Tradeoffs between fisheries harvest and the resilience of coral reefs

Significance

Fisheries management must avoid adverse impacts on the ecosystem. Doing so can be challenging in highly complex systems, particularly if the target species serves an important ecosystem function. Caribbean coral reefs provide a classic example in which herbivorous parrotfish are both an important fishery and key driver of ecosystem resilience. We developed and tested a multispecies fisheries model of parrotfish and linked it to a coral reef ecosystem experiencing climate change. We found that corals can remain resilient if less than 10% of the fishable parrotfish biomass is harvested and a minimum size of 30 cm is implemented. To our knowledge, this work is the first attempt to identify harvest levels that have little adverse effect on corals.

Abstract

Many countries are legally obliged to embrace ecosystem-based approaches to fisheries management. Reductions in bycatch and physical habitat damage are now commonplace, but mitigating more sophisticated impacts associated with the ecological functions of target fisheries species are in their infancy. Here we model the impacts of a parrotfish fishery on the future state and resilience of Caribbean coral reefs, enabling us to view the tradeoff between harvest and ecosystem health. We find that the implementation of a simple and enforceable size restriction of >30 cm provides a win:win outcome in the short term, delivering both ecological and fisheries benefits and leading to increased yield and greater coral recovery rate for a given harvest rate. However, maintaining resilient coral reefs even until 2030 requires the addition of harvest limitations (<10% of virgin fishable biomass) to cope with a changing climate and induced coral disturbances, even in reefs that are relatively healthy today. Managing parrotfish is not a panacea for protecting coral reefs but can play a role in sustaining the health of reefs and high-quality habitat for reef fisheries.