Preheat the oven to 350°F.
Lightly coat a baking sheet with nonstick cooking spray.
Place the salmon fillets on a clean cutting board.
Using a sharp knife, cut a slit through the center of each salmon fillet to create a pocket. Do not cut all the way through.
Season the salmon fillets evenly with Cajun seasoning, including the inside of each pocket.
In a large mixing bowl, combine the drained crab meat, cooked shrimp, mayonnaise, shredded Parmesan cheese, fresh lemon juice, chopped green onions, and 1/4 c Italian breadcrumbs.
Mix gently until the stuffing is evenly combined.
Spoon the crab and shrimp mixture into the center pocket of each salmon fillet.
Divide the stuffing evenly between the two fillets.
Sprinkle the remaining 3 tbsp Italian breadcrumbs over the top of the stuffed salmon.
Place the prepared salmon fillets on the greased baking sheet.
Bake for approximately 30 minutes, or until the salmon flakes easily with a fork and the stuffing is heated through.
Remove the salmon from the oven.
Sprinkle with fresh chopped parsley.
Serve warm.