As an island nation, Ireland is connected to and responsible for the seas that surround it. Fishing has historically been one of the major anthropogenic activities linking Irish society to the marine environment. Deriving an approach from historical ecology, we investigated temporal patterns in the diversity of seafood landed, traded and marketed in Ireland by collating long-term datasets acquired from government sources and through conducting contemporary product surveys. Our findings suggest that consumer preferences have not adapted to changes in local resource supply. From the beginning of the 20th century, Irish landings of some of the traditionally most important seafood products have gradually grown, then sharply declined within the most recent 10–20 years, but access to ample supply appears to have been maintained in the Irish marketplace. Our results indicate that this trend has been concealed from consumers through import, aquaculture production and mislabelling. Future intentions of responsible management must incorporate policy implementation and enforcement, consumer education and industry transparency.