Effect Of Salinities On New GIFT Tilapia Cultured With Biofloc Technology

Biofloc technology(BFT) is considered to be an effective way to solve the problem of sustainable development of the aquaculture when facing with environmental constraints and resources utilization. BFT is biological floc that generated through assimilating inorganic nitrogen and nutrients in manure bait in the water to biomass by heterotrophic bacteria,and then can be ingested by aquaculture animal at present,most study applied BFT technology on freshwater,and the effect of different salinities remains to be further studied.In this study, tilapia was served ascultured species, Three salinity groups was set labeled groups A(salinity of 0 g/L), B(salinity of 10 g/L) and C(salinity of 20 g/L),In different salinities,the water quality,biological flocculation properties and nutritional composition,rapid three nitrogen transformation ability of biofloc,the growth performance of fish and the blood biochemical index of biofloc technology were monitored and analysised respectivelyin 150 d. The main research results were as follows:1. Water quality and biofloc performance of biofloc technology under the condition ofdifferent salinities.Ammonia concentration of group A, B, C in each group all increased in initial stage and then declined inthe first 55 days and reached the peak at 25 days, the ammonia concentration was 23.67 ± 6.61 mg/L, 49.67 ± 4.25 mg/L, 21.47 ± 1.03 mg/L respectively,55 d to 150 d ammonia concentration fluctuation of each group range was very small, and basically remained at 3 mg/L or less. Nitrite concentration of each experimental group increased first and then decreased at the early stage A, B, C eachgroup reached the peak for the first at the 40 d, the 35 d, the 60 d, with the concentration of 28.08 ± 2.67 mg/L, 17.4 ± 0.1 mg/L, 13.27 ± 10.15 mg/L respectively. The variation trend of nitrate concentrations were similar as nitrite. each group reached the peak at 50 d, 60 d, 65 d, with the concentration of 75 ± 5.26 mg/L, 54.52 ± 6.54 mg/L,44.27 ± 3.54 mg/L respectively,During startup, each group of ammonia, nitrite concentration, nitrate concentrations varied widely. After the completion of the startup,the three nitrogen concentration started to stabilize, and ammonia concentration of each group was maintained at 3 mg/L or less, nitrite concentration was maintained at 0.5mg/L or less, the basic nitrate concentration was maintained at 10 mg/L. At the end of the culturing,FV-5min of group C was significantly lower than groups A and B,were 81± 2 ml/L, 96.7 ± 8.1 ml/L and 93.3 ± 4.7 ml/L respectivly. At the end of the experiment,there was no significant difference between group A, B, C with the floc crude protein conten,and it were 36.68 ± 0.11%, 34.85 ± 0.24%, 35.68 ± 0.28%,(P> 0.05) respectivly;crude fat contents were 2.24 ± 0.15%, 2.05 ± 0.2%, 1.8 ± 0.25%, which indicated that there was a significant difference(P <0.05) between group A and group C; ash content was 5.98 ± 01%, 5.86 ± 0.06%, 5.61 ± 0.08%, indicating ash of group C was less than the A, B groups(P <0.05) significantly. Floc density increases with the rise of salinity of water.2. Rapid three nitrogen transformation ability of bioflocunder the condition of differentsalinities.At each group, rapid transformation capacity of inorganic nitrogen of biofloc showed that, ammonia removalability for 10 mg/L of group A, B, C were 90.07 ± 0.44%, 88.76± 1%, 84.97 ± 2.24% respectively after flocculated 7 h. Group C was less than the group A, B(P <0.05) significantly, rapid conversion of ammonia absorption is heterotrophic bacteria removed by assimilation; nitrite nitrogen removal ability for 5mg/L were 74.93 ± 5.88%, 98.71± 0.75%, 93.37 ± 1.15% respectively after flocculated40 h, Group C significantly lower than Group A and B(P <0.05), assimilation nitrite is removed by heterotrophic bacteria. 52 h nitrate removal rates for 100 mg/L were 93.56 ±5.09%, 76.05 ± 14.53%, 69.8 ± 28.77% after flocculated 52 h, which indicated no significant difference(P> 0.05) between each group, rapid conversion of nitrateassimilation have heterotrophic bacteria and denitrification in two ways, heterotrophic bacteria assimilation is the main way. Floc of biofloc technology possess good ability of transforming ammonia, nitrite, nitrate quickly under the condition of different salinities.3. The growth performance of fish and the blood biochemical index of biofloctechnology under the condition of different salinities.Fishes of each group were in good health. After the cultivation, final body weight of fishes of groups A, B, Cwere 228.49 ± 33.14 g/tail, 230.32 ± 24.35 g/tail, 218.97 ±35.13 g/tail respectivly, which indicated no significant difference(P> 0.05) between each group(P> 0.05). The survival rate were 0.97 ± 0.03、0.99 ± 0.01、0.95 ± 0.03 without significant difference. Breeding density in each group were 34.79 ± 1.33kg/m3,35.83 ± 1.08 kg/m3,32.6 ± 1.04 kg/m3, showed that group C was significantly lower than group B(P <0.05).However, there were no significant difference between group A and C(P> 0.05). Feed conversion rate(FCR) were 1.4 ± 0.02,1.39 ± 0.03,1.46± 0.03, showed that group C was significantly higher than group A and B(P <0.05).Protein efficiency ratio(PER) were 2.56 ± 0.03,2.57 ± 0.07,2.45 ± 0.04, showed that group C was significantly lower than groups A and B(P <0.05). Each group survival rate(SR), specific growth rate(SGR), weight gain(WG) had no significant difference(P> 0.05). Fish muscle protein contentof group A, B, C were88.35 ± 0.67%, 88.8 ±1.65%, 88.48 ± 1.93% respectivly, showed no significantdifference(P> 0.05). Crude fat contents were 6.85 ± 0.3%, 5.72 ± 0.24%, 4.88 ± 0.28% respectivly, showed a significant difference(P <0.05). Fish blood TP, ALB, GLU, UREA, TG, TC,ALTlevelsof each group hadno significant differences at the end of the culturing(P<0.05).This study showed that salinity of 10 g/L and 20 g/L had no influence on tilapia culturing. And biofloc technology can be applied to tilapia culturing in brackish conditions.