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ARS Home » Southeast Area » Stuttgart, Arkansas » Harry K. Dupree Stuttgart National Aquaculture Research Cntr » Research » Publications at this Location » Publication #313432
Title: Comparison of water quality and channel catfish production in earthen ponds or a biofloc technology production system

Author
item Green, Bartholomew - Bart
item Oneal Jr, Ernest

Submitted to: Aquaculture America 2015-Book of Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: 1/12/2015
Publication Date: 2/19/2015
Citation: Green, B.W., Oneal Jr, E.G. 2015. Comparison of water quality and channel catfish production in earthen ponds or a biofloc technology production system [abstract]. Aquaculture America 2015-Book of Abstracts. p. 530.

Interpretive Summary:

Technical Abstract: Biofloc technology (BFT) production systems are being used more commonly to produce high yields of fish or shrimp because very high feed rates are possible. In an outdoor BFT production system, a complex of living organisms is closely associated with particulate organic matter and is maintained in suspension by continuous aeration. Ammonia excreted by the culture animal is utilized by the phytoplankton and bacteria that are part of this complex of living organisms. Channel catfish have been grown successfully in an outdoor experimental BFT production system, which differs substantially from traditional earthen pond grow-out. In this 210-d study, we evaluated variation in water quality and fish growth for channel catfish (47 g/fish) stocked in earthen ponds (14,820 fish/ha) or the BFT production system (12.6/m2 or 126,000/ha). Ponds were equipped with electric paddlewheel aerators (13.8 kW/ha) that were activated by datalogger to maintain minimum dissolved oxygen concentration above 40% of saturation. BFT tanks were lined with HDPE and aerated continuously. Fish were fed a 32% protein commercially extruded feed daily to apparent satiation. Water quality varied between culture systems. Chlorophyll a increased rapidly in the BFT system after stocking whereas in ponds concentration remained static. During the first 60 d chlorophyll a averaged 1,720 mg/m3 in the BFT compared to 144 mg/m3 in ponds. Subsequently, chlorophyll a concentration in both treatments converged to a mean of 534 mg/m3 that persisted throughout the remainder of the experiment. Dissolved inorganic nitrogen concentrations in the BFT system were driven by nitrification: an initial ammonia spike was followed by a nitrite spike followed subsequently by increasing nitrate concentration. In comparison, pond concentrations of ammonia and nitrite were higher and more variable, and nitrate was lower. Fish were sampled periodically for growth and growth curve analysis showed intercepts and slopes did not differ significantly. However, at harvest, fish from ponds (0.630 kg/fish) were significantly larger than those from the BFT system (0.542 kg/fish). A significantly greater percentage of fish harvested from ponds were of market-size (0.57-2.04 kg/fish). Despite this, gross and net yields of market-size fish from the BFT system (3.1 and 2.8 kg/m3, respectively) were significantly higher than from ponds (1.0 and 0.9 kg/m3, respectively). Survival did not differ between production environments and averaged 96.7 and 92.2% for the BFT system and ponds, respectively. Feed conversion ratio was significantly higher in the BFT system (2.0) compared to ponds (1.6). Density-related social interactions appear to have affected fish growth more in the BFT system.