Are sword Fish kosher?
No not according to kashrut.com, kosher fish have fins & scales, swordfish have skin rather than scales is the shortest answer, longer answer below:
"The halachic [status] of swordfish (xiphias gladius): it is a non-kosher fish. It has been presented to halachic giants of our generation such as Rabbi Moshe Feinstein and from previous generations such as Rabbi Itzel of Ponovitz, and they have all concluded that it is not kosher.
"The biblical term for scaled kosher fish is 'kaskeses.' Nachmanides comments in Leviticus XI:9 that based on Biblical and Talmudic sources this refers to a type of structure like the nail of a human which can be removed from the skin of the fish by hand or with a knife. But if it be affixed to the skin and not separated therefrom at all (i.e. no free margins), then the bearer of these 'scales' may not be eaten.
"Ichthyologists recognize four types of fish scale. The kosher variety of scales are cycloid (round) and ctenoid (comblike). The ganoid scale found on sturgeon, or the placoid scale of the shark are specifically excluded from the Biblical term kaskeses since they are not 'removable' scales without tearing the skin from the flesh. Even an educated layman would not see any similarity between the heavy bony plates of the sturgeon or the needle-like projections on the shark skin and the classic kosher scale of the whitefish or carp.
What aliwaks said.
The Conservative movement considers swordfish kosher. It would depend on which branch of Judaism you follow.