THE IMPACT OF PREDATION BY THE GIRDLED GOBY, NESOGOBIUS SP 1, ON ABUNDANCES OF MEIOFAUNA AND SMALL MACROFAUNA

It is now widely accepted that benthic meiofauna and small macrofauna are an important food source for numerous species of benthic fish. The effect of fish predation on prey populations, however, has been contr oversial. The girdled goby, Nesogobius sp. I, is a benthic marine fish that is abundant on the mudflats of Swan Bay, Victoria. A short-term (48 h) held caging experiment, where gobies were excluded or included at low and high densities, was used to determine the effect of predati on. Predation by gobies was found to significantly affect the abundanc e of their main prey item, juvenile amphipods. However, this effect on ly occurred at fish densities higher than those normally found in the environment. There were no significant effects on other prey items, an d no significant effect on amphipods at ''natural'' fish densities. Ca lculations based on the feeding rates of gobies and the abundances of prey at the study site were consistent with the experimental results. Therefore, we conclude that, in the short term at least, predation by Nesogobius sp. 1 is unlikely to influence the abundances of its prey. Calculations based on feeding rates suggest that a long-term effect of predation by gobies on amphipods may be possible depending on the tur nover rate of prey populations.