Effects of chronic nitrite exposure on growth in juvenile Atlantic cod, Gadus morhua

The effects of nitrite concentration on growth and feed intake in juvenile cod, Gadus morhua, were examined. In the experiment, juvenile cod with a mean (S.D.) live weight of 7.0 (1.9) g were exposed to four concentrations of nitrite [0, (control), 1.0 (low), 2.5 (medium) and 5 mg NO2–N l− 1 (high)] for 96 days at 8.0 °C, salinity 33 ppt and pH 8.0. No mortality occurred in any of the experimental groups throughout the study. Growth was significantly reduced in fish exposed to all treatment levels, with reduced growth in the high concentration group in the first period of the experiment (day 1–31) and in all experimental concentrations during later periods. No significant difference in feed intake or food conversion efficiency was observed between treatment groups. The fish from the exposed groups displayed an acclimatory response to nitrite. These results indicate that management of intensive aquaculture systems of G. morhua, should avoid levels of nitrite even at 1.0 mg NO2–N l− 1 not to impair growth.