I've ordered every single raw fish dish I came across -- all for the sake of research. It's a tough job, but someone's got to do it. Here are some trends that I noticed and my thoroughly opinionated comments.
Moroccan Lemon is the New Soy Sauce
At least half of the raw fish dishes used Moroccan Lemon for seasoning. Moroccan Lemons (aka Preserved lemons) are salty and briny with a huge kick of umami, and work well with any raw fish. I give this trend two thumbs up. I used to make preserved lemons myself, but now I just buy them at Formaggio's (some Whole Foods markets carry them too). None of these places display them, but if you ask in the cheese department, they'll be able to get you some.
Nuts and Grains
Pine nuts and farro might not be the first ingredients that come to mind, but they make lovely accompaniments to raw fish. The crunch of the nuts provides a nice textural contrast to the flesh of the fish. We like tempura crumbs with raw fish, so why not nuts? And if rice goes so incredibly well with raw fish, why not farro or quinoa?
Some fruit worked: grapefruits, oranges, tart apples. Some fruit didn't: rhubarb (too sour) and cherries (too sweet). Rhubarb had potential. If it was cut paper thin, it might have worked. That's true about most of the ingredients in raw fish dishes. Size is crucial since it controls the texture and flavor intensity.
When all else fails, try fennel
Fennel was used a lot and for a good reason. Its subtle minerality complements the flavor of the fish without overpowering it.
Tartars are out, slices are in (unfortunately)
Only one of the raw fish dishes that we could order was a tartar and that was a shame. Slices work well in Japanese preparations because they are served with soy sauce, a liquid seasoning that can be easily and evenly distributed oven a slice to season it. I found the seasoning to be very inconsistent in all the sliced preparations that we ordered. In some cases, the fish was topped with chunky salty ingredients, like moroccan lemons, olives, and capers. You either got a bite of fish that was too bland, or a bite that was overpowered by a big salty chunk. The sprinkling of salt on the slices was very inconsistent. It's hard to distribute salt evenly over such a thin slice, especially since it doesn't have a chance to absorb. That's when tartars would have come in very handy. By cutting the ingredients small and mixing them together, it would be possible to make the seasoning much more even.
Why are slices more prevalent than tartars these days? I am guessing it has to do with presentation. Tartars look good shaped with a cylinder mold and that's the vertical food look that is now passe. These days, chef like to keep things low. Have you noticed how all the vegetable purees are now smeared over wide rectangular plates? Thinly sliced fish helps to keep things flat. I just think it's a shame that the looks come before the taste.
I was so inspired by all the ideas I got in Seattle that our first meal in Boston was an arctic char tartar.
If you decide to make this dish, make sure you first learn how to manage risk when working with raw fish. This dish requires very accurate cutting technique. Here are some videos on keeping knives sharp and using a claw grip.
Arctic Char Tartar with Quinoa
Serves 6 as the first coarse
Fish substitutions: farm-raised salmon frozen for 7 days (or sold as sushi-grade), branzino, hamachi
1 Lb arctic char, skinned, bones removed, cut into 1/2 inch dice
3/4 cup cooked and cooled white quinoa
3/4 cup zucchini, cut into 1/8 inch dice (about 1 small)
1/4 cup minced shallots
1/4 preserved lemon (skin only), very finely minced (it's a quarter of a lemon, not 1/4 cup!)
1/4 cup finely minced fresh herbs (any mix of cilantro, chives, tarragon, dill, mint)
a few shakes of cinnamon, cardamom, and coriander (optional)
1 Tbsp freshly squeezed lemon juice, plus more as needed
3 Tbsp olive oil, plus more as needed
Black pepper to taste
Combine all ingredients, and stir very well. Taste and add more salt, lemon juice, or olive oil as needed. Serve immediately. Quinoa and all the vegetables can be prepped in advance, and fish can be diced. But don't add lemon juice, oil, salt and pepper until ready to serve.