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item Green, Bartholomew - Bart
item Perschbacher, Peter
item Schrader, Kevin

Submitted to: Catfish Farmers of America Research Symposium
Publication Type: Abstract Only
Publication Acceptance Date: 12/16/2005
Publication Date: 2/24/2006
Citation: Green, B.W., Perschbacher, P., Schrader, K. 2006. Impact of horizontal or vertical circulation on water quality, plankton, and catfish production [abstract]. 2006 Catfish Farmers of America Research Symposium Book of Abstracts. p. 38.

Interpretive Summary: Not required.

Technical Abstract: Mechanical circulators have been used to manipulate water quality in water bodies that range from ponds to lakes. Horizontal discharge, and up-welling and down-welling vertical discharge circulators are the three designs that have been used. Circulator-induced impact on water quality has been variable, particularly in terms of the effect on phytoplankton abundance and species composition. Circulator design and duration of operation may increase the impact of circulation. The purpose of this experiment was to evaluate the effect of a low-revolutions per minute horizontal discharge or an up-welling vertical discharge circulator on water quality, plankton and channel catfish production. Green algae predominated in all treatments ponds through mid-June, after which blue-green algae predominated until harvest. Chlorophyll a concentrations were similar among treatments, and averaged 240.3, 197.2, and 194.7 mg/m3 for the control, horizontal and vertical circulation treatments, respectively. Off-flavor algae were present in treatment ponds from mid-July through early September. No treatment differences were detected among water quality variable means. However, temperature and dissolved oxygen concentration profiles were uniform to the 30-in depth in circulated ponds. Thus, excess photosynthetically produced dissolved oxygen was retained in circulated ponds. Net catfish yield was similar among treatments and averaged 7,484 lb/acre, of which 86% exceeded 1.25 lb average weight. Mean individual weight at harvest among treatments was 1.99 lb. At harvest, fish from all treatments were classified as being off-flavor. Pond circulation impacted positively pond temperature and dissolved oxygen, but had no significant impact on fish production, plankton, or water quality variables.