Abstract:The breeding of fish species that tolerate saline-alkaline is of great importance in the usage of salinity-alkalinity water bodies and in the sustainable development of aquaculture industry. Due to their fast growth rate and excellent adaptability to different environments, Nile tilapia Oreochromis niloticus could be a good candidate for the saline-alkaline tolerance breeding. In this study we evaluated the tolerance and growth performance of three strains of juvenile Nile tilapia (Shanghai, Shandong and Hebei strains) in salinity-alkalinity water. During a 60-day culture experiment we compared the average growth rates of the three strains in different salinity-alkalinity water (S0A0, S10A0, S10A2, S10A4, and S10A6) and their median lethal saline/alkaline concentrations. The results showed that in the 96 h culture the median lethal salinities for juvenile Shanghai, Shandong, Hebei strain were 18.528 g/L, 20.347 g/L, and 19.342 g/L respectively; the median lethal NaHCO3 alkalinities were 8.827 g/L, 8.540 g/L, and 8.542 g/L respectively. For mixed salinity-alkalinity test, at salinity 10 the 96-h lethal alkalinity was 4.377 g/L for Hebei strain, 3.561 g/L for Shanghai strain, and 3.108 g/L for Shandong strain; at salinity 15, it was 2.144 g/L for Hebei strain, 2.183 g/L for Shandong strain, and 2.183 g/L for Shanghai strain (P>0.05). The alkaline tolerance of Nile tilapia at high salinity was significantly lower than that at low salinity (P<0.05). The growth experiment results showed that there was no significant difference in the average growth rate between S0A0, S10A0 and S10A2. However, the average growth rate decreased at S10A4 and was significantly lower at S10A6 (P<0.05). Hebei strain showed a higher growth rate than Shanghai and Shandong strains at S10A2, S10A4 and S10A6 (P<0.05). Our results should provide important clues about the suitable salinity and alkalinity of the culture water bodies and about the selected breeding of Nile tilapia.
