Place the shallots and scallions in a medium-size skillet with the stock.
Cook over low to medium heat until the scallions are wilted.
Stir in the celery and add the water.
Cover and steam for 1 to 2 minutes, then stir in the watercress.
Remove from the heat when the watercress is wilted.
In a medium-size bowl, combine the dill, bread crumbs, walnuts, and celery mixture.
Sprinkle with the tamari and toss lightly.
If you prefer to serve the fish with heads and tails on, stuff each fish with one-fourth of the filling.
Place each fish on a lightly oiled piece of aluminum foil or kitchen parchment and fold over the ends to protect the head and tail from scorching.
Arrange some orange slices over the exposed middle section of each fish to prevent drying out in the oven.
Bake at 350° just until the fish is opaque and cooked through, about 15 to 20 minutes.
Carefully remove the fish to a serving platter, remove the orange slices, and garnish with watercress, if desired.