Effects of stocking densities on growth and water quality in Litopenaeus vannamei indoor culture

Four stocking densities from 150 ind·m-3 to 850 ind·m-3 were applied in this study under the condition without using medicine and water change,and the effects of the stocking densities on survival,growth characteristics and water quality were analysed by sixty day period of freshwater culture indoor.The results show that water quality deteriorated with the increase of the stocking density:DO decreased from 6.65 mg·L-1 to 6.18 mg·L-1,and pH decreased from 8.31 to 8.15;while TAN and CODMn showed an uptrend from 0.313 mg·L-1 to 0.538 mg·L-1,and from 14.36 mg·L-1 to 23.29 mg·L-1,respectively.There are significant(P0.05) or very significant(P0.01) differences among the indexes of above four groups except NO2——N(P0.05);the survival rate decreased from 90.5% to 24.2% with the increase of the stocking density,there is no difference(P0.05) between the group 3 and the group 4(35.4% and 24.2%),and very significant difference(P0.01) among others,but the water quality indexes kept in the suited range for shrimp growth;There were no significant difference among group 1,group 2 and group 3(P0.05) in the increase of body length(6.07~6.23 cm),body weight(4.042~4.575 g) and growth rate(430.3%~551.1%),but those of differences between group 1～group 3 and group 4 are very significant(P0.01) or significant(P0.05);the yield of group 3(the highest yield of 799.6 mg·m-3) was 1.8 times of group 4(lowest).The relation between body length and culture days shows a linear correlation(L=at+b)(a,0.0751~1.0440;b,0.8979~1.1893),and power function relation between body weight and body length(W=aL3)(a,0.0116~0.0139).According to the results,350~550 ind·m-3 could be the reference density range for Litopenaeus vannamei freshwater culture indoor base on practical situation.