A 37-year-old man was found dead in the Fens yesterday afternoon, but authorities said there does not appear to be signs of foul play.The man was identified by police, but his name was not released.Suffolk District Attorney Daniel F. Conley’s office said the victim had no fixed address. He was discovered by a passer-by who called 911 to report an “unresponsive person” about 2:30 p.m.