Submitted to: Book of Abstracts Aquaculture America
Publication Type: Abstract only
Publication Acceptance Date: 12/13/2006
Publication Date: 2/26/2007
Citation: Green, B.W. 2007. Physical Manipulation of Phytoplankton Blooms [abstract]. Book of Abstracts Aquaculture America. p. 360. Interpretive Summary:
Technical Abstract: Channel catfish (Ictalurus punctatus) are reared in large earthen ponds, and in the southern U.S. the growing season duration varies from about 140 to 200 days. During the growing season, catfish are fed to satiety on a daily basis, daily feeding rates average 75-125 kg/ha, and maximum daily feed ration ranges from 130 to 245 kg/ha. Because channel catfish retain 15-25% of feed nitrogen and 20-30% of feed phosphorus, the nutrient load to ponds during the growing season is high. Dense phytoplankton blooms typically develop in catfish production ponds in response to high catfish feeding rates. Mean phytoplankton biomass and variation in biomass among ponds were greatest during late summer, which also is when algal communities have low species diversity that result in unstable populations and sudden die-offs. Control of excessive phytoplankton biomass must be an integral part of pond management given the role of phytoplankton biomass as a determining factor in catfish production pond water quality and loading limits. Physical manipulation of phytoplankton populations by circulators, filtration units, and other means will be discussed.