How to remove fish otoliths
OTOLITHS (ear bones) help fish orientate themselves and maintain balance, acting like our middle ear. Otoliths are composed of a form of calcium carbonate and protein which is laid down at different rates throughout a fish's life. This process leaves bands (alternating opaque and translucent bands) on the otolith like the growth rings in a tree.
Fisheries programs across Australia use discarded fish frames donated by recreational anglers to compile fish age data. But have you ever wondered how the otoliths is removed? Many anglers are able to remove the otoliths from mulloway due to their large size and robustness. Snapper, on the other hand, have much more fragile otoliths and more care has to be taken when removing them. This information may prove useful for anglers if they are away on a trip and unable to donate an entire frame for ageing.
Firstly, the gills are removed to expose the base of the skull. Removing the internal organs allows clean and easy access to this area.
Using a small set of pliers or side cutters, remove the protective bone plate as shown. In some larger specimens, this can be quite thick and will need to be removed in pieces.
With a firm twist, the section of bone will come loose exposing the cavity where the otoliths are located.
Once the bone has been removed you can clearly see the otoliths in position either side of the cavity.
The otoliths can be removed using a small set of tweezers. It should be easy to identify the otoliths as they make a distinct noise when touched by the metal tweezers compared to other sections of bone.
For more information: www.dpi.nsw.gov.au