Adaptive management implies a system in which policy and practice are constantly revised in a continuous circular process to accommodate new ecological knowledge. In the case of current fish stocking practices, there is an evident gap between science and practice indicating a lack of adaptability. While fish stocking is perceived as a solution to many problems of modern fishery management, scientific researchers warn that current practices, including introducing alien populations, seriously threaten the sustainability of fish stocks. The aim of this study was to address, explain the existence of and, finally, discuss the prospect of narrowing this gap. For this purpose, the characteristics of the policy subsystem were analyzed. The empirical findings highlight the wickedness of the policy problem. The substantial and institutional uncertainties surrounding the issue are proposed as the main reasons for the deficits in adaptability. Fish stocking decisions are made within a complex policy subsystem that involves multiple actors and policy-making institutions, conflicting goals and competing notions of the problem. Cross-coalition learning—learning between coalitions of actors with different problem definitions, forming a joint view—is a necessary and, in the case of fish stocking, lacking variable in the adaptive management process.