Maine Maritime Academy’s graduation rate is about half of what officials want it to be and is lower than many other Maine colleges, a dip that may be related to ongoing fallout from the pandemic. Only 34% of students who started at the public Castine college in the fall of 2019 graduated within four years, and 39% had a degree within six, according to numbers shared at its board of trustees meeting this month. The academy’s goal is for at least …