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.
1 Arrange the trout fillets on large piece of aluminum foil. Whisk together the butter, lemon juice, paprika, and cayenne pepper; brush the mixture onto the fillets.  Cook on the preheated grill until the fish flakes easily with a fork, about 10 minutes; brush the fillets with the barbeque sauce; cook another 2 minutes.