Inland saline aquaculture may offer an opportunity for income diversification and a potentially productive use of land that can no longer support traditional agriculture in salt-affected parts of inland production and investment levels are characteristically low. It needs to develop in a manner that both prevents the further degradation of agricultural land and provides opportunities for an alternative and sustained economic base for dependent rural communities. Most central areas of Iran are under high risk of salinization through shallow water tables. Using saline groundwater for aquaculture production is a potential adaptive use of this otherwise degraded resource. Expansion of aquaculture in these areas is limited by some factors such as shortage of suitable sites and strict environmental regulations. These limitations, together with an abundance of salt-affected land and water resources, have led to the logical progression of investigating the suitability of these resources for aquaculture. Rainbow trout, which appear to be well adapted to rapid changes in salinity, have been promoted as a potential candidate for aquaculture in these regions. By using appropriate production system well-set to climate condition, trout farming in brackish water is a profitable method to develop inland aquaculture in Iran

The aim of this study was to assess the effects of dietary protein levels on growth and reproduction performance of paradise fish, Macropodus opercularis. A total of 540 fish (0.5±0.01 g) was offered one of six experimental diet comprising different protein levels (i.e., 25, 30, 35, 40, 45 and 50 %). Diet of 40 % crude protein produced significantly higher mean weight gain, daily growth rate, and specific growth rate and feed conversion ratio (p≤0.01). The analysis made based on the second order polynomial regression curve (R 2 =0.79), revealed that optimum protein levels based on fish SGR and FCR were 40 and 45 %, respectively. The average total egg production increased with increasing dietary protein levels up to 45 %. There was no significant difference in the egg diameter among groups, but egg hatchability was significantly higher (96%±2) in the fish fed diet containing 45% protein. The highest and lowest GSI was obtained in the 45 and 25% dietary protein, respectively. Fecundity was highest in the fish fed diet containing 45% (107.4±12.1) and followed by 50 (91.4±8.5) and 40 (68.5±2.6) % dietary protein. There were no significant effects of dietary protein level on egg biochemical composition and amino acid profile. The results suggest optimum dietary protein levels of 40 and 45 % for maximum growth and reproduction performance in paradise fish, respectively.

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