Is it permissible for me to shorten the prayer when working at sea for two consecutive months?

If the questioner is a sailor on a seagoing ship, he is permitted to shorten the four-rak'ah prayers and to break the fast in Ramadan (definition), and so forth, if the travel distance is 83 kilometers and his journey is permissible, unless he is a resident on the ship. However, if he works in a stable location, such as offshore oil fields, and intends to reside there for more than four days, then he must perform the prayers in full and is not permitted the concessions of travel, because he is then considered a resident.