National Research Institute of Fisheries Science, Ueda 386-0031, Japan
Maximum length of Japanese dace preyed on by smallmouth bass was investigated in aquaria. To prey on dace, smallmouth bass dashed into the school of dace or attacked solitary dace approaching bass or staying still in the bottom of aquaria. The estimated maximum standard length of dace preyed on by smallmouth bass was 47-66% of bass standard length. The measurements of smallmouth bass mouth sizes and Japanese dace body height and width showed that the maximum length of dace preyed on by bass was shorter than that estimated from bass mouth size. Smallmouth bass occasionally vomitted or released large dace, indicating that some dace captured by bass were not ingested. Mouth size was not a limiting factor for smallmouth bass to prey on Japanese dace with long and narrow body shape.