In a small bowl, stir together lemon zest, garlic, pepper, soy sauce, sugar, water and vegetable oil until sugar is dissolved. Place fish in a bowl with the marinade, cover with cling wrap and refrigerate for at least 2 hours.
Preheat barbecue for medium heat.
Lightly oil cooking grate. Place salmon on the preheated barbecue, and discard marinade. Cook salmon for 6 to 8 minutes per side, or until it flakes easily with a fork. Garnish with chopped chives and lemon slices, if desired.