AGE DETERMINATION AND GROWTH STUDIES OF BAGRUS BAYAD IN THE NOZHA-HYDRODROME.

AGE DETERMINATION AND GROWTH STUDIES OF BAGRUS
BAYAD IN THE NOZHA-HYDRODROME.
ABSTRACT
Age determination and growth studies of Bagrus bayad were
made from the examination of vertebrae of 778 fish, taken from
the Nozha-hydrodrome during commercial fishing in 1968-1970.
Direct observation of the centre of vertebrae revealed the presence
of clear annual rings, which were shown to be true year marks,
when checked by the usual tests of validity. Body-vertebra relationship was characterised by two straight lines rneating in an obvious inflection at a total body length of 440 mm., and appropriate
corrections were made in all calculations.
Sizes attained at previous ages were calculated for separate
sexes and the means of observed and calculated lengths for corresponding ages compared well. The mean length and weight of males
at corresponding ages were less than that of females. For both
sexes, growth in length was greatest during the first three years and
abrupt decrease was observed in the fourth year. Growth in Weight,
on the other hand, was small in the first year, and rapidly increases
with age reaching maximum increment in the 6th year of life.