Everything you always wanted to know and more about northern snakehead, they do eat carp. There are several types of snakehead, we have some in my neighborhood, but something else must keep them in check as they don't seem to pose a problem. A snakehead population was introduced into a resevoir in Singapore for fishing and failed to provide enough sport so the fishery introduced peacock bass whiched turned out to very popular with the fishermen but, not so with the snakehead, apparently the peacock like the taste.
http://nas.er.usgs.gov/taxgroup/fish/northernsnakeheaddistribution.asp
http://www.dnr.state.md.us/irc/ssap_report.html
http://fisc.er.usgs.gov/Snakehead_circ_1251/html/channa_argus.html

1/4 & 3/4 acre ponds. A thousand miles from no where and there is no place I want to be...
Dwight Yoakam