Ever wondered how you can age fish? Ask them?
There’s a technique whereby the bone from middle ear is sectioned and the growth rings (much like the tree’s) can give you an indication as to the fish’s age.
“The otolith layers are generally oriented parallel to the outer surface of the otolith and are most densely aligned during periods of slower growth (usually associated with cooler months), thus forming characteristic, concentric opaque rings in otolith cross sections (Blacker 1974). Layers that are less densely spaced during periods of faster growth during warmer months make up the translucent ring. When the formation of successive opaque and translucent rings occur on an annual basis, they are collectively referred to as an annual growth zones….”
Unfortunately, this can only be done in a dead fish.
This technique is also used to age manatees (because asking them doesn’t work, especially if they’ve already passed on).
This information can be downloaded from this link (38Mb).
"A Practical Handbook for Determining the Ages of Gulf of Mexico Fishes".
This link was shared by a fellow classmate (Johnny Shelley) at Aquavet II.
