养殖密度和换水量及频率对凡纳滨对虾生长的影响

Effects of culturing density and water exchange rate and frequency on growth of Litopenaeus vannamei

在26℃下,将体长(2.089±0.021)cm的凡纳滨对虾(Litopenaeus vannamei)饲养在15 L聚乙烯圆形水桶中,设置400尾/m^3和800尾/m^32个密度和5个换水条件(不换水、日换水量20%、日换水量50%、3 d全量换水、5 d全量换水)双因素处理,研究不同养殖密度和日换水条件对水质和凡纳滨对虾幼虾生长的影响,并根据养殖密度、日换水量及养殖天数对自污染因子的影响,建立了各污染指标与养殖密度、日换水量及养殖天数的回归关系模型。结果显示:养殖密度和日换水量对水体p H无显著性影响(P>0.05);水中NO_2^--N、NH_4^+-N及COD浓度均随换水量增大而降低,其中日换水量50%组累积量最低,显著低于其他组(P<0.05);3 d全量换水和5 d全量换水试验组中,NO_2^--N、NH_4^+-N及COD浓度在换水前达峰值,在换水次日骤降至最低值,然后逐渐升高,如此循环,但仍低于对照组;相同换水条件下,密度400尾/m^3时自污染因子浓度均低于800尾/m^3组;NO_2^--N(Y_1)、NH_4^+-N(Y_2)和COD(Y_3)浓度指标与养殖密度(X_1)、日换水量(X_2)及养殖天数(X_3)的回归关系模型分别为:Y_1=0.048-0.002X_2-0.001X_3;Y_2=0.163+0.04X_1-0.018X_2+0.01X_3;Y_3=4.85+0.429X_1-0.199X_2。研究表明:在养殖密度400尾/m^3、换水率50%的养殖条件下,可以保证水体自污染程度最低,凡纳滨对虾生长良好。

With Litopenaeus vannamei of(2.089±0.021)cm long kept in a 15 L polythene circular bucket at 26℃and two factors set:density of 400 shrimps/m 3 and 800 shrimps/m 3 and five water exchange conditions(no exchange,daily water exchange rate 20%,daily water exchange rate 50%,full water exchange every 3 d and full water exchange every 5 d),effects of various culturing densities and daily water exchange conditions on water quality and growth of juvenile Litopenaeus vannamei were studied,and regression model of the pollution indexes with culturing density,daily water exchange rate and culturing days was established based on effects of culturing density,daily water exchange rate and culturing days on self-pollution factors.The results showed that culturing density and daily water exchange rate had no significant influence on pH of the water(P>0.05);the concentration of NO-2-N,NH+4-N and COD was decreased with the increase of water exchange rate,their cumulative amount was minimum in the groups of 50%daily water exchang rate,significantly lower than that of other groups(P<0.05);in groups of full water exchange every 3 d and full water exchange every 5 d,the concentration of NO-2-N,NH+4-N and COD reached the peak before water exchange dropped to the minimum in the next day,and then gradually increased,which,though repeating in this cycle,was still lower than the control group.Under the same water exchange condition,the self-pollution factor concentration for density of 400 shrimps/m 3 was lower than that for 800 shrimps/m 3;the regression models of concentration indexes NO-2-N(Y 1),NH+4-N(Y 2)and COD(Y 3)with culturing density(X 1),daily water exchange rate(X 2)and culturing days(X 3)were respectively:Y 1=0.048-0.002 X 2-0.001 X 3,Y 2=0.163+0.04 X 1-0.018 X 2+0.01 X 3,Y 3=4.85+0.429 X 1-0.199 X 2.The study indicates that the minimum degree of self-pollution and good growth of Litopenaeus vannamei can be guaranteed at culturing density of 400 shrimps/m 3 and water exchange rate of 50%.