Season trout fillets with salt, pepper and lemon juice. Let stand at room temperature for 10 – 15 minutes. Combine 2 tablespoons of bread crumbs with pecans in blender or food processor. Grind pecans finely, combine with remaining bread crumbs and rosemary and transfer to plate.
Dredge fillets in flour, shake off excess. Dip in egg wash. Place fillets skin-side up on crumb mixture, pressing into flesh. In large skillet heat 1 tablespoon each of oil and butter over medium-high heat.
Place 2 fillets, skin-side up in skillet and cook until golden brown, about 3 minutes. Using spatula, turn fillets and cook until opaque in center, about 3 more minutes. Transfer to plate. Repeat with remaining butter, oil and fillets.