Nathaniel (Than) Hitt, PhD (Former Employee)
Science and Products
Filter Total Items: 16
Enabling AI for citizen science in fish ecology
Artificial Intelligence (AI) is revolutionizing ecology and conservation by enabling species recognition from photos and videos. Our project evaluates the capacity to expand AI for individual fish recognition for population assessment. The success of this effort would facilitate fisheries analysis at an unprecedented scale by engaging anglers and citizen scientists in imagery collection...
Changing Freshwater Flows Affect Fish Populations in the Potomac River
Issue: Millions of people rely on the Potomac River for drinking water and recreational opportunities. The Potomac is Maryland’s most popular freshwater fishing destination, and the second largest river that enters the Chesapeake Bay. Restoring fisheries is also an important goal for the Chesapeake Bay Partnership restoration efforts.
Brook Trout Population Responses to Climate Variation Across the Southeast USA
Brook trout are the only native fish from the salmon family in the southeastern United States. Despite their recreational and cultural significance, human activities, such as habitat degradation and introduction of non-native species, have led to serious declines of brook trout populations in the region. Stream temperature and flow alterations from climate change are projected to impact...
Restoring a native fish to Catoctin Mountain Park
Native species conservation is a fundamental purpose of National Parks. Catoctin Mountain Park (CATO) in Maryland supports a prized trout fishery and a healthy community of native fishes, with one exception: native Blue Ridge Sculpin ( Cottus caeruleomentum) appear to have been extirpated from Big Hunting Creek above Cunningham Falls. Infection by a fungal-like protist Dermocystidium is...
Project eTrout—Linking Research and Education with Virtual Reality
In the Chesapeake Bay headwaters, native brook trout are economically and culturally important and require high-quality, cold-water habitats. Project eTrout, led by the U.S. Geological Survey (USGS), explores the use of crowdsourcing and virtual reality (VR) to estimate the abundance of brook trout in headwater streams of the Chesapeake Bay watershed. Project eTrout engages students, anglers, and...
A hydrological framework to improve precision of Vital Signs metrics in the Appalachian highlands
Stream flow is a fundamental driver of ecological structure and function, but its influence on bioassessment measures is poorly understood. Although extreme flow conditions (e.g., floods and droughts) have long been known to play a central role in structuring stream communities, a mechanistic understanding of the linkages between flow variables, landscape and local physical characteristics, and...
Filter Total Items: 21
Stream temperature observations during summer 2021 for sites in the Antietam Creek watershed, Maryland Stream temperature observations during summer 2021 for sites in the Antietam Creek watershed, Maryland
This Data Release contains stream temperature observations for 28 sites in the Antietam Creek Watershed (Maryland) during summer 2021. Data were collected using Onset ProV2 temperature gages within perforated PVC cases attached to stream substrates with rebar. Temperature gages were deployed and retrieved by volunteers with the Antietam-Conococheague Watershed Alliance. Temperature...
Brook trout imagery data for individual recognition with deep learning Brook trout imagery data for individual recognition with deep learning
This Data Release provides imagery data for the development of deep-learning models to recognize individual brook trout (n=435). Images were collected at the Paint Bank State Fish Hatchery (Paint Bank, VA) on August 9, 2021 using a GoPro Hero 9 camera mounted approximately 50 cm above a fish board. The Paint Bank State Fish Hatchery is operated by the Virginia Department of Wildlife...
USGS EcoDrought Stream Discharge, Gage Height, and Water Temperature in Shenandoah National Park, Virginia USGS EcoDrought Stream Discharge, Gage Height, and Water Temperature in Shenandoah National Park, Virginia
The U.S. Geological Survey (USGS) Water Mission Area (WMA) - Ecosystems Mission Area (EMA) EcoDrought project is comprised of interdisciplinary teams in five pilot regions across the country. The over-arching project goal is to measure streamflow in headwater streams and to relate flow variation to stream fish population dynamics. For the catchments located in Shenandoah National Park...
USGS EcoDrought Stream Discharge, Gage Height and Water Temperature Data in Massachusetts (ver. 2.1, August 2025) USGS EcoDrought Stream Discharge, Gage Height and Water Temperature Data in Massachusetts (ver. 2.1, August 2025)
The USGS Water Mission Area (WMA) - Ecosystems Mission Area (EMA) EcoDrought project is comprised of interdisciplinary teams in five pilot regions across the country. The over-arching project goal is to measure streamflow in headwater streams and to relate flow variation to stream fish population dynamics. In the northeast, the New England Water Science Center (NewEngWSC) partnered with...
Stream temperature observations during summer 2021 for sites in the Sleepy Creek watershed, West Virginia Stream temperature observations during summer 2021 for sites in the Sleepy Creek watershed, West Virginia
This Data Release contains stream temperature observations for 10 sites in the Sleepy Creek Watershed (West Virginia) during summer 2021. Data were collected using Onset ProV2 temperature gages within perforated PVC cases attached to stream substrates with rebar. Temperature gages were deployed and retrieved by volunteers with the Sleepy Creek Watershed Association. Temperature records...
Annotated fish imagery data for individual and species recognition with deep learning Annotated fish imagery data for individual and species recognition with deep learning
We provide annotated fish imagery data for use in deep learning models (e.g., convolutional neural networks) for individual and species recognition. For individual recognition models, the dataset consists of annotated .json files of individual brook trout imagery collected at the Eastern Ecological Science Center's Experimental Stream Laboratory. For species recognition models, the...
Filter Total Items: 52
Effects of episodic stream dewatering on brook trout spatial population structure Effects of episodic stream dewatering on brook trout spatial population structure
Stream dewatering is expected to become more prevalent due to climate change, and we explored the potential consequences for brook trout (Salvelinus fontinalis) within a temperate forest ecosystem in eastern North America.We estimated fish density within stream pools (n = 386) from electrofishing surveys over 10 years (2012–2021) to compare a stream that exhibits episodic dewatering...
Authors
Nathaniel P. Hitt, Karli M. Rogers, Karmann G. Kessler, Martin A. Briggs, Jennifer H. Fair, Andrew C. Dolloff
Strong variation in Brook Trout trends across geology, elevation, and stream size in Shenandoah National Park Strong variation in Brook Trout trends across geology, elevation, and stream size in Shenandoah National Park
Objective Landscape context structures fish abundance and dynamics, and understanding trends in fish abundance across the landscape is often prerequisite for effective conservation. In this study, we evaluated the status and trends of Brook Trout Salvelinus fontinalis in Shenandoah National Park to understand how these are structured across bedrock geology, elevation, and stream size...
Authors
Evan S. Childress, David E Demarest, John E.B. Wofford, Nathaniel P. Hitt, Benjamin Letcher
Aging contrast: A contrastive learning framework for fish re-identification across seasons and years. Aging contrast: A contrastive learning framework for fish re-identification across seasons and years.
The fields of biology, ecology, and fisheries management are witnessing a growing demand for distinguishing individual fish. In recent years, deep learning methods have emerged as a promising tool for image-based fish recognition. Our study is focused on the re-identification of masu salmon from Japan, wherein fish were individually marked and photographed to evaluate discriminative body
Authors
Weili Shi, Z. Zhou, Benjamin Letcher, Nathaniel P. Hitt, Yoichiro Kanno, R. Futamura, O. Kishida, K. Morita, Sheng Li
Spatial asynchrony and cross-scale climate interactions in populations of a coldwater stream fish Spatial asynchrony and cross-scale climate interactions in populations of a coldwater stream fish
Climate change affects populations over broad geographic ranges due to spatially autocorrelated abiotic conditions known as the Moran effect. However, populations do not always respond to broad-scale environmental changes synchronously across a landscape. We combined multiple datasets for a retrospective analysis of time-series count data (5–28 annual samples per segment) at 144 stream...
Authors
George Valentine, Xinyi Lu, Evan S. Childress, C. Andrew Dolloff, Nathaniel P. Hitt, Matthew Kulp, Benjamin Letcher, Kasey C. Pregler, Jacob Rash, Mevin B. Hooten, Yoichiro Kanno
Karst terrain promotes thermal resiliency in headwater streams Karst terrain promotes thermal resiliency in headwater streams
The response of stream ecosystems to climate change will depend in part on groundwater processes that reduce the sensitivity of streams to atmospheric conditions. We investigated the thermal sensitivity of streams across a gradient of groundwater inputs defined by karst terrain (carbonate parent materials) in the headwaters of the Potomac River basin in eastern North America. We...
Authors
Karmann G. Kessler, Karli M. Rogers, Charles Marshak, Nathaniel P. Hitt
Stabilising effects of karstic groundwater on stream fish communities Stabilising effects of karstic groundwater on stream fish communities
Although groundwater exchange processes are known to modulate atmospheric influences on stream temperature and flow, the implications for ecological stability are poorly understood. Here, we evaluated temporal change in stream fish communities across a gradient of groundwater influence defined by karst terrain (carbonate parent materials) within the Potomac River basin of eastern North...
Authors
Nathaniel P. Hitt, Karli M. Rogers, Karmann G. Kessler, Martin A. Briggs, Jennifer H. Fair
Non-USGS Publications**
Hitt, N.P. and M. Hendryx. 2010. Ecological integrity of streams linked to human cancer mortality rates. EcoHealth 7:91-104.
Hitt, N.P. and P.L. Angermeier. 2008. River-stream connectivity affects fish bioassessment performance. Environmental Management 42:132-150.
Hitt, N.P. and P.L. Angermeier. 2008. Evidence for fish dispersal from spatial analysis of stream network topology. Journal of the North American Benthological Society 27:304-320.
Hitt, N.P. and B.R. Murphy. 2007. An inquiry-based case study for conservation biology. Journal of Virginia Science Education 2:43-50.
Hitt, N.P. and P.L. Angermeier. 2006. Effects of adjacent streams on local fish assemblage structure in western Virginia: implications for biomonitoring. American Fisheries Society Symposium 48:75-86.
Vignieri, S.N., E.M. Hallerman, B.J. Bergstrom, D.J. Hafner, A.P. Martin, P. Devers, P. Grobler and N.P. Hitt. 2006. Mistaken view of taxonomy undermines conservation of an evolutionarily distinct mouse: a response to Ramey et al. Journal of Animal Conservation 9:237-243.
Allendorf, F.W., R. Leary, N.P. Hitt, K. Knudsen, M. Boyer and P. Spruell. 2005. Cutthroat trout hybridization and the U.S. Endangered Species Act: one species, two policies. Conservation Biology 19:1326-1328.
Hitt, N.P. and C.A. Frissell. 2004. A case study of surrogate species in aquatic conservation planning. Aquatic Conservation: Marine and Freshwater Ecosystems 14:625-633.
Allendorf, F.W., R. Leary, N.P. Hitt, K. Knudsen, L. Lundquist, and P. Spruell. 2004. Intercrosses and the U.S. Endangered Species Act: should hybridized populations be included as westslope cutthroat trout? Conservation Biology 18: 1203-1213.
Hitt, N.P., C.A. Frissell, C.C. Muhlfeld and F.W. Allendorf. 2003. Spread of hybridization between native westslope cutthroat trout, Oncorhynchus clarki lewisi, and non-native rainbow trout, O. mykiss. Canadian Journal of Fisheries and Aquatic Sciences 60:1440-1451.
Hitt, N.P. 2003. Immediate effects of wildfire on stream temperature. Journal of Freshwater Ecology 18:171-173.
**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.
Science and Products
Filter Total Items: 16
Enabling AI for citizen science in fish ecology
Artificial Intelligence (AI) is revolutionizing ecology and conservation by enabling species recognition from photos and videos. Our project evaluates the capacity to expand AI for individual fish recognition for population assessment. The success of this effort would facilitate fisheries analysis at an unprecedented scale by engaging anglers and citizen scientists in imagery collection...
Changing Freshwater Flows Affect Fish Populations in the Potomac River
Issue: Millions of people rely on the Potomac River for drinking water and recreational opportunities. The Potomac is Maryland’s most popular freshwater fishing destination, and the second largest river that enters the Chesapeake Bay. Restoring fisheries is also an important goal for the Chesapeake Bay Partnership restoration efforts.
Brook Trout Population Responses to Climate Variation Across the Southeast USA
Brook trout are the only native fish from the salmon family in the southeastern United States. Despite their recreational and cultural significance, human activities, such as habitat degradation and introduction of non-native species, have led to serious declines of brook trout populations in the region. Stream temperature and flow alterations from climate change are projected to impact...
Restoring a native fish to Catoctin Mountain Park
Native species conservation is a fundamental purpose of National Parks. Catoctin Mountain Park (CATO) in Maryland supports a prized trout fishery and a healthy community of native fishes, with one exception: native Blue Ridge Sculpin ( Cottus caeruleomentum) appear to have been extirpated from Big Hunting Creek above Cunningham Falls. Infection by a fungal-like protist Dermocystidium is...
Project eTrout—Linking Research and Education with Virtual Reality
In the Chesapeake Bay headwaters, native brook trout are economically and culturally important and require high-quality, cold-water habitats. Project eTrout, led by the U.S. Geological Survey (USGS), explores the use of crowdsourcing and virtual reality (VR) to estimate the abundance of brook trout in headwater streams of the Chesapeake Bay watershed. Project eTrout engages students, anglers, and...
A hydrological framework to improve precision of Vital Signs metrics in the Appalachian highlands
Stream flow is a fundamental driver of ecological structure and function, but its influence on bioassessment measures is poorly understood. Although extreme flow conditions (e.g., floods and droughts) have long been known to play a central role in structuring stream communities, a mechanistic understanding of the linkages between flow variables, landscape and local physical characteristics, and...
Filter Total Items: 21
Stream temperature observations during summer 2021 for sites in the Antietam Creek watershed, Maryland Stream temperature observations during summer 2021 for sites in the Antietam Creek watershed, Maryland
This Data Release contains stream temperature observations for 28 sites in the Antietam Creek Watershed (Maryland) during summer 2021. Data were collected using Onset ProV2 temperature gages within perforated PVC cases attached to stream substrates with rebar. Temperature gages were deployed and retrieved by volunteers with the Antietam-Conococheague Watershed Alliance. Temperature...
Brook trout imagery data for individual recognition with deep learning Brook trout imagery data for individual recognition with deep learning
This Data Release provides imagery data for the development of deep-learning models to recognize individual brook trout (n=435). Images were collected at the Paint Bank State Fish Hatchery (Paint Bank, VA) on August 9, 2021 using a GoPro Hero 9 camera mounted approximately 50 cm above a fish board. The Paint Bank State Fish Hatchery is operated by the Virginia Department of Wildlife...
USGS EcoDrought Stream Discharge, Gage Height, and Water Temperature in Shenandoah National Park, Virginia USGS EcoDrought Stream Discharge, Gage Height, and Water Temperature in Shenandoah National Park, Virginia
The U.S. Geological Survey (USGS) Water Mission Area (WMA) - Ecosystems Mission Area (EMA) EcoDrought project is comprised of interdisciplinary teams in five pilot regions across the country. The over-arching project goal is to measure streamflow in headwater streams and to relate flow variation to stream fish population dynamics. For the catchments located in Shenandoah National Park...
USGS EcoDrought Stream Discharge, Gage Height and Water Temperature Data in Massachusetts (ver. 2.1, August 2025) USGS EcoDrought Stream Discharge, Gage Height and Water Temperature Data in Massachusetts (ver. 2.1, August 2025)
The USGS Water Mission Area (WMA) - Ecosystems Mission Area (EMA) EcoDrought project is comprised of interdisciplinary teams in five pilot regions across the country. The over-arching project goal is to measure streamflow in headwater streams and to relate flow variation to stream fish population dynamics. In the northeast, the New England Water Science Center (NewEngWSC) partnered with...
Stream temperature observations during summer 2021 for sites in the Sleepy Creek watershed, West Virginia Stream temperature observations during summer 2021 for sites in the Sleepy Creek watershed, West Virginia
This Data Release contains stream temperature observations for 10 sites in the Sleepy Creek Watershed (West Virginia) during summer 2021. Data were collected using Onset ProV2 temperature gages within perforated PVC cases attached to stream substrates with rebar. Temperature gages were deployed and retrieved by volunteers with the Sleepy Creek Watershed Association. Temperature records...
Annotated fish imagery data for individual and species recognition with deep learning Annotated fish imagery data for individual and species recognition with deep learning
We provide annotated fish imagery data for use in deep learning models (e.g., convolutional neural networks) for individual and species recognition. For individual recognition models, the dataset consists of annotated .json files of individual brook trout imagery collected at the Eastern Ecological Science Center's Experimental Stream Laboratory. For species recognition models, the...
Filter Total Items: 52
Effects of episodic stream dewatering on brook trout spatial population structure Effects of episodic stream dewatering on brook trout spatial population structure
Stream dewatering is expected to become more prevalent due to climate change, and we explored the potential consequences for brook trout (Salvelinus fontinalis) within a temperate forest ecosystem in eastern North America.We estimated fish density within stream pools (n = 386) from electrofishing surveys over 10 years (2012–2021) to compare a stream that exhibits episodic dewatering...
Authors
Nathaniel P. Hitt, Karli M. Rogers, Karmann G. Kessler, Martin A. Briggs, Jennifer H. Fair, Andrew C. Dolloff
Strong variation in Brook Trout trends across geology, elevation, and stream size in Shenandoah National Park Strong variation in Brook Trout trends across geology, elevation, and stream size in Shenandoah National Park
Objective Landscape context structures fish abundance and dynamics, and understanding trends in fish abundance across the landscape is often prerequisite for effective conservation. In this study, we evaluated the status and trends of Brook Trout Salvelinus fontinalis in Shenandoah National Park to understand how these are structured across bedrock geology, elevation, and stream size...
Authors
Evan S. Childress, David E Demarest, John E.B. Wofford, Nathaniel P. Hitt, Benjamin Letcher
Aging contrast: A contrastive learning framework for fish re-identification across seasons and years. Aging contrast: A contrastive learning framework for fish re-identification across seasons and years.
The fields of biology, ecology, and fisheries management are witnessing a growing demand for distinguishing individual fish. In recent years, deep learning methods have emerged as a promising tool for image-based fish recognition. Our study is focused on the re-identification of masu salmon from Japan, wherein fish were individually marked and photographed to evaluate discriminative body
Authors
Weili Shi, Z. Zhou, Benjamin Letcher, Nathaniel P. Hitt, Yoichiro Kanno, R. Futamura, O. Kishida, K. Morita, Sheng Li
Spatial asynchrony and cross-scale climate interactions in populations of a coldwater stream fish Spatial asynchrony and cross-scale climate interactions in populations of a coldwater stream fish
Climate change affects populations over broad geographic ranges due to spatially autocorrelated abiotic conditions known as the Moran effect. However, populations do not always respond to broad-scale environmental changes synchronously across a landscape. We combined multiple datasets for a retrospective analysis of time-series count data (5–28 annual samples per segment) at 144 stream...
Authors
George Valentine, Xinyi Lu, Evan S. Childress, C. Andrew Dolloff, Nathaniel P. Hitt, Matthew Kulp, Benjamin Letcher, Kasey C. Pregler, Jacob Rash, Mevin B. Hooten, Yoichiro Kanno
Karst terrain promotes thermal resiliency in headwater streams Karst terrain promotes thermal resiliency in headwater streams
The response of stream ecosystems to climate change will depend in part on groundwater processes that reduce the sensitivity of streams to atmospheric conditions. We investigated the thermal sensitivity of streams across a gradient of groundwater inputs defined by karst terrain (carbonate parent materials) in the headwaters of the Potomac River basin in eastern North America. We...
Authors
Karmann G. Kessler, Karli M. Rogers, Charles Marshak, Nathaniel P. Hitt
Stabilising effects of karstic groundwater on stream fish communities Stabilising effects of karstic groundwater on stream fish communities
Although groundwater exchange processes are known to modulate atmospheric influences on stream temperature and flow, the implications for ecological stability are poorly understood. Here, we evaluated temporal change in stream fish communities across a gradient of groundwater influence defined by karst terrain (carbonate parent materials) within the Potomac River basin of eastern North...
Authors
Nathaniel P. Hitt, Karli M. Rogers, Karmann G. Kessler, Martin A. Briggs, Jennifer H. Fair
Non-USGS Publications**
Hitt, N.P. and M. Hendryx. 2010. Ecological integrity of streams linked to human cancer mortality rates. EcoHealth 7:91-104.
Hitt, N.P. and P.L. Angermeier. 2008. River-stream connectivity affects fish bioassessment performance. Environmental Management 42:132-150.
Hitt, N.P. and P.L. Angermeier. 2008. Evidence for fish dispersal from spatial analysis of stream network topology. Journal of the North American Benthological Society 27:304-320.
Hitt, N.P. and B.R. Murphy. 2007. An inquiry-based case study for conservation biology. Journal of Virginia Science Education 2:43-50.
Hitt, N.P. and P.L. Angermeier. 2006. Effects of adjacent streams on local fish assemblage structure in western Virginia: implications for biomonitoring. American Fisheries Society Symposium 48:75-86.
Vignieri, S.N., E.M. Hallerman, B.J. Bergstrom, D.J. Hafner, A.P. Martin, P. Devers, P. Grobler and N.P. Hitt. 2006. Mistaken view of taxonomy undermines conservation of an evolutionarily distinct mouse: a response to Ramey et al. Journal of Animal Conservation 9:237-243.
Allendorf, F.W., R. Leary, N.P. Hitt, K. Knudsen, M. Boyer and P. Spruell. 2005. Cutthroat trout hybridization and the U.S. Endangered Species Act: one species, two policies. Conservation Biology 19:1326-1328.
Hitt, N.P. and C.A. Frissell. 2004. A case study of surrogate species in aquatic conservation planning. Aquatic Conservation: Marine and Freshwater Ecosystems 14:625-633.
Allendorf, F.W., R. Leary, N.P. Hitt, K. Knudsen, L. Lundquist, and P. Spruell. 2004. Intercrosses and the U.S. Endangered Species Act: should hybridized populations be included as westslope cutthroat trout? Conservation Biology 18: 1203-1213.
Hitt, N.P., C.A. Frissell, C.C. Muhlfeld and F.W. Allendorf. 2003. Spread of hybridization between native westslope cutthroat trout, Oncorhynchus clarki lewisi, and non-native rainbow trout, O. mykiss. Canadian Journal of Fisheries and Aquatic Sciences 60:1440-1451.
Hitt, N.P. 2003. Immediate effects of wildfire on stream temperature. Journal of Freshwater Ecology 18:171-173.
**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.