Recent studies on age determination of Indian fishes using scales, otoliths and other hard parts

Abstract

At present it is customary to use the growth rings found in the scales, otoliths
or other hard parts of fishes to assess the age at different periods of their lives.
Though such rings were sometimes discovered in the past in India also, they
were rejected in view of the absence of clear summers and winters in our waters
as occurring in temperate waters where clear growth differences are known
in the fishes and in their above said hard parts. Examination of the scales
of Cynoglossus semifasciatus Day at Calicut in the middle of this century
proved not only the annual periodicity of the ring formation but also the causes
of the same. Such rings or annuli were later found in the other species of
Cynoglossus at Calicut and also in many other fishes elsewhere by other
workers, though in a few cases there were difficulties because of the occasional
occurrence of abnormalities and false checks in the scales, making the
interpretations a bit difficult. Later, coverage of more species from different
centres revealed the widespread occurrence of growth rings (also called annuli)
caused by factors other than seasons alone and their usefulness in age
determinations. In the present paper the recent developments made in india
in this discipline of fishery biology are briefly reviewed.