The premier knife for those slicing is the Yanagiba. It's a single bevel knife with a concave interior finish meaning the steel barely touches the flesh of the fish.
Yanagibas are made in 30cm increments - starting around 180 working right up to 360cm - the ultimate (maybe only) knife for massive tuna slicing. We are starting with one at the low end of size (I'm a terrible fisherman!)