A few miles outside this college town, down a gravel road that runs through rolling woodlands, Rex Dunham has turned a set of muddy ponds into a high-security prison for fish.
Electric wire keeps the raccoons at bay.
Netting blocks the herons from swooping in. Filters stop the fish from slipping out with the waste water. Federal officials asked Dunham to protect the local environment from the catfish he grows here because nothing like them has ever cut the waters of the Earth. That could help farmers feed more people for less money and boost efforts to end world hunger. But there also is a chance that fast-growing fish might touch off an environmental disaster, according to scientists who have studied the matter.