Effects of alcohol, congeners, and acetaldehyde on aggressive behavior of the convict cichlid.

Ethanol and three beverage alcohols were examined for their effects on the aggressive responses of the convict cichlid. At an ethanol concentration that gave negligible effects on the basal level of these responses, rum was observed to depress aggression. As its concentration of acetaldehyde was significantly higher than that of the other beverage alcohols, we assessed the effects of acetaldehyde on the aggressive responses, as well as the locomotor activity of the fish. At 4 mg/l, acetaldehyde completely inhibited aggressive responses, without affecting locomotor activity. It is likely, however, that acetaldehyde does not explain the entire inhibitory effect of rum on the aggressive responses of the cichlid.