池塘中亚硝酸盐对草鱼种的毒害及防治

TOXICITY OF NITRITE TO GRASS CARP (CTENOPHARYNGODON IDELLUS)IN PONDS AND ITS WAY OF PREVENTION

亚硝酸盐对草鱼种有很高的毒性,特别是水温超过30℃以上时。它主要是诱导草鱼血液中的血红蛋白转变为高铁血红蛋白,高铁血红蛋白超过血红蛋白总量的23.0％时,容易诱发草鱼出血病。随着草鱼血液中高铁血红蛋白的增高,红细胞数量和血红蛋白含量逐渐减少。池中亚硝酸盐氮含量到0.099±0.03毫克/升时,草鱼会出现出血病。清除水中亚硝酸盐氮的方法是在池塘中施加次氯酸钠,亚硝酸盐氮超过0.15毫克/升时,最好在池塘中先施加熟石灰,然后施加次氯酸钠,且以分次施用,效果较好。

Nitrite has been shown to be highly toxic to grass carp. It can in-duce hemoglobin (Hb) to become methemoglobin (MHb). If methemoglobin isover 23.0% of total Hb, the grass carp will easily get hemorrhage disease. The ex-periment shows that 96-h LC_(50) values of NO_2-N was 4.62mg/L at the average watertemperature 30℃, especially over 32℃. As the number of methemoglobin increasesin the blood of grass carp, the number of erythrocyte and total hemoglobin gra-dually decrease. The way to remove nitrite-nitrogen from water is by adding so-dium hypochlorite. When the concentration of NO_2-N is over 0.15 mg/L, at firstcalcium hydroxide [Ca(OH)_2] is added before the addition of sodium hypochlorite.