For the swordfish: Stir together 8 cups water, the salt, sugar and peppercorns in a deep pot. Bring to a boil just to dissolve the salt and sugar; cool completely. Submerge the swordfish in the brine. Refrigerate for 12 hours.
Remove the swordfish from the brine and rinse well under cold water. Pat dry and allow to air dry for at least 1 hour. The exterior of the fish should feel sticky to the touch before smoking.
Prepare a smoker with maplewood chips and to an internal temperature of 200 to 225 degrees F.
Brush the fish very lightly with canola oil and sprinkle with salt and pepper. Smoke the fish for about 2 hours, adding chips through the first hour as necessary. You can keep adding chips the second hour if you prefer a much smokier flavor. Transfer the smoked fish to a large platter.
For the clam sauce: Remove the meat from half the clams and chop roughly. Heat the canola oil in a medium saucepan over high heat. Add the garlic and chile and cook for a few seconds. Add the chopped clams and cook, stirring, for another minute. Add the wine, bring to a simmer and cook until reduced by half.
Add the whole clams, cover the saucepan and cook, shaking the pan occasionally, until the clams open, 5 to 10 minutes. Stir in the butter. Remove from the heat and stir in the chopped parsley and lemon zest. Taste, and season with salt and pepper. Pour the sauce over and around the smoked swordfish, and scatter the parsley leaves on top.