Water temperature affects aggressive interactions in a Neotropical cichlid fish

Abstract

Changes in water temperature may affect the aggressive behavior of aquatic organisms, such as fish, either by changing some physiological mechanisms or by increasing the probability of encounters between individuals as a result of variation in their swimming activity. In our study, we evaluated the influence of increasing and decreasing temperature on the aggressive behavior of the Neotropical cichlid fish Cichlasoma paranaense. Firstly, we tested the critical thermal maximum (CTMax) tolerated by this species. Then, we tested the effect of decreasing or increasing the water temperature in 6o C (starting at 27° C) on the aggressive interactions of fish under isolation or housed in groups. We found a CTMax value of 39° C for C. paranaense. We also observe that a 6° C decrease in water temperature lowers swimming activity and aggressive interactions in both isolated and group-housed fish, as expected. On the other hand, the increase in temperature had no effect on the fish’s aggressive behavior, neither for isolated nor for grouped fish. We concluded that C. paranaense shows high tolerance to elevated temperatures and, in turn, it does not affect aggressive behavior. Nevertheless, we cannot dismiss possible effects of elevated temperatures on aggressive interactions over longer periods.

Water warming increases aggression in a tropical fish

“…Although we cannot be certain, we suspect that the increase in aggression in the individuals exposed to the higher temperature was driven by changing metabolic demands. Similar to other fish taxa [71][72][73][74] , as well as other ectotherms [75][76][77][78] , metabolic rate has been shown to increase with increasing temperature in J. ornatus 27 and other cichlids 55 . For example, using a similar approach to assess aggression as our own, overt aggressive behaviours associated with locomotion (e.g., biting, tail-slapping) in Oreochromis mossambicus, another African cichlid, were found to be positively correlated with metabolic rate 55 .…”

“…Even though aggression in African cichlids like Julidochromis ornatus is common in nature 80,81 , our observed long-lasting increase in aggression suggests that this behaviour is not canalized. This finding is important as it indicates the potential for this behavioural adjustment to help buffer this species, and perhaps others like it, against environmental change such as water warming.…”

“…Given this uncertainty, more work is needed to help us better understand whether, for example, increased metabolic rate itself, hunger associated with increased metabolic needs, some other physiological change such as altered stress hormone levels, lost reproductive fitness, or their combination underlies the long-lasting effect that increased temperature had on aggression. In addition to having the metabolic data, knowing the time-course of aggression (i.e., when it first emerged) and stress levels of fish (e.g., corticosteroid levels) 79 would have been helpful in delineating the proximal mechanism(s).…”

Increase in environmental temperature affects exploratory behaviour, anxiety and social preference in Danio rerio

“…At 34 °C, a shorter latency to the first bite was observed compared with the controls. Similarly, when the Neotropical cichlid fish Cichlasoma paranaense was subjected to a thermal increment from 27 °C to 33 °C, it showed an increased tendency for aggressive episodes, and significant differences were detected over a wider thermal range (21-33 °C) 52 . Overall, our MBT results are consistent with an increase in zebrafish boldness at high temperature.…”

Social Behavior and Welfare in Nile Tilapia

“…This type of interaction is not only observed in adult males and females, but also in juveniles, which show a very similar aggressive behavior to that of adults. For example, the angelfish Pterophylum scalare and the Cichlasoma parananese show a similar social interaction, their social rank being clearly established when they are juveniles [12,18]. Aggressive behavior is, therefore, part of the competition for resources, for example, food, reproductive partners, spawning and brood care site, in which dominant individuals have priority over others to access such resources [19].…”