Although carp farming had a key role in the Blue Revolution at a global level, European carp aquaculture has stagnated over the past 25 years without achieving any productivity gains. The objective of this study was to identify the factors and mechanisms constraining production and productivity growth in pond-based carp farming in Hungary, as the country is a good representative of the EU pond-based farming sector. By using data from 44 carp farms, different specifications of the Cobb-Douglas production function were parameterized to investigate the determinants of yields and to assess the extent of economies of scale. Descriptive statistics show that large differences exist in productivity between individual farms, meaning that it is hard to implement technical standards and to ensure repeatability in extensive carp farming technology. Econometric analysis demonstrates that economies of scale do not prevail in pond-based farming in Hungary, so a concentration of farms would not stimulate a growth in carp farming. This may explain the stagnation of carp aquaculture, as the only European aquaculture segments which can grow are those that can exploit economies of scale. Further analysis demonstrates that labour is an important factor of production, and a decreasing workforce may constrain the intensification process of production. On the other hand, mechanisation did not prove to be a significant contributing factor to yields, indicating that large investment in equipment has a limited role in carp farming.