Role of the wider Azores region as a nursery ground for North Atlantic blue shark (Prionace glauca)

Tese de Doutoramento, Ciências do Mar (Ecologia Marinha)O tubarão azul tornou-se uma importante captura acessória na pescaria de palangre do Atlântico norte ou até, nalguns casos, a espécie alvo da pescaria quando a abundância de espadarte é reduzida. Contudo, a sua complexa estrutura populacional e ciclo de vida permanecem largamente desconhecidos, limitando os actuais esforços de conservação e gestão desta espécie. Em particular, é preocupante a possível sobreposição da pescaria com zonas de maternidade, pois a sobrevivência juvenil foi demonstrada ser essencial para a manutenção das suas populações. O objectivo principal desta dissertação foi, assim, melhorar o conhecimento da ecologia espacial desta espécie no Atlântico norte, centrada no segmento juvenil e na área central desta bacia oceânica. Esta região foi identificada como possível maternidade e tem sido intensamente explorada pelas frontas palangreiras espanhola e portuguesa. A análise detalhada da demografia e abundância sazonal de tubarão azul no Atlântico norte central baseada em dados independentes da pescaria e em dados de observadores demonstrou o papel central da área para a população norte Atlântica. As capturas variaram significativamente ao longo do ano, reflectindo a presença variável dos diferentes sexos e componentes etários da população na área, e foram fortemente influenciadas por factores ambientais como a temperatura de superfície, as anomalias de altura superficial, e o ciclo lunar. Em geral, as capturas foram dominadas por tubarão azul juvenil, sobretudo nos meses de inverno. Os juvenis de primeiro ano de ambos os sexos encontram-se na região durante todo o ano enquanto os de maior idade alternam sazonalmente a sua presença. A presença de fêmeas maturas em estado de gravidez avançado sugere também que a área possa ser usada como zona de desova. Machos maturos aparecem sobretudo no verão, provavelmente para se alimentar. A presença periódica destas componentes populacionais enfatiza o papel central da área pois algumas estão também sazonalmente associadas a um dos lados do Atlântico. Este papel central da área foi corroborado por uma experiência de telemetria de satélite desenhada para investigar os movimentos de longa duração, distribuição e uso do habitat dos juvenis. Desta experiência resultaram fortes evidências da existência de uma maternidade anual para os juvenis pequenos de tubarão azul no Atlântico norte central. Os padrões de larga escala de segregação sexual e as mudanças na distribuição e movimentos ao longo da vida da espécie são revelados e discutidos à luz das adaptações evolutivas dos tubarões pelágicos no seu ambiente oceânico. Finalmente, o habitat pelágico dos juvenis de tubarão azul foi inferido usando uma modelação estatística ambiental desenvolvida para quantificar a preferência do habitat baseado em dados de telemetria e das pescarias. Os modelos demonstraram que os padrões de distribuição espacio-temporal dos juvenis e de segregação são moldados, em larga medida, pelas diferentes preferências, e revelaram a existência de estratégias distintas para explorar alguns habitates mais productivos dentro da área de distribuição. Pela primeira vez são feitas predicções do habitat essencial pelágico de juvenil de tubarão azul para o Atlântico norte, oferecendo um enquadramento unificador da dinâmica especial estruturadora da população juvenil à escala da bacia oceânica.ABSTRACT: In the North Atlantic, blue shark has become an important by-catch for the pelagic swordfish fisheries, and, in some cases, even the target species of the fishery when swordfish abundance is low. Still, their complex life cycle and population structure remain poorly understood, limiting current management and conservation efforts for this species. Particular concern exists regarding the possible overlap between pelagic longline fisheries and putative juvenile grounds, given that juvenile survival was shown to be essential for the maintenance of blue shark populations. The main goal of this dissertation was therefore to improve the knowledge on the spatial ecology of North Atlantic blue shark, particularly focusing on the juvenile segment of the population and the central area of the oceanic basin. This region in the central North Atlantic has been identified as a putative nursery area and is being heavily exploited by pelagic longline fleets from Spain and Portugal. A detailed analysis of the demography and seasonal abundance of blue shark in the central North Atlantic based on detailed analyses of fishery independent and observer data, demonstrated the central role of the area for North Atlantic blue shark population. Catch rates varied greatly over the year, reflecting the changing presence of different sex and life stages in the area, and were strongly influenced by environmental factors, namely sea surface temperature, sea surface height anomalies and lunar cycle. In general, the catches were strongly dominated by juvenile blue sharks, with higher catch rates during winter months. Young-of-the-year juveniles of both sexes were present throughout the year, while the presence of older juveniles of both sexes alternated seasonally. The presence of mature females in advanced stages of pregnancy during spring further suggests that the area is used as a pupping ground. Mature males appear mainly during summer, probably for feeding. The periodic presence of all these life stages emphasises the central role of the area, as some of these population components are seasonally associated with one of either sides of the North Atlantic. This central role was corroborated by a satellite tagging experiment that was designed to investigate the long-term movements, distribution and habitat use of mainly juvenile blue shark. This experiment provided strong evidence for the existence of a year round oceanic nursery for small juvenile blue shark in the central North Atlantic. Moreover, large scale patterns of sexual segregation and shifts in distribution and movements across the species’ life history were revealed and discussed in light of the evolutionary adaptations of pelagic sharks to their oceanic environment. Finally, the pelagic habitats juvenile blue shark were inferred using a statistical modeling approach that was developed to quantify habitat preference based on both satellite telemetry data and fisheries data. The models demonstrated that the spatio-temporal distributions of juveniles and patterns of segregation are shaped to a large extend by differential habitat preferences and revealed the existence of different strategies to exploit some of the most productive habitats within their range. For the first time, predictions of essential pelagic habitats of juvenile blue shark in the North Atlantic provide a unifying framework to understand the dynamic spatial structuring of the juvenile blue shark population at the scale of entire ocean basin.Fundação para a Ciência e a Tecnologia (FCT, Grant number SFRH/BD/46891/2008).EU FP7 (FP7 KBBE/2007/1/210496)

Environmental drivers of large-scale movements of baleen whales in the mid-North Atlantic Ocean

© The Author(s), 2020. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Perez-Jorge, S., Tobena, M., Prieto, R., Vandeperre, F., Calmettes, B., Lehodey, P., & Silva, M. A. Environmental drivers of large-scale movements of baleen whales in the mid-North Atlantic Ocean. Diversity and Distributions, 00, (2020): 1-16, doi:10.1111/ddi.13038.Aim Understanding the environmental drivers of movement and habitat use of highly migratory marine species is crucial to implement appropriate management and conservation measures. However, this requires quantitative information on their spatial and temporal presence, which is limited in the high seas. Here, we aimed to gain insights of the essential habitats of three baleen whale species around the mid‐North Atlantic (NA) region, linking their large‐scale movements with information on oceanographic and biological processes. Location Mid‐NA Ocean. Methods We present the first study combining data from 31 satellite tracks of baleen whales (15, 10 and 6 from fin, blue and sei whales, respectively) from March to July (2008–2016) with data on remotely sensed oceanography and mid‐ and lower trophic level biomass derived from the spatial ecosystem and population dynamics model (SEAPODYM). A Bayesian switching state‐space model was applied to obtain regular tracks and correct for location errors, and pseudo‐absences were created through simulated positions using a correlated random walk model. Based on the tracks and pseudo‐absences, we applied generalized additive mixed models (GAMMs) to determine the probability of occurrence and predict monthly distributions. Results This study provides the most detailed research on the spatio‐temporal distribution of baleen whales in the mid‐NA, showing how dynamic biophysical processes determine their habitat preference. Movement patterns were mainly influenced by the interaction of temperature and the lower trophic level biomass; however, this relationship differed substantially among species. Best‐fit models suggest that movements of whales migrating towards more productive areas in northern latitudes were constrained by depth and eddy kinetic energy. Main conclusions These novel insights highlight the importance of integrating telemetry data with spatially explicit prey models to understand which factors shape the movement patterns of highly migratory species across large geographical scales. In addition, our outcomes could contribute to inform management of anthropogenic threats to baleen whales in sparsely surveyed region.We are very grateful to Cláudia Oliveira, Irma Cascão, Maria João Cruz, Miriam Romagosa and many volunteers, skilled skippers, crew and spotters that participated in the tagging fieldwork. This work was supported by Fundação para a Ciência e Tecnologia (FCT), Azores 2020 Operational Programme and Fundo Regional da Ciência e Tecnologia (FRCT) through research projects FCT‐Exploratory project (IF/00943/2013/CP1199/CT0001), TRACE (PTDC/MAR/74071/2006) and MAPCET (M2.1.2/F/012/2011) co‐funded by FEDER, COMPETE, QREN, POPH, ESF, ERDF, Portuguese Ministry for Science and Education, and Proconvergencia Açores/EU Program. We also acknowledge funds provided by FCT to MARE, through the strategic project UID/MAR/04292/2013. SPJ was supported by a postdoctoral grant (REF.GREENUP/001‐2016), MT by a DRCT doctoral grant (M3.1.a/F/028/2015), MAS by an FCT‐Investigator contract (IF/00943/2013), FV by an FCT Investigator contract (CEECIND/03469/2017) and RP by an FCT postdoctoral grant (SFRH/BPD/108007/2015). LMTL modelling work has been supported by the CMEMS Service Evolution GREENUP project, funded by Mercator Ocean. We are grateful to Elliott Hazen for offering guidance and advice, and to two anonymous referees whose comments greatly improved this work

Sea turtle (Reptilia, Testudines) diversity and occurrence in the Azores Archipelago (NE Atlantic)

BACKGROUND: Six species of marine turtles occur in the Azores Archipelago. The loggerhead, Caretta caretta (Linnaeus, 1758), is by far the most common species and is being constantly monitored and tagged by a joint project between the University of the Azores and the University of Florida since 1989. With the implementation of the tuna fishery observers (for dolphin safe seals), an increment of sea turtle reports has been verified as expected. The leather back turtle, Dermochelys coriacea (Vandelli, 1761) is the second most observed species in the Azores' EEZ, a fact probably also linked to the tuna fishery observation programme. All other species are occasional/vagrant albeit the green turtle, Chelonia mydas (Linnaeus, 1758) is more commonly seen than the others. Historically, sea turtles were occasionally taken for food in specific fishing villages and ports. Since 1986, sea turtles, as well as all marine mammals, are fully protected in the Azores although human-related activities (e.g. plastics, discarded fishing gear) do generate serious injuries and deaths. NEW INFORMATION: In this paper, we update sea turtle species' checklist for the Azores and give detailed geographic coordinates on their known occurrences.FUNDING: Funding Institutions: AZORESBIOPORTAL – PORBIOTA (Azores PO 2020 - ACORES-01-0145-FEDER-000072). This project was financed by FEDER in 85% and by Azorean Public funds by 15% through Operational Program Azores 2020. This work is also funded by FEDER funds through the COMPETE 2020 Programme and National Funds through FCT - Portuguese Foundation for Science and Technology under the Research Infrastructure PORBIOTA - Portuguese E-Infrastructure for Information and Research on Biodiversity, project number POCI-01-0145-FEDER-022127. For the period 2022-2023- Portal da Biodiversidade dos Açores (2022-2023) - PO Azores Project - M1.1.A/INFRAEST CIENT/001/2022. OPEN ACCESS will be supported by the project FCT-UIDB/00329/2020-2024 (Thematic Line 1 – integrated ecological assessment of environmental change on biodiversity).info:eu-repo/semantics/publishedVersio

The multi-annual residency of juvenile smooth hammerhead shark in an oceanic island nursery

The increased risk of local extinction becomes critical for sharks depending on the narrow and isolated coastal habitats of oceanic islands. This includes large pelagic oceanic sharks that use such habitats as nurseries, as previously hypothesized for the smooth hammerhead Sphyrna zygaena, the least known of cosmopolitan large hammerhead sharks. We used a combination of acoustic and satellite telemetry in a juvenile population of Faial and Pico islands, Azores, mid-north Atlantic, to confirm if this isolated archipelago holds nurseries, and to answer questions related to their function and spatial-temporal stability. Our long-term acoustic tracking data showed a cluster of individual core home ranges in specific areas of north shore Faial, and surface positions from five Argos-linked tagged individuals also showed a clustering overlap in those areas for up to 1 year. These patterns seem to reveal a true habitat preference within the Faial-Pico island (sub) population of juvenile smooth hammerhead shark, and thus constitute strong evidence for this area to be considered a nursery. Some individuals remained in this nursery for up to 4 years, especially during summers. Sharks also showed a strong diel behavior, typically using the inshore nurseries during the day and moving further offshore during the night, during which they increased activity and dove deeper, most possibly to feed. We speculate that a combination of increased feeding opportunities, expanded trophic niche, and reduced predatory pressure may be a key evolutionary driver for the existence, prolonged use, and even preference of coastal nurseries at oceanic islands by juvenile smooth hammerhead shark. Given that these nurseries may constitute essential fish habitat for this species, they should be explicitly included in spatial management measures at the local and regional scales, as they may also play a role of greater importance to the north Atlantic population of this oceanic species.info:eu-repo/semantics/publishedVersio

Sea turtles : University of Florida – University of the Azores connection 1984 – present. A review

The loggerhead (Caretta caretta) is the most common sea turtle in the Azores. Since they do not nest in the area, a tagging program was started in the 1980’s to try to discover their origin. The result based on size distribution, suggested that they mainly are coming from beaches in SE United States. A collaboration between University of Florida and the University of the Azores began in 1984 in order to proceed with further research.info:eu-repo/semantics/publishedVersio

Reply to: Shark mortality cannot be assessed by fishery overlap alone

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Reply to: Caution over the use of ecological big data for conservation

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Global Spatial Risk Assessment of Sharks Under the Footprint of Fisheries

Effective ocean management and conservation of highly migratory species depends on resolving overlap between animal movements and distributions and fishing effort. Yet, this information is lacking at a global scale. Here we show, using a big-data approach combining 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 high-seas fishing effort. Results demonstrate an urgent need for conservation and management measures at high-seas shark hotspots and highlight the potential of simultaneous satellite surveillance of megafauna and fishers as a tool for near-real time, dynamic management

Priorities for Mediterranean marine turtle conservation and management in the face of climate change

As climate-related impacts threaten marine biodiversity globally, it is important to adjust conservation efforts to mitigate the effects of climate change. Translating scientific knowledge into practical management, however, is often complicated due to resource, economic and policy constraints, generating a knowledge-action gap. To develop potential solutions for marine turtle conservation, we explored the perceptions of key actors across 18 countries in the Mediterranean. These actors evaluated their perceived relative importance of 19 adaptation and mitigation measures that could safeguard marine turtles from climate change. Of importance, despite differences in expertise, experience and focal country, the perceptions of researchers and management practitioners largely converged with respect to prioritizing adaptation and mitigation measures. Climate change was considered to have the greatest impacts on offspring sex ratios and suitable nesting sites. The most viable adaptation/mitigation measures were considered to be reducing other pressures that act in parallel to climate change. Ecological effectiveness represented a key determinant for implementing proposed measures, followed by practical applicability, financial cost, and societal cost. This convergence in opinions across actors likely reflects long-standing initiatives in the Mediterranean region towards supporting knowledge exchange in marine turtle conservation. Our results provide important guidance on how to prioritize measures that incorporate climate change in decision-making processes related to the current and future management and protection of marine turtles at the ocean-basin scale, and could be used to guide decisions in other regions globally. Importantly, this study demonstrates a successful example of how interactive processes can be used to fill the knowledge-action gap between research and management.This work was conducted under FutureMares EU project that received funding from the European Union's Horizon 2020 research and innovation programme under grant agreement No 869300. The Mediterranean Marine Turtle Working Group was established in 2017 and is continuously supported by MedPAN and the National Marine Park of Zakynthos. The work of AC was supported by the Hellenic Foundation for Research and Innovation (H.F.R.I.) under the “First Call for H.F.R.I. Research Projects to support Faculty members and Researchers and the procurement of high-cost research equipment grant” (Project Number: 2340).Peer reviewe

Swirling in the ocean: Immature loggerhead turtles seasonally target old anticyclonic eddies at the fringe of the North Atlantic gyre

In a highly heterogeneous open ocean, swirling oceanographic structures such as eddies drive ocean productivity and aggregate many predators, including oceanic sea turtles. During early life, juvenile loggerhead turtles can spend more than a decade feeding on gelatinous zooplankton in the open ocean, but the way they use mesoscale eddies is still poorly understood. Here, we investigated the relationships between (1) the distribution and (2) the diving behaviour of immature loggerhead turtles of the North-East Atlantic and mesoscale eddies. For this purpose, 28 turtles were satellite tracked from the Azores archipelago. Using the Residence Time (RT) analysis as a proxy to identify high-use areas, the tracks and dive data of the turtles as well as drifter trajectories were analysed in relation to eddy characteristics, which include eddy radius, amplitude, type (cyclonic vs. anticyclonic), lifetime and region (inner core, outer core, periphery). The turtles dispersed widely using many distinct high-use areas. Although there were always more cyclones than anticyclones over the study region, the individuals seasonally associated more with the inner cores of old anticyclonic eddies, likely due to the higher productivity of decaying anticyclones. The comparison between passive drifters and turtles’ movements showed an active swimming behaviour from the turtles rather than a passive advection through currents. Three dive types were identified, and the one associated with the highest RT was characterized by dives of medium duration and depths in the inner cores of eddies. This study is the first to highlight strong affinities of oceanic loggerhead turtles for old anticyclonic eddies around the Azores, suggesting a greater complexity of these warm-core eddies that appear to be much more productive than cyclones