Intensive Rotifer Production in a Pilot-Scale Continuous Culture Recirculating System Using Nonviable Microalgae and an Ammonia Neutralizer
JOURNAL OF THE Vol. 39, No. 5 WORLD AQUACULTURE SOCIETY October, 2008
Intensive Rotifer Production in a Pilot-scale Continuous Culture Recirculating System Using Nonviable Microalgae and an Ammonia Neutralizer
C. D. BENTLEY,P.M.CARROLL, AND W. O. WATANABE1,2 Center for Marine Science, University of North Carolina Wilmington, Wilmington, North Carolina 28403-5927 USA
A. M. RIEDEL Aquatic Eco-Systems, Apopka, Florida 32703 USA
Abstract A study was conducted to test the performance of a high-density (.3000 individuals/mL) continuous recirculating system for rotifers (B. rotundiformis) fed nonviable Nannochloropsis oculata and using sodium hydroxymethanesulfonate to neutralize ammonia. Three different microalgae feed rates (g of N. oculata [68 3 109 cells/mL] per million rotifers/d) were tested in successive trials. In Trial 1 (feed rate 5 1.5), during a 30-d period, rotifers were harvested daily to 3000 individuals/mL, for an average yield of 178 million/d. Feed efficiency (million rotifers/g/d) was 0.33. In Trial 2 (feed rate 5 1.1), during a 32-d period, an average of 106 million rotifers were harvested daily, and feed efficiency was 0.26. In Trial 3 (feed rate 5 1.3), during a 30-d period, an average of 107 million rotifers was harvested daily, and feed efficiency was 0.23. An economic analysis based on a feed rate of 1.5 showed that production cost was 40% lower than the traditional batch culture method (US$ 0.29 vs. 0.46 per million rotifers/d). The continuous culture system tested reliably produced large quantities of rotifers on a daily basis without the use of a biofilter and with a lower production cost than a batch culture system.
One of the factors limiting seed production in space requirements and labor, eliminating the a marine finfish hatchery operation is the produc- need for multiple tanks, and improve culture sta- tion of the rotifers Brachionus rotundiformis and bility by stabilizing the bacterial populations in B. plicatilis as a food source for first feeding lar- the culture (James and Abu-Rezeq 1989; Fu et al. vae. It has been estimated that 400 billion rotifers 1997; Yoshimura et al. 1997; Rombaut et al. are required to produce 10 million gilthead seab- 2001). Recently, a recirculating system for continu- ream, Sparus aurata, fry in Mediterranean hatch- ous high-density rotifer culture was described eries (Zmora et al. 1991 cited by Lubzens et al. (Suantika et al. 2000, 2003). This system not only 2001). Many marine finfish hatcheries rely on reduced water consumption but also replaced the traditional ‘‘batch culture’’ method for rotifer microalgae with a cost-effective formulated diet. production in which several tanks are maintained For an intensive culture of rotifers to operate and harvested at timed intervals to ensure a con- efficiently, there must be an adequate supply of tinual supply. This method is labor intensive, re- food to maintain the rotifers in a satiated condi- quires a large portion of a hatchery’s floor space, tion (Hirayama et al. 1973). The development of and is often unstable and unpredictable (Dhert commercially available concentrated microal- et al. 2001). High-density continuous rotifer gae has allowed the culturist to provide the roti- culture systems are currently being developed fers with sufficient amounts of feed without the worldwide to provide daily harvests from one need to produce live microalgae in the hatchery tank. These systems, utilizing microalgae as feed, (Lubzens et al. 1995). This has greatly reduced have been shown to significantly reduce hatchery the need to allocate time and space to live feed production; however, the use of concentrated
1 Corresponding author. microalgae in high-density rotifer culture still 2 Present address: 601 S. College Road, Wilmington, NC represents 86% of production costs (Fu et al. 28403. 1997).