Tokyo stocks opened mixed Friday as bargain-hunting a day after the Nikkei fell to a three-week low was offset by selling amid caution ahead of the release of U.S. employment data later in the day. In the first 15 minutes of trading, the 225-issue Nikkei Stock Average rose 53.49 points, or 0.15 percent, from Thursday to 36,710.58. The broader Topix index was down 5.26 points, or 0.20 percent, at 2,615.50. On the top-tier Prime Market, gainers were led by electric power and gas, and construction issues, while iron and steel, and electric appliance issues led decliners. The U.S. dollar hit a one…