Consequences of high-density fish culture as monitored by growth, behavior and immune responses of nile tilapia (Oreochromis niloticus) [electronic reource].

Includes references.

An experiment was performed to appraise the biological performances and ingestive behavior of Nile tilapia (Oreochromis niloticus). In this respect, we examined three tilapia stocking densities; low density (LD, 100 fish m-3), medium density (MD, 200 fish m-3) and high density (HD, 400 fish m-3). Lately, Aeromonas hydrophila defied fish evaluated through calculating the cumulative mortality (%). Stocking density had no influence on survival rate while, the final weight markedly reduced with increased density. The ingestive behavior was higher in MD- reared fish than the LD-reared group, however, fish at HD had a higher feed intake (%) and feed conversion ratio. Fish at LD showed marked higher levels of total protein, albumin and globulin compared with those reared at HD. The plasma glucose and cortisol levels elevated in HD-raised fish contrast to LD and MD groups. LD-raised fish had more elevated RBCs and WBCs parallel to MD and HD. Similarly, lymphocytes, neutrophils, and monocytes (%) decreased with increasing density. Also, Serum antioxidant and lysozyme enzymes were considerably (P<0.05) higher in LD compared with MD and HD groups. Meanwhile, the Phagocytic index expressively increased in MD-raised fish compared with LD and HD groups. Finally, the HD -raised fish showed a markedly higher cumulative mortality (%) (χ2= 6.257**) than the MD and LD-raised fish. In light of these results, a high-density culture evolved chronic stress in Oreochromis niloticus and consequently altered the biological performances, ingestive behavior with a subsequent immune depressive effect as displayed by the cumulative mortality (%).

Summary in Arabic