A swordfish is not considered kosher food. The Torah says a fish must have fins and scales to be kosher. Only fish that have visible scales that can be easily removed are considered kosher, and swordfish do not meet this requirement.
An adult swordfish has no scales. However, when the fish is young, it does have visible scales. It is an accepted rule that this does not make the fish kosher. Conversely, a fish that acquires its scales later in life may be eaten at any point, even at the stage with no scales. The entire fish does not need to be covered in scales to be considered kosher.