Fighting behaviour in native fish: the Mexican mojarra (Cichlasoma istlanum) wins when confronted with the non-native convict cichlid fish (Amatitlania nigrofasciata)

Abstract

The convict cichlid fish Amatitlania nigrofasciata, an aggressive fish species, was introduced in 1987 into the Balsas River basin in central Mexico, which is home to the native cichlid Mexican mojarra, Cichlasoma istlanum. Local populations of the Mexican mojarra have been hypothesized to be negatively affected by the introduction of the non-native convict cichlid fish, and the two species have been observed engaging in aggressive behaviours over resources such as food and shelter along this basin. Thus, we evaluated agonistic interactions between the native Mexican mojarra and the non-native convict cichlid fish. In experimental contests between the species, chases, bites, refuge use and defence, and food consumed were recorded and analysed. Contrary to expectation, the Mexican mojarra engaged in a greater number of chases and bites than the convict cichlid fish and was more successful in obtaining the resource under dispute (a refuge and food).