White Shark Offshore Habitat: A Behavioral and Environmental Characterization of the Eastern Pacific Shared Offshore Foraging Area

BACKGROUND: Although much is known about the behavior of white sharks in coastal regions, very little is known about their vertical movements offshore in the eastern Pacific where they spend up to five months. We provide the first detailed description of the offshore habitat use of white sharks in the eastern North Pacific. METHODOLOGY/PRINCIPAL FINDINGS: This study uses 2-min data from four recovered pop-up satellite archival tags deployed at Guadalupe Island (2002 and 2005). Deployments ranged from 5.4 to 8.2 months. Two predominant vertical patterns were described. The first was a bimodal vertical pattern with time spent at the surface and at depth, which was observed while traveling. The second was a repetitive oscillatory diving mode displayed by sharks in the Shared Offshore Foraging Area (SOFA). For all four datasets the average maximum daily dive depths ranged from 442.5 to 492.8 m and were typically associated with dissolved oxygen concentrations of above 1.7 ml L(-1). Although infrequent, occasional dives to near 1000 m with a minimum temperature of 3.9 degrees C and a minimum O(2) level of 0.3 ml L(-1) were observed. CONCLUSIONS/SIGNIFICANCE: Recovered pop-up satellite tags from Guadalupe Island white sharks advance our understanding of the vertical habitat use of white sharks while offshore. The bimodal vertical pattern during traveling is most likely related to geolocation. The oscillatory dive pattern is likely associated with foraging. While feeding is not documented, foraging is likely occurring in association with the deep scattering layer. Diving depths were not limited by temperature but were constrained by O(2) levels below approximately 1.5 ml L(-1). While oxygen may limit the extent of sharks' vertical movements, it will also impact prey distribution. Consequently, the shallow oxygen minimum zone in the SOFA may act to concentrate prey, thus enhancing foraging opportunities in these oligotrophic waters

Seasonal Movements, Aggregations and Diving Behavior of Atlantic Bluefin Tuna (Thunnus thynnus) Revealed with Archival Tags

Electronic tags were used to examine the seasonal movements, aggregations and diving behaviors of Atlantic bluefin tuna (Thunnus thynnus) to better understand their migration ecology and oceanic habitat utilization. Implantable archival tags (n = 561) were deployed in bluefin tuna from 1996 to 2005 and 106 tags were recovered. Movement paths of the fish were reconstructed using light level and sea-surface-temperature-based geolocation estimates. To quantify habitat utilization we employed a weighted kernel estimation technique that removed the biases of deployment location and track length. Throughout the North Atlantic, high residence times (167±33 days) were identified in four spatially confined regions on a seasonal scale. Within each region, bluefin tuna experienced distinct temperature regimes and displayed different diving behaviors. The mean diving depths within the high-use areas were significantly shallower and the dive frequency and the variance in internal temperature significantly higher than during transit movements between the high-use areas. Residence time in the more northern latitude high-use areas was significantly correlated with levels of primary productivity. The regions of aggregation are associated with areas of abundant prey and potentially represent critical foraging habitats that have seasonally abundant prey. Throughout the North Atlantic mean diving depth was significantly correlated with the depth of the thermocline, and dive behavior changed in relation to the stratification of the water column. In this study, with numerous multi-year tracks, there appear to be repeatable patterns of clear aggregation areas that potentially are changing with environmental conditions. The high concentrations of bluefin tuna in predictable locations indicate that Atlantic bluefin tuna are vulnerable to concentrated fishing efforts in the regions of foraging aggregations

A Dynamic Ocean Management Tool to Reduce Bycatch and Support Sustainable Fisheries

Seafood is anessential sourceofprotein formore than3billionpeopleworldwide, yet bycatchof threatened species in capture fisheries remains a major impediment to fisheries sustainability. Management measures designed to reduce bycatch often result in significant economic losses and even fisheries closures. Static spatial management approaches can also be rendered ineffective by environmental variability and climate change, as productive habitats shift and introduce new interactions between human activities and protected species. We introduce a new multispecies and dynamic approach that uses daily satellite data to track ocean features and aligns scales of management, species movement, and fisheries. To accomplish this, we create species distribution models for one target species and three bycatch-sensitive species using both satellite telemetry and fisheries observer data. We then integrate species-specific probabilities of occurrence into a single predictive surface, weighing the contribution of each species by management concern. We find that dynamic closures could be 2 to 10 times smaller than existing static closures while still providing adequate protection of endangered nontarget species. Our results highlight the opportunity to implement near real time management strategies that would both support economically viable fisheries and meet mandated conservation objectives in the face of changing ocean conditions. With recent advances in eco-informatics, dynamic management provides a new climate-ready approach to support sustainable fisheries

Comparative feeding ecology of shortfin mako, blue and thresher sharks in the California Current.

Abstract This study describes the feeding ecology of three pelagic shark species in the California Current: shortfin mako (Isurus oxyrinchus); blue (Prionace glauca); and thresher (Alopias vulpinus) sharks. Stomach contents of sharks collected from 2002 to 2008 were identified to the lowest taxonomic level and analyzed using univariate and multivariate methods. Of 330 mako sharks sampled (53 to 248 cm fork length [FL]), 238 stomachs contained 42 prey taxa, with jumbo squid (Dosidicus gigas) and Pacific saury (Cololabis saira) representing the most important prey based on the geometric index of importance (GII). In addition, 158 blue sharks were sampled (76 to 248 cm FL) and 114 stomachs contained 38 prey taxa, with jumbo and Gonatus spp. squids representing the most important prey. Lastly, 225 thresher sharks were sampled (108 to 228 cm FL) and 157 stomachs contained 18 prey taxa with northern anchovy (Engraulis mordax) and Pacific sardine (Sardinops sagax) identified as the most important prey. Overall, mako sharks had the most diverse diet based upon Simpson's diversity index (1/D) (8.43±1.16), feeding on many species of teleosts and cephalopods, followed by blue sharks (6.20±2.11) which consumed a wide range of prey (primarily cephalopods), while thresher sharks were most specialized (2.62±0.34), feeding primarily on coastal pelagic teleosts. Dietary overlap was lowest between blue and thresher sharks (Sørensen similarity index00.321 and Simplified Morisita Horn index0 0.006), and seasonal variability in diet was greatest for blue sharks (Simplified Morisita Horn index0 0.260, Analysis of Similarity (ANOSIM) p<0.001). In addition, size class, and subregion were significant factors that affected diet of each species differently (ANOSIM p<0.001). Despite similarities in life history characteristics and spatial and temporal overlap in habitat, diets of these three common shark species are distinct in the California Current

Comparative feeding ecology of shortfin mako, blue and thresher sharks in the California Current.

Abstract This study describes the feeding ecology of three pelagic shark species in the California Current: shortfin mako (Isurus oxyrinchus); blue (Prionace glauca); and thresher (Alopias vulpinus) sharks. Stomach contents of sharks collected from 2002 to 2008 were identified to the lowest taxonomic level and analyzed using univariate and multivariate methods. Of 330 mako sharks sampled (53 to 248 cm fork length [FL]), 238 stomachs contained 42 prey taxa, with jumbo squid (Dosidicus gigas) and Pacific saury (Cololabis saira) representing the most important prey based on the geometric index of importance (GII). In addition, 158 blue sharks were sampled (76 to 248 cm FL) and 114 stomachs contained 38 prey taxa, with jumbo and Gonatus spp. squids representing the most important prey. Lastly, 225 thresher sharks were sampled (108 to 228 cm FL) and 157 stomachs contained 18 prey taxa with northern anchovy (Engraulis mordax) and Pacific sardine (Sardinops sagax) identified as the most important prey. Overall, mako sharks had the most diverse diet based upon Simpson's diversity index (1/D) (8.43±1.16), feeding on many species of teleosts and cephalopods, followed by blue sharks (6.20±2.11) which consumed a wide range of prey (primarily cephalopods), while thresher sharks were most specialized (2.62±0.34), feeding primarily on coastal pelagic teleosts. Dietary overlap was lowest between blue and thresher sharks (Sørensen similarity index00.321 and Simplified Morisita Horn index0 0.006), and seasonal variability in diet was greatest for blue sharks (Simplified Morisita Horn index0 0.260, Analysis of Similarity (ANOSIM) p<0.001). In addition, size class, and subregion were significant factors that affected diet of each species differently (ANOSIM p<0.001). Despite similarities in life history characteristics and spatial and temporal overlap in habitat, diets of these three common shark species are distinct in the California Current

Fit to Predict? Ecoinformatics for Predicting the Catchability of a Pelagic Fish in Near Real-Time

The ocean is a dynamic environment inhabited by a diverse array of highly migratory species, many of which are under direct exploitation in targeted fisheries. The timescales of variability in the marine realm coupled with the extreme mobility of ocean-wandering species such as tuna and billfish complicates fisheries management. Developing ecoinformatics solutions that allow for near real-time prediction of the distributions of highly mobile marine species is an important step towards the maturation of dynamic ocean management and ecological forecasting. Using 25 years (1990-2014) of NOAA fisheries\u27 observer data from the California drift gillnet fishery, we model relative probability of occurrence (presence-absence) and catchability (total catch) of broadbill swordfish Xiphias gladius in the California Current System (CCS). Using freely-available environmental datasets and open source software, we explore the physical drivers of regional swordfish distribution. Comparing models built upon remotely-sensed datasets with those built upon a data-assimilative configuration of the Regional Ocean Modelling System (ROMS), we explore trade-offs in model construction and address how physical data can affect predictive performance and operational capacity. Swordfish catchability was found to be highest in deeper waters (\u3e1500m) with surface temperatures in the 14-20 degrees C range, isothermal layer depth (ILD) of 20-40m, positive sea surface height anomalies and during the new moon

Integrating Dynamic Subsurface Habitat Metrics Into Species Distribution Models

Species distribution models (SDMs) have become key tools for describing and predicting species habitats. In the marine domain, environmental data used in modeling species distributions are often remotely sensed, and as such have limited capacity for interpreting the vertical structure of the water column, or are sampled in situ, offering minimal spatial and temporal coverage. Advances in ocean models have improved our capacity to explore subsurface ocean features, yet there has been limited integration of such features in SDMs. Using output from a data-assimilative configuration of the Regional Ocean Modeling System, we examine the effect of including dynamic subsurface variables in SDMs to describe the habitats of four pelagic predators in the California Current System (swordfish Xiphias gladius, blue sharks Prionace glauca, common thresher sharks Alopias vulpinus, and shortfin mako sharks lsurus oxyrinchus). Species data were obtained from the California Drift Gillnet observer program (1997-2017). We used boosted regression trees to explore the incremental improvement enabled by dynamic subsurface variables that quantify the structure and stability of the water column: isothermal layer depth and bulk buoyancy frequency. The inclusion of these dynamic subsurface variables significantly improved model explanatory power for most species. Model predictive performance also significantly improved, but only for species that had strong affiliations with dynamic variables (swordfish and shortfin mako sharks) rather than static variables (blue sharks and common thresher sharks). Geospatial predictions for all species showed the integration of isothermal layer depth and bulk buoyancy frequency contributed value at the mesoscale level (\u3c 100 km) and varied spatially throughout the study domain. These results highlight the utility of including dynamic subsurface variables in SDM development and support the continuing ecological use of biophysical output from ocean circulation models

Mismatches in scale between highly mobile marine megafauna and marine protected areas

Marine protected areas (MPAs), particularly large MPAs, are increasing in number and size around the globe in part to facilitate the conservation of marine megafauna under the assumption that large-scale MPAs better align with vagile life histories; however, this alignment is not well established. Using a global tracking dataset from 36 species across five taxa, chosen to reflect the span of home range size in highly mobile marine megafauna, we show most MPAs are too small to encompass complete home ranges of most species. Based on size alone, 40% of existing MPAs could encompass the home ranges of the smallest ranged species, while only < 1% of existing MPAs could encompass those of the largest ranged species. Further, where home ranges and MPAs overlapped in real geographic space, MPAs encompassed < 5% of core areas used by all species. Despite most home ranges of mobile marine megafauna being much larger than existing MPAs, we demonstrate how benefits from MPAs are still likely to accrue by targeting seasonal aggregations and critical life history stages and through other management techniques.Fil: Conners, Melinda G.. University of Washington; Estados Unidos. State University of New York. Stony Brook University; Estados UnidosFil: Sisson, Nicholas B.. Old Dominion University; Estados UnidosFil: Agamboue, Pierre D.. Wildlife Conservation Society; GabónFil: Atkinson, Philip W.. British Trust For Ornithology; Reino UnidoFil: Baylis, Alastair M. M.. Macquarie University; Australia. South Atlantic Environmental Research Institute; Reino UnidoFil: Benson, Scott R.. Noaa National Marine Fisheries Service Southwest Regional Office; Estados Unidos. Moss Landing Marine Laboratories; Estados UnidosFil: Block, Barbara A.. University of Stanford; Estados UnidosFil: Bograd, Steven J.. Noaa National Marine Fisheries Service Southwest Regional Office; Estados UnidosFil: Bordino, Pablo. Mote Marine Laboratory; Estados UnidosFil: Bowen, W.D.. Bedford Institute Of Oceanography, Fisheries And Oceans Canada; Canadá. Dalhousie University Halifax; CanadáFil: Brickle, Paul. South Atlantic Environmental Research Institute; Reino Unido. University of Aberdeen; Reino Unido. University Of Aberdeeen; Reino UnidoFil: Bruno, Ignacio Matias. Instituto Nacional de Investigaciones y Desarrollo Pesquero; ArgentinaFil: González Carman, Victoria. Instituto Nacional de Investigaciones y Desarrollo Pesquero; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones Marinas y Costeras. Universidad Nacional de Mar del Plata. Facultad de Ciencias Exactas y Naturales. Instituto de Investigaciones Marinas y Costeras; ArgentinaFil: Champagne, Cory D.. University of Washington; Estados UnidosFil: Crocker, Daniel E.. Sonoma State University; Estados UnidosFil: Costa, Daniel P.. University of California; Estados UnidosFil: Dawson, Tiffany M.. University Of Central Florida; Estados Unidos. Old Dominion University; Estados UnidosFil: Deguchi, Tomohiro. Yamashina Institute For Ornithology; JapónFil: Dewar, Heidi. Noaa National Marine Fisheries Service Southwest Regional Office; Estados UnidosFil: Doherty, Philip D.. University of Exeter; Reino UnidoFil: Eguchi, Tomo. Noaa National Marine Fisheries Service Southwest Regional Office; Estados UnidosFil: Formia, Angela. Wildlife Conservation Society; Gabón. African Aquatic Conservation Fund; Estados UnidosFil: Godley, Brendan J.. University of Exeter; Reino UnidoFil: Graham, Rachel T.. Maralliance; PanamáFil: Gredzens, Christian. Padre Island National Seashore; Estados UnidosFil: Hart, Kristen M.. United States Geological Survey; Estados UnidosFil: Hawkes, Lucy A.. University of Exeter; Reino UnidoFil: Henderson, Suzanne. Scottish Natural Heritage; Reino UnidoFil: Henry, Robert William. Groundswell Coastal Ecology; Estados UnidosFil: Hückstädt, Luis A.. University of Exeter; Reino Unido. University of California; Estados Unido

Effects of antiplatelet therapy on stroke risk by brain imaging features of intracerebral haemorrhage and cerebral small vessel diseases: subgroup analyses of the RESTART randomised, open-label trial

Background Findings from the RESTART trial suggest that starting antiplatelet therapy might reduce the risk of recurrent symptomatic intracerebral haemorrhage compared with avoiding antiplatelet therapy. Brain imaging features of intracerebral haemorrhage and cerebral small vessel diseases (such as cerebral microbleeds) are associated with greater risks of recurrent intracerebral haemorrhage. We did subgroup analyses of the RESTART trial to explore whether these brain imaging features modify the effects of antiplatelet therapy