This paper reverses the common emphasis in the literature on public understanding of science by examining “experts’ understanding of the public.” This research uses the case of aquaculture in Canada, a highly contested mode of production that has divided the scientific community and public opinion. Using a survey of 300 aquaculture experts in Canada, we examine three dimensions of experts’ understanding of public “contributions” to this controversy. These are (1) stakeholder participation in aquaculture regulation and policy, (2) the media as an interpreter and communicator of expert claims, and (3) the knowledge and values basis of general public opinion. We find that experts’ views on lay knowledge and participation in the debate swing from strongly positive to strongly negative. Using quantitative and qualitative data from the survey, we argue that these swings in experts’ views of the public coincide with issues of control over knowledge. Experts on all sides of the aquaculture controversy are markedly open to incorporating lay knowledge into scientific practices (a situation where expert control over knowledge is retained), but are highly critical of lay “consumption” of expert claims (a situation where expert control over knowledge is lost).