The aim of this paper is to provide insights into how implementation of co-management systems can be a way in building trust between authorities and the users of a CPR. It is shown that a new co-management system can be developed and "triggered" by an ecological crisis and that trust and social networks are crucial factors for successful institutional development.The trawl fishery for vendus (Coregonus albula) in the northern part of the Gulf of Bothnia, has been top-down regulated by the State. At the beginning of the 1990s, catches started to decrease dramatically. In response to the poor performance of the fishery, a co-management system, with sharing of power and responsibilities between the authorities and the trawl fishermen, was implemented.It is concluded that managing fisheries with unexpected changes and complexity in linked social-ecological systems requires actors who learn from failures and, when necessary, initiate and achieve institutional change. The creation of social-ecological resilience can be looked upon as a process - a socially generated collective good - which is likely to result in better governance systems. In this context, the role of institutions in building adaptive capacity and supporting collective rationality is important.