Study of Pinna nobilis growth from inner record: How biased are posterior adductor muscle scars estimates?

► We describe a new methodology to study Pinna nobilis growth from empty shells. ► We show why posterior adductor muscle scars produced biased estimates. ► For our new method we use the inner record formed annually. ► We calculated growth parameters from a population in the Western Mediterranean. ► The new methodology saves much time and money compared to previous ones.