FIGURE 9.

Distance to stimulus screen is affected by prior fish density. Panel (A) shows the average distance the fish were from the stimulus screen during the entire 12 min behavioral test period. The size of the housing tank is shown on the X-axis and the fish density is shown by the legend. Bars marked by at least one common letter represent groups that are not different significantly (p > 0.05). Note the lack of significant differences among any groups found by Tukey’s HSD test despite the significant fish density effect revealed by ANOVA. Panel (B) shows the distance zebrafish were from the stimulus screen as a function of 30-s intervals. The upper line-graph shows the performance of fish housed in 1.5 L tanks, the middle line-graph the performance of fish housed in 10 L tanks and the lower line-graph the performance of fish housed in 50 L tanks. The fish density of fish is shown by the legend. The vertical semi-transparent gray bars indicate the period during which still images of zebrafish were shown on the computer screen, and the broken lines with the arrowhead indicate the short periods of administering a computer animated expanding dot. Mean + S.E.M. are shown. For detailed statistical results, see Table 1 and the section “Results.”