Effect of Shrimp Stocking Density on Size-fractionated Phytoplankton and Ecological Groups of Ciliated Protozoa within Zero-water Exchange Shrimp Culture Systems

摘要

Zero-water exchange shrimp culture systems are being investigated to reduce water and pathogens input and effluent output. The relative abundance and diversity of ciliates have been used as indicators of water quality and ecosystem dynamics in natural systems; however, their occurrence and role in shrimp production systems have not been investigated. The objectives of this research were to describe the succession of the ciliate community in a shrimp grow out system, to investigate the impact of increasing shrimp stocking density on the characteristics of the ciliated protozoa community, and to correlate this with shrimp performance. A growth trial with Litopenaeus vannamei was conducted outdoors with zero-water exchange and three stocking densities (50, 75 and 100 shrimp/mpo). In all treatments, free-swimming ciliates were dominant in the early weeks, while substrate-associated ciliates appeared later. The 100 shrimp/mpo treatment exhibited a lower abundance of free-swimming ciliates but higher abundance of hypotrichous ciliates in the second half of production and higher shrimp mortality and lower shrimp growth in the last 2 wk. These results provide a preliminary examination of the role of ciliates in shrimp culture systems and direction for future work in determining the role of protozoa as indicators of water quality.