For the bouillabaisse: Preheat the oven to 350 degrees F.
Place the fish carcasses in a roasting pan and roast for 30 minutes.
Add the roughly chopped carrot, celery and onion to a blender. Add the tomatoes, bell pepper, garlic, anchovy paste and Calabrian chile paste and process until pureed. Pour the vegetable puree into a large pot with 2 cups of water and bring to a simmer. Add the roasted fish carcasses and reserved shrimp shells to the pot and simmer for 40 minutes. Strain the puree and set aside.
Preheat the oven to 450 degrees F.
Bring 1 quart of water to a boil in a medium pot. Add the pasta, saffron and some salt and pepper and cook the pasta according to the package directions. Drain and set aside.
Heat 1 tablespoon of canola oil in a large cast-iron skillet over high heat. Place the fish filets skin-side down in the skillet and press down for 10 seconds. Place the skillet in the oven and bake until the center is just cooked through, about 5 minutes. Remove from the oven, flip the fish and allow to rest for 1 minute in the skillet.
Gently cook the diced carrot, onion, celery and fennel in a large saucepan over medium heat until translucent. Add the shrimp, clams and mussels. Add the red wine and scrape the bottom of the pan with a wooden spoon to release any brown bits. Add the reserved vegetable puree, cover and continue to cook until the clams and mussels open. Immediately remove from the heat and discard any clams or mussels that haven't opened up. Add the parsley, basil, chives and pasta.
For the uni toast: Combine the egg yolks, lemon juice and sea salt in a medium bowl. With an immersion blender running, slowly add the grapeseed oil to make an emulsion. Lightly toast the slices of sourdough bread, top with uni and drizzle with some of the lemon emulsion.
To serve: Divide the bouillabaisse among bowls. Place a sea bass filet in the middle of each and garnish with 1 uni toast, some petite carrot fern, petite sea grass and black pepper.