Water flow requirements in the intensive production of Atlantic salmon (Salmo salar L.) fry: growth and oxygen consumption

Atlantic salmon (Salmo salar L.) fry (1-10 g) were exposed to three water f low rates: 1.4 (control), 1.0 (medium) and 0.7 1 kg(-1) min(-1) (low). Ther e were four replicate tanks in each group. Alkalinity was low (0.03-0.04 mM ). Oxygen was added to the inlet water to maintain discharge water oxygen c oncentration higher than 7 mg l(-1), at 16 degrees C. The mean weight of fi sh in the low water flow group was significantly lower than in the control Bow group after 2 months. No significant differences in mean fish length an d condition factor between groups were found. There was no significant diff erence in the frequency of occurrence of gill lesions among the groups. Mor tality was low in all groups (0.3-0.4%). In the majority of tanks (nine of 12), oxygen consumption rates decreased significantly as the mean fish size increased. An overall range of 5-12 mg O-2 kg(-1) min(-1) was observed. Th ere were no significant differences between the b-values (weight exponent: log oxygen consumption versus log body weight) of the three groups. The ran ge of the weight exponents for the combined groups (between -0.19 and -0.23 ) was narrower than that of the individual tanks (between -0.12 and -0.27). The wide range in the individual tanks may be a result of relatively few o xygen measurements. No significant differences were found in the oxygen con sumption levels of the three groups. The oxygen consumption rate was howeve r higher than predicted by earlier oxygen consumption models. The mathemati cal corrections df oxygen consumption rates due to reaeration of oxygen wer e generally within +/-3% of the measured oxygen consumption rates (in all t anks). Further studies are needed both to quantify water how requirements a nd oxygen consumption rates for Atlantic salmon fry. (C) 1999 Elsevier Scie nce B.V. All rights reserved.