Graduate Program

Biological Sciences

Degree Name

Master of Science (MS)

Semester of Degree Completion

2007

Thesis Director

Stephen Mullin

Thesis Committee Member

Scott Meiners

Thesis Committee Member

Charles Pedersen

Abstract

Predatory fish can have devastating effects on populations of amphibians, many of which are already declining around the world. Land managers seeking to restore disturbed woodland ponds to more historically-accurate conditions may consider removing fish, a potentially difficult or costly process. I report on the effects of introduced sunfish (Lepomis spp.) and black bullhead catfish (Ameiurus melas), and their removal, on the reproductive efforts of three species of amphibians: smallmouth salamanders (Ambystoma texanum), American toads (Bufo americanus) and wood frogs (Rana sylvatica). Using drift fences and pitfall traps around four woodland ponds, amphibians were monitored for one year prior to and one year following removal of fish from two ponds (two control ponds never contained fish). Prior to treatment, few adult amphibians entered the pond with sunfish, while more American toads were found in association with the pond with bullhead than at other ponds. Numbers of adult amphibians using ponds did not increase as a result of fish removal. Sunfish decreased amphibian recruitment more severely than bullhead catfish. American toads bred successfully with bullheads, although recruitment of toads increased after removal of the fish. In the year following treatment, recruitment estimates increased in treated ponds for all species examined, but were unchanged in control ponds. Conservationists should consider Lepomis a threat to many native amphibian populations and Ameiurus a threat to some. Removal of predatory fish can be an effective method of improving conditions for some pond-breeding amphibians.

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