along the coastline during the summer months. The exceptions to this were diamond rays tagged on the east coast that were not found to migrate seasonally, which supports previous research that there is intraspecific variability in migrations for ray species. These findings have implications for understanding ray migration not only on a global scale but also locally for spatial management interventions and population delineation., (© 2024 The Authors. Journal of Fish Biology published by John Wiley & Sons Ltd on behalf of Fisheries Society of the British Isles.)

The Arctic is a global warming 'hot-spot' that is experiencing rapid increases in air and ocean temperatures and concomitant decreases in sea ice cover. These environmental changes are having major consequences on Arctic ecosystems. All Arctic endemic marine mammals are highly dependent on ice-associated ecosystems for at least part of their life cycle and thus are sensitive to the changes occurring in their habitats. Understanding the biological consequences of changes in these environments is essential for ecosystem management and conservation. However, our ability to study climate change impacts on Arctic marine mammals is generally limited by the lack of sufficiently long data time series. In this study, we took advantage of a unique dataset on hooded seal (Cystophora cristata) movements (and serum samples) that spans more than 30 years in the Northwest Atlantic to (i) investigate foraging (distribution and habitat use) and dietary (trophic level of prey and location) habits over the last three decades and (ii) predict future locations of suitable habitat given a projected global warming scenario. We found that, despite a change in isotopic signatures that might suggest prey changes over the 30-year period, hooded seals from the Northwest Atlantic appeared to target similar oceanographic characteristics throughout the study period. However, over decades, they have moved northward to find food. Somewhat surprisingly, foraging habits differed between seals breeding in the Gulf of St Lawrence vs those breeding at the "Front" (off Newfoundland). Seals from the Gulf favoured colder waters while Front seals favoured warmer waters. We predict that foraging habitats for hooded seals will continue to shift northwards and that Front seals are likely to have the greatest resilience. This study shows how hooded seals are responding to rapid environmental change and provides an indication of future trends for the species-information essential for effective ecosystem management and conservation., (© 2024 His Majesty the King in Right of Canada. Global Change Biology published by John Wiley & Sons Ltd. Reproduced with the permission of the Minister of Fisheries and Oceans Canada.)

Recent studies have uncovered mosaic patterns of allometric and isometric growth underlying ontogenetic shifts in the body form of elasmobranch species (shark and rays). It is thought that shifts in trophic and spatial ecology through ontogeny drive these morphological changes; however, additional hypotheses relating to developmental constraints have also been posed. The bull shark (Carcharhinus leucas) is a large-bodied coastal shark that exhibits strong ontogenetic shifts in trophic and spatial ecology. In this study, we utilise a large data set covering a large number of morphological structures to reveal ontogenetic shifts in the body form of C. leucas, stratifying analyses by sex and size classes to provide fine-scale, more ecomorphologically relevant results. Our results indicate shifts in functional demands across the body through ontogeny, driven by selective pressures relating to trophic and spatial ecology driving the evolution of allometry. We also find significant differences in scaling trends between life stages, and between the sexes, highlighting the importance of utilising large, diverse datasets that can be stratified in this way to improve our understanding of elasmobranch morphological evolution. Ultimately, we discuss the implications of these results for existing ecomorphological hypotheses regarding the evolution of specific morphological structures, and pose novel hypotheses where relevant., (© 2024 The Authors. Journal of Morphology published by Wiley Periodicals LLC.)

Understanding the behaviour and ecological role of elasmobranchs is essential for their conservation, particularly in regions harbouring threatened and data-deficient species like the Inhambane coastline in southern Mozambique, southwestern Indian Ocean. This study employed long-life remote underwater video cameras (LL-RUV) to observe elasmobranch occurrence and behaviour at a rocky reef near Praia do Tofo known for frequent elasmobranch sightings. Between 2021 and 2024, 524 hours of LL-RUV data were collected, revealing the presence of 14 threatened and data-deficient elasmobranch species. Reef manta rays (Mobula alfredi), small eye stingrays (Megatrygon microps), and oceanic manta rays (Mobula birostris) were identified as the primary elasmobranch users of the studied cleaning stations (n = 81, n = 72 and n = 61 respectively), engaging in mutualistic interactions with cleaner fish and spending significant amounts of time at the studied reef. In contrast, spotted eagle rays (Aetobatus narinari) and blacktip sharks (Carcharhinus limbatus) were solely observed cruising over the reef without engaging in cleaning interactions (n = 40 and n = 27 respectively). In addition, this study provides evidence of intra- and inter-specific interactions between reef and oceanic manta rays, small eye stingrays and bowmouth guitarfish (Rhina ancylostoma) and co-occurrences of both manta ray species and smalleye stingrays with "hitchhiker" species including cobia (Rachycentron canadum) and remoras (Echeneis spp.). The use of LL-RUV cameras represents a significant advancement in marine research. These cameras enable continuous, non-intrusive, long-term monitoring of marine environments, capturing natural behaviours, while minimising disturbances caused by divers. As a result, more accurate observations of elasmobranch behaviour and cleaning station dynamics can be recorded, which might be missed during short-term surveys. This research highlights the potential of LL-RUV cameras as powerful tools for advancing our understanding of elasmobranch occurrence and behaviour and underscores their value in informing targeted and effective conservation strategies. Beyond elasmobranch research, LL-RUVs hold tremendous potential for studying a wide range of marine species and habitats, offering a versatile tool for ecological monitoring and conservation efforts across diverse marine ecosystems. [ABSTRACT FROM AUTHOR]

Introduction: Elasmobranchs, such as sharks and rays, are among the world's most endangered vertebrates, with over 70% loss in abundance over the past 50 years due to human impacts. Zooarchaeological baselines of elasmobranch diversity, distribution, and exploitation hold great promise for contributing essential historical contexts in the assessment of contemporary patterns in their taxonomic diversity and vulnerability to human-caused extinction. Yet, the historical ecology of elasmobranchs receives relatively less archaeological attention compared to that of ray-finned fishes or marine mammals, largely due to issues of taxonomic resolution across zooarchaeological identifications. Methods: We explore the use of Zooarchaeology by Mass Spectrometry (ZooMS) for species identification in this unstudied group, using an archaeological case study from the marine environments of the Florida Keys, a marine biodiversity hotspot that is home to an array of elasmobranch species and conservation efforts. By comparison with 39 modern reference species, we could distinguish 12 taxa within the zooarchaeological assemblage from the Clupper archaeological site (Upper Matecumbe Key) that included nine sharks, two rays and a sawfish. Results and discussion: The results indicate that, through additional complexity of the collagen peptide mass fingerprint, obtained due to the presence of the cartilaginous type II collagen, ZooMS collagen peptide mass fingerprinting provides exceptionally high taxonomic resolution in this group, yielding species-level identifications in all cases where sufficient reference material was used. This case study also highlights the added value of ZooMS for taxa that are more difficult to distinguish in zooarchaeological analyses, such as vertebrae of the Atlantic sharpnose shark (Rhizoprionodon terraenovae) and the hammerhead sharks (Sphyrna spp.) in the Florida Keys. Therefore, the application of collagen peptide mass fingerprinting to elasmobranchs offers great potential to improve our understanding of their archaeological past and historical ecology. [ABSTRACT FROM AUTHOR]

Introduction: Predators, such as sharks, play important ecological roles in coastal ecosystems when abundant and these roles change over ontogeny. However, these shifts in ecological role are often not evaluated in light of feeding performance. Bite force is an ecologically relevant metric of feeding performance that has been associated with a species' foraging niche, which may serve as a key factor that constrains prey selection both within and among sympatric species. Methods: This study applies an interdisciplinary approach to discern the ecomechanical relationships of sympatric bull (Carcharhinus leucas), blacktip (Carcharhinus limbatus), and bonnethead sharks (Sphyrna tiburo) using feeding biomechanics and bulk stable isotopes (δ13C, δ15N). We sought to (1) estimate theoretical bite force and scaling patterns over ontogeny of each species, (2) quantify niche breadth and overlap among species, and (3) characterize the relationship between ecological niche shifts and changes in bite force over ontogeny. Results: Importantly, we found that smaller conspecifics exhibited positive allometric scaling of bite force, whereas larger conspecifics exhibited isometric scaling. Associations between bite force and ontogenetic niche shifts in habitat and diet were found in bull and bonnethead sharks, but not in blacktip sharks. Additionally, isotopic niche breadth was greatest in generalist bull sharks, followed by specialist bonnethead and blacktip sharks. Discussion: These findings highlight animal performance measures as critical drivers ofecological relationships both within and among species. Size-based differences in bite force scaling should be considered when evaluating feeding performance in other taxa, which may be an important determinant of ontogenetic dietary shifts. [ABSTRACT FROM AUTHOR]

Arctic ecosystems are especially vulnerable to the impacts of climate change because of the limit to possible northward shifts for species dependent on land or continental shelf and because the rate of warming of the region has been 2-4 x the global average in recent decades. The decline in sea ice in the Arctic has both direct and indirect impacts on the species that live in association with ice, breeding on it, traveling over it, feeding on other ice-dependent species or avoiding competition with subarctic species that cannot exploit resources in ice-covered areas. Herein, we present a metamodel of a top-level predator, the polar bear (Ursus maritimus), and two of its key prey species, ringed seals (Pusa hispida) and bearded seals (Erignathus barbatus), which are important in maintaining current polar bear densities and in turn are strongly influenced by bear predation. We used a metamodel that links Population Viability Analyses of the three species in order to examine how the impacts of declining spring land-fast sea ice on the fjords of Svalbard (Norway) and Frans Josef Land (Russia) can cascade through this predator-prey system. As the ice conditions that allow ringed seals to raise pups in snow-covered lairs on the frozen fjords diminish, or even disappear, ringed seal populations using the land-fast sea ice will collapse due to lack of successful recruitment. Consequently, the polar bear population, which relies heavily on hunting ringed seals in the land-fast sea ice to be able to raise their own offspring is also likely to decline. Our models suggest time-lags of decades, with the polar bear population not entering into decline until the lack of recruitment of ringed seals results in the depletion of breeding age ringed seals – starting in the third decade from the start point of the model and dropping below the initial population size only some decades later. Although lags between climate change and impacts on the ice-associated fauna are expected, the sea ice conditions have already changed dramatically in the northern Barents Sea region, including the Svalbard Archipelago, and the collapse of this Arctic species assemblage might already be underway. [ABSTRACT FROM AUTHOR]

The establishment of a well-adapted and accurate feeding regimen is a fundamental determining factor in the maintenance of shark species in captivity. Replicating the natural diet in captivity is commonly accepted and recommended. Given the diverse nutritional composition of prey, supplementation may become necessary. The captive environment poses unique challenges, making sharks susceptible to an array of health issues, including numerous diseases. Mitigating these risks demands detailed husbandry practices, an appropriate physical environment and a balanced diet. Supplementation, encompassing vitamins and minerals, becomes imperative for the provision of essential nutrients. This complexity has rendered the formulation of an adapted feeding plan for aquarists exceptionally challenging. The scarcity of information in these species adds to the issue, mandating extrapolation from various shark groups and to species with analogous characteristics. This literature review concentrates predominantly on benthic and pelagic shark species prevalent in contemporary aquariums. The central argument posits that dietary choices in captivity rely on factors such as availability, quality and consistency of supply. The advocated approach highlights the importance of a balanced, diverse feeding that closely mirrors natural diets. It is then crucial to emphasize that these are general guidelines, and the specific dietary requisites may diverge between shark species. Collaborating with experts in marine biology, shark husbandry and veterinary care is imperative for the formulation and perpetuation of an adapted diet for captive sharks. [ABSTRACT FROM AUTHOR]

The reproductive state of wild, free-swimming tiger sharks (Galeocerdo cuvier) , was assessed using underwater ultrasonography at a diving site in Fuvahmulah, a Maldivian atoll within the central Indian Ocean. The presence of embryos were observed in 93% of the adult sharks (26/28) and two distinct embryonic size groups were observed within the subset of scanned adult females. The results suggest that the observed dive site functions as a gestation ground and builds upon previous work that emphasizes the importance of dive sites for the collection of biological data for shark conservation and management. [ABSTRACT FROM AUTHOR]

Cognitive enrichments have gained popularity in the past two decades in both farm animal and zoological settings. In this study, we present a cognitive enrichment device that, for the first time, allowed testing for prosocial food-sharing actions in dolphins. The device was made of a PVC tube and two caps with rope handles; one handle was fixed to the poolside whereas the other was available for the dolphins. Its internal structure kept five fish in place while maintaining a closed status. The dolphin who pulled the rope handle could not access the fish but allowed another individual to access it. Once the handle was released, however, the device closed back. The device was tested with a male and a female group, separately. The males obtained approximately a third, while the females acquired none of the fish using the device. Moreover, the males were observed to open the device more frequently and longer in the presence of their group members and with consistent roles. These results provide the first support of male dolphins' willingness to engage in food-sharing that could be considered as an altruistic action. It also provides basis for further investigations on more detailed and long-term monitoring of the emergence and consequences of such cooperative actions. [ABSTRACT FROM AUTHOR]

Historical data are often overlooked in risk assessments and recovery plans for marine animals, resulting in the "shifting baselines." Historical ecological studies demonstrate the "surprising" extent to which contemporary assumptions misrepresent premodern baselines. The Florida manatee, a subspecies of the West Indian manatee found primarily in Florida, USA, faces several existential threats, but risk assessments and recovery targets for the species are hindered by poor understanding of historical baselines. We conducted systematic and opportunistic reviews of archaeological and historical records of manatee occurrence in Florida, USA. Our data reveal that manatee populations in Florida were very small in the Precolonial and Colonial Periods, possibly representing infrequent in-migration from the Caribbean during favorable climate conditions. Manatees expanded in number and range across the Florida peninsula during the Territorial/Early Statehood and Early Modern Periods, first northward on the Atlantic Coast and later along the coast of the Gulf of Mexico. These expansions track increasing human populations, associated anthropogenic landscape alterations, and social and policy changes. Historical ecology is critical for "shaping a better Anthropocene" for humans and manatees in Florida. [ABSTRACT FROM AUTHOR]

In contemporary wildlife conservation, drones have become essential for the non-invasive monitoring of animal populations and habitats. However, the sensitive data captured by drones, including images and videos, require robust encryption to prevent unauthorized access and exploitation. This paper presents a novel encryption algorithm designed specifically for safeguarding wildlife data. The proposed approach integrates one-dimensional and two-dimensional memory cellular automata (1D MCA and 2D MCA) with a bitwise XOR operation as an intermediate confusion layer. The 2D MCA, guided by chaotic rules from the sine-exponential (SE) map, utilizes varying neighbor configurations to enhance both diffusion and confusion, making the encryption more resilient to attacks. A final layer of 1D MCA, controlled by pseudo-random number generators, ensures comprehensive diffusion and confusion across the image. The SHA-256 hash of the input image is used to derive encryption parameters, providing resistance against plaintext attacks. Extensive performance evaluations demonstrate the effectiveness of the proposed scheme, which balances security and complexity while outperforming existing algorithms. [ABSTRACT FROM AUTHOR]

Kishorekumar, M.; Jayakumar, N.; Jawahar, P.; Neethiselvan, N.; Padmavathy, P.; Karuppasamy, K.; Sudhan, C., and Chandravanshi, S., 2024. Length–weight relationship of nine elasmobranch species landed along the south Tamil Nadu coast, India. Journal of Coastal Research, 40(6), 1160–1165. Charlotte (North Carolina), ISSN 0749-0208. The present study was conducted to establish the length–weight relationship of nine elasmobranch species from the coast of southern Tamil Nadu, India. In total, 2686 specimens of nine species of elasmobranchs belonging to five orders, seven families, and eight genera were collected fortnightly from commercial catches with different fishing gear, such as trawl net, gill net, and deep-sea longline, from the Thoothukudi, Mandapam, and Thengapattanam fishing harbors from December 2022 to November 2023. The results showed that most species exhibited positive allometric growth and that values of b were within the expected range of 2.5 to 3.5. The maximum b value (3.17) was observed for male Pateobatis bleekeri. The total length–weight relationship or disc width–weight relationship showed good fit with r2 values, varying from 0.8374 to 0.9969. The calculated b values in the current study showed that all males, females, and combined sexes of P. bleekeri, Aetobatus ocellatus, and Acroteriobatus variegatus showed negative allometric growth (b < 3). In the study, a new maximum total length is reported for P. bleekeri, and this study provides the first estimate,, of the length–weight relationship for the critically endangered species A. variegatus. The study provides baseline information for biological studies, stock assessment and management, and conservation of elasmobranch resources in a sustainable way along this coast. [ABSTRACT FROM AUTHOR]

Mortality resulting from interactions with fishing gears represent an important threat to sensitive species globally. In this study, we address this issue by defining five species groups of marine megafauna (marine mammals, seabirds, demersal and pelagic elasmobranchs, and sea turtles), and conducting a productivitysusceptibility analysis (PSA) within the context of data-limited fisheries in the Mediterranean and Black Sea. Although there are significant differences among species within each group, this approach has been considered much more direct and functional for management purposes. The productivity (P) of each species group was determined by evaluating a set of attributes averaged across representative species within each group. Species groups' susceptibility (S) to bycatch was assessed through a comprehensive review of existing literature and expert judgment, considering a series of semi-quantitative attributes. Our analysis identified areas and fishing gears posing potential risks to the species groups assessed, highlighting that sea turtles and elasmobranchs face the potential risk of incidental captures from various fishing gears operating in both neritic (bottom trawls, set nets and bottomlonglines) and pelagic (drifting longlines) environments. Marine mammals exhibit moderate risk across most fishing gears, with particular concern for the harbour porpoise Phocoena phocoena relicta in the Black Sea, primarily due to the interaction with set nets, which can severely impact entire population even capturing few specimens due the species low productivity. Seabirds face reduced impact with fishing activities, irrespective of the type of gear examined or the specific area under investigation. Overall, our study highlights the specific basins and fishing gears requiring focused management measures, mitigation strategies, and enhanced monitoring activities to mitigate the impacts of bycatch on vulnerable marine megafauna. [ABSTRACT FROM AUTHOR]

Round goby (Neogobius melanostomus) is an invasive fish present in all five Great Lakes and is becoming increasingly common in their tributaries. Johnny darter (Etheostoma nigrum) is a native species that often coexists with N. melanostomus. In this work, historic factors are addressed as a source of genomic variation in study populations of these species. To do this, patterns of variation in the mitochondrial gene NADH dehydrogenase subunit 2 (ND2) were characterized for both species throughout Lower Michigan. Populations of N. melanostomus and E. nigrum were sampled from 17 localities representing both eastern and western basins of Lower Michigan to test the hypothesis that populations differ between the eastern and western basins of the Great Lakes. Neogobius melanostomus populations were largely homogenous with no significant differences detected among populations or between the eastern and western basins. Additionally, N. melanostomus exhibited no evidence of overarching historical genetic structure, consistent with the recent invasion and rapid expansion of this species. Etheostoma nigrum exhibited significant differentiation among local populations; however, similarity among mtDNA haplotypes indicated that differences among populations are recent, suggesting that local forces are a more important factor in shaping patterns of variation than historical factors. Contrary to predictions, there were no significant differences detected between the eastern and western basins of the Great Lakes; however, construction of a neighbor‐joining tree with FST estimates revealed clustering of populations by basin with some anomalies. These anomalies may be the result of recent stream capture events facilitating gene flow between the two basins. [ABSTRACT FROM AUTHOR]

Habitat‐based approaches to animal conservation are bolstered by an understanding of resource selection, that is, use of resources (i.e., habitat features) relative to their availability in the environment. Quantifying resource selection is especially valuable when data characterizing animal space use are limited, as is often the case with mobile and/or cryptic species. Documenting associations with habitat features can better inform management in space in time, while also revealing key insight into movement ecology and behavior. Here, we evaluate resource selection by a megaomnivore whose highly mobile nature within marine habitats has resulted in an incomplete understanding of drivers of space use. We used satellite telemetry to track 29 green turtles (Chelonia mydas) from an eastern Pacific foraging aggregation in San Diego Bay, California, USA during 2013–2023. Tracking produced 5023 Fastloc‐GPS points which we used to model selection for local environmental resources relative to their availability. We employed logistic models to evaluate associations with seagrass, bathymetry, and water temperatures, implementing a framework that additionally allowed us to explore the roles of season, diel period, and turtle body size. Our methods demonstrate an approach for down‐weighting observations according to assumed telemetry error and autocorrelation. Results from fine‐scale resource selection models provide evidence that green turtles in San Diego Bay select for eelgrass meadows (Zostera marina), particularly during the warmest months of the year, but the strength of this selection changes from day to night. We additionally found day–night shifts in depth and temperature selection that changed with turtle body size and season. We discuss these findings in the context of diel patterns in resting and foraging behavior in addition to seasonal changes in thermally sensitive metabolic rates. Our study documents resource associations and provides quantitative information for the management of sea turtle foraging populations and their habitats. We offer key insight into habitat use by green turtles in the eastern Pacific at a pivotal time when multiple indicators point to population growth and expansion within the region. [ABSTRACT FROM AUTHOR]

Marine turtles are a group of imperiled marine megafauna particularly vulnerable to anthropogenic stressors. Most long‐term studies of marine turtles are based on nesting surveys which focus on numbers of eggs, hatchlings, and nesting females. However, we know less about long‐term abundance trends of immature and adult turtles in the marine environment. To address this data gap, we examined records from 35,000 underwater visual census (UVC) dives (1993–2019) and short‐term in‐water turtle survey data (2009–2014) at Cocos Island, Costa Rica. During UVCs, trained divemasters from UnderSea Hunter recorded observations of two species of marine turtles—green Chelonia mydas and hawksbill Eretmochelys imbricata. Our short‐term in‐water surveys revealed that most turtles at Cocos are greens, but both immature and mature greens occur at Cocos. We analyzed long‐term UVC data using a hierarchical modeling approach and we modeled a 26% decrease in the relative abundance of turtles observed on dives each year. Our model also revealed potential interactions between tiger sharks and turtles, finding that for each additional tiger shark present during a dive, the predicted relative abundance of turtles decreased by 43%. Lastly, our model suggested the influence of environmental variation on marine turtle relative abundance; a 1°C increase in sea surface temperature (SST) decreased the predicted relative abundance of turtles by 7%. Our results suggest that marine turtles are sensitive to long‐term environmental and oceanographic changes, and potentially avoid certain areas to reduce exposure to tiger sharks. Given our study area is already protected, there needs to be more focus on protecting adult turtles during their movements across the Eastern Tropical Pacific. Our work also highlights the importance of long‐term underwater surveys to monitor adult turtles. [ABSTRACT FROM AUTHOR]

Predators can affect ecosystems through non‐consumptive effects (NCE) on their prey, which can lead to cascading effects on the vegetation. In mammalian communities, such cascading effects on whole ecosystems have mainly been demonstrated in protected areas, but the extent to which such effects may occur in more human‐dominated landscapes remains disputable. With the recolonisation of wolves Canis lupus in Europe, understanding the potential for such cascading processes becomes crucial for understanding the ecological consequences of wolf recovery and making appropriate management recommendations. Here, we investigate the evidence for non‐consumptive effects of wolves on their wild ungulate prey and cascading effects on the vegetation in European landscapes. We reviewed empirical studies reporting wild ungulate responses to wolves involving spatio‐temporal behaviour at large and fine spatial scales, activity patterns, vigilance, grouping, physiological effects, and effects on the vegetation. We reveal that non‐consumptive effects of wolves in Europe have been studied in few regions and with focus on regions with low human impact, are highly context‐dependent, and might often be overruled by human‐related factors. Hence, we highlight the need for a description of human influence in NCE studies. We discuss challenges in NCE research and the potential for advances in future research on NCE of wolves in a human‐dominated landscape. We emphasise the need for wildlife management to restore ecosystem complexity and processes, to allow non‐consumptive predator effects to occur. [ABSTRACT FROM AUTHOR]

Reef shark species have undergone sharp declines in recent decades, as they inhabit coastal areas, making them an easy target in fisheries (i.e., sharks are exploited globally for their fins, meat, and liver oil) and exposing them to other threats (e.g., being part of by-catch, pollution, and climate change). Reef sharks play a critical role in coral reef ecosystems, where they control populations of smaller predators and herbivorous fishes either directly via predation or indirectly via behavior, thus protecting biodiversity and preventing potential overgrazing of corals. The urgent need to conserve reef shark populations necessitates a multifaceted approach to policy at local, federal, and global levels. However, monitoring programmes to evaluate the efficiency of such policies are lacking due to the difficulty in repeatedly sampling free-ranging, wild shark populations. Over nine consecutive years, we monitored juveniles of the blacktip reef shark (Carcharhinus melanopterus) population around Moorea, French Polynesia, and within the largest shark sanctuary globally, to date. We investigated the roles of spatial (i.e., sampling sites) and temporal variables (i.e., sampling year, season, and month), water temperature, and interspecific competition on shark density across 10 coastal nursery areas. Juvenile C. melanopterus density was found to be stable over 9 years, which may highlight the effectiveness of local and likely federal policies. Two of the 10 nursery areas exhibited higher juvenile shark densities over time, which may have been related to changes in female reproductive behavior or changes in habitat type and resources. Water temperatures did not affect juvenile shark density over time as extreme temperatures proven lethal (i.e., 33°C) in juvenile C. melanopterus might have been tempered by daily variation. The proven efficiency of time-series datasets for reef sharks to identify critical habitats (having the highest juvenile shark densities over time) should be extended to other populations to significantly contribute to the conservation of reef shark species., (© 2023 Fisheries Society of the British Isles.)

Trawl surveys within and surrounding two northwestern Australian marine parks revealed banded sand catsharks Atelomycterus fasciatus (family Atelomycteridae) taking refuge within large sponges of the family Irciniidae (Demospongiae: Dictyoceratida) and the genus Agelas (Demospongiae: Agelasida: Agelasidae). Five sponges contained a total of 57 A. fasciatus, comprising both sexes and both immature and mature individuals ranging from 102 to 390 mm total length (TL). In the same surveys, only five A. fasciatus were captured unassociated with sponges, suggesting that sponges are an important microhabitat for A. fasciatus and may provide a daytime refuge from predators. A southerly range extension is also reported for this species., (© 2023 The Authors. Journal of Fish Biology published by John Wiley & Sons Ltd on behalf of Fisheries Society of the British Isles.)

The abundances of migratory shark species observed throughout the Mid-Atlantic Bight (MAB) during productive summer months suggest that this region provides critical habitat and prey resources to these taxa. However, the principal prey assemblages sustaining migratory shark biomass in this region are poorly defined. We applied high-throughput DNA metabarcoding to shark feces derived from cloacal swabs across nine species of Carcharhinid and Lamnid sharks to (1) quantify the contribution of broad taxa (e.g., invertebrates, fishes) supporting shark biomass during seasonal residency in the MAB and (2) determine whether the species displayed distinct dietary preference indicative of resource partitioning. DNA metabarcoding resulted in high taxonomic (species-level) resolution of shark diets with actinopterygian and elasmobranch fishes as the dominant prey categories across the species. DNA metabarcoding identified several key prey groups consistent across shark taxa that are likely integral for sustaining their biomass in this region, including Atlantic menhaden (Brevoortia tyrannus), Atlantic mackerel (Scomber scombrus), and benthic elasmobranchs, including skates. Our results are consistent with previously published stomach content data for the shark species of similar size range in the Northwest Atlantic Ocean, supporting the efficacy of cloacal swab DNA metabarcoding as a minimally invasive diet reconstruction technique. The high reliance of several shark species on Atlantic menhaden could imply wasp-waist food-web conditions during the summer months, whereby high abundances of forage fishes sustain a diverse suite of migratory sharks within a complex, seasonal food web., (© 2023 Fisheries Society of the British Isles.)

Holohalaelurus regani and Scyliorhinus capensis are relatively small catsharks, which both occur off the continental shelf around South Africa and are often caught together as by-catch in demersal trawls. The present study used data collected during annual demersal research surveys conducted between 2009 and 2015 and is a first attempt at modeling the potential intra- and interspecific associations, by maturity stage and depth, of H. regani and S. capensis to elucidate species-specific patterns in their distributions in South African waters. Intraspecifically, both species displayed a wide overlap in distribution between maturity stages, but only H. regani displayed marked changes in distribution with maturity stage, with mature individuals found further eastwards and occupying deeper waters than immature individuals. Interspecifically, the two catsharks displayed an inverse relationship in their distribution, with an increase in the abundance of H. regani and a decrease in the abundance of S. capensis when moving from the south coast to the west coast. Some localized patches of co-occurrence were, however, evident between species and maturity stages, especially in offshore areas. Overall, our results indicated a stronger co-occurrence of mature and immature stages within each species and a rather weak co-occurrence of maturity stages between the two species. The spatial information provided in the present study provides useful information on how sharks with similar morphologies and lifestyles may partition their habitat as a mechanism for potentially reducing competition between them., (© 2023 Fisheries Society of the British Isles.)