Evidence for managing herbivores for reef resilience

Abstract

Herbivore management is an important tool for resilience-based approaches to coral reef conservation, and evidence-based science is needed to enact successful management. We synthesized data from multiple monitoring programs in Hawai‘i to measure herbivore biomass and benthic condition over a 10-year period preceding any major coral bleaching. We analysed data from 20 242 transects alongside data on 27 biophysical and human drivers and found herbivore biomass was highly variable throughout Hawai‘i, with high values in remote locations and the lowest values near population centres. Both human and biophysical drivers explained variation in herbivore biomass, and among the human drivers both fishing and land-based pollution had negative effects on biomass. We also found evidence that herbivore functional group biomass is strongly linked to benthic condition, and that benthic condition is sensitive to changes in herbivore biomass associated with fishing. We show that when herbivore biomass is below 80% of potential biomass, benthic condition is predicted to decline. We also show that a range of management actions, including area-specific fisheries regulations and gear restrictions, can increase parrotfish biomass. Together, these results provide lines of evidence to support managing herbivores as an effective strategy for maintaining or bolstering reef resilience in a changing climate.

Rarity mediates species‐specific responses of tropical reef fishes to protection

“…Protected areas are recognized as prominent tools for safeguarding biodiversity against anthropogenic impacts, but most studies addressing this topic are conducted at the community scale (Cinner et al, 2022) or on particular functional groups (e.g. Donovan et al, 2023) and taxa (Smallhorn-West et al, 2020). By investigating species-specific responses of tropical reef fishes to protection in terms of occurrence, abundance and biomass, at a global scale, and controlling for a wide range of socio-environmental factors and space, we reveal that although many species appear to be benefiting from the current global MPA networks, more than a third of the fish species studied are negatively related to protection.…”