Aggression in captivity and the implication for interspecific aggression between once sympatric species of Mexican goodeid

Many species of fish show increased aggression in captivity, but studies normally focus on intraspecific aggression rather than interspecific interactions. Ameca splendens, a goodeid originally from Mexico, exhibits increased levels of intra-specific agonistic behaviour in captivity, and this increases further with density. This study compared agonistic interactions occurring in single species aquaria (A. splendens) with those in aquaria shared with Skiffia francesae. S. francesae are extinct in the wild, but were once sympatric with A. splendens. To improve captive rearing conditions and chances of successful reintroduction of S. francesae, programs must consider possible future co-habitation. Given the heightened aggression of captive bred A. splendens there is potential for negative effects on S. francesae in mixed species aquaria. This study undertook to reveal whether there was a direct quantifiable inter-specific aggression between captive-bred A. splendens and S. francesae. Results indicate that A. splendens males do not target S. francesae, regardless of density and instead focused their aggression towards other A. splendens males. Suggesting that higher levels of intraspecific aggression in captive A. splendens do not translate into increased levels of interspecific aggression, and specifically that S. francesae are unlikely to be directly impacted by captive A. splendens, at least in the short term.