Is replacement of wild fish by stocked fish an emergent property of community-based recreational fisheries management in a stochastic world?

The social mechanisms underlying the widespread belief of angler communities in stocking being a useful tool to maintain or enhance wild fish stocks are only anecdotally understood. We constructed a coupled social-ecological model to examine the evolution of stocking decisions when recruitment of the wild fish population is stochastic and stocking decisions by managers are influenced by harvest-dependent angler satisfaction. By integrating basic human properties of memory and forgetting our model predicts replacement of wild fish by stocked fish to be an emergent property over a wide range of decision making scenarios. The ratcheting up of stocking levels maintaining wild population does not occur if the relative survival rate of stocked fish is low or if anglers forget past fishing successes when determining expectations about fishing quality in the future. The latter is unlikely to occur in reality. Thus, our model predicts that community-based fish stocking management by angler communities, as it is typical in central Europe, is likely to promote and then maintain intensive stocking on a regular basis. This might have repercussions for the biodiversity of wild fish. Fostering of the adaptive capacity of the recreational fisheries management system is needed to resolve the dilemma.