Water warming effects on the behavior of the African cichlid, Julidochromis ornatus
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Date
2016-05
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The Ohio State University
Abstract
Human-induced rapid environmental change (HIREC) is threatening the world’s flora and fauna. Aquatic ecosystems have proven to be particularly vulnerable to HIREC. Many of the world’s largest lakes (e.g., Lake Tanganyika, East Africa) have seen rapid increases in water temperature. While previous research have shown that increased environmental temperature generally increases metabolic rates in ectotherms (e.g., fish), we know little about how this increase might affect their behavior (e.g., aggression). Since a heightened metabolism would raise the required energy for basic life functions, we hypothesized that aggression levels would be higher in individuals exposed to
warmer temperatures relative to cooler ones. To test this hypothesis, we conducted a controlled laboratory experiment in which adult Julidochromis ornatus from Lake Tanganyika were exposed to low and high temperature treatments. As expected, average aggression levels were significantly higher in the warm (projected future) temperature treatment relative to the cooler (baseline) temperature. Despite this change in average aggression, individual aggression levels (measured
before and at the end of the experiment) were positively correlated when all individuals were analyzed together. Collectively, these findings indicate that, while aggression in J. ornatus is plastic, individuals also have a personality that might constrain their response to HIREC. Ultimately, our findings suggest that continued warming in Lake Tanganyika, and many similar ecosystems, will change the behavior of its native fish fauna. As behavior appears critical to the reproductive success
and social standing in many cichlid fishes, such changes might have major consequences for the ability of these fish species to persist in the face of continued HIREC.
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Keywords
climate change, aquatic ecology, behavioral ecology, climate warming, cichlid, fish