Just FYI:
Sushi is pressed rice. That's ALL it means. It can be seasoned or left plain. If seasoned, it will be either with a bit of salt, or a vinegar/sugar syrup - both help keep the rice from spoiling on hot days.
There are no rules for fillings or toppings. Leftover ham or grilled chicken? A slice or two of steak? Feel free to use it up! Grilled eggplant, lightly brushed with miso, is a wonderful filling when rolled up with rice in a sheet of nori (seaweed, toasted or not, as preferred). Carrots - cucumber - asparagus; anything goes.
Sashimi is raw fish. All sushi-grade fish brought into this country must be frozen for 3-7 days to kill parasites. A properly flash-frozen fish is virtually indistinguishable from fresh-caught. The best fish is processed right on the boat that catches it; these are huge trawlers, not a friend's 16-footer.
It is a mistake to think that freshly-caught means "free of parasites". That is not true. However, most parasites in fish, especially fresh-water fish, are not fatal to eat.
You should always check regularly with your state water authorities to find out how clean that lake really is. Water quality is not a static thing.
There are two kinds of "wasabi". The cheap kind is the bright green, smooth paste. That's reconstituted from canned powder and is mostly horseradish and/or mustard powder.
The real wasabi root is very expensive. It will be finely grated - a soft heap. The color is green but not quite so neon as the powdered paste. True wasabi has a lovely floral fragrance and just a hint of bite, but without harshness. It is quite unlike the paste, and will usually be charged for separately, if it's available at all.