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item Green, Bartholomew - Bart
item Ludwig, Gerald

Submitted to: University of Arkansas-Pine Bluff Aquaculture Field Day
Publication Type: Abstract Only
Publication Acceptance Date: 9/20/2004
Publication Date: 10/7/2004
Citation: Green, B.W., Perschbacher, P., Ludwig, G.M. 2004. Plankton dynamics in channel catfish production ponds costocked with threadfin shad[abstract]. University of Arkansas-Pine Bluff Aquaculture Field Day, October 7, Aquaculture/Fisheries Center of Excellence, University of Arkansas Pine Bluff, Pine Bluff, AR. p.14.

Interpretive Summary: Summary not required.

Technical Abstract: Catfish farmers have stocked production ponds with threadfin shad (Dorosoma petenense) in an effort to control the biomass of algae responsible for off-flavor. We report on the impact of threadfin shad on phytoplankton and zooplankton populations in ponds where channel catfish (Ictalurus punctatus) are fed daily or every third day. Threadfin shad had a significant impact on chlorophyll a in ponds fed on a daily basis, but not in ponds fed every third day. Mean chlorophyll a concentration in ponds fed daily was 194.4 mg/m3 where shad were stocked, lower (p = 0.058) than the 319.9 mg/m3 in ponds where shad were absent. In ponds fed every third day, mean chlorophyll a concentrations were 208.5 and 154.3 mg/m3 (p = 0.336) where shad were present or absent, respectively. The number of phytoplankters in ponds with and without shad was variable and averaged 6,426 and 7,798/mL, respectively. The composition of the phytoplankton population was affected by the presence of shad. Diatoms were significantly higher in ponds with shad on 5 of 15 sample dates and diatom percentages (40-74%) were highest during July, August and September. Bluegreen algae were lower by an order of magnitude in shad ponds on 8 of 15 sample dates. Bluegreen algae were high in May and June (11-56%) in ponds with shad, but declined continuously thereafter, while in ponds without shad bluegreens comprised 65-91% of algae numbers during May, August and September. Shad also affected zooplankton populations. Copepod and cladocerans numbers decreased 60-86% within a month of stocking shad and remained low throughout the experiment. Rotifer numbers were high in all ponds from April through June, and were significantly higher in ponds without shad during July through September.