Timothy O'Brien is a Supervisory Fisheries Biologist based in Ann Arbor, MI.
I spent my formative years exploring the outdoors, particularly the lakes and streams of Michigan. I was always interested in freshwater environments and the fish that made their homes there. These early experiences impelled me to pursue the study of fish biology and ecology.
While pursuing my undergraduate degree at the University of Michigan, I began working for USGS at the Great Lakes Science Center in 2003. I began a project studying deepwater sculpin Myoxocephalus thompsonii diets in Lake Huron and was eager to contribute to our understanding of this enigmatic native species. Early on in my career I also learned larval fish identification and became interested in larval fish ecology. Ultimately, I began working in support of the large vessel fish assessment program where most of my work is now focused. While working as a fisheries technician I had the opportunity to return to school to study fishery science and in 2010 I completed a Master of Science degree at Michigan State University studying rainbow smelt Osmerus mordax population dynamics in Lake Huron.
I am involved with both technical and programmatic aspects of the Deepwater Fisheries program:
Supervise a team of technicians supporting ecosystem and fishery studies.
Project lead for the Lake Huron acoustics program where I am responsible for leading a team to carry out a large-scale integrated trawl and acoustics survey of pelagic fishes in Lake Huron.
Large vessel coordinator for fishery research vessels on Lake Huron and Michigan, assist Branch Chief with managing, scheduling, and staffing the GLSC large vessel program.
Oversee fish aging laboratory.
Education and Certifications
M.S. 2010. Fisheries and Wildlife. Michigan State University, Department of Fisheries and Wildlife
B.S. 2004. Resource Ecology and Management. The University of Michigan, School of Natural Resources and Environment
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Publications by this scientist
Filter Total Items: 35
Comparison of traditional and geometric morphometrics using Lake Huron ciscoes of the Coregonus artedi complex
Here we determine how traditional morphometrics (TM) compares with geometric morphometrics (GM) in discriminating among morphologies of four forms of ciscoes of the Coregonus artedi complex collected from Lake Huron. One of the forms comprised two groups of the same deepwater cisco separated by capture depth, whereas the other three forms were shallow-water ciscoes. Our three groups of shallow-wat
Status and trends of the Lake Huron prey fish community, 1976-2019
The USGS Great Lakes Science Center has assessed annual changes in the offshore prey fish community of Lake Huron since 1973. Assessments are based on a bottom trawl survey conducted in October of each year and an acoustics-midwater trawl survey, which began in 2004 and is conducted in September-October. Both surveys were completed in their entirety in 2019. Prey fish biomass in Lake Huron in 2019
Status and trends of the Lake Huron prey fish community, 1976-2020
The USGS Great Lakes Science Center (GLSC) has assessed annual changes in the offshore prey fish community of Lake Huron since 1973. Assessments are based on a bottom trawl survey conducted in October and an acoustics-midwater trawl survey conducted in September-October. In 2020, USGS-GLSC vessels were not permitted to cross into Canada due to the COVID-19 pandemic, so prey fish surveys sampled
Replacement of the typical artedi form of Coregonus artedi in Lake Huron by endemic shallow-water Ciscoes, including putative hybrids
Various ecomorphs of shallow-water Cisco Coregonus artedi were the dominant fish planktivores in each of the Great Lakes until invasive species and over fishing resulted in extirpations and extinctions. In this paper we describe the present morphological diversity and distribution of shallow-water Ciscoes in each of Lake Huron’s three basins: the main basin, Georgian Bay, and North Channel. Typica
Status and trends of pelagic prey fish in Lake Huron, 2018
Scientists from the U.S. Geological Survey’s Great Lakes Science Center conducted integrated acoustic and mid-water trawl surveys of Lake Huron annually from 2004-2018. The 2018 survey was conducted during September and included transects in Lake Huron’s main basin, Georgian Bay, and North Channel. Mean lake-wide pelagic fish density was 1532 fish/ha and mean pelagic fish biomass was 4151 g/ha in
Spatial patterns of rainbow smelt energetic condition in Lakes Huron and Erie in 2017: Evidence for Lake Huron resource limitation
Rainbow smelt (Osmerus mordax) is a key planktivore and prey fish in Lake Huron. Given the declining offshore productivity in the lake since the early 2000s, we described the energy content of rainbow smelt in 2017 across five different regions (North Channel, Georgian Bay, Saginaw Bay, northern main basin, southern main basin) where phytoplankton and zooplankton productivity likely varied. To inc
Phenology and species diversity in a Lake Huron ichthyoplankton community: Ecological implications of invasive species dominance
Ichthyoplankton communities are dynamic and vary spatiotemporally based on factors such as wind, water currents, and phenology. Nonetheless, ichthyoplankton are an indicator of spawning success in fish populations and examining their community diversity and composition can serve to provide information on ecosystem integrity. Although some ichthyoplankton species may be transient, understanding the
Status and trends of pelagic prey fish in Lake Huron, 2017
Scientists from the U.S. Geological Survey’s Great Lakes Science Center conducted integrated acoustic and mid-water trawl surveys of Lake Huron in 1997 and annually from 2004-2017. The 2017 survey was conducted during September and included transects in Lake Huron’s main basin, Georgian Bay, and North Channel. Mean lake-wide pelagic fish density was 1582 fish/ha and mean pelagic fish biomass was 1
Status of pelagic prey fishes in Lake Michigan, 2017
Acoustic surveys were conducted in late summer/early fall during the years 1992-1996 and 2001-2017 to estimate pelagic prey fish biomass in Lake Michigan. Midwater trawling during the surveys as well as target strength provided a measure of species and size composition of the fish community for use in scaling acoustic data and providing species-specific abundance estimates. The 2017 survey consi
Continued feeding on Diporeia by deepwater sculpin in Lake Huron
Monitoring changes in diets of fish is essential to understanding how food web dynamics respond to changes in native prey abundances. In the Great Lakes, Diporeia, a benthic macroinvertebrate and primary food of native benthivores, declined following the introduction of invasive Dreissena mussels and these changes were reflected in fish diets. We examined the diets of deepwater sculpin Myoxocephal
Large-scale changes in bloater growth and condition in Lake Huron
Native Bloaters Coregonus hoyi have exhibited multiple strong year-classes since 2005 and now are the most abundant benthopelagic offshore prey fish in Lake Huron, following the crash of nonnative AlewivesAlosa pseudoharengus and substantial declines in nonnative Rainbow Smelt Osmerus mordax. Despite recent recoveries in Bloater abundance, marketable-size (>229 mm) Bloaters remain scarce. We used
Age and growth of round gobies in Lake Huron: Implications for food web dynamics
Although the round goby (Neogobius melanostomus) has become established throughout the Laurentian Great Lakes, information is scarce on spatial variation in round goby growth between and within lakes. Based on a sample of 754 specimens captured in 2014, age, growth, and mortality of round gobies at four locations in Lake Huron were assessed via otolith analysis. Total length (TL) of round gobies r
Non-USGS Publications**
O’Brien, T. 2003. “Salvelinus confluentus” (On-line), Animal Diversity Web
**Disclaimer: The views expressed in Non-USGS publications are those of the author and do not represent the views of the USGS, Department of the Interior, or the U.S. Government.
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Publications by this scientist
Filter Total Items: 35Comparison of traditional and geometric morphometrics using Lake Huron ciscoes of the Coregonus artedi complex
Here we determine how traditional morphometrics (TM) compares with geometric morphometrics (GM) in discriminating among morphologies of four forms of ciscoes of the Coregonus artedi complex collected from Lake Huron. One of the forms comprised two groups of the same deepwater cisco separated by capture depth, whereas the other three forms were shallow-water ciscoes. Our three groups of shallow-watStatus and trends of the Lake Huron prey fish community, 1976-2019
The USGS Great Lakes Science Center has assessed annual changes in the offshore prey fish community of Lake Huron since 1973. Assessments are based on a bottom trawl survey conducted in October of each year and an acoustics-midwater trawl survey, which began in 2004 and is conducted in September-October. Both surveys were completed in their entirety in 2019. Prey fish biomass in Lake Huron in 2019Status and trends of the Lake Huron prey fish community, 1976-2020
The USGS Great Lakes Science Center (GLSC) has assessed annual changes in the offshore prey fish community of Lake Huron since 1973. Assessments are based on a bottom trawl survey conducted in October and an acoustics-midwater trawl survey conducted in September-October. In 2020, USGS-GLSC vessels were not permitted to cross into Canada due to the COVID-19 pandemic, so prey fish surveys sampledReplacement of the typical artedi form of Coregonus artedi in Lake Huron by endemic shallow-water Ciscoes, including putative hybrids
Various ecomorphs of shallow-water Cisco Coregonus artedi were the dominant fish planktivores in each of the Great Lakes until invasive species and over fishing resulted in extirpations and extinctions. In this paper we describe the present morphological diversity and distribution of shallow-water Ciscoes in each of Lake Huron’s three basins: the main basin, Georgian Bay, and North Channel. TypicaStatus and trends of pelagic prey fish in Lake Huron, 2018
Scientists from the U.S. Geological Survey’s Great Lakes Science Center conducted integrated acoustic and mid-water trawl surveys of Lake Huron annually from 2004-2018. The 2018 survey was conducted during September and included transects in Lake Huron’s main basin, Georgian Bay, and North Channel. Mean lake-wide pelagic fish density was 1532 fish/ha and mean pelagic fish biomass was 4151 g/ha inSpatial patterns of rainbow smelt energetic condition in Lakes Huron and Erie in 2017: Evidence for Lake Huron resource limitation
Rainbow smelt (Osmerus mordax) is a key planktivore and prey fish in Lake Huron. Given the declining offshore productivity in the lake since the early 2000s, we described the energy content of rainbow smelt in 2017 across five different regions (North Channel, Georgian Bay, Saginaw Bay, northern main basin, southern main basin) where phytoplankton and zooplankton productivity likely varied. To incPhenology and species diversity in a Lake Huron ichthyoplankton community: Ecological implications of invasive species dominance
Ichthyoplankton communities are dynamic and vary spatiotemporally based on factors such as wind, water currents, and phenology. Nonetheless, ichthyoplankton are an indicator of spawning success in fish populations and examining their community diversity and composition can serve to provide information on ecosystem integrity. Although some ichthyoplankton species may be transient, understanding theStatus and trends of pelagic prey fish in Lake Huron, 2017
Scientists from the U.S. Geological Survey’s Great Lakes Science Center conducted integrated acoustic and mid-water trawl surveys of Lake Huron in 1997 and annually from 2004-2017. The 2017 survey was conducted during September and included transects in Lake Huron’s main basin, Georgian Bay, and North Channel. Mean lake-wide pelagic fish density was 1582 fish/ha and mean pelagic fish biomass was 1Status of pelagic prey fishes in Lake Michigan, 2017
Acoustic surveys were conducted in late summer/early fall during the years 1992-1996 and 2001-2017 to estimate pelagic prey fish biomass in Lake Michigan. Midwater trawling during the surveys as well as target strength provided a measure of species and size composition of the fish community for use in scaling acoustic data and providing species-specific abundance estimates. The 2017 survey consiContinued feeding on Diporeia by deepwater sculpin in Lake Huron
Monitoring changes in diets of fish is essential to understanding how food web dynamics respond to changes in native prey abundances. In the Great Lakes, Diporeia, a benthic macroinvertebrate and primary food of native benthivores, declined following the introduction of invasive Dreissena mussels and these changes were reflected in fish diets. We examined the diets of deepwater sculpin MyoxocephalLarge-scale changes in bloater growth and condition in Lake Huron
Native Bloaters Coregonus hoyi have exhibited multiple strong year-classes since 2005 and now are the most abundant benthopelagic offshore prey fish in Lake Huron, following the crash of nonnative AlewivesAlosa pseudoharengus and substantial declines in nonnative Rainbow Smelt Osmerus mordax. Despite recent recoveries in Bloater abundance, marketable-size (>229 mm) Bloaters remain scarce. We usedAge and growth of round gobies in Lake Huron: Implications for food web dynamics
Although the round goby (Neogobius melanostomus) has become established throughout the Laurentian Great Lakes, information is scarce on spatial variation in round goby growth between and within lakes. Based on a sample of 754 specimens captured in 2014, age, growth, and mortality of round gobies at four locations in Lake Huron were assessed via otolith analysis. Total length (TL) of round gobies rNon-USGS Publications**
O’Brien, T. 2003. “Salvelinus confluentus” (On-line), Animal Diversity Web**Disclaimer: The views expressed in Non-USGS publications are those of the author and do not represent the views of the USGS, Department of the Interior, or the U.S. Government.
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