Navigating social-ecological trade-offs in small-scale fisheries management: an agent-based population model of stoplight parrotfish (Sparisoma viride) for a Caribbean coral reef fishery

Parrotfish (family Scaridae) consume macroalgae, an essential process for sustaining the ecological health of coral reefs. They have become fisheries targets in several Caribbean locations, a practice that provisions food and income but also puts reefs at risk. Some countries have banned parrotfish harvest, but this would inflict substantial hardship for resource-poor fishers in some places, given the high proportion of parrotfish species in their catches. This research informs development and assessment of options for achieving the greatest level of population rebuilding with the least hardship imposed on fishers. Fishery models can help compare management options in the absence of real-world examples of how to manage parrotfish populations. We built an agent-based population model for the stoplight parrotfish (Sparisoma viride), a key herbivore and protogynous hermaphrodite, to predict ecological and social outcomes of various fishery management options. We parameterized the model to represent a heavily fished fishery, the context for which assessing different management options is most pertinent. We compared several management options selected through discussions with stakeholders and the scientific literature on fisheries management. We found that all options immediately began to increase population biomass. The more restrictive options led to greater increases in steady-state biomass and revenue from catch, representing a long-term win-win. However, all management options also caused an initial decrease in monetary value of the catch before the eventual rebound, hence a temporal trade-off between short- and long-term economic outcomes. Although there is no perfect strategy, managers and stakeholders can use this information to weigh the costs and benefits of different possible management options in different social ecological contexts.