Predator-prey interactions are fundamental processes that act to mediate aquatic ecosystem dynamics. However, the temporal and spatial interactions that control these dynamics, in addition to the role of environmental factors, remain elusive. Fine-scale habitat use by fishes is difficult to observe in dynamic estuarine systems and, to date, habitat utilization information is primarily inferred from direct capture of organisms. In addition, the temporal domain of nekton movement and behavior remains largely undescribed as traditional observational techniques (i.e., optical methods) are impeded by physical characteristics of estuarine ecosystems (e.g., suspended load). We report on a recent effort to integrate high-resolution multibeam imaging sonar (DIDSON) at the confluence of the intertidal and subtidal creek to evaluate the density, abundance, and patterns in predators and prey moving through these two adjacent, interconnected habitats. We examine the fine-scale temporal and spatial interactions of predators and prey through complete tidal cycles across the confluence of the intertidal-subtidal zone. Specifically, we investigate how predator density and abiotic factors mediate prey habitat use in a tidally driven estuarine ecosystem.
Results/Conclusions
Fish abundance and movement were highly coordinated with tidal stage, suggesting that nekton were cued into moving between interconnected habitats at specific depths, irrespective of time of day. Channel habitats were consistently preferred by both predators and prey relative to adjacent edge habitats. Our results revealed that the utilization of the estuarine intertidal-subtidal complex by small-bodied nekton is mediated by both tidally-modulated variation in abiotic factors and risk-adverse habitat use patterns. Our study highlights complex interactions between these important biotic and abiotic processes that can act at multiple temporal and spatial scales and further describes the highly-dynamic nature of estuarine ecosystems. This study provides the first evidence of fine-scale asynchronous timing in the use by predators and prey of the intertidal-subtidal highway. Using advanced survey technology, fine-scale temporal and spatial nekton habitat use and behavior patterns can be explored, providing novel insights into the value of tidally-available estuarine habitats at scales not previously described.