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. The objective of this experiment was to evaluate chlorophyll a, plankton composition, and catfish production in ponds stocked with threadfin shad at three rates. Although initial shad biomass was different, 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. Diatoms and green algae were the major plankton groups in all ponds during April and May. In ponds stocked with shad, diatoms and green algae represented 26-75% and 4-45%, respectively, of the plankton population during the remainder of the experiment. Blue green algae comprised 50-80% of the plankton population on 6 sampling dates from Aug-Oct in ponds not stocked with shad, whereas in shad ponds, blue green algae exceeded 50% of the population only once in the low shad treatment. Off-flavor blue green algae species were numerically higher from mid-Aug through Oct in ponds not stocked with shad. 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.