Methods Three hundred and twenty-seven fish of the Catia catla (Ham.) species
(abbreviated as Catla) were randomly drawn from a natural pond adjacent to the laboratory
(in the nortbern industrial suburbs of Calcutta, India). The pond was 27 m wide, 46 m long,
and 4.5 m deep along the central line. It had been rtocked mainly with Catla at the
postembryonic stage following batching, but also with immature Catla fron other sources. As
a result, the Calla population of the pond had a mixed age distribution. Two months before …