Study of growth ring formation on scales of mullet Liza saliens in the Caspian Sea

This study is attempted to compare the number of rings and circular scales that are formed during various ages on Liza saliens. Sampling was carried out monthly during ۲۰۱۲-۲۰۱۳ using beach sine fishing nets. ۱۰۲ specimens of different sizes were collected and transferred to the laboratory in boxes containing ice. The age of fish was determined by the number of annual rings as well as, the number of rings in each annual area. The distance between rings in each annual area was also measured. The results showed that the maximum growth was demonstrated in the first and second years. In the first year of life, the scale radius was nearly ۲۸۲۳.۳±۳۶۶.۵(µm) which decreased to ۱۲۲۳.۹±۲۳۶.۰(µm). The result indicated that ۴۸ percentage of growth scales occurred in the first year and this value is only ۲۱.۸% in the second year. The number of growth rings in the annual regions decreased with increase in age. The result demonstrated that the average number of rings was ۹۵.۵±۱۷.۶ in the first life year of the fish. If you take into account the number of growth ring through years in comparison with the number of days in a year, it is clear  that one ring was nearly made in four days in the first life year and it gradually reached ۷.۵, ۱۵.۹, ۲۱.۹ and ۳۱.۷ in the second, fourth and sixth years of life, respectively. One ring was approximately made in each month at higher ages.

Keywords:

Caspian Sea , Liza saliens , Growth rings , Scales , Circular