You will be given a trivia clue, and the category it belongs to. You should answer with the best answer that belongs in the category and is described by the clue. For simplicity, answers should be in all lower cased letters.

Category: NATURE 
Clue: Like a tree, you can tell the age of a fish by counting these on its scales
rings

Category: RELIGION 
Clue: Some 3 million pilgrims visit this small French town annually
lourdes

Category: FRENCH CUISINE 
Clue: To make mousse d'ecrevisses, you need at least 30 of these freshwater crustaceans

crayfish