For marinade: Combine all ingredients in a large, resealable plastic bag or glass baking dish. Add fish and seal bag or cover dish. Turn several times for marinade to coat fish completely. Let sit at room temperature for 1 hour, turning occasionally.
Melt butter in a medium saucepan. Add parsley, ground pecans, lemon juice, scallion, nutmeg and hot pepper sauce. Simmer on low for 1 minute. Add pecan halves, tossing well with mixture. Turn off heat until ready to reheat and serve.