If I'm not mistaken tuna has Omega 3 which is good for the heart. But I don't know if swordfish have it as well. Tuna is also good source of protein which is good for the body.
Tuna and swordfish, which are huge, maritime fish, can accumulate mercury in its flesh. As indicated by the FDA, the vast majority are not influenced by the low dimensions of mercury in most fish, yet delicate populaces like pregnant ladies and youngsters should limit eating tuna to one serving, or six ounces, every week.
Either you should not eat sowrdfish at all or if you do, make wise and proper consumption else it will result in health consequences. Swordfish contains very high level of mercury and for pregnant lady it is advisable not to eat this fish at all. While seafood is good for health, some of the categories of fishes contain very high concentration of some components and minerals and hence those are not good for health.