STOCK prices opened slightly lower yesterday in light trading on the New York Stock Exchange, pressured by weak bond prices. The Dow Jones industrial average, which slipped 6.15 points on Monday, was down shortly after the market opened. Prices also headed slightly lower on the American Stock Exchange and the Nasdaq Stock Market. Treasury securities headed lower, while the US dollar was mixed. The bellwether 30-year Treasury bond, which rose on Monday to yield 6.23 per cent, was down. Analysts said pressure from weak bond prices was the main reason Wall Street opened slightly lower. They said stocks could again follow the lead of the bond market, whose focus was expected to shift from oil to economic news. Stocks closed modestly lower on Monday after an oil-induced bond rally lost power in late trading and set off computer-guided sell programs that erased early gains. They said that with several other key US economic reports due out this week, most professional players were unwilling to make any large bets, leaving the dollar trading in narrow ranges.