Brian G. Gall

Date of Graduation

Summer 2008


Master of Science in Biology



Committee Chair

Alicia Mathis


The introduction of nonnative fishes often results in the local extinction of native amphibians due to a lack of evolutionary history and therefore, minimally-adapted antipredator behaviors toward the introduced fishes. Populations of hellbenders (Cryptobranchus alleganiensis) in Missouri have declined considerably since the 1980's, coinciding with a rapid increase in trout introductions for recreational angling. I examined hellbender and fish predator-prey interactions by: (1) examining the foraging behavior of predatory fishes in response to a hellbender secretion; (2) comparing the number of secretion and control-soaked food pellets consumed by trout; and (3) comparing the response of larval hellbenders to chemical stimuli from introduced (trout) and native fish predators. Brown trout, walleye and large banded sculpin respond to hellbender secretions with increased activity while small banded sculpin responded by decreasing activity. In addition, brown trout ingested more hellbender secretion-soaked food pellets than control pellets, while rainbow trout expelled secretion-soaked food pellets. Finally, larval hellbenders exhibited weak fright behavior in response to chemical stimuli from nonnative trout relative to their responses to native predatory fish stimuli. These combinations of responses indicate that predation by nonnative fishes may be a plausible hypothesis for the decline of hellbender populations in Missouri.


Predator-prey interactions; Amphibian declines; Introduced trout; Cryptobranchus alleganiensis; hellbender

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