This study was carried out in a fish farm at Fowwa, Kafr El-Sheik Governorate, A.R.A. The study aimed to investigate the growth performance of eel, grey mullet and Nile tilapia fishes reared in earthen ponds as well as pond productivity as affected by dietary protein levels. Nine earthen ponds, each of total area of 2000 m2 represented three dietary protein levels (20, 32 and 44%) with three replicates for each protein level. Fish species were stocked in each pond at densities of 2000, 1000 and 800 with an average initial weight of 20, 29 and 31 g for tilapia, mullet and eel, respectively. The study started in 15.4. 2000 and lasted in 15.12.2000. Results obtained are summarized in the following: 1- Final body weight of Nile tilapia increased significantly with each increase in the dietary protein level from 20 to 32 or 44%. 2- Final body weight of eel increased significantly with each increase in the protein level fed, however for mullet final weights of fish fed on 32 or 44% protein level were significantly superior than those fed on the lower protein level (20%). 3- Final body length of both Nile tilapia and eel increased significantly with each increase in the protein level fed, while in mullet final body length of fish groups fed the 32 or 44% protein level were significantly higher than that of the 20% protein level. 4- Specific growth rate during the whole experimental period improved significantly in tilapia and eel as the level of protein increased from 20 to 32 or 44%, however the specific growth rate of mullet fed the 32 or 44% dietary protein was significantly higher than those fed the 20% protein diet. 5- Protein levels fed seemed to have no significant effects on dressing percentages of tilapia, while it released significant effects on this trait in eel and mullet. 6- Protein levels fed had significant effects on the proximate analysis of whole bodies of tilapia, eel and mullet. Based on results obtained in this study and on the economical evaluation it could be concluded that tilapia, mullet and eel can be cultured together in earthen ponds and growth performance of the three species improved with each increase in the protein level fed from 20 to 32 and 44%, however from the economical point of view a diet containing 32% protein seemed to be the best in terms of ratio of returns to total costs. |
