Effects of different levels of exogenously introduced plankton on growth of common carp reared under favourable water quality

Abstract

One-hundred-ninety-eight fry of common carp were placed into each of nine outdoor tanks (9580 1) and subjected to three different levels (dry weight) of exogenously introduced plankton, viz. 134 mg l −1 (normal), 264 mg l −1 (two-fold) and 412 mg 1 −1 (four-fold) every other day. Frequency distribution of different weight groups of fishes at the time of harvest after a 90-day growing period revealed significant differences between the normal live food system and the two-fold or four-fold treatments, but no marked differences between the latter two treatments. Mean weight of common carp was 20.76, 23.82 and 24.04 g in the normal, two-fold and four-fold treatments, respectively, whereas yield per tank ranged from 3.69 to 4.37 kg. Carp growth in these three systems was found to be strongly dependent on plankton density. The mortality of common carp did not differ from one system to another, with values ranging from 8 to 10% in the three treatments. Fish production in the four-fold treatment was not proportionate to the rise in Zooplankton density and, hence, the two-fold treatment was the most appropriate for carp growth.