Effect of stocking density on growth, survival and development of asp Aspius aspius (L.), ide Leuciscus idus (L.) and chub Leuciscus cephalus (L.) larvae during initial rearing under laboratory conditions

This study was aimed at determining the effect of stocking density on growth, survival and development of asp Aspius aspius (L.), ide Leuciscus idus (L.) and chub Leuciscus cephalus (L.) larvae, reared under laboratory conditions. Fish larvae were obtained during artificial reproduction. The larvae were fed ad libitum with freshly hatched Artemia sp. nauplii. Eight density variants from 50 to 400 individuals per 1 L (at the interval of 50 individuals L −1 ) were tested. The initial rearing was carried out for 21 days at 25°C in a recirculation system especially designed for that purpose consisting of 16 tanks with a capacity of 1 L each. The fastest growth rate for all three species, expressed as the greatest average total length, weight and most advanced ontogenetic stage at the end of the experiment was obtained at the lowest stocking density. Fish from other treatments, particularly at densities exceeding 150 individuals L −1 , were characterized by similar body sizes and the same ontogenetic stage on the last day of rearing. The recorded differences in the length of larvae among treatments became visible during the first (asp) or third (chub, ide) week of rearing. No effects of stocking density on larval mortality were found during the experiment.