Date of Graduation


Document Type


Degree Type



Davis College of Agriculture, Natural Resources and Design


Wood Science and Technology

Committee Chair

Kyle J. Hartman.


Reliable fish condition estimates are valued by fisheries ecologists and managers. Fish condition is used as an indicator of ecosystem health or to assess the population status for a species of interest. In aquaculture, proximate composition estimates are often wanted because of their relationship to fillet quality. Past researchers have used bioelectrical impedance analysis (BIA) to provide nonlethal mass based estimates of proximate composition for fish. Percent dry weight (PDW) of a fish is highly correlated to proximate composition values and energy density, therefore reliable predictions of PDW would eliminate the need for costly and laboratory analyses lethal to the fish. Past researchers have had limited success predicting percent based estimates of proximate composition using BIA, indicating that improvements in the method are needed. Therefore, objectives were to determine if electrode location influences BIA models, develop methods for small fish, develop temperature corrections for BIA measures, and field validate laboratory derived BIA models. To determine electrode location influence and develop small fish methods, 270 brook trout (50-300 mm TL) had BIA measurements taken at seven different electrode locations. Temperature corrections were developed by sampling 270 fish at three different temperatures (5, 12.5, and 20ºC). Field validation of BIA models was accomplished by sampling brook trout monthly at nine Appalachian Mountain headwater stream sites for an entire year. For adult brook trout, one set of measurements should be taken by placing the electrodes along the dorsal midline of the fish and a second set should be taken at the dorsal to ventral pre dorsal fin location (DTV). For age-0 fish the DTV location should be used in combination with a second set taken at the dorsal total length location. Temperature correction equations were successfully developed and improved model performance. Field validation demonstrated that BIA can provide reliable estimates of mean percent dry weight or energy density but estimates for individual fish were unreliable. The BIA model predictions were able to demonstrate that large changes in adult Appalachian brook trout body condition occurred. These changes were likely related to energy depletion from reproduction and changes in terrestrial invertebrate consumption.