Tidal Stage Mediates Periodic Asynchrony Between Predator and Prey Nekton in Salt Marsh Creeks

Abstract

In marine ecosystems, predator-prey interactions are known to structure critical processes (e.g., trophic transfer, nutrient regeneration) and have important implications for mediating community dynamics. However, the temporal and spatial scales over which these processes operate remain poorly understood mainly because the resolution provided by traditional sampling techniques is low. In particular, tides and physical forcing pose challenges due to sampling dynamics in coastal ecosystems. Examining the fine-scale temporal and spatial dynamics of predators and prey in tidally driven estuarine ecosystems requires implementing techniques that are robust to these challenges. Here, we examine data from a high-resolution multibeam imaging sonar (DIDSON) at the confluence of an intertidal and subtidal creek over six ebb-flood cycles and quantify the temporal and spatial scales of variance between the density of predators and prey. Densities of both groups were strongly and inversely related to tidal stage, irrespective of time of day. The potential for an encounter between functional groups and utilization of the estuarine intertidal-subtidal complex was mediated by the tidal stage. When the intertidal creek was flooded, both predator and prey fishes occupied the channel more than the slopes adjacent to the marsh edge. In addition, our study demonstrated fine-scale asynchronous timing in the distribution of predators and prey, with prey densities generally peaking prior to those of predators. This suggests that the scale of variation of prey occupying the intertidal creek, which is often thought to provide refuge, drives coincidental utilization by predators and mediates their interactions.