Frozen fish

Fish is an excellent source of protein, and efficient freezing processes have enabled fish to be kept fresh and transported to different parts of the world to meet consumer demand. 

MY children love dory fish and I cook it quite often as it is easily available, boneless and relatively cheap compared to other fish. I would like to know if it is healthy to consume so much dori fish. Is it high in bad cholesterol? Also, does deep-frozen fish need to be treated with preservative, especially if they are flown in from a distant country? – Cynthia Lim