How Fish Use an Otolith on their Ocean Odyssey

Fish spend their entire lives swimming all over the ocean. But have you ever seen one trip or fall on the journey? A major reason why fish are not the klutzes of the ocean is due to the otolith that they posses.


Halibut otoliths (

The otolith of a fish is a hard, calcium carbonate structure that is located behind the brain of osteicthyes (bony fish). Due to the otolith bony fish are able to detect sound waves and gravitational forces that are present in the water. This in turn aids with their ability to hear and maintain balance while swimming all around the world.




Otoliths help fish detect sound waves in the water (

Although all bony fish have an otolith, however it ranges in both size and shape depending on the species. There are also three different types of otolith that may aid a fish with their balance and hearing:

  1. The first of the otolith types is the Sagitta. This is the largest of the types and helps fish in their ability to hear by allowing them to convert sound waves into electrical signals that in turn allows them to detect any sound present in the water.
  2. Asteriscus, the second type of otolith, helps a fish detect sounds in the water as well.
  3. The final type of otolith, Lapillus, is how bony fish are able to detect not just sound waves, but gravitational forces as well.

Otoliths help fish keep their balance (

Something else extremely awesome about the otolith of a bony fish is that it allows scientists to detect their age! Just like the rings of trees an otolith has growth rings present on it that allow scientists to estimate how old that fish may be. Not only that, but each individual ring is essentially its own unique fingerprint. This helps scientists examine the feeding habits and even migration patterns of each individual fish!

Thin section of a rockfish otolith (University of Texas)

Although the otolith is extremely useful for our bony fish friends, not all fish possess one. When it comes to our cartilaginous fish friends (sharks, rays, and skates) they must rely on different adaptations present in their bodies to aid with balance and hearing due to their lack on an otolith.

Written By: Alex Feltes