Home user. I have 3 frozen salmon filet / sides in my freezer. Each is 2 to 4 pounds, they have been cleaned, no bones, skin on one side. I bought them like that vacuum sealed. (This is similar to what you see at Costco but frozen and wild caught bla bla fancy.)
We can't can't eat a 4 pound piece in my house in one go. I assume its stupid to defrost, eat half, and re-freeze half due to quality going down.
Should I cut it in half frozen with a bread knife or take my sawz all or some other carpentry tool to it. No j knives obviously.
I cut and break apart all kinds of frozen foods at my house and at work all the time. At home example would be something like cutting a two pound block of frozen ground beef in half or a bag of chicken breasts all in one container in half. You could use a a serrated knife or you could use a cleaver, or possibly just a beefy knife that you don't care about. You can bang foods that are stuck together on the edge of a sink, countertop, or cutting board or even go out in your garage so you don't damage anything in your kitchen. Sounds barbaric but the whole idea of attaining nourishment can be.
Also be careful, it can get a bit dangerous trying to apply a lot of force with a knife to something that doesn't want to give!!!
If it were me I would break out my handy dandy cutco chef knife which is great for this sort of task and just try even downward pressure to start and if that didn't work I might try puncturing the fish in several spots until it breaks apart, which is a bit dangerous as I mentioned. Good luck!!!
A hacksaw w/a clean blade might work pretty well. If you have a sharp, clean hatchet available that might work, but be careful what you put under your product - you don't want to mess up a good cutting board. A good old fashioned heavy cleaver is an option as well.
Hacksaw with a fresh or very carefully cleaned blade. Any my typical knife, even a western cleaver, is an inefficient and more dangerous tool for this. It won't be as clean, of course, but you could trim it up with a knife when you defrost it.