A New Zealand aquaculture company last week dropped its test program for breeding genetically modified chinook salmon and said it will kill and bury all the experimental fish, in the wake of government and public concerns that the fish, some of which were deformed, could escape into the wild and breed with native strains. The company successfully introduced an extra growth hormone gene into salmon, enabling it to grow chinook of up to 550 pounds, five times larger than the maximum size of wild chinook salmon. Opponents of the project have fought for more than a year to stop it after leaked secret papers from the company indicated that some of the salmon had deformed heads and other abnormalities. In the U.S., a number of activists share similar concerns that genetically modified fish could escape from their pens and wreck havoc by breeding with wild stocks.