Habitat preference of three common fishes for seagrass, Caulerpa taxifolia, and unvegetated substrate in Moreton Bay, Australia

A decrease in seagrass cover and a commensurate increase in Caulerpa taxifolia distribution in Moreton Bay have prompted concern for the impact that habitat change may have on faunal communities. Therefore, it is important to understand the patterns of habitat use. We examined habitat selection of three common seagrass species: double-ended pipefish (Syngnathoides biaculeatus), eastern trumpeter (Pelates quadrilineatus), and fan-bellied leatherjacket (Monacanthus chinensis) using a mesocosm experiment. Fish were given three possible habitat pairings (1) seagrass and C. taxifolia, (2) seagrass and unvegetated, and (3) C. taxifolia and unvegetated. Observation trials were conducted during the day and night over two days. In all trials, fish preferred vegetated habitat (seagrass or C. taxifolia) over unvegetated habitat (sand). In seagrass and C. taxifolia trials, all species preferred seagrass significantly over C. taxifolia. Habitat use patterns did not differ between day and night trials. Caulerpa taxifolia provides a valuable structured habitat in the absence of seagrass; however, it is unclear if C. taxifolia meadows provide other resource benefits to fishes beyond that of shelter.