Feeding performance of the Hawaiian sleeper,Eleotris sandwicensis (Gobioidei: Eleotridae): correlations between predatory functional modulation and selection pressures on prey

The eleotrid fish Eleotris sandwicensis inhabits lower reaches of streams in the Hawaiian Archipelago, where it feeds on juveniles of native amphidromous gobiid fishes migrating upstream from the ocean. Using high‐speed video and geometric modelling, we evaluated the feeding kinematics and performance of E. sandwicensis on free swimming prey, including two species with juveniles of different characteristic sizes, and compared successful and unsuccessful strikes. With fast jaw movements and a highly expansive buccal cavity, E. sandwicensis achieves high suction performance that enables the capture of elusive prey. Our analyses indicated that the species with larger juveniles (Sicyopterus stimpsoni) could be captured from a distance of up to 18.6% of the predator's body length (BL), but capture of the smaller species (Awaous guamensis) required a closer distance (12.2% BL). Predator–prey distance appears to be the predominant factor determining strike outcome during feeding on juvenile A. guamensis. However, during feeding on juvenile S. stimpsoni, E. sandwicensis shows modulations of strike behaviour that correlate with capture success. Moreover, the ability of E. sandwicensis to capture larger prey fish from longer distances suggests a potential biomechanical basis underlying observations that predation by eleotrids imposes significant selection against large body size in juvenile gobies. © 2013 The Linnean Society of London, Biological Journal of the Linnean Society, 2014, 111 , 359–374.