The Bombay Stock Exchange Sensex declined by over 161 points in opening trade today amid a weakening trend on other Asian bourses and heightened worries over the euro zone debt crisis. The 30-share Sensex, which gained over 463 points in the previous three sessions, fell to 16,772 in opening trade today, with capital goods and banking stocks leading the fall. In a similar fashion, the wide-based National Stock Exchange Nifty shed 42 points, to 5,042.