The other option is a smaller size saw (easier to handle in the kitchen). Yes wear clean gloves for the cold and in case you slip. Don't saw directly on the counter of course.
Frozen meat and fish are sawn with a bandsaw in the food service industry. If you can do it with an electric knife, that ́s very admirable. Perhaps a hand saw with relatively fine teeth might do it.
I hope I am not being too obvious here, but the point of cutting off of a frozen carcass is to only cut what is necessary for a meal without defrosting the whole animal which would mean having to cook everything right then and there.
Have never tried to cut frozen fish, but did meat. First begin with a smaller knife, than make a couple of deep cuts with a pointy knife, and then use a huge thick knife (migros cucina & tavola has some).
But I guess you probably have tried something similar If I had a huge board and a small ax, I would have given it a try. The only danger is the fish slipping away - you may again try small cuts first and hope to be precise enough with the ax
Just thaw it the first time. Cut in pieces you need for several dishes. Chuck back in freezer. Problem only arises when you freeze and thaw things regulary. One time is fine. En guete.
By the way, Sam Ali was correct before in saying that fish can be thawed once. Most fish are immediately snap frozen at sea anyway, then thawed for the shops to appear 'fresh'.
If you defrost the frozen fish slowly in the refrigerator overnight, fillet, and re-freeze in snap lock plastic bags, the fish keeps quite well.
Again, surely the fish monger you purchase the fish from will have the equipment available to reduce the size into consumable portions.
.... albeit at an additional cost, it should still be less than the amount you need to fork out on a suitable tool to hack through the equivalent of a block of ice.
JBZ isn't completely off-base. Many foods are much easier to cut when slightly frozen as opposed to deep-frozen or fully thawed. Leave the fish (or chicken, beef, whatever) covered in the fridge for about an hour after you take it from the freezer. It won't thaw completely but just enough that you can do your chopping and then chuck what you don't use back in the freezer. Same goes if you just bought fresh meat. Chuck in the freezer for about 30 minutes until it's slightly frozen and viola! Easier to cut!