Conibear 110's work very well for muskrat removal.

Not only will they hurt the dam if they burrow into it, in a year or 2 the banks around the pond where they burrowed into to make a home will start to collapse, leaving you with good sized depressions that twist ankles and make cutting the grass interesting.

www.hoosierpondpros.com

[Linked Image from lh6.ggpht.com]
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3/4 to 1 1/4 ac pond LMB, SMB, PS, BG, RES, CC, YP, Bardello BG, (RBT & Blue Tilapia - seasonal).