Abstract
Fish social behavior can be affected by artificial environments, particularly by factors that act upon species that show aggressive behavior to set social rank hierarchy. Although aggressive interactions are part of the natural behavior in fish, if constant and intense, such interactions can cause severe body injuries, increase energy expenditure, and lead the animals to suffer from social stress. The immediate consequence of these factors is a reduced welfare in social fish species. In this paper, we consider the factors that impact on the social behavior and welfare of Nile tilapia, an African cichlid fish widely used both in fish farms and in research; this species is frequently used as a model for physiology and behavior research. This is a polygynous species whose males interact aggressively, establishing a territorial based hierarchy, where a dominant male and several subordinate males arise. When social stability is shrunk, the negative effects of prolonged fighting emerge. In this paper, we summarized how some of the common practices in aquaculture, such as classifying individuals by matching their sizes, water renewal, stock density, and environment lighting affect Nile tilapia social aggressive interactions and, in turn, impact on its welfare. We also discuss some ways to decrease the effects of aggressive interactions in Nile tilapia, such as environment color and body tactile stimulation.
Highlights
Social behavior is defined as any kind of interaction between conspecifics, in such a way that it influences their immediate or future behavior [1]
We present a synthesis on social impairment and welfare of Nile tilapia, Oreochromis niloticus (Linnaeus, 1758), an African cichlid fish widely used both in fish farms and as a research model due to its physiology and behavior
According to Martinez-Chavez et al [66], Nile tilapia shows a daily variation in melatonin levels, which follows a clock-controlled rhythm; it allows us to hypothesize that the day length can affect social aggressive interactions as it happens for other cichlids
Summary
Social behavior is defined as any kind of interaction between conspecifics, in such a way that it influences their immediate or future behavior [1]. Some species show cooperative behavior as helpers in the group [3] Despite these behavioral variations, all cichlid species engage in aggressive interactions to establish social rank and territory [16], which is marked by biting, mouth fighting, tail beating (known as overt fight), and by signals such as threats and other displays (restrained aggression). All cichlid species engage in aggressive interactions to establish social rank and territory [16], which is marked by biting, mouth fighting, tail beating (known as overt fight), and by signals such as threats and other displays (restrained aggression) This type of interaction is observed in adult males and females, and in juveniles, which show a very similar aggressive behavior to that of adults. It is necessary to consider factors affecting the species’ welfare to propose adequate technology for the improvement of tilapia farming and housing
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