First Sushi - I can't see that it's tremendously high in calories re the rice - there's only a teaspoon or so in each portion - like most things though - the simple answer is 'it depends how many you eat!'
The prawns - I've not come across a sushi recipe that uses raw prawn, but that doesn't mean to say that they don't exist - the Japanese eat raw fish frequently but I don't know about prawns.
Salmon - it depends what you're catering for.
If you're catering for a buffet with a lot of people, then a whole salmon is best I would say -
if it's for a dinner party - then one fillet or steak per portion.
Do you mean wild or farmed?
Wild has a superior texture because it builds muscle swimming with natural currents - farmed is a little flabbier and tends to have the brown bits close to the skin which are not always nice to eat/or nice in texture.
Once again - it will depend on what you intend to do with it - if it's going to be plainly served, then you can tell the difference between wild and farmed and I would choose wild if I could get it or afford it.
If your salmon is going to be dressed with sauces then I would not necessarily spend a lot more to get wild - if it was just a little bit more in cost, then I would - if it was twice as much again, then I wouldn't.
Hope that makes sense - the questions have been very wide - if you want further information then please ask.
If anybody else wants to come in with some comment/opinion - please do so.
