Submitted to: Global Aquaculture Advocate
Publication Type: Trade Journal
Publication Acceptance Date: 5/1/2002
Publication Date: 8/1/2002
Citation: LUDWIG, G.M., PFEIFFER, T.J. TRIAL FINDS MICROALGAE PASTE SUITABLE FOR ROTIFER NUTRITION. GLOBAL AQUACULTURE ADVOCATE. 2002. v.5 (4). p.22-23.
Interpretive Summary: Most commercially cultured fish require zooplankton, particularly rotifers when they are fry. Rotifers are usually difficult to culture. A rotifer culture system was developed that could be easily used by fish culterists. Four tanks were filled with brackish water (25-30 ppt) and a starter population of rotifers. Temperatures were kept between 25 and 30°C. A paste composed of concentrated microalgae was diluted and then constantly fed to the rotifers by using a peristaltic pump. When the rotifer population reached 1500/ml a third of the culture was harvested daily. The water was replenished daily. The system was kept running for three weeks and 70% of the days the culture reached the desired concentration.
Technical Abstract: The primary food of many larval fish is zooplankton, often rotifers. Brachionus plicatilis, a brackish-water rotifer is often cultured to feed to the fry of many commercially grown fish. A culture system to efficiently produce large quantities of this rotifer was developed. The system is composed of four 60-L conical polyethylene tanks filled to 45 L. Water temperatures were kept between 25 and 30°C and salinity at 25-30 ppt. A sponge filter removed waste particulate matter. Commercially available Nannochloropsis algal paste was continuously pumped to the system to feed the rotifers at the rate of 75,000 algal cells/rotifer/day. Total daily amounts of paste depended upon rotifer concentrations that were determined daily. The algal paste was diluted with salt water to 2.4 L, kept in an electric cooler and constantly transferred to the culture chamber with a peristaltic pump at 100 ml/hr. A population of rotifers at 500 to 1500 rotifers/ml was maintained for 21 days. Fifteen liters per day was harvested when the population was 1500/ml or greater. The four tanks were at the 1500 rotifers/ml for 64-73% of the time. An estimated 20-135 million rotifers (average 75 million) per day were harvested. The cost for salt and algal paste was estimated at $0.23-0.26/million rotifers harvested.