Influence of salinity on food consumption, growth and energy conversion efficiency of common carp (Cyprinus carpio) fingerlings

Food consumption, growth rate, digestibility, nitrogenous excretion rate and oxygen consumption rate of common carp (Cyprinus carpio L.) fingerlings (5.6-8.8 cm in body length) were measured at salinities from 0.5 to 14.5 parts per thousand at a temperature of 13.8-22.5 degrees C for 92 days, The specific growth rate in weight gain was high (2.32% day(-1)) in fresh water, reduced with increase in salinity, and reached a negative percentage at 10.5 parts per thousand. The daily food consumption rate of the fingerlings was high (4.39 +/- 1.53%) in fresh water and diminished with an increase in salinity up to 6.5 parts per thousand. The fingerlings had a high digestibility (96.6 +/- 1.99%) of dry matter in feed at a salinity of 2.5 parts per thousand and in fresh water. The range of the nitrogenous excretion rate (mu g N g(-1) day (-1)) at various salinities varied as follows: 2.5 parts per thousand, 24.77 +/- 11.36; fresh water, 41.51 +/- 5.85; 4.5 parts per thousand, 55.69 +/- 10.49; 6.5 parts per thousand, 64.75 +/- 5.00; 8.5 parts per thousand, 101.20 +/- 25.47; 10.5 parts per thousand, 130.96 +/- 12.96. Oxygen consumption rate was low in fresh water and at 2.5 parts per thousand salinity, The high growth rate in fresh water was correlated with the high daily food consumption rate and high digestibility of feed.