1. Methods of Age Determination using Hard Parts

2. Scales
For age and growth study, 3-4 scales from the region between dorsal fin and lateral line are removed.
Lateral scale radius and the distance between the focus and annuli are measured for a relationship between scale radius and fish length.
Opercular bones
The opercular length O-A, the annuli O-A1, O-A2, O-A3,….O-An are measured and regression analysis of opercular length and fish length is carried out

3. Vertebrae
Vertebrae lying below the dorsal fin has to be studied.
Study large number of vertebrae for the clarity of rings before actually using the vertebra for age determination.
Frontal bones
Growth rings are observed under reflected polarized light against dark back ground.
Cleithra
These can be viewed under stereoscopic binocular microscope.

4. Otoliths
Sagitta, lapillus and asteriscus are the three otolith present in the membranous labyrinth of fish on each side.
Of these, sagitta is the largest and often used in age determination.