Aggressive interactions and dominance in fights staged between pearl cichlids and Nile tilapia.

<p>Unfamiliar fish were paired interspecifically in a neutral arena subsequent to 5 days of isolation, and aggressive behaviour was observed for 30 min. The fish differed in body size. The mean values (±SD; A - attack frequency; B – dominance index) that do not share the same letter are statistically different among fish of different body sizes for each species (<i>P</i><0.01; one-way ANOVA with repeated measures followed by a Student-Newman-Keuls test). * <i>P</i><0.01, ** <i>P</i><0.001 denote that mean (±SD) values between species within the same condition are statistically different (one-way ANOVA with repeated measures followed by a Student-Newman-Keuls test). ø indicates that these values were not included in the statistical analyses (see the text for details).