Effects of chemical pollution on the behaviour of cichlid fish.

Pollution is one of the most relevant issues for the conservation of freshwater environments. Fishes are the main group of organisms studied in aquatic toxicology, and their behaviours, including feeding, courtship, parental care, and territoriality, are essential to their health. Cichlids are one of the most abundant fish families and are both economically and ecologically relevant. In this review, we found that metals, pesticides, pharmaceutical products, and endocrine disruptor chemicals are the main groups of pollutants that have been studied in the context of cichlid behaviour. African tilapias are the most evaluated cichlids on this topic, and Nile tilapia was the most frequently studied species. Exposure to these pollutants has been shown to affect cichlid fish behaviours in aspects including erratic swimming, activity versus inactivity, preference for the bottom and/or the surface of the tank, aggressiveness, feeding, predation, and reproduction. Oxidative stress, failures in neurotransmission, energetic imbalances, and histopathological damage are among the most common mechanisms underlying the behavioural changes. It is necessary to establish a set of integrative criteria for evaluating the ecotoxicological behaviour of cichlid fish, given the current lack of standardised methods. It is also important to consider more pollutants—both individually and in combination—such as polyaromatic hydrocarbons, flame retardants such as polybrominated diphenyl ethers, perfluoroalkyl substances, and microplastics, due the increasing relevance of these pollutants of emerging concern. In line with this, cichlid fish species with reduced native distributions are suitable study species to provide information for the conservation of freshwater environments. [ABSTRACT FROM AUTHOR]