Donald Orth

Donald J. Orth,
Thomas Jones Professor


Ph.D., Oklahoma State University, 1980 
M.S., Oklahoma State University, 1977 
B.S., Eastern Illinois University, 1975

Teaching Portfolio
Stream Habitat Management Blog
Ichthyology Blog
Ichthyology Class on Flickr 

Office: 106D Cheatham Hall
Phone: (540) 231-5919

Department of Fish and Wildlife Conservation
310 West Campus Drive
Virginia Tech, Cheatham Hall, Room 106 (MC 0321)
Blacksburg, VA 24061


I investigate the habitats used by fishes in streams and rivers and develop protocols or habitat suitability criteria for maintaining sustainable populations in the face of various human modifications, such as water withdrawals and habitat modifications.   I also study ecological drivers that influence fish population dynamics and develop and evaluate a variety of instream flow assessment methods in order to derive environmental flows for sustainability.     Finally, I investigate trophic connections between the various food web components to assist in the development of ecosystem based management.

Courses Taught:

  • NR 1234 First Year Experience in Natural Resources and Environment

  • FiW 4424 Ichthyology

  • FiW 5814 Stream Habitat Management

Current Research Projects:

Dynamics and Role of Blue Catfish Ictalurus furcatus in Tidal Rivers of Virginia (Virginia Department of Game and Inland Fisheries, 2012-2016)

Blue catfish were stocked in tidal rivers of Virginia, rapidly expanded and now  support commercial and recreational fisheries in these waters.  White catfish Ameirus catus the only native catfish in Atlantic slope streams have been greatly reduced.  Effective management of fisheries in tidal rivers of Chesapeake Bay depends on reducing uncertainty regarding population trends of blue catfish in each tidal river, and their potential effects on other species.  In this study we (1) conduct a multi-year, multi-river sampling program to quantify prey consumption by blue catfish, (2) develop hierarchical demographic models to predict exploitation and population trends of blue catfish, and (3) apply the model to inform managers of efficacy of proposed control strategies. 

Quantifying the trophic impact of non-native blue catfish in Virginia’s tidal rivers. (Virginia Sea Grant, 2015-2018)

There are no valid methods for estimating the consumption by Blue Catfish per day, per year, or over a lifetime.   Our objectives are: 1) estimate prey consumption by non-native blue catfish Ictalurus furcatus in Virginia’s tidal rivers as it varies by river, season, and year. 2) Estimate daily ration and metabolic rates as they change with temperature, prey type, and fish size. This information can then be integrated with food habits data to quantify gravimetric consumption of important species including river herring, American shad, and blue crab. 3) Explore potential competition between native white catfish Ameirus catus and non-native blue catfish through the development of diet overlap indices

Distribution of Chrosomus dace with respect to status of Clinch Dace Chrosomus sp. cf. saylori in the Upper Clinch River    (Virginia Department of Game and Inland Fisheries, 2013-2016)

Clinch Dace (Chrosomus sp. cf. saylori), an undescribed species, was discovered in 1999 and based on status surveys it may be one of the rarest fish species in the United States, occurring in only two Virginia counties.   Populations are small and separated by large distances of unfavorable habitat.   Our research questions are threefold.  1. What is the species’ current distribution? 2. Which sampling gear is best to monitor and survey for populations and are habitat conditions correlated to site occupancy? 3. Is eDNA sampling feasible for Clinch Dace?

Development of environmental DNA protocols for detecting occurrence of imperiled daces (genus Chrosomus) in Virginia   (Virginia Department of Game and Inland Fisheries, 2013-2015)

Environmental DNA shows promise in surveying potential new locations of rare or invasive fish.   The study will evaluate alternative primer for amplifying DNA from water samples.  Screening of different molecular markers will continue until we determine markers specific enough for the purpose of detecting presence of Clinch dace without risk of false positives. 

Select Recent Publications:


Last updated July, 2016