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Brian B Hatfield

Brian Hatfield is a Scientist Emeritus at the Western Ecological Research Center.

Brian Hatfield has been involved with sea otter research since the late 1970s and has been employed with USGS (migrating from USFWS and NBS) since the mid-1980s.  Currently, he coordinates the range-wide sea otter surveys in California, including those at San Nicolas Island, and co-coordinates the sea otter stranding network.  Brian maintains rebreather diving certification in order to capture sea otters for tagging and sample collection.  He has participated in sea otter research in the Commander and Aleutian Islands, Prince William Sound, SE Alaska, Vancouver Island, Washington, as well as California.  His current interests include the increasing shark bite-caused sea otter mortality,  sea otter-fisheries interactions, recolonization of the California Islands by sea otters and the colonization of the Point Piedras Blancas, California, area by northern elephant seals. 

Recent Accomplishments

Education

  • MSc, Biology, California Polytechnic State University San Luis Obispo, 1979
  • BA, Biology (with honors), University of California Santa Cruz, 1975

Professional Studies/Experience

Mentorship/Outreach

Professional societies/affiliations/committees/editorial boards

Honors, awards, recognition, elected offices

Scientific/Oral Presentations, Abstracts

Science and Products

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WERC Sea otter research in Big Sur, California

California Sea Otter Stranding Network

The California Sea Otter Stranding Network is part of the USGS effort to monitor southern sea otters (Enhydra lutris nereis) and provide data to the U.S. Fish and Wildlife Service. WERC's sea otter team works with multiple institutions and partners to report, recover, and examine stranded sea otters. In addition, instructions on how to report a stranded sea otter are included in this webpage.
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Ecosystems, Wildlife Program, Western Ecological Research Center (WERC)
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California Sea Otter Stranding Network

The California Sea Otter Stranding Network is part of the USGS effort to monitor southern sea otters (Enhydra lutris nereis) and provide data to the U.S. Fish and Wildlife Service. WERC's sea otter team works with multiple institutions and partners to report, recover, and examine stranded sea otters. In addition, instructions on how to report a stranded sea otter are included in this webpage.
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WERC sea otter

California Sea Otter Surveys and Research

WERC collaborates with other research scientists to conduct annual population surveys of the southern sea otter -- a federally listed threatened species. In coordination with the California Department of Fish and Game and other institutions, ongoing surveys and research continues to inform the southern sea otter recovery plan for the U.S. Fish and Wildlife Service, and contributes to our...
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Ecosystems, Wildlife Program, Western Ecological Research Center (WERC)
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California Sea Otter Surveys and Research

WERC collaborates with other research scientists to conduct annual population surveys of the southern sea otter -- a federally listed threatened species. In coordination with the California Department of Fish and Game and other institutions, ongoing surveys and research continues to inform the southern sea otter recovery plan for the U.S. Fish and Wildlife Service, and contributes to our...
Learn More
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Sea otter Elkhorn Slough National Estuarine Research Reserve (WERC)

Population Biology and Behavior of Sea Otters

WERC's sea otter researchers are developing and utilizing a variety of methodological and analytical tools to understand the causes of biological and ecological trends in sea otter populations, and to predict the ecological consequences of management practices on these populations and their ecosystems.
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Ecosystems, Western Ecological Research Center (WERC)
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Population Biology and Behavior of Sea Otters

WERC's sea otter researchers are developing and utilizing a variety of methodological and analytical tools to understand the causes of biological and ecological trends in sea otter populations, and to predict the ecological consequences of management practices on these populations and their ecosystems.
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Image: Sea Otter Ready for a Nap

Pacific Nearshore Project

Sea otters are crucial indicators of the health of our nearshore waters and coastal resources, from kelp forests to fisheries. What clues does the sea otter's decline hold for our knowledge of ecosystem and global change? WERC's sea otter team and U.S. and Canadian researchers have teamed together to investigate. Relevance to USGS Missions:This research project has direct relevance for the...
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Ecosystems, Western Ecological Research Center (WERC)
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Pacific Nearshore Project

Sea otters are crucial indicators of the health of our nearshore waters and coastal resources, from kelp forests to fisheries. What clues does the sea otter's decline hold for our knowledge of ecosystem and global change? WERC's sea otter team and U.S. and Canadian researchers have teamed together to investigate. Relevance to USGS Missions:This research project has direct relevance for the...
Learn More
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Photo of scientist climbing an island off the coast of Big Sur

Santa Cruz Field Station

Scientists at the Santa Cruz Field Station study sea otters and seabirds in their environment. The USGS Western Ecological Research Center has two research missions based in the Santa Cruz region:
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Western Ecological Research Center (WERC)
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Santa Cruz Field Station

Scientists at the Santa Cruz Field Station study sea otters and seabirds in their environment. The USGS Western Ecological Research Center has two research missions based in the Santa Cruz region:
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Annual California Sea Otter Census-2018 Spring Census Summary

The spring 2018 mainland sea otter count began on April 26, and was completed by May 24, 2018. Overall viewing conditions this year were good and rounded off to the same conditions experienced during the 2017 spring census (View Score 2.4, where 0=poor, 1=fair, 2=good, 3=very good, and 4=excellent). The surface canopies of kelp (Macrocystis sp.) were considered by most participants to be above nor
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Western Ecological Research Center (WERC)

Annual California Sea Otter Census-1985-2014 Spring Census Summary

This dataset represents an archived record of annual California sea otter surveys from 1985-2014. Survey procedures involve counting animals during the "spring survey" -- generally beginning in late April or early May and usually ending in late May early June but may extend into early July, depending on weather conditions. Annual surveys are organized by survey year and within each year, three sha
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Western Ecological Research Center (WERC)

Annual California sea otter census2017 spring census summary

The spring 2017 mainland sea otter count began on April 30, and although the shore-based counts were completed by May 12, 2017, the aerial counts were not completed until July 12, 2017. Overall viewing conditions this year were good, although not as good as conditions experienced during the 2016 spring census (View Score 2.4 versus 3.1, where 0=poor, 1=fair, 2=good, 3=very good, and 4=excellent).
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Western Ecological Research Center (WERC), Western Ecological Research Center (WERC)

Annual California Sea Otter Census: 2016 Spring Census Summary

The spring 2016 mainland sea otter count began on 1 May and was completed on 11 May. Overall viewing conditions this year were very good, being more favorable than those during the 2015 spring census (3.1 vs. 2.6, where 0=poor, 1=fair, 2=good, 3=very good, and 4=excellent) and contributed to the relatively short duration of the count. The surface canopies of kelp (Macrocystis sp.) were considered
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Western Ecological Research Center (WERC)

Annual California Sea Otter Census - 2015 Spring Census Summary

The spring 2015 mainland sea otter count began on 2 May and wasn't completed until 2 July. The delay in finishing the census was due primarily to limited availability of the survey plane (because of the need for the plane during the oil spill in the Refugio State Beach area). Overall viewing conditions this year were more favorable than those during the 2014 spring census (View Score = 2.6 vs.
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Western Ecological Research Center (WERC)
Filter Total Items: 18

An integrated population model for southern sea otters

Southern sea otters (Enhydra lutris nereis) have recovered slowly from their near extinction a century ago, and their continued recovery has been challenged by multiple natural and anthropogenic factors. Development of an integrated population model (IPM) for southern sea otters has been identified as a management priority, to help in evaluating the relative impacts of known threats and guide best
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Ecosystems, Western Ecological Research Center (WERC)

Sea otter population collapse in southwest Alaska: Assessing ecological covariates, consequences, and causal factors

Sea otter (Enhydra lutris) populations in southwest Alaska declined substantially between about 1990 and the most recent set of surveys in 2015. Here we report changes in the distribution and abundance of sea otters, and covarying patterns in reproduction, mortality, body size and condition, diet and foraging behavior, food availability, health profiles, and exposure to environmental contaminants
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Ecosystems, Alaska Science Center, Western Ecological Research Center (WERC)

Habitat features predict carrying capacity of a recovering marine carnivore

The recovery of large carnivore species from over‐exploitation can have socioecological effects; thus, reliable estimates of potential abundance and distribution represent a valuable tool for developing management objectives and recovery criteria. For sea otters (Enhydra lutris), as with many apex predators, equilibrium abundance is not constant across space but rather varies as a function of loca
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Ecosystems, Western Ecological Research Center (WERC)

Southern (California) sea otter population status and trends at San Nicolas Island, 2017–2020

The southern sea otter (Enhydra lutris nereis) population at San Nicolas Island, California, has been monitored annually since the translocation of 140 sea otters to the island was completed in 1990. Monitoring efforts have varied in frequency and type across years. In 2017, the U.S. Navy and the U.S. Fish and Wildlife Service initiated a sea otter monitoring and research plan to determine the eff
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Ecosystems, Western Ecological Research Center (WERC)

California sea otter (Enhydra lutris nereis) census results, spring 2019

The 2019 census of southern sea otters (Enhydra lutris nereis), also known as California sea otters, was conducted from early May to early July along the mainland coast of central California and in April at San Nicolas Island in southern California. The range-wide index, defined as the 3-year average of combined counts from the mainland range and San Nicolas Island, was 2,962, a decrease of 166 se
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Ecosystems, Western Ecological Research Center (WERC)

Drift and beaching patterns of sea otter carcasses and car tire dummies

Enumerating and examining marine animal carcasses is important for quantifying mortality rates and determining causes of mortality. Drifter experiments are one tool for estimating at‐sea mortality and determining factors affecting carcass drift, but they require validation to confirm drifters accurately replicate the drift characteristics of the species of interest. The goal of this study was to d
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Ecosystems, Western Ecological Research Center (WERC)

California sea otter (Enhydra lutris nereis) census results, spring 2018

The 2018 census of southern sea otters (Enhydra lutris nereis) was conducted from late April to mid-May along the mainland coast of central California and in April at San Nicolas Island in southern California. The 3-year average of combined counts from the mainland range and San Nicolas Island was 3,128, a decrease of 58 sea otters from the previous year. The 5-year average trend in abundance, inc
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Ecosystems, Western Ecological Research Center (WERC)

California sea otter (Enhydra lutris nereis) census results, Spring 2017

The 2017 census of southern sea otters (Enhydra lutris nereis) was conducted between late April and early July along the mainland coast of central California and in April at San Nicolas Island in southern California. The 3-year average of combined counts from the mainland range and San Nicolas Island was 3,186, down by 86 sea otters from the previous year. This is the second year that the official
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Ecosystems, Western Ecological Research Center (WERC)

California sea otter (Enhydra lutris nereis) census results, Spring 2016

The 2016 census of southern sea otters Enhydra lutris nereis was conducted in May along the mainland coast of central California and in April at San Nicolas Island in southern California. The 3-year average of combined counts from the mainland range and San Nicolas Island was 3,272. This is the first year that the official index has exceeded 3,090, the Endangered Species Act delisting threshold su
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Ecosystems, Western Ecological Research Center (WERC)

Dramatic increase in sea otter mortality from white sharks in California

Although southern sea otters (Enhydra lutris nereis) are not considered prey for white sharks (Carcharodon carcharias), sharks do nonetheless bite sea otters. We analyzed spatial and temporal trends in shark bites on sea otters in California, assessing the frequency of shark bite wounds in 1,870 carcasses collected since 1985. The proportion of stranded sea otters having shark bites has increased
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Ecosystems, Western Ecological Research Center (WERC)

A multi-decade time series of kelp forest community structure at San Nicolas Island, California

San Nicolas Island is surrounded by broad areas of shallow subtidal habitat, characterized by dynamic kelp forest communities that undergo dramatic and abrupt shifts in community composition. Although these reefs are fished, the physical isolation of the island means that they receive less impact from human activities than most reefs in Southern California, making San Nicolas an ideal place to eva
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Ecosystems, Western Ecological Research Center (WERC)

Sea otter mortality in fish and shellfish traps: Estimating potential impacts and exploring possible solutions

Sea otters Enhydra lutris can be bycaught and drowned in fishing pots and traps, which may pose a threat to the welfare of otter populations. We explored this potential problem and its solutions using a wide variety of analyses. We exposed live California (USA) sea otters to finfish traps, lobster traps, and mock Dungeness crab traps in captive trials and found that the animals attempted to enter
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Ecosystems, Western Ecological Research Center (WERC)

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