To the fisheries biologist, the otolith is one of the most important tools for understanding the life of fish and fish populations. Growth rings (annuli) not unlike those of a tree record the age and growth of a fish from the date of hatch to the time of death.

Daily growth rings, formed in the first year of life, and visible only through a microscope, record daily age and growth patterns in surprising detail. In addition, sophisticated chemical techniques allow the reconstruction of everything from the year of hatch, to migration pathways, to the temperature of the water. Indeed, virtually the entire lifetime of the fish is recorded in the otolith.

For that reason, otoliths are used and studied in almost every fisheries laboratory in the world. They also make ideal class or science projects, suitable for both high school and supervised elementary school students.