About

Steven J. Bograd is an Adjunct Professor in the Ocean Sciences Department at the University of California, Santa Cruz, and a researcher affiliated with NOAA's Southwest Fisheries Science Center. His research interests include climate impacts on marine ecosystems, physical oceanography, fisheries oceanography, and Eastern Boundary Upwelling Systems. He holds a B.S. in Physics and Atmospheric Sciences from the University of Arizona, an M.S. in Atmospheric Sciences from the University of Washington, and a Ph.D. in Physical Oceanography from the University of British Columbia. His work focuses on understanding the interactions between climate and marine environments, contributing to the scientific knowledge of oceanic and ecosystem dynamics.

Research topics

• Oceanography
• Ecology
• Environmental science
• Geology
• Climatology
• Geography
• Biology
• Computer Science
• Environmental resource management
• Business
• Medicine
• Fishery
• Virology
• Pathology
• Environmental health
• Atmospheric sciences

Selected publications

• Revealing climate impacts on recruitment drivers of small pelagic fish through Dynamic Factor Analysis

  Marine Ecology Progress Series · 2026-03-19

  article
  PublisherDOI

• Marine cold-spells in the California Current System: Modeling changes in frequency and impacts on endangered species habitat

  PLOS Climate · 2026-01-21

  articleOpen access

  Marine cold-spells are an understudied phenomena which can both negatively impact marine wildlife and provide thermal refugia for species displaced by climate change. To develop forward-looking and climate-ready management schemes, it is critical to examine how marine species respond to cold-spells, how long-term warming will affect marine cold-spells over the next century, and how these future cold-spells will in turn affect species of conservation concern, particularly in marine protected areas. To this end, we detect marine cold-spells across the California Current System, a productive Eastern Boundary Upwelling System, relative to a fixed baseline (1980–2009) and to a detrended time series that isolates cold-spells from long-term climate change. We then project the impact of future marine cold-spells on habitat suitability for two endangered top predators: leatherback turtles ( Dermochelys coriacea ) and blue whales ( Balaenoptera musculus ). Models project that 68–99% of the California Current System will no longer experience fixed baseline marine cold-spells by 2099 under a high emissions scenario, though marine cold-spells will still occur relative to a detrended time series. Blue whales lost 5% of their core habitat in National Marine Sanctuaries during historical marine cold-spells and are projected to gain 1–2% more core habitat during future, fixed baseline marine cold-spells. Leatherback sea turtles had little core habitat change during historical marine cold-spells but are projected to gain 4–5% more core habitat during future marine cold-spells. It is plausible that both species gain habitat during future marine cold-spells because these events provide thermal refugia to their prey. We urge conservationists and ecologists to increase their attention to marine cold-spells as potential thermal refugia and prioritize collecting data on endangered species’ prey in order to understand more deeply how species will respond to extreme temperature events.

  PublisherDOI

• A collaborative climate vulnerability assessment of California marine fishery species

  PLOS Climate · 2025-02-12 · 3 citations

  articleOpen accessCorresponding

  Climate change and the associated shifts in species distributions and ecosystem functioning pose a significant challenge to the sustainability of marine fisheries and the human communities dependent upon them. In the California Current, as recent, rapid, and widespread changes have been observed across regional marine ecosystems, there is an urgent need to develop and implement adaptive and climate-ready fisheries management strategies. Climate Vulnerability Assessments (CVA) have been proposed as a first-line approach towards allocating limited resources and identifying those species and stocks most in need of further research and/or management intervention. Here we perform a CVA for 34 California state-managed fish and invertebrate species, following a methodology previously developed for and applied to federally managed species. We found Pacific herring, warty sea cucumber, and California spiny lobster to be three of the species expected to be the most sensitive to climate impacts with California halibut, Pacific bonito, and Pacific hagfish expected to be the least sensitive. When considering climate sensitivity in combination with environmental exposure in both Near (2030–2060) and Far (2070–2100) Exposure climate futures, red abalone was classified as a species with Very High climate vulnerability in both periods. Dungeness and Pacific herring shifted from High to Very High climate vulnerability and Pismo clam and pink shrimp shifted from Moderate to Very High climate vulnerability as exposure conditions progressed. In providing a relative and holistic comparison of the degree to which state-managed marine fishery species are likely to be impacted as climate change progresses, our results can help inform strategic planning initiatives and identify where gaps in scientific knowledge and management capacity may pose the greatest risk to California’s marine resource dependent economies and coastal communities.

  PublisherDOI

• Water column structure influences variability of micronekton distribution and biodiversity in the California Current

  Progress In Oceanography · 2025-08-12 · 2 citations

  articleOpen access

  • No trend in mixed layer depth (MLD) was found in the 34-year time series. • A shallower MLD was associated with higher relative abundance for 4 species. • Species richness decreased with an increase (deepening) in MLD. • 11 species displayed positive relationships with trawl depth and 6 were negative. Vertical water column characteristics are important features for understanding pelagic species’ distribution patterns, although they are rarely included as covariates in model-based abundance indices derived from fisheries-independent surveys. The mixed layer depth (MLD) is one such metric of the physical water column structure that could improve model-based estimates of abundance. In eastern boundary upwelling systems, water column stratification alters abiotic parameters, including temperature and availability of nutrients and light, above and below the MLD, potentially impacting the distribution and concentration of zooplankton and micronekton. To evaluate the role of MLD on individual species abundance and community biodiversity metrics, we examined 34 years (1990–2023) of catch and hydrographic data from a fisheries-independent midwater trawl survey of the epipelagic micronekton in the California Current. While global ocean models project a shoaling of the MLD with long-term ocean warming, we found no trend in MLD through time in our study area. However, we did find significant relationships between the abundance, or presence, of several species (krill, young-of-the-year [YOY] northern anchovy, YOY Pacific hake, adult Pacific sardine, YOY sanddabs, sergestid shrimp, and YOY widow rockfish), and overall species richness with MLD, which indicates that the catchability of some species may be influenced by the vertical water column structure. Additionally, we used auxiliary depth-stratified tows to assess vertical catch distributions and found significant relationships between trawl depth and species abundance and richness. Thus, accounting for MLD may reduce uncertainty in indices developed for both stock assessments and ecosystem status reports, as well as provide insights into the potential impacts of climate change on survey procedures.

  PublisherDOI

• Pan-basin warming now overshadows robust Pacific Decadal Oscillation

  Nature Climate Change · 2025-11-07 · 5 citations

  articleOpen access

  Abstract The Pacific Decadal Oscillation (PDO) has served as a key index linking basin-scale climate variability to marine ecosystem changes in the North Pacific. However, recent apparent breakdowns of PDO–ecosystem correlations have raised concerns about the stability of the mode and its continued relevance in a warming climate. Here we show that basin-wide warming now overwhelms PDO-related sea surface temperature (SST) variability, although neither the PDO’s spatial pattern nor its strength have changed. We introduce the pan-basin pattern as a complementary index to describe the non-stationary SST baseline of the North Pacific. Regional SSTs increasingly reflect the superposition of these two signals, providing an explanation for weakened or inverted PDO–ecosystem correlations. Future use of the PDO index in management will require discerning the effects of internal dynamics from those of absolute changes in SST as extreme and no-analogue ocean conditions driven by interacting natural variability and anthropogenic warming become more common.

  PublisherOA PDFDOI

• FISHGLOB: a collaborative infrastructure to bridge the gap between scientific monitoring and marine biodiversity conservation.

  2025-02-03

  preprintOpen access

  FISHGLOB brings together experts in, and users of, fish monitoring data to support biodiversity research and conservation across oceans.

  PublisherDOI

• Projected changes to the extent and seasonality of seabird habitat in the California current and implications for marine spatial planning

  PLOS Climate · 2025-11-10

  articleOpen accessCorresponding

  Climate-induced changes in ocean conditions are likely to affect species habitat use across current management boundaries (e.g., marine protected areas). Therefore, it is important to identify potential future risks that may reduce the effectiveness of fixed boundaries or cause negative interactions between wildlife and human ocean-use sectors. Here, we used presence and absence records from a compilation of > 132,000 ship-based and aerial at-sea visual survey transect segments collected from 1980-2017 to fit species distribution models (SDMs) for five abundant and ecologically important seabird species in the California Current Ecosystem (CCE), including both resident (common murre, Cassin’s auklet, and rhinoceros auklet) and seasonal migrant (sooty shearwater, black-footed albatross) species with different life-histories. We then projected their daily habitat suitability from 1980-2100 using an ensemble of three dynamically downscaled, high-resolution (0.1°) climate projections for the CCE. We compared long-term changes in both mean conditions and intra-annual (seasonal) variability within four National Marine Sanctuaries and four proposed areas for offshore wind energy development in the CCE. Sea surface temperature, bottom depth, daylength, and biogeographic province were the most important variables, with relative importance being species-specific. Each species displayed a negative relationship with increasing temperatures that was most pronounced in the two auklet species. Accordingly, habitat suitability scores declined across the CCE, most prominently south of Point Conception, emerging from historical variability for all species except sooty shearwater. Despite long-term negative trends in habitat suitability, we identified extensive species-specific seasonal refugia, highlighting potential changes in the intra-annual occurrence of suitable habitat. Our results suggest that perceptions of conservation benefits of marine sanctuaries and potential interactions between seabirds and new ocean-use development could be notably different by 2100, and that many impacts may occur by mid-century. Thus, it is critical to consider future projections of species habitat suitability within marine spatial management and planning processes.

  PublisherDOI

• <scp>FISHGLOB</scp> : A collaborative infrastructure to bridge the gap between scientific monitoring and marine biodiversity conservation

  Conservation Science and Practice · 2025-05-10 · 2 citations

  articleOpen access

  Abstract Large‐scale biodiversity assessments and conservation applications require integrated and up‐to‐date datasets across regions. In the oceans, monitoring is fragmented, which affects knowledge exchange and usage. Among existing monitoring programs, scientific bottom‐trawl surveys (SBTS) are long‐term, rich, and well‐maintained data sources at the scale of each sampled region, but these data are under‐utilized in biodiversity applications, especially across regions. This is hampered by the lack of an international community and database maintained through time. To address this, we created FISHGLOB, an infrastructure gathering SBTS and experts. In 5 years, we developed an integrated database of SBTS and a consortium gathering more than 100 experts and users. Here, we are sharing the project history, achievements, challenges, and outlooks. In particular, we reflect on the infrastructure‐building social and technical processes which will guide the development of similar infrastructures. The FISHGLOB project takes ocean monitoring one step forward in working as a unified community across disciplines and regions of the world.

  PublisherOA PDFDOI

• Vulnerability of marine megafauna to global at‐sea anthropogenic threats

  Conservation Biology · 2025-11-14 · 2 citations

  articleOpen access

  Marine megafauna species are affected by a wide range of anthropogenic threats. To evaluate the risk of such threats, species' vulnerability to each threat must first be determined. We build on the existing threats classification scheme and ranking system of the International Union for Conservation of Nature (IUCN) Red List of Threatened Species by assessing the vulnerability of 256 marine megafauna species to 23 at-sea threats. The threats we considered included individual fishing gear types, climate-change-related subthreats not previously assessed, and threats associated with coastal impacts and maritime disturbances. Our ratings resulted in 70 species having high vulnerability (v > 0.778 out of 1) to at least 1 threat, primarily drifting longlines, temperature extremes, or fixed gear. These 3 threats were also considered to have the most severe effects (i.e., steepest population declines). Overall, temperature extremes and plastics and other solid waste were rated as affecting the largest proportion of populations. Penguins, pinnipeds, and polar bears had the highest vulnerability to temperature extremes. Bony fishes had the highest vulnerability to drifting longlines and plastics and other solid waste; pelagic cetaceans to 4 maritime disturbance threats; elasmobranchs to 5 fishing threats; and flying birds to drifting longlines and 2 maritime disturbance threats. Sirenians and turtles had the highest vulnerability to at least one threat from all 4 categories. Despite not necessarily having severe effects for most taxonomic groups, temperature extremes were rated among the top threats for all taxa except bony fishes. The vulnerability scores we provide are an important first step in estimating the risk of threats to marine megafauna. Importantly, they help differentiate scope from severity, which is key to identifying threats that should be prioritized for mitigation.

  PublisherOA PDFDOI

• Identifying climate refugia and bright spots for highly mobile species

  npj Ocean Sustainability · 2025-07-08 · 7 citations

  articleOpen access

  Abstract Climate-driven shifts in species distributions can undermine the effectiveness of protected areas. We present a framework to facilitate climate change adaptation planning by identifying where highly migratory species habitats will persist (climate refugia), emerge (bright spots), disappear (dark spots), or remain unsuitable based on model analysis by 2100. When applied to eight species in the California Current System, we found that, on average, 37% of habitats are expected to be climate refugia, 9% are bright spots, and 13% are dark spots within National Marine Sanctuaries by 2100. Species responses differ: leatherback turtles may find refuge near U.S. coastal waters (18%), blue whales may show increased bright spots (41%), and humpback whales may exhibit more dark spots (44%). These findings highlight the need to integrate species projections into spatial planning to enhance species conservation. Our approach can be applied globally to evaluate the effectiveness of protected areas in safeguarding biodiversity under climate change.

  PublisherOA PDFDOI

Frequent coauthors

• Elliott L. Hazen

  NOAA National Marine Fisheries Service Southwest Fisheries Science Center

  562 shared

• Michael G. Jacox

  408 shared

• Stephanie Brodie

  University of California, Santa Cruz

  209 shared

• Isaac D. Schroeder

  NOAA National Marine Fisheries Service Southwest Fisheries Science Center

  151 shared

• Mercedes Pozo Buil

  University of California, Santa Cruz

  117 shared

• Jarrod A. Santora

  NOAA National Marine Fisheries Service Southwest Fisheries Science Center

  115 shared

• Heather Welch

  Montana Department of Public Health and Human Services

  106 shared

• William J. Sydeman

  Farallon Institute

  102 shared