The OED defines an elder, simply, as the senior of two or more individuals - no age specified. 'Elder', as an adjective, conveys the same meaning. This is an interesting question. There are no standard industry answers, just as there isn't a standard label (senior, senior citizen, elderly, old, 65+, etc.)
Bake the trout for 10 minutes, then unfold the packet far enough to check the doneness. When done, trout is moist and flaky with an opaque appearance. Return the fish to the oven and continue baking if necessary. Trout usually cooks within 20 minutes, but may require up to 30 minutes, depending on the size of the fish.
Take the fillets from under the broiler, and set your oven to 325 degrees Fahrenheit. When your oven is at the proper temperature, place the pan on a lower rack for an additional 10 minutes. The time will depend on how long the fillets take to be flaky at the thickest parts. Fix your steelhead trout on the barbecue. Combine 1/4 cup of softened butter or margarine, 2 tablespoons of lemon juice, 1/4 teaspoon of paprika and 1/8 teaspoon of cayenne pepper. Add the mixture to the fillets, put them onto a piece of aluminum foil and place them onto the grill.