Browsing by Author "Chan, Matthew D."
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- Fish ecomorphology: predicting habitat preferences of stream fishes from their body shapeChan, Matthew D. (Virginia Tech, 2001-03-24)This research tested the ability of fish morphology to predict membership of fishes in habitat guilds, their swimming performance, and habitat preference. Further, it considered methods for choosing a surrogate species to identify habitat of target species. Morphological discriminant functions were developed using morphological traits of fishes from one river to identify membership in two habitat guild systems (mesohabitat and microhabitat). Functions were then used to test factors influencing classification success of holdout tests and validated using fishes of a second river. Morphology was only partly successful (50%) at predicting membership in habitat guilds. Morphology identified species by shape, i.e., classifying test species into guilds with members of their genus, but not habitat use, because morphology and habitat were not strongly linked through function. By improving guild definition, relationships between morphology and habitat (Froude number) were identified for all fish groups examined (darters, benthic minnows, pelagic minnows, and suckers). Relationships were not transferable among groups. Further, morphology of eight minnows was linked to swimming performance, a key task for using habitat, in lab measurements of critical swimming speeds. In turn, swimming performance was related to habitat (Froude number). Morphology will be most successful at predicting habitat use of fishes when (1) more, discrete guilds are used, (2) guilds are identified within families, (3) variation in lifestyles (benthic vs. pelagic) is considered, and (4) key tasks related to using habitat are strongly associated with morphology. Finally, I examined a phylogenetic approach to identifying useable habitat. Closely related surrogate species were not more accurate in identifying habitat of target species than surrogates chosen by other methods. When a target species used only one mesohabitat, the highest overlap in habitat use occurred with other fishes of the same family using that mesohabitat (within a physiographic province). For target species using several mesohabitat types, surrogates from the next highest taxonomic unit, e.g., genus or subgenus, provided the most accurate information. Ecomorphology offers a mechanistic and defensible method for identifying habitat preferences of fishes and should be more widely considered as a tool for establishing habitat relationships of stream fishes.
- Stream Habitat Modeling to Support Water Management Decisions for the North Fork Shenandoah River, VirginiaAverett, Adrienne W.; Persinger, Jason; Chan, Matthew D.; Lozinski, Jennifer L.; Orth, Donald J. (Virginia Tech, 2004-12)This four-year instream flow study was initiated to evaluate the hydraulics, habitat, and water quality of the North Fork Shenandoah River, Virginia, during low flow conditions. Virginia Tech in cooperation with the United States Geological Survey (USGS) collected hydraulic, fish habitat, and water quality data throughout the basin during periods of extreme drought in 1999 and 2002. This report summarizes the cumulative results, hydraulic, fish habitat, and water quality conditions in the North Fork Shenandoah River (NFSR). These results were used to establish a stepwise process for implementing aquatic conservation flow management in the NFSR basin and facilitate water use conservation measures at appropriate times during extreme droughts of the future. We applied the Instream Flow Incremental Methodology to provide a comparison of usable habitat conditions under baseline and alternative hydrologic time series corresponding to water use restrictions. Six study sites (with a total of 36 transects) were selected to characterize the mesohabitats (riffle, run, pool, and pocket run) of the entire river. Aquatic conservation thresholds were developed for three river reaches and were directly related to three long-term gauging stations: Cootes Store (mile 92 in Rockingham County), Mount Jackson (mile 70 in Shenandoah County), and Strasburg (mile 10 in Warren County).