餌料生物換水器暨高密度輪蟲連續生產系統之研發

Abstract

輪蟲高密度連續生產的瓶頸在於難以換水，以致於水質惡化，限制輪蟲增殖。本研究研發一台餌料生物換水器，創造出新的輪蟲連續生產模式。該餌料生物換水器係以浮游生物濾網包覆滾筒，以馬達驅動滾筒旋轉，換水時滾筒僅1/3沒入水中，內有幫浦將水抽出。滾筒的旋轉會在濾網與水體間產生剪力，避免輪蟲吸附於網布上，因此能保持濾網自淨，能減少換水對輪蟲的傷害。本研究先探討不同輪蟲密度與換水速率所需要的自淨轉速，再探討不同輪蟲密度與換水時間對輪蟲存活率與帶卵率的影響，最後進行兩次高密度輪蟲 (Brachionus plicatilis) 生產試驗。養殖水體為100 L，餌料為濃縮淡水小球藻 (Chlorella vulgaris)，每天以換水器換水1-4次，每次換水量為60 %，輪蟲密度由約600 ind./ml開始，經過一週即可開始收穫。第一次生產試驗平均收穫密度可達6,569 ind./ml，持續7天；第二次生產試驗平均收穫密度可達6,638 ind./ml，持續8天。每日收穫量為水體的20 %，平均收穫量分別為1.31 × 108、1.33 × 108隻輪蟲，比增殖率分別為0.252/day與0.234/day。生產期間氨氮 (NH3-N) 濃度因換水而震盪，變化幅度在1.05-8.5 mg/L與1.1-10 mg/L之間。每次收穫時輪蟲已幾乎將水中微藻吃完，故甚少浪費。由於每次換水時，水位會降低，有利於清除底泥，能降低原生動物大量孳生的風險。本系統設備簡單，成本低，能隨時啟動生產輪蟲，適合對輪蟲有即時需求的業者使用，亦可用於商業化的量產。本換水器對生物傷害小，有潛力應用於其他餌料生物或長浮游期幼苗的生產。

Changing water is a demanding task in high-density rotifer culture. This study develops a zooplankton filter for high density rotifer continuous production. The zooplankton filter has a rotating drum which is covered by a plankton screen and driven by a motor. One-third of the rotating drum is submerged into the water. A small pump inside the drum pumps water out of the drum. The rotation of the drum produces a shearing force between the plankton screen and the surrounding water making the screen self-clean. This could not only avoid the rotifers being attached onto the screen, but also could reduce injuries of rotifers in the water changing process. The optimal rotation speeds of the drum were determined by experiment for different rotifer densities and water changing rates. The effects of rotifer density and the length of water changing time to rotifer survival rate and egg-carrying ratio were studied. Two high density rotifer production tests were then carried out. The culture volume is 100 L were fed which concentrated freshwater chlorella (Chlorella vulgaris). Water was changed 1-4 times by the zooplankton filter, each time changing 60% of water in volume per day. The rotifer density was approximately 600 ind./ml in the beginning of each test. Harvesting started after a week, daily harvested volume is 20%. The rotifer densities at harvest at 6,569 in the first test, and 6,638 in the second test. The average harvests were 1.31 × 108 and 1.33 × 108 rotifers, respectively. The growth rates were 0.252/day and 0.234/day, respectively. Ammonia-nitrogen (NH3-N) ranged between 1.05-8.5 mg/L and 1.1-10 mg/L, respectively. Microalgae in the water usually was fully consumed by the rotifer before harvesting times, thus minimizing waste. No protozoan blooming was observed in both tests, presumable due to the manual removing of the sediment after each harvest. This high-density rotifer production system is simple, inexpensive, and requires little prior effort to start. Thus, it is suitable for those who have immediate demand for rotifers and for the mass production of rotifers in commercial operations as well. The zooplankton filter system also has the potential to apply to other live food and crustacean larvae production.