Rinse fish under cold water; pat dry. In shallow dish, combine soy sauce, honey, vinegar, wasabi and ginger. Add fish and turn to coat; refrigerate for 30 minutes or up to 2 hours.

In medium heavy-bottomed saucepan, combine water and rice; cover and bring to boil.  Reduce heat to low; simmer for 12 to 15 minutes or until water is absorbed. Remove from heat. Let stand, covered, for 15 minutes. Gently stir in seasoned vinegar with fork.
Divide into 4 portions and cover with damp cloth.

Spray grill pan or grill with cooking spray. Remove trout from marinade; place, skin-side down, on grill over medium-high heat. Cover with lid; cook for 1 to 2 minutes. Turn fish with spatula; cover and cook for 2 minutes or until fish flakes easily with fork. Remove skin and sprinkle both sides with toasted sesame seeds.

Place sheet of nori on clean dishcloth or bamboo sushi mat lined with plastic wrap. Dampen fingers with water; lightly press one portion of rice into thin layer to cover nori, leaving 1-inch (2.5 cm) section at the top edge without rice.

Make shallow groove along centre of rice; place a few slivers of yellow pepper and carrot inside groove. Top with one-quarter of the trout, broken into narrow pieces with your fingers, and a few sprigs watercress. Curl edge of mat to help form toasted nori into cylinder, pressing firmly to enclose filling; seal edge with water. Repeat with remaining ingredients to make 4 rolls. Slice each roll into bite-sized pieces.