Invasive Cichlids Display Higher Aggression During Nest Defence Compared to the Native Mexican Mojarra

Nest defence is one component of parental investment by which individuals can increase the survival of their offspring. Aggressive behaviours and the time spent protecting nests are determining factors in the reproductive success of cichlid species. The Mexican mojarra is the only cichlid native to the Balsas River Basin in Mexico. At least four invasive cichlids have been introduced, including the convict cichlid and the spotcheek cichlid. These three species establish their nests in the River and defend them aggressively. We quantified the number of nests, aggressive behaviours and time spent in the nest by parents of the native species and these two invasive species. We expected that the invasive parents would be more aggressive during defence, spent more time protecting the eggs, and would have a higher density of nests. We also explored differences in nest defence between the sexes within each species. We found that invasive cichlids had a greater number of nests than the Mexican mojarra. In the two invasive species, there was no difference between males and females in the time spent in the nest or the number of aggressive behaviours. In contrast, male Mexican mojarras spent less time in the nest and performed fewer aggressive behaviours than their mates. The smaller number of nests and nest defence behaviour of this native species could compromise its reproductive success and population size. This differential nest defence between the Mexican mojarra and the invasive cichlids could have negative implications for the physiology, reproduction, and health of this native cichlid.