All swordfish have the same gender and can mate with any other swordfish. Swordfish have an extra sense that can tell which way north is. Swordfish will attempt to mate with fish that have artificial "swords" attached to them. Swordfish don't have scales.
In f2p you can only find swordfish on karajma. to go there go to port sarim and look around the docks for people in blue and talk to them. on of them should offer to take you to karajma for 30gp. be warned it costs 30gp to get back aswell.