**7. Conclusion**

The present work contributes to the literature on Nile Tilapia farming "*O. niloticus*" in fresh waters (using enclosures placed in Smati Reservoir) and in geothermal waters (deploying cages installed in the large basin of Bechima experimental station) in Tunisia. This study was made March and August 2017, a period with abiotic conditions which are optimal for the rearing of this species. Larval rearing monitoring in the nursery located at the level of the greenhouse in Bechima Station has shown that the earliest larval stages are much more vulnerable than the most advanced stages. This vulnerability can be explained by the physical and physiological weakness associated to the fragility of larvae during their early stages of development, as well as their sensitivity to the manipulations associated to the rearing procedure. The larvae used in this study were collected from 13 broodstock in March 2017. During the 60 days of larval rearing, the average final weight increased from 0.01 to 0.85–2.55 g, and the survival rate recorded (70%) was within the range of values found by other authors.

*Nile Tilapia "Oreochromis niloticus" Farming in Fresh and Geothermal… DOI: http://dx.doi.org/10.5772/intechopen.106646*

The analysis of the evolution of the physico-chemical parameters measured in situ (temperature, dissolved oxygen, salinity and pH) as well as nutrients (nitrates, nitrites, ammonium and orthophosphates) shows that the values are well within the range recommended for Nile Tilapia rearing.

The preliminary results of the breeding phase in cages placed in the grow-out basin in Bechima station and in pens set in Smati Reservoir are quite encouraging. The comparison of the results obtained in cages placed in geothermal waters and in pens placed in the reservoir, has demonstrated that the breeding of frays in fresh waters shows a much better growth performance than in geothermal waters. The conversion rate obtained in fry, with body weights ranging from 3 to 19 g, reared in pens (0.87) is lower than that obtained in cages (1.62 and 1.58). In the grow-out phase, the results obtained after 30 days show that the fish reared in freshwater maintain the best growth performance compared to that reared in geothermal water. The preliminary results of the grow-out phase in Smati Reservoir are very encouraging compared to those achieved in Bechima Station. This observation highlights the great potential of this species' breeding and seeding in Tunisian reservoirs. The mortalities recorded in the two study areas are essentially due to cannibalism associated with the heterogeneity of the sizes and masses of the reared fish.

The in-depth diagnosis of this activity as well as the global evaluation of the results reveal the presence of anomalies and problems that must be addressed for the next reproduction and larval rearing campaigns in order to better manage this process and improve the production in the hatchery.

The results obtained shows that this type of fish farming has significant production potential. However, it presents two problems that must be solved, namely the massive production of calibrated fry of *O. niloticus* and the elaboration of a quality feed to meet the nutritional needs of fish. Thus, important improvements remain to be made in feeding and nutrition in order to specify and determine the standards of manufacturing and distribution of fish feed. This would ensure increased production and economic profitability along with a better coverage of the feed requirements of tilapia taking into account the economic context and the locally available compounds.
