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item Green, Bartholomew - Bart

Submitted to: Book of Abstracts Aquaculture America
Publication Type: Abstract Only
Publication Acceptance Date: 12/16/2005
Publication Date: 2/13/2006
Citation: Green, B.W., Perschbacher, P. 2006. Effect of threadfin shad stocking rate on plankton in channel catfish production pond [abstract]. Aquaculture America 2006 Book of Abstracts. p. 114.

Interpretive Summary: Not required.

Technical Abstract: Threadfin shad (Dorosoma petenense) sometimes are stocked into channel catfish (Ictalurus punctatus) ponds to graze on phytoplankton or to serve as a forage fish for catfish brood fish. Generally, ponds are stocked with a low biomass of threadfin shad brood fish. Stocking a higher biomass of threadfin shad brood fish may result in higher standing stocks of shad to graze on plankton. We report on the impact of threadfin shad brood fish biomass on phytoplankton biomass and composition and channel catfish production ponds. Twelve 0.1-ha earthen ponds each were stocked with pre-spawn adult threadfin shad at 0, 56, or 224 kg/ha. Three weeks later stocker channel catfish (4,817 kg/ha) and fingerling channel catfish (14,820/ha) were stocked. At harvest, 151 days after stocking, catfish were separated into three size groups: 0.57 kg and larger, 0.34-0.57 kg, and 0.34 kg and smaller. Catfish were tested for off-flavor at harvest by sensory evaluation. Although initial shad biomass differed by a factor of four, final shad biomass was similar and averaged 691 and 662 kg/ha for the 56 and 224 kg/ha stocking rates, respectively. Catfish yield was unaffected by final shad biomass. Yields of market-sized catfish averaged 7,409, 9,569, and 8,657 kg/ha for the 0, 56, or 224 kg/ha shad stocking rates, respectively. Total yield of catfish averaged 15,677, 17,548, and 16,004 kg/ha respectively. Chlorophyll a concentrations were unaffected by threadfin shad stocking rate. Chlorophyll a treatment means were 385.6, 351.5, and 289.5 mg/m3 for the 0, 56, or 224 kg/ha stocking rate treatments, respectively. Catfish flavor scores at harvest were independent of shad biomass and averaged 2.70, 2.40, and 2.43 (out of 5) for the 0, 56, or 224 kg/ha stocking rate treatments, respectively. Catfish with these scores are considered to be off-flavor.