*6.1.4.3 Growth parameters of Tilapia during fattening phase*

The grow-out phase started in mid-July, so the monitoring period was quite restricted (30 days), and the young individuals were fed 3 times a day. Therefore, we will base our results on the daily growth rate. The following table (**Table 9**) summarizes the different zootechnical parameters recorded after 1 month of rearing.

The comparison of the growth performances between fresh and geothermal waters has shown high potentialities in favor of fish placed in the reservoir. Indeed, after 30 days, the total masses obtained varied between 30 and 59 g respectively in geothermal water and fresh water. Moreover, the highest growth rate is recorded in the


#### **Table 9.**

*Zootechnical parameters of tilapia grown in Bechima Station and Smati reservoir.*


#### **Table 10.**

*Comparative growth performance of Nile Tilapia in different environments.*

pens placed in Smati Reservoir (ICJ = 0.4–1.54 g/d) against 0.65 g/d in the cages of Bechima Station.

On the other hand, we recorded very important survival rates compared to those obtained by other authors. This shows that Tunisian fresh waters and geothermal waters allow the growth and survival of this species. However, we recommend the maintenance of favorable conditions for the growth and survival of individuals including fish sorting which must be conducted in the future into 3 enclosures and 3 cages in order to homogenize the stock.

To highlight the results found in this study, we compared them with other authors' findings (**Table 10**).

The results show that the growth values found during this study are slightly below those attained by other researchers. On the other hand, fish grown in freshwater show daily growth rates close to those estimated by other authors who have worked in Tunisian reservoirs. In China, reported growth rates are high due to the use of large fry at the beginning of the grow-out phase and the good quality of the supplemented feed.
