R code: planktivorous fishes withstand 20 years of major coral cover oscillations

Planktivorous fishes play a crucial role in coral reef ecosystems by converting pelagic planktonic resources into reef biomass. They serve as key vectors of energy transfer from the pelagic zone to the reef, thereby enhancing overall productivity. However, the habitats that support many planktivorous species are under unprecedented stress from global change, foremost due to widespread coral mortality induced by ocean warming.We analyzed 20 years (2004–2024) of benthic and fish monitoring data around Mo’orea Island (French Polynesia, South Pacific) across three reef types (fringing reef, backreef, and forereef). Our results show that planktivorous fish density was, albeit weakly, correlated with coral cover. On the forereef, planktivorous fish communities were more responsive to disturbances affecting coral cover (e.g., heatwaves, cyclones, or Crown-of-Thorns starfish outbreaks). There, fishes showed relatively large fluctuations in density and community composition, in contrast to the more stable backreef and coastal zones. Indeed, zones with low coral cover (<25%) and low planktivorous density exhibited a moderate but detectable increase after successive disturbances. Oscillations in coral cover driven by these disturbances have long-term cascading effects on associated fish assemblages, as evidenced by the gradual decline of Pycnochromis vanderbilti unveiled in our study. Collectively, our findings imply a relative resilience of planktivorous fishes facing repeated and severe coral cover decline and rebound.