对虾养殖池塘内混养鲻鱼和罗非鱼对水环境及对虾生长的影响

Effects of mullet and tilapia on the water quality and growth of shrimp in polyculture ponds of shrimp Litopenaeus Vannmei

通过比较对虾—鲻鱼(SM)、对虾—罗非鱼(ST)混养池塘内营养盐含量、颗粒物质、浮游生物以及对虾生长性能等指标变化,研究了鲻鱼(Mugil cephalus)、罗非鱼(Oreochromis niloticus)在对虾养殖池塘内(1000 m2)的生态效益。实验时间为100 d。结果显示,实验期间SM和ST组池塘水体中氨氮(NH_4^+—N)、总氮(TN)、总磷(TP)、活性磷(SRP)、颗粒物质(TPM)等均表现出增加的趋势;在实验中后期,SM组池塘水体中的溶解态氮(NH_4^+—N、NO_3~–—N)低于ST组,然而TN含量却高于ST组,且在实验后期表现出显著差异(P<0.05);同时,SM组池塘水体中的颗粒物质含量高于ST组,表明SM池塘水体中较高的TN含量是源于悬浮颗粒物质。2个混养池塘内浮游生物和叶绿素a含量变化范围分别为5.72—16.83μg·L^(–1)和4.35—15.32μg·L^(–1),无显著差异。实验表明,鲻鱼的扰动可以促进底部有机质向上层水体迁移,有利于降低NH_4^+—N、NO_3~–—N等物质的积累和促进养殖系统内物质循环;对虾存塘率和鱼类取样结果表明,鲻鱼可以与对虾直接混养,罗非鱼通过围网隔离养殖可以取得更好的效果。鲻鱼和罗非鱼对养殖系统不同粒径浮游植物的滤食能力需要进一步研究。

To study the effects of polyculture of mullet and tilapia on the water in the shrimp ponds, we investigated the water quality such as N and P contents, particulate material, particulate organic material and plankton in the water during a 100 d period. The results showed that the increasing tendency was found in the contents of ammonia nitrogen （NH＋4-N）, total nitrogen （TN）, total phosphorus （TP）, soluble reactive phosphorus （SRP） and particulate material during the experiment. The dissolved inorganic nitrogen CNH＋--N, NO3--N） in the SM pond was lower than that in the ST pond; however, the total nitrogen in the water was higher than that in the ST pond in the late culturing period. Meanwhile, the particulate material in SM pond was higher than that in the ST pond. The content of chlorophyll a and plankton in the 2 ponds had the similar varying tendency during the experiment. These results indicated that the bioturbation of mullet could partly boost the upward transportion of particulate material in the sediment, and it was conductive to the nutrient circulation in the culturing system. The results of survival rate of shrimp and fish sampling suggested that the mullet can be cultured with shrimp in the pond without isolation measures, but the tilapia should be cultured in the isolation measures for its prey on the shrimp. The feed-taking capacity of mullet and tilapia for different phytoplankton needs more study because of the importance of phytoplankton in the water.