Assessment of stresful ambient water salinity on growth, feed utilization and hematological indices of European sea bass, Dicentrarchus labrax, juveniles

The present study was conducted to investigate the effect of two water salinity levels (10 and 15‰) on growth, feed utilization and hematological indices of European sea bass, Dicentrarchus labrax juveniles reared in net enclosures for 60 days. Fish were fed an experimental diet contained 45% crude protein and gross energy of 21.97 Mj kg diet to apparent satiation for six days a week. A total of 120 D. labrax with an average initial body weight of 13.0±0.5 g fish were randomly distributed into six net enclosures measuring 3 x 8 x 1.25 m each representing two treatment groups (in triplicate) at a stocking density of 20 fish per net enclosure. Over the 60-days feeding period, growth, feed utilization efficiency and survival rate of D. labrax juveniles improved significantly (p < 0.05) with salinity 15‰. The same trend was observed with feed conversion ratio (FCR). No significant difference (p ≥ 0.05) was observed for the whole body proximate analysis of D. labrax juveniles with the tested salinities. Significant (p < 0.05) increase for mean red blood cells count (RBCs), mean white blood cells count (WBCs), hematocrit (Hct), hemoglobin (Hb), total plasma protein, total plasma globulin, plasma sodium chloride and glucose level of D. labrax juveniles was recorded with salinity level 15‰. An opposite trend was observed for plasma cortisol, albumin, aspartate aminotransferase (AST) and alanine aminotransferase (ALT) values. The result indicates that the tested salinity levels could be considered as stress factors. Thus, the present study highlights that the growth, feed utilization and hematological indices of D. labrax fingerlings improves at 15‰ salinity.