How do scientists determine the age of a fish?
Scientist are able to determine the age of fish by counting growth rings. These growth rings are found on vertebrae, otoliths (ear bones), and some types of scales. While many bony fish can be aged with scales and otoliths, elasmobranchs, which lack otoliths and suitable scales, are typically aged using vertebrae. The cause of the ring formation is not known, but may be related to seasonal changes in the environment or some endogenous cue such as hormone levels. There are typically two types of growth rings, wide opaque rings usually representing summer growth, and thin translucent rings usually representing winter growth, with one pair of rings representing one year of growth. However, before scientists can accurately age the animal, they must verify when the rings are deposited on the vertebrae, otolith, or scale.
