Fish Ageing Laboratory

The Ageing Laboratory ages about 2,000 fish per year using sagittal otoliths. Otoliths (ear bones) are located in the fish’s head behind the eye and directly below the brain.

Photo of a hacksaw being used to saw through a southern kingfish head just prior to removing the otoliths

Photo of where otoliths are located inside the head of a fish

 

 

 

 

 

 

 

 

 

Otoliths are used by the fish for orientation and to maintain balance, acting a lot like our middle ear, and are composed of calcium carbonate.  Every year a layer of material is deposited.  This process results in annual bands (i.e., annuli) forming on the otolith like the rings in a tree.

The otoliths among species vary in shapes and sizes.  Some otoliths are large and chunky like those found in red drum and black drum while others are thin and fragile like the ones found in southern flounder and sheepshead.

Photo of otoliths from different species of fish in the drum family, and all fish are nearly the same size

 

Otoliths are removed, cleaned, and dried before they are stored. Later, a thin section is cut from the otolith using a Buehler low-speed Isomet saw with two diamond wafering blades and a spacer.  A section is made through the core yielding a clear view of annuli formed in the otoliths.

Photo of a sectioned spotted seatrout otolith showing the annual rings.

 

By knowing the age of fish scientists can determine the age composition of the catch, age-at-maturity, age at capture in the fishery, and the maximum age that fish species lives.  This yields information on the health of fish populations and the sustainability of the fisheries.

Some of the fish aged include: spotted seatrout, red drum, southern kingfish (whiting), Atlantic croaker, tripletail, sheepshead, and southern flounder.