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20 pages, 3 tables, 5 figures.-- Samantha Andrzejaczek ... et al.-- Distributed under a Creative Commons Attribution NonCommercial License 4.0 (CC BY-NC), 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, Data analysis was funded by the Bertarelli Foundation through the Marine Science program through grants to D.J.C., B.A.B., and S.A. D.J.C. is also funded through Research England, UK. S.A. and B.A.B. thank the Moore Foundation and the Packard Foundation. F.G.-M. thanks the Instituto Politecnico Nacional for fellowships (COFAA, EDI). S.B.W. thanks funding from the Darwin Initiative (DPLUS046). A.D.M.D. acknowledges funding from the Research and Conservation Budget at Georgia Aquarium, including philanthropic gifts from several anonymous donors. K.F. acknowledges funding from the Rolex Awards for Enterprise and the Whitley Fund for Nature

Groups of basking sharks engaged in circling behaviour are rarely observed, and their function remains enigmatic in the absence of detailed observations. Here, underwater and aerial video recordings of multiple circling groups of basking sharks during late summer (August and September 2016–2021) in the eastern North Atlantic Ocean showed groups numbering between 6 and 23 non-feeding individuals of both sexes. Sharks swam slowly in a rotating “torus” (diameter range: 17–39 m), with individuals layered vertically from the surface to a maximum depth of 16 m. Within a torus, sharks engaged in close-following, echelon, close-flank approach or parallel-swimming behaviours. Measured shark total body lengths were 5.4–9.5 m (mean LT: 7.3 m ± 0.9 s.d.; median: 7.2 m, n = 27), overlapping known lengths of sexually mature males and females. Males possessed large claspers with abrasions that were also observed on female pectoral fins. Female body colouration was paler than that of males, similar to colour changes observed during courtship and mating in other shark species. Individuals associated with most other members rapidly (within minutes), indicating toroidal behaviours facilitate multiple interactions. Sharks interacted through fin–fin and fin–body contacts, rolling to expose the ventral surfaces to following sharks, and breaching behaviour. Toruses formed in late summer when feeding aggregations in zooplankton-rich thermal fronts switched to non-feeding following and circling behaviours. Collectively, the observations explain a courtship function for toruses. This study highlights northeast Atlantic coastal waters as a critical habitat supporting courtship reproductive behaviour of endangered basking sharks, the first such habitat identified for this species globally. (https://www.youtube.com/watch?v=7i2H1wVOmb4) yes

REPLYING TO H. Murua et al. Nature https://doi.org/10.1038/s41586-021-03396-4 (2021) Our previously published paper1 provided global fine-scale spatiotemporal estimates (1° × 1°; monthly) of overlap and fishing exposure risk (FEI) between satellite-tracked shark space use and automatic identification system (AIS) longline fishing effort. We did not assess shark mortality directly, but in addition to replying to the Comment by Murua et al.2, we confirm—using regression analysis of spatially matched data—that fishing-induced pelagic shark mortality (catch per unit effort (CPUE)) is greater where FEI is higher. We focused on assessing shark horizontal spatiotemporal overlap and exposure risk with fisheries because spatial overlap is a major driver of fishing capture susceptibility and previous shark ecological risk assessments (ERAs) assumed a homogenous shark density within species-range distributions3,4,5 or used coarse-scale modelled occurrence data, rather than more ecologically realistic risk estimates in heterogeneous habitats that were selected by sharks over time. Furthermore, our shark spatial exposure risk implicitly accounts for other susceptibility factors with equal or similar probabilities to those commonly used in shark ERAs3,5.

18 pages, 5 figures, supplementary data https://doi.org/10.1016/j.biocon.2021.109175.-- The data supporting the findings of this study are available in the Supplementary Materials (Appendix 3–5, Table A3-A5). Raw datasets (where available) and results summary tables for each analysis of human mobility and empirical datasets are deposited in a github repository: https://github.com/rjcommand/PAN-Environment, The global lockdown to mitigate COVID-19 pandemic health risks has altered human interactions with nature. Here, we report immediate impacts of changes in human activities on wildlife and environmental threats during the early lockdown months of 2020, based on 877 qualitative reports and 332 quantitative assessments from 89 different studies. Hundreds of reports of unusual species observations from around the world suggest that animals quickly responded to the reductions in human presence. However, negative effects of lockdown on conservation also emerged, as confinement resulted in some park officials being unable to perform conservation, restoration and enforcement tasks, resulting in local increases in illegal activities such as hunting. Overall, there is a complex mixture of positive and negative effects of the pandemic lockdown on nature, all of which have the potential to lead to cascading responses which in turn impact wildlife and nature conservation. While the net effect of the lockdown will need to be assessed over years as data becomes available and persistent effects emerge, immediate responses were detected across the world. Thus initial qualitative and quantitative data arising from this serendipitous global quasi-experimental perturbation highlights the dual role that humans play in threatening and protecting species and ecosystems. Pathways to favorably tilt this delicate balance include reducing impacts and increasing conservation effectiveness, The Canada Research Chairs program provided funding for the core writing team. Field research funding was provided by A.G. Leventis Foundation; Agence Nationale de la Recherche, [grant number ANR-18-32–0010CE-01 (JCJC PEPPER)]; Agencia Estatal de Investigaci; Agência Regional para o Desenvolvimento da Investigação Tecnologia e Inovação (ARDITI), [grant number M1420-09-5369-FSE-000002]; Alan Peterson; ArcticNet; Arkadaşlar; Army Corp of Engineers; Artificial Reef Program; Australia's Integrated Marine Observing System (IMOS), National Collaborative; Research Infrastructure Strategy (NCRIS), University of Tasmania; Australian Institute of Marine Science; Australian Research Council, [grant number LP140100222]; Bai Xian Asia Institute; Batubay Özkan; BC Hydro Fish and Wildlife Compensation Program; Ben-Gurion University of the Negev; Bertarelli Foundation; Bertarelli Programme in Marine Science; Bilge Bahar; Bill and Melinda Gates Foundation; Biology Society of South Australia; Boston University; Burak Över; California State Assembly member Patrick O'Donnell; California State University Council on Ocean Affairs, Science & Technology; California State University Long Beach; Canada Foundation for Innovation (Major Science Initiative Fund and funding to Oceans Network Canada), [grant number MSI 30199 for ONC]; Cape Eleuthera Foundation; Centre National d'Etudes Spatiales; Centre National de la Recherche Scientifique; Charles Darwin Foundation, [grant number 2398]; Colombian Institute for the Development of Science and Technology (COLCIENCIAS), [grant number 811–2018]; Colombian Ministry of Environment and Sustainable Development, [grant number 0041–2020]; Columbia Basin Trust; Commission for Environmental Cooperation; Cornell Lab of Ornithology; Cultural practices and environmental certification of beaches, Universidad de la Costa, Colombia, [grant number INV.1106–01–002-15, 2020–21]; Department of Conservation New Zealand; Direction de l'Environnement de Polynésie Française; Disney Conservation Fund; DSI-NRF Centre of; Excellence at the FitzPatrick Institute of African Ornithology; Ecology Project International; Emin Özgür; Environment and Climate Change Canada; European Community: RTD programme - Species Support to Policies; European Community's Seventh Framework Programme; European Union; European Union's Horizon 2020 research and innovation programme, Marie Skłodowska-Curie, [grant number 798091, 794938]; Faruk Eczacıbaşı; Faruk Yalçın Zoo; Field research funding was provided by King Abdullah University of Science and Technology; Fish and Wildlife Compensation Program; Fisheries and Oceans Canada; Florida Fish and Wildlife Conservation Commission, [grant numbers FWC-12164, FWC-14026, FWC-19050]; Fondo Europeo de Desarrollo Regional; Fonds québécois de la recherche nature et technologies; Foundation Segré; Fundação para a Ciência e a Tecnologia (FCT Portugal); Galapagos National Park Directorate research, [grant number PC-41-20]; Gordon and Betty Moore Foundation, [grant number GBMF9881 and GBMF 8072]; Government of Tristan da Cunha; Habitat; Conservation Trust Foundation; Holsworth Wildlife Research Endowment; Institute of Biology of the Southern Seas, Sevastopol, Russia; Instituto de Investigación de Recursos Biológicos Alexander von Humboldt; Instituto Nacional de Pesquisas Espaciais (INPE), Brazil; Israeli Academy of Science's Adams Fellowship; King Family Trust; Labex, CORAIL, France; Liber Ero Fellowship; LIFE (European Union), [grant number LIFE16 NAT/BG/000874]; María de Maeztu Program for Units of Excellence in R&D; Ministry of Science and Innovation, FEDER, SPASIMM,; Spain, [grant number FIS2016–80067-P (AEI/FEDER, UE)]; MOE-Korea, [grant number 2020002990006]; Mohamed bin Zayed Species Conservation Fund; Montreal Space for Life; National Aeronautics and Space Administration (NASA) Earth and Space Science Fellowship Program; National Geographic Society, [grant numbers NGS-82515R-20]; National Natural Science Fund of China; National Oceanic and Atmospheric Administration; National Parks Board, Singapore; National Science and Technology Major Project of China; National Science Foundation, [grant number DEB-1832016]; Natural Environment Research Council of the UK; Natural Sciences and Engineering Research Council of Canada (NSERC), Alliance COVID-19 grant program, [grant numbers ALLRP 550721–20, RGPIN-2014-06229 (year: 2014), RGPIN-2016-05772 (year: 2016)]; Neiser Foundation; Nekton Foundation; Network of Centre of Excellence of Canada: ArcticNet; North Family Foundation; Ocean Tracking Network; Ömer Külahçıoğlu; Oregon State University; Parks Canada Agency (Lake Louise, Yoho, and Kootenay Field Unit); Pew Charitable Trusts; Porsim Kanaf partnership; President's International Fellowship Initiative for postdoctoral researchers Chinese Academy of Sciences, [grant number 2019 PB0143]; Red Sea Research Center; Regional Government of the Azores, [grant number M3.1a/F/025/2015]; Regione Toscana; Rotary Club of Rhinebeck; Save our Seas Foundation; Science & Technology (CSU COAST); Science City Davos, Naturforschende Gesellschaft Davos; Seha İşmen; Sentinelle Nord program from the Canada First Research Excellence Fund; Servizio Foreste e Fauna (Provincia Autonoma di Trento); Sigrid Rausing Trust; Simon Fraser University; Sitka Foundation; Sivil Toplum Geliştirme Merkezi Derneği; South African National Parks (SANParks); South Australian Department for Environment and Water; Southern California Tuna Club (SCTC); Spanish Ministry for the Ecological Transition and the Demographic Challenge; Spanish Ministry of Economy and Competitiveness; Spanish Ministry of Science and Innovation; State of California; Sternlicht Family Foundation; Suna Reyent; Sunshine Coast Regional Council; Tarea Vida, CEMZOC, Universidad de Oriente, Cuba, [grant number 10523, 2020]; Teck Coal; The Hamilton Waterfront Trust; The Ian Potter Foundation, Coastwest, Western Australian State NRM; The Red Sea Development Company; The Wanderlust Fund; The Whitley Fund; Trans-Anatolian Natural Gas Pipeline; Tula Foundation (Hakai Institute); University of Arizona; University of Pisa; US Fish and Wildlife Service; US Geological Survey; Valencian Regional Government; Vermont Center for Ecostudies; Victorian Fisheries Authority; VMRC Fishing License Fund; and Wildlife Warriors Worldwide, With funding from the Spanish government through the ‘Severo Ochoa Centre of Excellence’ accreditation (CEX2019-000928-S

REPLYING TO A. V. Harry & J. M. Braccini Nature https://doi.org/10.1038/s41586-021-03463-w (2021) Our global analysis1 estimated the overlap and fishing exposure risk (FEI) using the space use of satellite-tracked sharks and longline fishing effort monitored by the automatic identification system (AIS). In the accompanying Comment, Harry and Braccini2 draw attention to two localized shark–longline vessel overlap hotspots in Australian waters, stating that 47 fishing vessels were misclassified as longline and purse seine vessels in the Global Fishing Watch (GFW)3 2012–2016 AIS fishing effort data product that we used. This, they propose2, results in misidentifications that highlight fishing exposure hotspots that are subject to an unexpected level of sensitivity in the analysis and they suggest that misidentifications could broadly affect the calculations of fishing exposure and the central conclusions of our study1. We acknowledged in our previously published paper1 that gear reclassifications were likely to occur for a small percentage of the more than 70,000 vessels studied, however, here we demonstrate that even using much larger numbers of vessel reclassifications than those proposed by Harry and Braccini2, the central results and conclusions of our paper1 do not change.

Effective ocean management and the conservation of highly migratory species depend on resolving the overlap between animal movements and distributions, and fishing effort. However, this information is lacking at a global scale. Here we show, using a big-data approach that combines satellite-tracked movements of pelagic sharks and global fishing fleets, that 24% of the mean monthly space used by sharks falls under the footprint of pelagic longline fisheries. Space-use hotspots of commercially valuable sharks and of internationally protected species had the highest overlap with longlines (up to 76% and 64%, respectively), and were also associated with significant increases in fishing effort. We conclude that pelagic sharks have limited spatial refuge from current levels of fishing effort in marine areas beyond national jurisdictions (the high seas). Our results demonstrate an urgent need for conservation and management measures at high-seas hotspots of shark space use, and highlight the potential of simultaneous satellite surveillance of megafauna and fishers as a tool for near-real-time, dynamic management., Data analysis was funded in part by the Marine Biological Association (MBA) and the UK Natural Environment Research Council (NERC) (NE/R00997X/1) (to D.W.S.) with additional research support from the Save Our Seas Foundation and the NERC Oceans 2025 Strategic Research Programme, in which D.W.S. was a principal investigator. D.W.S. was supported by an MBA Senior Research Fellowship, N.Q. by European Regional Development Fund (FEDER) via the Programa Operacional Competitividade e Internacionalização (COMPETE), National Funds via Fundação para a Ciência e a Tecnologia (FCT) under PTDC/MAR/100345/2008 and COMPETE FCOMP-01-0124-FEDER-010580 (to N.Q. and D.W.S.), and Norte Portugal Regional Operational Programme (NORTE 2020) under the PORTUGAL 2020 Partnership Agreement through the European Regional Development Fund (ERDF) in project MarInfo (NORTE-01-0145-FEDER-000031). Additional support was provided by an FCT Investigator Fellowship IF/01611/2013 (N.Q.), FCT Doctoral Fellowship PD/BD/52603/2014 (M.V.), PTDC/MAR-BIO/4458/2012, Xunta de Galicia - Isabel Barreto Program 2009-2012 (G.M.), Australian Research Council (ARC) grant DE170100841 and operational funds from the Australian Institute for Marine Science (AIMS) (both to A.M.M.S.).

Understanding the mechanisms linking oceanographic processes and marine vertebrate habitat use is critical to effective management of populations of conservation concern. The basking shark Cetorhinus maximus has been shown to associate with oceanographic fronts – physical interfaces at the transitions between water masses – to exploit foraging opportunities resulting from aggregation of zooplankton. However, the scale, significance and variability of these observed associations have not yet been established. Here, we quantify the influence of mesoscale (10s – 100s km) frontal activity on habitat use over timescales of weeks to months. We use animal-mounted archival tracking with composite front mapping via Earth Observation (EO) remote sensing to provide an oceanographic context to individual shark movements. We investigate levels of association with fronts occurring over two spatio-temporal scales, (i) broad-scale seasonally persistent frontal zones and (ii) contemporaneous mesoscale thermal and chl-a fronts. Using random walk simulations and logistic regression within an iterative generalised linear mixed modelling (GLMM) framework, we find that seasonal front frequency is a significant predictor of shark presence. Temporally-matched oceanographic metrics also indicate that sharks demonstrate a preference for productive regions, and associate with contemporaneous thermal and chl-a fronts more frequently than could be expected at random. Moreover, we highlight the importance of cross-frontal temperature change and persistence, which appear to interact to affect the degree of prey aggregation along thermal fronts. These insights have clear implications for understanding the preferred habitats of basking sharks in the context of anthropogenic threat management and marine spatial planning in the northeast Atlantic.

The use of archival depth telemetry as a means of remotely assessing the reproductive rates of free-ranging fishes is explored. This is achieved by electronically tracking the vertical movements of individual female small spotted catsharks Scyliorhinus canicula in the natural environment, whilst simultaneously evaluating the temporal and vertical distributions of egg-laying in this species. Distinctive patterns of short-term (0·3-3·7 h), shallow-water activity are documented in the time-depth profiles of female S. canicula that occur at an appropriate depth (1·0-2·3 m) and periodicity (every 10-12 days) to represent egg-laying behaviour. Putative egg-laying behaviour was exhibited simultaneously by two individually tracked female S. canicula during late-spring and early-summer. The results highlight that, provided species behaviour is suitable and complementary methods such as previous data, laboratory experiments and field surveys can be used to validate the patterns observed, archival depth telemetry offers an unobtrusive means by which egg production and egg-laying behaviour of free-living fishes can be estimated. As precise information regarding life-history parameters is difficult to obtain for free-ranging fish species, this technique could be used to improve the parameterization of species demographic models that are relevant to the management of wild fish populations.

Within-species sexual segregation is a widespread phenomenon among vertebrates, but its causes remain a topic of much debate. Female avoidance of male coercive mating attempts has the potential to influence the social structure of animal populations, yet it has been largely overlooked as a driver of sexual separation. Indeed, its potential role in long-term structuring of natural populations has not been studied. Here we use a comparative approach to examine the suitability of multiple hypotheses forwarded to account for sexual segregation (i.e., activity budget, predation risk, thermal niche–fecundity, and social factors) as drivers underlying sex-specific habitat use in a monomorphic model vertebrate, the small-spotted catshark, Scyliorhinus canicula. Using this hypothesis-driven approach, we show that year-round sexual habitat segregation in S. canicula can be accounted for directly by female avoidance of male sexual harassment. Long-term electronic tracking reveals that sperm-storing female catsharks ...

Commercial fishing and climate change have influenced the composition of marine fish assemblages worldwide, but we require a better understanding of their relative influence on long-term changes in species abundance and body-size distributions. In this study, we investigated long-term (1911‐2007) variability within a demersal fish assemblage in the western English Channel. The region has been subject to commercial fisheries throughout most of the past century, and has undergone interannual changes in sea temperature of over 2.01C. We focussed on a core 30 species that comprised 99% of total individuals sampled in the assemblage. Analyses showed that temporal trends in the abundance of smaller multispecies size classes followed thermal regime changes, but that there were persistent declines in abundance of larger size classes. Consistent with these results, larger-growing individual species had the greatest declines in body size, and the most constant declines in abundance, while abundance changes of smaller-growing species were more closely linked to preceding sea temperatures. Together these analyses are suggestive of dichotomous size-dependent responses of species to long-term climate change and commercial fishing over a century scale. Small species had rapid responses to the prevailing thermal environment, suggesting their life history traits predisposed populations to respond quickly to changing climates. Larger species declined in abundance and size, reflecting expectations from sustained size-selective overharvesting. These results demonstrate the importance of considering species traits when developing indicators of human and climatic impacts on marine fauna.

Patterns of vertical movement in pelagic predators can be highly complex, reflecting behaviours such as foraging, thermoregulatory excursions and spawning. Here we used fast Fourier analysis to identify periodicity in the vertical movements of 6 basking sharks Cetorhinus maximus from archival tagging data that totalled 595 d. We analysed quantitatively fine-scale vertical movements of basking sharks over seasonal scales (May to February) and detected predominant periodicities related to the vertical movements of the sharks' zooplankton prey. Normal and reverse diel vertical migration (DVM) represented the main periodic dive behaviour, occurring for 11 to 72% of individual track times. A tidal pattern of vertical movement, previously unreported for sharks, was also identified. A possible mechanism for this behaviour appears related to the shark exploiting tidally-induced aggregations of zooplankton prey at depth. The youngest shark tagged showed a markedly different pattern of vertical behaviour. Long-term data sets of swimming depth are becom- ing increasingly available for pelagic predators from pressure-sensitive data loggers. This study demonstrates the utility of signal processing techniques in objectively identifying both expected and unexpected periodicity in these continuous, high-resolution tracks.

The basking shark Cetorhinus maximus is listed as Vulnerable (A1a,d, + 2d) worldwide, and Endangered (EN A1a,d) in the north-east Atlantic in the IUCN Red List. However, protection for this species is limited in European waters and varies spatially. Without information on the amount of time individuals spend in different areas, any potential risks to population levels from incidental capture, possible future exploitation and climate change will be difficult to assess. To quantify the annual space-use patterns within political–economic zones in the north-east Atlantic we used geolocation data from seven transmitter-tagged basking sharks tracked for 964 days (16,754 km). Basking sharks tagged within the UK protection zone off south-west England and north-west Scotland spent subsequently only about 22% (range, 2.4–47.7%) of time at liberty within this zone, and a further 30% in the UK fishing zone. Although only about 6% of time was spent in the territorial waters of Ireland and France, basking sharks remained in UK, Irish and French fishing and EEZ zones for over 71% of track time (range, 51.4–89.2%). Sharks did not occupy International waters away from the European shelf at any time. These results indicate basking sharks move between different economic zones and were not afforded statutory protection for the major part of the time (78%) they spent within preferred habitat on the European shelf. This demonstrates the limited capacity of the British protection zone for encompassing the greater part of shark space utilisation. Tracked basking sharks regularly crossed national zone boundaries suggesting that conservation measures for this species need to be framed on a European, rather than national, basis. This study highlights the need for better information about the movements and habitat use by marine animals if conservation strategies are to be truly effective.

Movements of wide-ranging top predators can now be studied effectively using satellite and archival telemetry. However, the motivations underlying movements remain difficult to determine because trajectories are seldom related to key biological gradients, such as changing prey distributions. Here, we use a dynamic prey landscape of zooplankton biomass in the north-east Atlantic Ocean to examine active habitat selection in the plankton-feeding basking shark Cetorhinus maximus . The relative success of shark searches across this landscape was examined by comparing prey biomass encountered by sharks with encounters by random-walk simulations of ‘model’ sharks. Movements of transmitter-tagged sharks monitored for 964 days (16 754 km estimated minimum distance) were concentrated on the European continental shelf in areas characterized by high seasonal productivity and complex prey distributions. We show movements by adult and sub-adult sharks yielded consistently higher prey encounter rates than 90% of random-walk simulations. Behavioural patterns were consistent with basking sharks using search tactics structured across multiple scales to exploit the richest prey areas available in preferred habitats. Simple behavioural rules based on learned responses to previously encountered prey distributions may explain the high performances. This study highlights how dynamic prey landscapes enable active habitat selection in large predators to be investigated from a trophic perspective, an approach that may inform conservation by identifying critical habitat of vulnerable species.

current concerns about the population levels of the basking shark (cetorhinus maximus) in the north-east atlantic have prompted a need to understand population distribution, habitat preference and centres of abundance. in this study, spatial distribution maps derived from satellite-tag geolocations, boat surveys and public sightings data were compared. the broad distribution patterns revealed by these different methods are similar, but there are considerable differences in density distributions. surface sightings data show high densities, or ‘hotspots’ in the hebridean sea, clyde sea, irish sea and close inshore around devon and cornwall. tag geolocations, in contrast, identified two areas where individuals spent considerable time outside the distributions indicated by surveys and public sightings: the celtic sea and western approaches of the english channel. the reason for this disparity and its implications for population estimates for the species are discussed.

video observation of oral gastric eversion in a free-living caribbean reef shark (carcharhinus perezi) shows voluntary gastric eversion followed by retraction not only occurs, but is extremely rapid (lasting ∼0.3 s). eversion may occur by stomach relaxation–oesophageal contraction coupled with increased abdominal pressures to enable prolapse, and retraction by a mechanism analogous to suction feeding. this behaviour provides a ‘cleansing’ function for removing indigestible food particles, parasites or mucus from the stomach lining. sharks, and possibly other animals with similar gut morphologies, may use this technique to help maintain a healthy alimentary tract.

the tendency for marine fish to refuge in natural and artificial structures underwater is well documented, but the incidence of this behaviour among predatory sharks is not widely known. a sub-adult male nursehound scyliorhinus stellaris was tracked by intermittent acoustic telemetry over 168 days in a tidal sea lough. this individual, in-between undertaking nocturnal foraging excursions, refuged in at least five different narrow-entrance holes. refuge location was validated by underwater and surface observations during which time other nursehounds (sub-adult male and female), were also seen refuging, sometimes together. this indicates nursehound display philopatric behaviour centred on aggregation in ‘home’ refuges that, in this case, were labyrinthine rock systems.

Summary 1. Megaplanktivores such as filter-feeding sharks and baleen whales are at the apex of a short food chain (phytoplankton‐zooplankton‐vertebrate) and are sensitive indicators of sea-surface plankton availability. Even though they spend the majority of their time below the surface it is still not known how most of these species utilize vertical habitat and adapt to short-term changes in food availability. 2. A key factor likely to control vertical habitat selection by planktivorous sharks is the diel vertical migration (DVM) of zooplankton; however, no study has determined whether specific ocean-habitat type influences their behavioural strategy. Based on the first high-resolution dive data collected for a plankton-feeding fish species we show that DVM patterns of the basking shark Cetorhinus maximus reflect habitat type and zooplankton behaviour. 3. In deep, well-stratified waters sharks exhibited normal DVM (dusk ascent‐dawn descent) by tracking migrating sound-scattering layers characterized by Calanus and euphausiids. Sharks occupying shallow, inner-shelf areas near thermal fronts conducted reverse DVM (dusk descent‐dawn ascent) possibly due to zooplankton predator‐prey interactions that resulted in reverse DVM of Calanus . 4. These opposite DVM patterns resulted in the probability of daytime-surface sighting differing between these habitats by as much as two orders of magnitude. Ship-borne surveys undertaken at the same time as trackings reflected these behavioural differences. 5. The tendency of basking sharks to feed or rest for long periods at the surface has made them vulnerable to harpoon fisheries. Ship-borne and aerial surveys also use surface occurrence to assess distribution and abundance for conservation purposes. Our study indicates that without bias reduction for habitat-specific DVM patterns, current surveys could under- or overestimate shark abundance by at least 10-fold.

The surface-swimming duration of basking sharks (Cetorhinus maximus) was determined in the western English Channel from May to July over a five-year period. Surface duration showed marked variation from 0·17 to 1·45 h over the short time period from late May to mid-June. Stepwise multiple regression was used to identify any relationships between surface-swimming duration and time of day, daily sea surface temperature (SST), and zooplankton density. There was no support for any effects of SST or two measures of zooplankton density (median and maximum densities). However, there were significant relationships for surface duration with time of day and minimum zooplankton density (r2=0·50) indicating basking sharks respond to the abundance of prey and its temporal availability. This suggests that the probability of sighting sharks at the surface will vary depending on the diel period and the surface abundance of zooplankton.

Habitat selection processes in highly migratory animals such as sharks and whales are important to understand because they influence patterns of distribution, availability and therefore catch rates. However, spatial strategies remain poorly understood over seasonal scales in most species, including, most notably, the plankton-feeding basking shark Cetorhinus maximus. It was proposed nearly 50 yr ago that this globally distributed species migrates from coastal summer- feeding areas of the northeast Atlantic to hibernate during winter in deep water on the bottom of con- tinental-shelf slopes. This view has perpetuated in the literature even though the 'hibernation theory' has not been tested directly. We have now tracked basking sharks for the first time over seasonal scales (1.7 to 6.5 mo) using 'pop-up' satellite archival transmitters. We show that they do not hiber- nate during winter but instead undertake extensive horizontal (up to 3400 km) and vertical (>750 m depth) movements to utilise productive continental-shelf and shelf-edge habitats during summer, autumn and winter. They travel long distances (390 to 460 km) to locate temporally discrete produc- tivity 'hotspots' at shelf-break fronts, but at no time were prolonged movements into open-ocean regions away from shelf waters observed. Basking sharks have a very broad vertical diving range and can dive beyond the known range of planktivorous whales. Our study suggests this species can exploit shelf and slope-associated zooplankton communities in mesopelagic (200 to 1000 m) as well as epipelagic habitat (0 to 200 m).

Efficient searching is crucial for timely location of food and other resources. Recent studies show that diverse living animals use a theoretically optimal scale-free random search for sparse resources known as a Lévy walk, but little is known of the origins and evolution of foraging behavior and the search strategies of extinct organisms. Here, using simulations of self-avoiding trace fossil trails, we show that randomly introduced strophotaxis (U-turns)--initiated by obstructions such as self-trail avoidance or innate cueing--leads to random looping patterns with clustering across increasing scales that is consistent with the presence of Lévy walks. This predicts that optimal Lévy searches may emerge from simple behaviors observed in fossil trails. We then analyzed fossilized trails of benthic marine organisms by using a novel path analysis technique and find the first evidence, to our knowledge, of Lévy-like search strategies in extinct animals. Our results show that simple search behaviors of extinct animals in heterogeneous environments give rise to hierarchically nested Brownian walk clusters that converge to optimal Lévy patterns. Primary productivity collapse and large-scale food scarcity characterizing mass extinctions evident in the fossil record may have triggered adaptation of optimal Lévy-like searches. The findings suggest that Lévy-like behavior has been used by foragers since at least the Eocene but may have a more ancient origin, which might explain recent widespread observations of such patterns among modern taxa.

International audience; The decisions animals make about how long to wait between activities can determine the success of diverse behaviours such as foraging, group formation or risk avoidance. Remarkably, for diverse animal species, including humans, spontaneous patterns of waiting times show random 'burstiness' that appears scale-invariant across a broad set of scales. However, a general theory linking this phenomenon across the animal kingdom currently lacks an ecological basis. Here, we demonstrate from tracking the activities of 15 sympatric predator species (cephalopods, sharks, skates and teleosts) under natural and controlled conditions that bursty waiting times are an intrinsic spontaneous behaviour well approximated by heavy-tailed (power-law) models over data ranges up to four orders of magnitude. Scaling exponents quantifying ratios of frequent short to rare very long waits are species-specific, being determined by traits such as foraging mode (active versus ambush predation), body size and prey preference. A stochastic-deterministic decision model reproduced the empirical waiting time scaling and species-specific exponents, indicating that apparently complex scaling can emerge from simple decisions. Results indicate temporal power-law scaling is a behavioural 'rule of thumb' that is tuned to species' ecological traits, implying a common pattern may have naturally evolved that optimizes move-wait decisions in less predictable natural environments.

for many decades, scientists at the marine biological association (mba) in plymouth and the centre for environment, fisheries and aquaculture science (cefas), formerly the directorate of fisheries research, at lowestoft have undertaken considerable research into the ecology and life histories of elasmobranch fish around the british isles.

It is an open question how animals find food in dynamic natural environments where they possess little or no knowledge of where resources are located. Foraging theory predicts that in environments with sparsely distributed target resources, where forager knowledge about resources’ locations is incomplete, Lévy flight movements optimize the success of random searches. However, the putative success of Lévy foraging has been demonstrated only in model simulations. Here, we use high-temporal-resolution Global Positioning System (GPS) tracking of wandering ( Diomedea exulans ) and black-browed albatrosses ( Thalassarche melanophrys ) with simultaneous recording of prey captures, to show that both species exhibit Lévy and Brownian movement patterns. We find that total prey masses captured by wandering albatrosses during Lévy movements exceed daily energy requirements by nearly fourfold, and approached yields by Brownian movements in other habitats. These results, together with our reanalysis of previously published albatross data, overturn the notion that albatrosses do not exhibit Lévy patterns during foraging, and demonstrate that Lévy flights of predators in dynamic natural environments present a beneficial alternative strategy to simple, spatially intensive behaviors. Our findings add support to the possibility that biological Lévy flight may have naturally evolved as a search strategy in response to sparse resources and scant information.

An optimal search theory, the so-called Levy-flight foraging hypothesis1, predicts that predators should adopt search strategies known as Levy flights where prey is sparse and distributed unpredictably, but that Brownian movement is sufficiently efficient for locating abundant prey2, 3, 4. Empirical studies have generated controversy because the accuracy of statistical methods that have been used to identify Levy behaviour has recently been questioned5, 6. Consequently, whether foragers exhibit Levy flights in the wild remains unclear. Crucially, moreover, it has not been tested whether observed movement patterns across natural landscapes having different expected resource distributions conform to the theory’s central predictions. Here we use maximum-likelihood methods to test for Levy patterns in relation to environmental gradients in the largest animal movement data set assembled for this purpose. Strong support was found for Levy search patterns across 14 species of open-ocean predatory fish (sharks, tuna, billfish and ocean sunfish), with some individuals switching between Levy and Brownian movement as they traversed different habitat types. We tested the spatial occurrence of these two principal patterns and found Levy behaviour to be associated with less productive waters (sparser prey) and Brownian movements to be associated with productive shelf or convergence-front habitats (abundant prey). These results are consistent with the Levy-flight foraging hypothesis1, 7, supporting the contention8, 9 that organism search strategies naturally evolved in such a way that they exploit optimal Levy patterns.

The first confirmed record of a smooth hammerhead shark (Sphyrna zygaena) in British waters for 140 years is described. The head section of the specimen was found washed ashore in relatively good condition at Portreath, south-west England, in December 2004. Evidence suggests it was not a fishery discard, and, like most other previous records of this species in British waters, probably came ashore moribund or dead.

Many free-ranging predators have to make foraging decisions with little, if any, knowledge of present resource distribution and availability1. The optimal search strategy they should use to maximize encounter rates with prey in heterogeneous natural environments remains a largely unresolved issue in ecology1, 2, 3. Lévy walks4 are specialized random walks giving rise to fractal movement trajectories that may represent an optimal solution for searching complex landscapes5. However, the adaptive significance of this putative strategy in response to natural prey distributions remains untested6, 7. Here we analyse over a million movement displacements recorded from animal-attached electronic tags to show that diverse marine predators—sharks, bony fishes, sea turtles and penguins—exhibit Lévy-walk-like behaviour close to a theoretical optimum2. Prey density distributions also display Lévy-like fractal patterns, suggesting response movements by predators to prey distributions. Simulations show that predators have higher encounter rates when adopting Lévy-type foraging in natural-like prey fields compared with purely random landscapes. This is consistent with the hypothesis that observed search patterns are adapted to observed statistical patterns of the landscape. This may explain why Lévy-like behaviour seems to be widespread among diverse organisms3, from microbes8 to humans9, as a 'rule' that evolved in response to patchy resource distributions.

Dermal denticles are unique tooth-like structures embedded in the skin of sharks and rays that protect them from predators and ectoparasites, reduce mechanical abrasion and possibly minimize swimming-induced drag. Here, we show that juvenile lesser spotted dogfish (Scyliorhinus canicula) also use this body armour to anchor food items near their tail so that bite-sized pieces can be torn away by rapid jaw and head movements. This scale-rasp behaviour is novel among fishes and suggests a new role for skin in the feeding ecology of sharks. Scale rasping may be important ecologically because it could function to increase the dietary breadth and growth potential of juveniles.

Comparatively little is known about reproductive behaviour in wild sharks as it has proved extremely difficult to study, especially in large pelagic sharks. Here we describe annual courtship-like behaviour in the second-largest fish species, the basking shark (Cetorhinus maximus), from 25 separate episodes observed and tracked during a five-year study period (1995-1999) off south-west England. Social behaviours observed between paired, or three or four, sharks were consistent with courtship behaviours seen in other shark species, namely nose-to-tail following, close following, close flank approach, parallel and echelon swimming. Mature individuals between 5 and 8 m total body length (L(T)) exhibited these behaviours whereas smaller sharks (3-4 m L(T)) did not. Lead individuals were identified as female on a number of occasions and interactions were prolonged; the longest continuous observation of socializing was 1.8 h, although intermittent track data indicates bouts may last for up to 5-6 h. Locations of courtship-like behaviour events were not distributed randomly and were significantly associated with thermal fronts. Our results indicate that putative courtship behaviour occurs between May and July along oceanographic fronts, probably as a consequence of individuals aggregating to forage in rich prey patches before initiating courtship. Thus, locating the richest prey patches along fronts may be important for basking sharks to find mates as well as food in the pelagic ecosystem. As courtship-like behaviours occur annually off south-west England we speculate that this region may represent an annual breeding area for this protected species, but mating itself probably takes place at depth as it was not seen at the surface.

Surface occurrence of ocean sunfish (Mola mola) was recorded during summer (May–September) in the western English Channel off Plymouth over a six-year period between 1995 and 2001. Fifteen individuals of between 0.5–0.7 m estimated total length were sighted during 1651 hours of observation. Nearly all sightings (93%) occurred in June and July in water between 13 and 17°C. Sunfish were mostly associated with frontal and stratified water masses (86%) rather than in cooler, mixed water.