Resource use by Enneapterygius rufopileus and other rockpool fishes

Abstract

Low-intertidal fish communities, including Enneapterygius rufopileus (Tripterygiidae), were studied in rockpools in Sydney, Australia to consider the role of physical factors and food availability in their distribution and abundance. The rockpool fish community in Sydney was speciose (23 species), of which 35% of individuals were E. rufopileus. Fish abundance and 13 physical and biological parameters were measured in twenty-two rockpools spread among 4 sites. Abundance of E. rufopileus was best predicted by the number of rock overhangs, algal cover (Zonaria sp. and Hormosira banksii), and the encrusting ascidian cunjevoi (Pyura sp.). Experimental increase or decrease in available shelter (mainly boulders and macroalgae) in rockpools did not significantly affect the abundance of fishes, however some pools consistently supported more fishes in total, despite repeated defaunation, indicating that underlying deterministic processes may have a significant effect on rockpool fish communities. The diet of Enneapterygius rufopileus included unidentified crustacean remains, harpacticoid copepods, and gastropods. Gastropod abundance was greater in the diets of larger fish, which also consumed more food overall. Total weight of food was not dependent on E. rufopileus density in pools or the densities of all fish species in pools. Therefore, the study does not support the hypothesis that resources were limiting for this fish species in rockpools.