Date of Graduation

Spring 2019


Master of Science in Biology



Committee Chair

Alicia Mathis


hellbender, Cryptobranchus, electrofishing, conservation, behavior, stress

Subject Categories



Electrofishing, a common method of freshwater fish sampling, has been shown to negatively affect some fish species, but the effects on non-target species, such as hellbenders, have not been well studied. I tested effects of electrofishing on the behavior of several life stages of captivereared Ozark (Cryptobranchus alleganiensis bishopi) and eastern (C. a. alleganiensis) hellbenders. Ozark hellbender eggs were exposed to different voltages in the laboratory, and embryos in higher voltages had higher incidences of twitching during exposures and higher numbers of morphological deformities after exposures. For hatchling Ozark hellbenders, which typically are sedentary, individuals moved more during exposure to higher voltages. Freeswimming larval eastern hellbenders were less active and spent more time twitching and immobilized during exposure to higher voltages. Immediately after exposures, larvae in the higher treatment groups were less active. Ozark hellbenders (~ 3-years old) exhibited a greater incidence of stress secretions, twitching, and immobilization during exposure to higher voltages. After exposures, they had lower righting reflex scores and longer latencies to right. Eastern hellbenders (~ 6-years old) were tested in both laboratory trials and in a natural river habitat. In laboratory trials, during exposure to higher voltages, individuals had greater incidences of stress secretions and spent more time twitching and immobilized. Following exposures to higher voltages, they had longer latencies to right and faster heartrates. During a double-shocking experiment, 6-year old eastern hellbenders spent more time twitching in the first shocking event and tended to spend more time immobilized in the second shocking event although this difference was not significant; latencies to secrete were longer in the second shocking event. In the river trials, shocked 6-year old had a higher incidence of stress secretions than controls. No behavioral differences appeared to persist after 3–5 months. Under the conditions of our experiments, exposure to voltages similar to those experienced during electrofishing caused at least short-term negative effects on hellbender behavior.


© Stephanie Kay Morrison

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