Dose dependent alcohol effects on the aggressive behavior of the convict cichlid ( Cichlasoma nigrofasciatum)

Previous research has indicated that the fish is a useful model system for research on the effects of alcohol on behavior. The present investigation examined the effect of known blood levels of alcohol, as ascertained from uptake data reported here, on conspecific aggression in the convict cichlid. In different groups, known doses of alcohol (0.2 and 0.5%) were added to a tank containing fish. At various intervals up to 6 hr, fish were sacrificed and the alcohol concentration of their blood compared with the tank ethanol concentration. The results indicate that 6 hr is required for the blood concentration to approach equilibrium with the tank at an average of 65% of the tank concentration. To investigate the effects of various alcohol doses (0.07, 0.18, or 0.33%) on the aggressive behavior of a single male convict cichlid, an intruding male was introduced into the resident fish's tank in a glass tube. At the highest ethanol dose almost half of the fish did not attack the intruder. Those fish which did attack were significantly less aggressive than fish in any of the other groups. The intermediate dose (0.18%) produced significantly more aggresssion than was observed in controls or at higher or lower alcohol doses. These results indicate that ethanol enhances aggression at moderate doses and reduces it at high levels.