THE EFFECT OF CONTINUOUS NOCTURNAL, OR NO AERATION ON WATER CHEMISTRY AND PLANKTON STANDING CROPS IN HEAVILY FERTILIZED SUNSHINE BASS FINGERLING PRODUCTION SIZE PONDS WITHOUT FISH.

Authors: Ludwig, Gerald

Submitted to: Journal of Applied Aquaculture
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/20/2002
Publication Date: 10/1/2003
Citation: LUDWIG, G.M. THE EFFECT OF CONTINUOUS NOCTURNAL, OR NO AERATION ON WATER CHEMISTRY AND PLANKTON STANDING CROPS IN HEAVILY FERTILIZED SUNSHINE BASS FINGERLING PRODUCTION SIZE PONDS WITHOUT FISH.. JOURNAL OF APPLIED AQUACULTURE. 2003. v.14.

Interpretive Summary: Sunshine bass initially require living food including high numbers of tiny animals called rotifers, followed by larger crustacean zooplankton. Nursury ponds are fertilized to promote growth of these live foods. Previous experiments showed that as more fertilizer is added to the ponds more zooplankton will grow, however, water quality for culturing sunshine bass fry deteriorates. This experiment was conducted to determine if aeration b paddlewheels could alleviate the water quality problems. The experimental results indicated that aeration increased numbers of zooplankton over those found in un-aerated ponds and also cooled the ponds to levels better for fish growth. Dissolved oxygen levels were also much better. However, un- ionized ammonia levels, which are dangerously high in heavily fertilized ponds, were even higher when ponds were aerated continuously, most likely because fertilizers and bottom sediments were held in suspension by the continuous use of paddlewheel aerators. Ponds prepared and managed in thi way would not be suitable for in-pond culture of young sunshine bass but would be very good for harvesting zooplankton to provide live feed for fish cultured in tanks.

Technical Abstract: High fertilization rates increases zooplankton production but often causes poor water quality that paddlewheel aeration may alleviate. This study was designed to determine the effects of constant and nocturnal aeration on water quality and plankton standing crops in heavily fertilized, but fishless nursery ponds. Four 0.04 ha ponds were aerated continuously and four ponds only at night with a 2 HP paddle wheel aerator; four additional ponds had no aeration. During 21 days after they were filled on July 21, 1999, the ponds received 1,224 kg/ha rice bran and 581kg/ha liquid 9-27-0 fertilizer. Water quality and plankton were sampled daily. The results showed that water temperatures were better for fish growth in the constant- ly aerated ponds than in un-aerated ponds. Dissolved oxygen concentrations were higher in the morning and lower during the afternoon in constantly aerated ponds. Constant mixing with aeration resulted in higher average pH Hand higher concentration of nitrite-N, nitrate-N, total ammonia-N and un- ionized ammonia. Phosphate levels did not differ among treatments. Chlorophyll a concentrations were highest in the constantly aerated ponds. Rotifers, first foods of sunshine bass fry, were initially highest in the constantly aerated ponds. The larger crustacean zooplankton also had highest concentrations in ponds that were aerated, particularly those receiving constant aeration. While constant aeration alleviated many poor water quality variables and promoted zooplankton growth it also resulted in elevated levels of un-ionized ammonia that is dangerous to fry. The constantly aerated ponds were the most suitable for cropping zooplankton for tank culture of sunshine bass fingerlings.