Submitted to: Global Aquaculture Advocate
Publication Type: Trade Journal
Publication Acceptance Date: 6/30/2002
Publication Date: 8/1/2002
Citation: Pfeiffer, T.J., Ludwig, G.M. Trial finds microalgae paste suitable for rotifer nutrition. Global Aquaculture Advocate.2002.v.5(4).p.22-23.
Technical Abstract: The mass production of the rotifer, Brachionus plicatilis, serves as a source of live food for the early stages of commercially cultivated fishes. Mass production of this rotifer can be based on different alimentary sources including microalgae paste. Information of the use of microalgae paste, a recently developed product, for the mass production of rotifers is scarce. Therefore, the effect of microalgae paste on rotifer growth and production was investigated. Rotifers were cultured in translucent, low-density polyethylene, conical tanks. The tank culture volume was 45 liters and the water temperature was kept above 25 0C by suspending a 100-watt immersion heater in each tank. Also suspended in each of the tanks was a sponge filter to remove particulate matter. During a 21-day production trial, four tanks were utilized for culturing rotifers using a commercially available Nannochloropsis sp. algal paste for feed. The algal feed concentration provided was 75,000 algal cells per rotifer per day. The required amount of paste was diluted with seawater to a volume of 2.4 liters. The algal paste and seawater dilution was kept in plastic containers placed inside an electric cooler to keep the feed chilled and prevent it from putrefying. A peristaltic pump connected to a timer delivered 100 mL of the feed solution every hour to the culture unit. The volume of algal paste in the feed solution varied daily and was based on the after harvest rotifer count. The rotifer population in each of four tanks was maintained between 500 and 1500 rotifers per mL. Daily counts in each tank were done with a 1-mL Sedgewick-Rafter counting cell. Counts were done in triplicate by counting a 1ml sample that was diluted 10 to 1 in saltwater. A volume of 15 liters was harvested when the rotifer count was above 1500 rotifers per mL. The harvested volume was replaced with fresh saltwater. The saltwater was artificial and was mixed to a concentration of approximately 25 ppt. The four tanks in production were at the designated 1500 rotifers per mL harvest levels 64 to 73% of the time. Based on the rotifers harvested, the average salt and algal paste cost ranged from $0.23 to $0.26 per million rotifers harvested. The simple and inexpensive system using algal paste as a food source appears appropriate for use as a basic unit for the mass production of rotifers in commercial fish hatcheries