Discrimination among Fish Models by Hawaiian Eleotris sandwicensis (Eleotridae) 1

I examined behavioral responses of the benthic fish Eleotris sandwicensis to painted models (dummies) of fish that Eleotris typically encounter in Hawaii. Eleotris sandwicensis were associated with coarse substrates where their mean (±SE) density was 1.5 (±0.30) fish/m 2 . I hypothesised that Eleotris would retreat from all models in open areas, but not when they were present in shelters. The five models represented Stenogobius hawaiiensis, Awaous guamensis, E. sandwicensis (female coloration), a male E. sandwicensis in breeding colors (black), and a 12 cm block of wood (control). Whether or not Eleotris held its position or retreated was not a function of body size. Differences among the responses of Eleotris to models depended on whether or not the fish was hidden or exposed on substrates. More retreats in response to models occurred when Eleotris were exposed on substrates than when fish were hidden. There were no significant differences in the response of E. sandwicensis to models when fish were exposed on substrates. In contrast, responses of E. sandwicensis to the models were not random for fish that were hidden, indicating that Eleotris discriminated among the models. The basis for discrimination among models was most likely visual. Although Eleotris are typically secretive, their presence on exposed substrates at this study site may be attributed to die lack of benthivorous fishes and few avian predators. The ability of Eleotris to distinguish among fishes when hidden as well as their tendency to retreat in response to all intruders whenever exposed on substrate surfaces could reduce potential interactions between Eleotris and other native and nonindigenous fishes.