Ear’s the way to tell a fish’s age

Determining the age and growth of fish provides fundamental information for the sustainable management of fish populations.

Kane Dysart with a 73cm golden snapper

Determining the age and growth of fish provides fundamental information for the sustainable management of fish populations.

Fisheries scientists generally use a combination of length measurements and otolith (earbone) examination to determine growth rates and the age of fish.

Otoliths contain a record of seasonal growth patterns and can be aged much like a tree by counting the rings.

Once removed from the fish the otoliths are mounted in resin, finely shaved into transparent cross sections and viewed under a microscope where the age can be determined.

Age studies provide fisheries’ managers with valuable information on fish population dynamics and provide data such as the age structure of a stock, recruitment success and the changes in populations due to fishing rates.

To establish an accurate assessment of the age structure of a population, several hundred samples are required as a minimum for analysis.

The data is then entered into a computer stock assessment model along with information on age at maturity, harvest levels and growth rate which provides managers with a status report on the health of the population.