About

Barbara Block is the Charles and Elizabeth Prothro Professor of Marine Sciences, a Professor of Oceans, and a Senior Fellow at the Woods Institute for the Environment at Stanford University. She is affiliated with the Department of Biology, where her research focuses on integrative and organismal biology, specifically thermal physiology, open ocean predators, ecological physiology, and tuna biology. Her work involves understanding the physiological adaptations and ecological roles of marine species, contributing to the broader knowledge of marine biology and oceanic ecosystems. She holds a B.A. in Zoology from the University of Vermont (1980) and a Ph.D. in Zoology from Duke University (1986).

Research topics

• Computer Science
• Biology
• Geography
• Artificial Intelligence
• Ecology
• Cartography
• Environmental science
• Geodesy
• Geology
• Oceanography
• Fishery
• Engineering
• Aerospace engineering
• Remote sensing
• Environmental resource management

Selected publications

• Non-invasive extraction of white shark swimming kinematics from unoccupied aircraft system (UAS) imagery

  Wildlife Research · 2025-07-15 · 2 citations

  articleSenior author

  Context Consumer-grade unoccupied aircraft systems (UAS) are increasingly being used by both scientists and hobbyists in the coastal environment. Marine megafauna are observed via UAS as part of monitoring programs, recreational interests, and scientific research, amassing aerial imagery datasets. Because manual documentation of these datasets is infeasible at scale, efficient approaches leveraging computer vision and deep learning have emerged to detect and classify marine megafauna. Aims This study provides a workflow to quantitatively estimate swimming kinematics tailbeat frequency (TBF) and tailbeat amplitude (TBA) of white sharks (Carcharodon carcharias) from aerial UAS video data. Methods Body pose estimation was performed using computer vision model DeepLabCut to track six key white shark body parts across UAS videos. The relative positions of these body part coordinates were used to compute tail position over time and quantify TBF and TBA across a population of white sharks in Monterey Bay, California. Key results With a training set of just 52 images, the deep residual neural network reaches human-level labeling accuracy of body parts (root mean square error of <1.3 cm). This workflow is applied to 76 focal follows representing 34 individuals to produce TBF (0.43 ± 0.07 Hz) and TBA (0.24 ± 0.10 BL) values similar to those derived from biologging devices previously deployed on individuals in this population. Conclusions The results indicated that body pose estimation via DeepLabCut can allow for the rapid extraction of quantitative kinematics such as TBF and TBA in juvenile white shark populations that aggregate in coastal habitats. Implications This approach provides a non-invasive, scalable method to understanding megafauna kinematics in sensitive species that overcomes the logistical barriers of traditional biologging approaches.

  PublisherDOI

• Climate change impacts to foraging seascapes for a highly migratory top predator

  Movement Ecology · 2025-05-09 · 3 citations

  articleOpen accessSenior author

  BACKGROUND: Climate change is impacting the distribution and movement of mobile marine organisms globally. Statistical species distribution models are commonly used to explain past patterns and anticipate future shifts. However, purely correlative models can fail under novel environmental conditions, or omit key mechanistic processes driving species habitat use. METHODS: Here, we used a unique combination of laboratory measurements, field observations, and environmental predictors to investigate spatial variability in energetic seascapes for juvenile North Pacific albacore tuna (Thunnus alalunga). This species undertakes some of the longest migrations of any finfish, but their susceptibility to climate-driven habitat changes is poorly understood. We first built a framework based on Generalized Additive Models to understand mechanisms of energy gain and loss in albacore, and how these are linked to ocean conditions. We then applied the framework to projections from an ensemble of earth system models to quantify changes in thermal and foraging habitats between historical (1971-2000) and future (2071-2100) time periods. RESULTS: We show how albacore move seasonally between feeding grounds in the California Current System and the offshore North Pacific, foraging most successfully in spring and summer. The thermal corridors used for migration largely coincide with minimum metabolic costs of movement. Future warming may result in loss of favorable thermal habitat in the sub-tropics and a reduction in total habitat area, but allow increased access to productive and energetically favorable sub-arctic ecosystems. Importantly, while thermal considerations suggest a loss in habitat area, forage considerations suggest that these losses may be offset by more energetically favorable conditions in the habitat that remains. In addition, the energetic favorability of coastal foraging areas may increase in future, with decreasing suitability of offshore foraging grounds. Our results clearly show the importance of moving beyond temperature when considering climate change impacts on marine species and their movement ecology. CONCLUSIONS: Considering energetic seascapes adds essential mechanistic underpinning to projections of habitat gain and loss, particularly for highly migratory animals. Overall, improved understanding of mechanisms driving migration behavior, physiological constraints, and behavioral plasticity is required to better anticipate how climate change will impact pelagic marine ecosystems.

  PublisherOA PDFDOI

• Reef manta ray habitat use and residency at a remote marine protected area

  Marine Ecology Progress Series · 2025-09-18

  articleSenior author

  Reef manta rays Mobula alfredi are large, filter-feeding elasmobranchs known to aggregate in coastal areas and island archipelagos. Effective spatial conservation strategies, such as marine protected areas (MPAs), for this mobile marine species rely on a comprehensive understanding of movement behavior. To better understand movement patterns, we externally deployed 58 acoustic tags on reef mantas at the Palmyra Atoll National Wildlife Refuge and monitored the presence of mantas on an extensive array of acoustic receivers (n = 85) for close to a decade. We documented an average maximum residency rate of 88% as well as consistent use of all 4 primary habitat types at Palmyra—the lagoon system, reef terrace, forereef, and channel. Notably, the highest rates of detection were recorded in the nutrient rich lagoon habitats (69% of detections). Manta movements displayed a diel structure, with a preference for the forereef, reef terrace, and channel during daylight hours, and the lagoon at night. We also found bimodal peaks of activity during new and full moons. In addition, detections around the atoll increased during the cooler periods of fall and winter. Our findings demonstrate that the no-fishing regulations at Palmyra Atoll are an effective spatial management strategy for this resident population of reef mantas and indicate that reef ecosystems in remote locations may be well-suited for designation as MPAs, offering protection for threatened elasmobranch species.

  PublisherDOI

• Global tracking of marine megafauna space use reveals how to achieve conservation targets

  Science · 2025-06-05 · 34 citations

  articleOpen access

  The recent Kunming-Montreal Global Biodiversity Framework (GBF) sets ambitious goals but no clear pathway for how zero loss of important biodiversity areas and halting human-induced extinction of threatened species will be achieved. We assembled a multi-taxa tracking dataset (11 million geopositions from 15,845 tracked individuals across 121 species) to provide a global assessment of space use of highly mobile marine megafauna, showing that 63% of the area that they cover is used 80% of the time as important migratory corridors or residence areas. The GBF 30% threshold (Target 3) will be insufficient for marine megafauna's effective conservation, leaving important areas exposed to major anthropogenic threats. Coupling area protection with mitigation strategies (e.g., fishing regulation, wildlife-traffic separation) will be essential to reach international goals and conserve biodiversity.

  PublisherOA PDFDOI

• Mapping Risk and Conservation Potential Across the Indo-Pacific with Reefshark Genomescapes

  bioRxiv (Cold Spring Harbor Laboratory) · 2025-09-24

  preprintOpen accessSenior author

  ABSTRACT Overfishing has severely depleted marine populations worldwide, including within protected areas. Illegal and unreported fishing are major contributors to this decline. Large-bodied apex predators such as sharks are among the most affected, with overfishing causing dramatic species declines and ecosystem destabilization due to trophic downgrading. Key barriers to effective marine conservation and management include: Data deficiencies that hinder population benchmarks and impact assessments, limited surveillance, allowing illegal fisheries to disproportionately affect apex predators, and insufficient capacity in vulnerable nations to monitor and protect species within their waters. Our study addresses these challenges through a novel genomic framework that enables assessment of shark population diversity and health, while also improving fisheries traceability by detecting instances of illegal fishing across the Indian and Pacific Oceans. We present the Reefshark Genomescape , the first genome-wide reference database for Indo-Pacific reef sharks, an assessment of genetic diversity, structure, and connectivity of two key species across their Indo-Pacific range and geographic assignment of fished individuals using population-specific genetic signatures. We show that grey reef shark ( Carcharhinus amblyrhynchos ) populations exhibit high genetic diversity, strong population structure, and elevated F st values, with previously unknown connectivity between the central and western Indian Ocean and clear isolation of populations in the Andaman Sea. In contrast, silvertip sharks ( Carcharhinus albimarginatus ) display high connectivity, but show genomic signals of declining population health, supporting a reassessment of their IUCN status. Using supervised machine learning with Monte Carlo cross-validation, we assigned geographic origins to fished grey reef sharks with 96% accuracy. These findings provide critical insights into population structure, connectivity, and health of two ecologically important reef shark species, while establishing a robust method for assigning geographic origin. We anticipate this framework will support regional conservation assessments and targeted management. Moreover, by enabling the identification of fishing hotspots and detection of IUU fishing, it lays the groundwork for a broader traceability system in marine ecosystems. Much like the landmark elephant ivory tracing study, our approach has the potential to transform marine conservation globally. Graphical Abstract We developed the Reefshark Genomescape, a genomic framework for assessing shark population health and fisheries traceability across the Indo-Pacific. Genome-wide data from grey reef and silvertip sharks revealed contrasting patterns, unexpected connectivity, and genomic signals of decline. Geographic assignment of fished individuals reached 96% accuracy, enabling detection of illegal fishing and identification of hotspots. This framework strengthens regional management, supports IUCN reassessments, and lays the foundation for global marine traceability systems.

  PublisherOA PDFDOI

• Annual migrations, vertical habitat use and fidelity of Atlantic bluefin tuna tracked from waters off the United Kingdom

  Scientific Reports · 2025-01-02 · 5 citations

  articleOpen access

  Understanding the spatial ecology of commercially exploited species is vital for their conservation. Atlantic bluefin tuna (Thunnus thynnus, ABT) are increasingly observed in northeast Atlantic waters, yet knowledge of these individuals' spatial ecology remains limited. We investigate the horizontal and vertical habitat use of ABT (158 to 241 cm curved fork length; CFL) tracked from waters off the United Kingdom (UK) using pop-up satellite archival tags (n = 63). Analyses reveal distinctive movements from the UK to the Bay of Biscay (BoB) and Central North Atlantic between September and December, and size-specific habitat preferences in May and July-all ABT < 175 cm CFL inhabiting the BoB and 73% of ABT ≥ 175 the Mediterranean Sea. All ABT tracked for more than 300 days (n = 25) returned to waters off the UK the following year, where most stayed (n = 22; 88%) and three continuing north with deployments ending off northwest Ireland. ABT mostly occupied waters between 0 and 20 m (daytime 49 ± 6% of time; nighttime 71 ± 6%). Vertical habitat use was coupled with illumination, mean depth occupied, maximum depth reached, and vertical movement rate increased during the daytime and when moons were brightest. These data provide valuable insights into the spatial ecology of ABT reoccupying northerly foraging areas following decades of absence.

  PublisherOA PDFDOI

• Seasonal patterns of adult and subadult white shark presence at coastal aggregation sites in central California

  Wildlife Research · 2025-05-05 · 2 citations

  articleSenior author

  Context Gaining insights into seasonal aggregations of marine megafauna and how patterns vary among demographic groups is pivotal for evaluating anthropogenic risk exposure and modeling populations and ecosystem dynamics. In California, adult and subadult white sharks recurrently aggregate on the coast near pinniped colonies in fall and winter months, facilitating comprehensive long-term field studies. Aims In this study, we used over 15 years of passive acoustic telemetry data to compare the seasonal dynamics of coastal habitat use for white sharks tagged in central California among four demographic groups (adult females, adult males, subadult females, and subadult males). Methods Acoustic tags were deployed on 355 white sharks at coastal aggregation sites and monitored across a coastal array of underwater receivers from 2006 to 2022. The main aggregation sites of the Northeast Pacific (Año Nuevo, the Farallon Islands and Tomales) were continuously monitored, with an expansion of the acoustic network to the south in the latter years of the study. Key results White sharks were tracked for an average duration of 594 ± 552 days (mean ± s.d.), with total track durations ranging up to 3235 days. Notably, adult male sharks exhibited the highest residency to central California coastal aggregation sites and demonstrated earlier seasonal peak densities in late October. Adult female presence peaked in early December. Adult sharks displayed distinct seasonal gaps in detection where they have been shown with satellite tags to migrate offshore, with females displaying much longer average detection gaps than for males (averaging 1.5 years vs 0.7 years). In contrast, subadults exhibited higher coastal affinity with more consistent and widespread detections across a higher number of coastal sites throughout the year, often extending beyond the main aggregation areas outside of the peak aggregation season. Conclusions We hypothesize that the observed differences between demographic groups are attributed to sex- and size-specific foraging and reproductive strategies. The extended receiver network also showed expansive coastal movements and identified potential undescribed aggregation sites. Implications Insights from our extensive acoustic dataset represent a significant advancement in assessing the timing of anthropogenic interactions and modeling both ecosystem and population dynamics.

  PublisherDOI

• First Chromosome Scale Reference Genomes of Carcharhinid Sharks Reveal Low Genetic Diversity, and Ancient Population Bottlenecks in the Cambrian Pleistocene

  SSRN Electronic Journal · 2025-01-01 · 1 citations

  preprintOpen accessSenior author
  PublisherDOI

• Density-dependent network structuring within and across wild animal systems

  Nature Ecology & Evolution · 2025-09-04 · 4 citations

  articleOpen access
  PublisherOA PDFDOI

• Publisher Correction: Annual migrations, vertical habitat use and fidelity of Atlantic bluefin tuna tracked from waters off the United Kingdom

  Scientific Reports · 2025-02-19

  erratumOpen access
  PublisherOA PDFDOI

Recent grants

• NIH Grant R29AR040246

  NIH · $528k · 1996

Frequent coauthors

• Taylor K. Chapple

  205 shared

• Robert J. Schallert

  Pacific University

  204 shared

• Aaron B. Carlisle

  University of Delaware

  163 shared

• Francesco Ferretti

  Virginia Tech

  143 shared

• David J. Curnick

  105 shared

• David Tickler

  100 shared

• David Jacoby

  98 shared

• Salvador J. Jorgensen

  88 shared

Labs

• Block LabPI

Education

• Ph.D., Marine Biology

  Stanford University

  1980

• M.S., Marine Biology

  University of California, Santa Barbara

  1976

• B.S., Marine Biology

  University of California, Santa Barbara

  1974