influence of Concentration of Dissolved Oxygen on the Growth of Japanese eel _{Anguilla japonica}

Abstract

Japanese eels _{Anguilla japonica}. 2g in average body weight, were raised for 22 days in 16 l-tanks with continuous supply of freshwater of 25plusmn;1°C with various dissolved oxygen concentrations, in order to obtain the lowest limit of dissolved oxygen concentration above which normal values for growth rate, feed efficiency and feeding rate could be maintained.
Oxygen concentration was controled by introuducing nitrogen gas in a reservoir of inflowing water.
The growth rate, feed effciency and feeding rate in each experiment were represented by the relative value.
The relative growth rate and the relative feed efficiency were kept almost constant above the oxygen concentration of about 4.5 mg/l and decreased remarkably below that level. The relative feeding rate began to decrease below the oxygen concentration of 4.0mg/l.
The occurrence of high mortality at the oxygen concentration of about 1.0 mg/l suggests that oxygen deficiency at this level is fatal to the fish.
From these results, it is concluded that the critical level of dissolved oxygen concentration for the normal growth of eel weighing about 2g must be about 4.5mg/l (54% saturation) at 25plusmn;1°C.