Non-lethal concentration of paraoxon impairs aggressive opercular display in male Siamese fighting fish, Betta splendens

Male Siamese fighting fish are highly territorial and aggressive towards conspecifics. We have suggested that aggressive behavior of Betta splendens males is highly sensitive and might be useful as a bioindicator of fresh water pollution. This was tested by determining opercular expansion count and duration when pollutant-exposed fish were confronted by naive fish. We found that paraoxon, a commonly used pesticide used as a model pollutant, inhibits aggressive behavior of Betta males. The results indicate that males treated with paraoxon for 24 hours were significantly less aggressive than control males. The findings suggest that aggressive behavior in Betta splendens may have use as a bioindicator of organophosphate pollution in fresh water.