A Theoretical Framework Against the Uncritical Use of Fish Stocking

Fish stocking is a popular tool used to manage fishery stocks and wildlife. However, the overall contribution of this technique to enhance or rehabilitate natural populations has been criticised, because of technical issues, inherent limitations and abuses. Multiple factors may affect the outcome of stocking, and a primary assumption is environmental feasibility, i.e., whether the action has the potential to generate positive effects in a specific scenario. To shed light on this important issue, our essay presents a theoretical and accessible framework to define the environmental feasibility of fish stocking applied to management systems associated with population enhancement, rehabilitation, or restoration. Our framework builds on the main concepts and theories of population ecology, particularly ecological carrying capacity ( K ), specific stressors, population size ( N ) and growth. Considering that feasibility is controlled by (i) the ratio N/K , (ii) population and environmental constraints and (iii) the possibility of natural recovery, we developed a simple equation to describe the relationship among these variables, and built scenarios and numerical simulations to illustrate how feasibility responds to different contexts. The framework shows that feasibility is highly sensitive to environmental settings, with potential application restricted to specific scenarios, which may explain why many actions have contributed little or nothing to the rehabilitation or conservation of populations in the real world. The proposed framework is simplistic and has no applied ambition, but intends to inform scientists, managers and authorities about critical aspects that constrain fish stocking, supporting a much‐needed debate about the uncritical use of management tools.