黄颡鱼夏花培育池水质及浮游生物数量和类型的变化

Changes in Water Quality and Density of Plankton in a Juvenile Yellow Catfish Rearing Pond

在两口100 m^(2)、深1.5 m的水泥池中投放200 kg的池塘淤泥,第2 d用20 kg生石灰消毒后注入过滤的池塘水至80 cm,10 d后放入黄颡鱼水花17.9万尾/667 m^(2),每天每个水泥池泼洒豆浆150 g+光合细菌150 g,连续3 d;第4 d开始投喂蛋白质含量40%的粉碎饲料+葡萄糖,使投放物中C/N比保持15~20∶1,连续10 d。每3 d取样一次测定水质和浮游生物,观察黄颡鱼夏花培育池水质及浮游生物数量和类型的变化,以稳定提高黄颡鱼夏花苗种培育成活率。结果表明,苗种培育期间,水质良好,pH平均(7.85±0.5),碱度平均5.75 mmol/L,氨氮在1.0 mg/L以下,连续阴雨时氨氮有所升高,亚硝酸盐0.05 mg/L;浮游植物密度范围8666~133733 ind/L,呈下降-上升-再到下降的过程;初期,浮游动物数量较低(83 ind/L),以无节幼体为主,之后桡足类和枝角类数量开始少量上升,到第8 d桡足类数量超过其他,成为主要种类,而第12 d天轮虫成为主要种类,之后开始大幅度增加,到第15 d达5149 ind/L,占据绝对优势。黄颡鱼夏花成活率达到94.58%,鱼苗体长平均4.25 cm。试验表明:适当提高碱度、补充碳源、添加光合细菌、集中增氧等措施很好地控制了水质,提高浮游动物生产力和黄颡鱼夏花成活率。

Yellow catfish fry was reared in two 100 m^(2)and 1.5 m deep cement ponds in which 200 kg of pond sludge was put and then sterilized with 20 kg of quicklime on the second day and filled with the filtered pond water to 80 cm depth 10 days later at a stocking density of 179,000 fish/667 m^(2).The ponds were splashed with 150 g of soybean milk and 150 g of photosynthetic bacteria for 3 days,and on the 4th day,the fry were fed crushed diet containing 40%protein and glucose at C/N ratio=15~20∶1 for 10 days.Water sampling was performed once every 3 days to determine the water quality and number and type of plankton,and to observe the changes in the water quality and the number and type of plankton in the yellow catfish rearing ponds in order to stably improve the survival rate of the fish.The results showed that the quality of water was good during the fry culture,with average pH of(7.85±0.5),average alkalinity of 5.75,and ammonia nitrogen level of below 1.0 mg/L,an increase in ammonia nitrogen level derived from continuous rai,and the average nitrite level of 0.05 mg/L.The density of phytoplankton was ranged from 8,666 ind/L to 133,733 ind/L,showing a process of decline to rise and then to decline.The number of zooplankton was shown to be continued to maintain a low level of 83 ind/L in the early stages,with dominant Nauplius.Since then,the numbers of copepods and cladocera were found to be increased slightly,and by the eighth day,the number of copepods exceeded that of other major species.The rotifers became the main species on the 12th day,and then began to increase significantly,reaching 5,149 ind/L on the 15th day,occupying an absolute advantage.The yellow catfish fry had survival rate of 94.58%,and the average body length of 4.25 cm.Therefore,measures such as increasing alkalinity,supplementing carbon sources,adding photosynthetic bacteria,and concentrating oxygen enhancement can well control water quality,increase in the productivity of zooplankton,and then increase the survival rate of yellow catfish fry.