Otoliths, also called earstones, are often referred to as the fish's black box. By analyzing otoliths, one can learn about the age, growth, type of fish (e.g. coastal cod/cod), temperature conditions, diet, migration pattern, maturation, number of spawning periods, genetic diversity and pollution. The Institute of Marine Research has collected large amounts of otoliths from the beginning of the 20th century to the present day.