The detrimental effects of stalked ciliate infestations are documented for commercially important crustaceans, but not bivalves. Our oyster hatchery has dealt with both light infestations of these pests and heavy infestations that result in slowed growth and mortality of oyster seed. This project had two main objectives. The first was to identify and quantify specific stalked ciliates that are causing infestations of oyster seed, and the second was to identify the seasonality of stalked ciliate infestations. Results indicate that most of the stalked ciliates during the sample period were Suctorian spp., however other species were also noted.