Highly repetitive space-use dynamics in parrotfishes

Understanding space-use patterns in parrotfish (Scarini) is especially important for coral reefs, where herbivores play a key role in maintaining reef health. However, we lack the long-term high-resolution data needed to understand parrotfish space-use patterns over time. We examine long-term space-use dynamics in parrotfish (median duration: 359 days) by tracking 23 terminal-males of three species along a coral reef in the Northern Red Sea Gulf of Aqaba. We used acoustic telemetry to track horizontal movement along the reef, depth, and activity (through tri-axial accelerometers), and quantify the effect of environmental factors such as water temperature and algal abundance on long-term patterns. We found that in the species examined, nearly all individuals maintained a highly consistent spatial pattern throughout the study duration, in which they repeatedly moved along a distinct route between nighttime sleeping areas and spatially constrained daytime areas. Individual patterns were surprisingly conserved over time, despite seasonal changes and variation in resource abundance. Individuals differed considerably in their daily travel distance, with some traveling up to 2000 m along the reef, while others moved only between deep and shallow areas. Activity levels consistently peaked around mid-day, regardless of the location of their daytime areas, which behavioral surveys confirm are associated with feeding activities. We also detected peaks in activity during early mornings when surveys detect that parrotfish interacted in large aggregates (typically 30–60 individuals). Our findings indicate that space-use patterns vary among individuals but are extremely conservative within individuals over long time periods. This in turn may have important consequences to the health of reefs, as individual parrotfish may be less likely to alter foraging patterns as conditions change. Furthermore, the high fidelity to limited sleeping and daytime areas may be a source of concern, as local small-scale disturbances may strongly disrupt individual space-use patterns.