siamese fighting fish sick symptomsMirrors are frequently used rather than a real opponent to check aggression in fish, yet they may disrupt the conventional sample of reveal behaviour. Here, using Siamese fighting fish, Betta splendens, we examine the competitive behaviour of males to a mirror image and real opponent behind a clear barrier. As this species is a facultative air breather, we also quantify surface respiratory, providing insights into underlying fight motivation. Consistent with old work, we found proof of population level lateralization, with a bias to current the left side and use the left eye when facing a real opponent. Contrary to expectations, there have been no alterations in the competitive shows to a mirror and real opponent, with constructive correlations between the behaviour in the two eventualities. However, there have been essential adjustments in floor respiratory, which was more frequent and of longer length in the mirror cure.