Environmental and individual effects on the behaviour and spawning movements of Lethrinus nebulosus on a coral reef

Abstract

Spatial management of fish populations can potentially be optimised by incorporating responses to environmental variables, such as diel, tidal, lunar and seasonal factors, but individual variability in habitat use and behaviour may complicate such efforts. Acoustic tagging and tracking of 84 Lethrinus nebulosus in the Ningaloo Marine Park indicated that sizes of individual habitat utilisation kernels were similar across diel and tidal cycles, but varied greatly among individuals. Clearly differentiated diel and tidal habitat use patterns were evident in significant proportions of individuals, particularly in relation to tidal phase. For the majority of residents, home-range sizes were reasonably stable over periods of 2–4 years, but in some cases core areas did shift over time. At seasonal time scales, peaks of seasonal activity and home range area were recorded during spawning season (October–December). Long-distance return migrations to spawning locations were observed that were among the longest observed for any reef fish (over 130km). Suspected spawning-related movements were recorded almost exclusively in fish >500-mm fork length, and were semilunar, following quarter moons in October–December. Significant individual-level variability in movement and habitat use patterns, evident across multiple temporal scales, has important implications for the management of L. nebulosus populations.