Effect of different salinity levels on growth, digestibility and evacuation time of Coptodon zillii fingerlings

Abstract

An open cultivation experiment performed on Coptodon. zillii fingerlings in mean of weight 21.39 ± 0.66 to recognize the effect of direct transmission from the control salinity 15psu which nearby to the sample station salinity in Shatt Albasrah Cannel to different salinity levels (1.5, 7.5, 15, 30 psu) on Growth Rate GR, Relative Growth Rate RGR, Specific Growth Rate SGR; Satiation level; evacuation time and apparent digestibility coefficient at the end period of  56 days. The salinity 7.5 psu had the highest GR, RGR and SGR. This salinity is considered to be the best salinity of lowering energy cost. However, the other salinities (1.5, 7.5, 15psu) had no statistical differences in GR, RGR and SGR which meant fishes can grow efficiently at these salinities. Satiation level decreased with salinity increase. The present study recorded an increase of evacuation time  for C. zillii fingerlings with salinity increase accompanied with decrease in total apparent digestibility coefficient TADC% and nutrient apparent digestibility coefficient NADC% for protein, fat and carbohydrate. C. zillii fingerlings had a general replace with specific one protein and fat NADC at salt concentrations (1.5, 7.5, 15 psu). Results showed that the salinity 7.5 psu is the best salinity for growth performance in fingerlings of C. zillii.