盐度对凡纳滨对虾生长和氮磷收支的影响

采用海水、河口水与淡水及简易设施开展室内封闭式高密度对虾养殖试验,探讨了盐度对虾生长与氮磷收支的影响。结果表明,100 d养殖试验中,未曾换水与用药,养殖试验池主要水质指标虽有程度不等差异,但均控制在对虾生长安全范围。3个试验组对虾成活率随盐度降低分别显著下降88.2%、53.9%和34.8%,(P<0.05);终末体重,河口水组(9.20 g)显著高于海水组(8.49 g)和淡水组(8.45 g)(P<0.05);单位水体产量随盐度降低极显著下降2 443.52、1 597.50和659.52 g.m-3(P<0.01)。试验池氮、磷收支估算结果显示:各试验组氮磷主要收与支的同类项所占比例较接近,特点相同,投入饲料氮与磷分别占氮与磷总收入98.9%、98.1%、96.4%与99.3%、98.9%、97.9%,水层与虾苗共含氮与磷分别占1.1%、2.0%、3.7%与0.7%、1.1%、2.1%;排污、不换水水泥池水层氮占氮总输出比例最高,略高于虾体;污水磷占磷总输出比例明显高于其余项,此不同于泥底虾塘为沉积物氮、磷占氮、磷总输出的比例最高。试验池水层与污水共含氮与磷分别占氮与磷总输出57.7%、61.3%、57.2%与67.9%、66.7%、73.3%,低于虾塘泥底沉积物与水层合计氮与磷占总氮与总磷输出比例;收获虾体氮、磷占氮、磷总输出:35.3%、34.5%、34.4%与19.3%、18.9%、19.0%,饲料利用转化率较好;池水蒸发渗漏与池壁吸附等损失输出氮、磷占氮、磷总输出:7.0%、4.2%、8.5%与12.8%、14.3%、7.6%。

Effects of salinity on the growth of Litopenaeus vannamei and the nitrogen, phosphorus budgets of the culture ponds

The growth of white shrimp Litopenaeus vannamei juveniles (0.11-0.15 g) and nitrogen, phosphorus budget of culture ponds were investigated under conditions of seawater, estuary water and fresh water. The results showed that main water quality parameters among these three style waters were different throughout whole rearing period. However, there were no significant differences in water quality parameters under different water style (P>0.05). Survival rates of white shrimp decreased significantly with decreased salinity (P<0.05). Average final weight of the shrimp grown in seawater, estuary water and fresh water was 8.49, 9.20 and 8.45 g, respectively, and shrimp final weight in estuary water was higher than that in fresh water (P<0.05). Final biomass loads of seawater groups (2 443.52 g·m^-3) were much higher than that of estuary groups (1 597.50 g·m^-3) and freshwater groups (659.52 g·m^-3) (P<0.01). Test data suggest that the results of N, P budgets within the ponds among three style waters were similar. Most of the N, P entered the rearing ponds as formulated shrimp feed 98.9%, 98.1%, 96.4% of the input N and 99.3%, 98.9%, 97.9% of the input P in seawater, estuary water and fresh water. Intake water and shrimp juveniles accounted for 1.1%, 2.0%, 3.7% and 0.7 %, 1.1%, 2.1% of the input N and P. Nitrogen was lost primarily from water layer nitrogen. Phosphorus was lost primarily from effluent P. The calculated outputs of P were different from that most output P was accumulated in the sediment in outdoor mud ponds. Within the ponds, 35.3%, 34.5%, 34.4% of the input N and 19.3%, 18.9%, 19.0% of input P were converted to harvest shrimp, 57.7%, 61.3%, 57.2% and 67.9%, 66.7%, 73.3 % of output P was remained in the layer and effluent. Only 7.0%, 4.2%, 8.5% of input N and 12.8%, 14.3% , 7.6% of input P were unaccounted for, and generally assumed to be consumed from evaporation and adsorb.