Symposium Abstract: Understanding the Complex Nature of Fish-Seagrass Associations
T. J. Anderson
Seagrass beds are rarely homogenous entities. Instead, they form a mosaic that is structured at many different scales. This has important implications for fish communities. However, while seagrass beds are known to have higher abundances of fishes and greater richness of species than unvegetated habitats, few studies have identified how fish dispersions are modified by the spatial structure inherent in most habitats. In this study a multi-scaled observational (meters to 30 km) and experimental approach was used to quantify the relationship between demersal fishes and subtidal seagrass areas in Port Phillip Bay, Melbourne, Australia. While most species were correlated with seagrass, either directly (e.g. seagrass density and length) or indirectly (e.g. patchiness), seagrass alone did not explain species distributions. Instead, the association of a fish with it’s ‘preferred’ habitat was conditional on the spatial structure of the habitat and the spatial location along the shore, and that these landscape elements operated additively, or synergistically. Additionally, a large-scale temporal dynamic both in the supply of larvae and in seagrass health and presence also operated across all scales examined. This study highlights that measuring the association between organisms and their habitat requires many levels of information, ranging from understanding individual habitat preferences at fine-scales, to understanding the spatially-explicit structure of fish and habitat at landscapes. Understanding and predicting fish assemblage structure in the face of habitat change is no simple task, and relies heavily on the integration of fine-scale empirical and landscape-level studies, but this study demonstrates it is achievable.