Feb 18 (Reuters) - Wall Street’s main indexes opened lower on Thursday as investors resumed a shift out of big technology firms, while an unexpected rise in weekly jobless claims underscored a fragile labor market recovery. The Dow Jones Industrial Average fell 54.4 points, or 0.17%, at the open to 31558.6. The S&P 500 fell 15.5 points, or 0.39%, at the open to 3915.86, while the Nasdaq Composite dropped 150.8 points, or 1.08%, to 13814.666 at the opening bell. (Reporting by Devik Jain in Bengaluru; Editing by Anil D’Silva)