Captive-bred angels react differently to predators

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Wild-caught and captive-bred angelfish (Pterophyllum scalare) behave differently in the presence of predators, according to research to be published in a forthcoming issue of the Journal of Applied Ichthyology.

The study by Rayan El Balaa and Gabriel Blouin-Demers from the University of Ottawa compared the anti-predator behaviour, specifically the ability to recognize and avoid predator cues, between wild-caught and captive-bred angelfish.

The authors used 12 captive-bred and 14 wild-caught angelfish for their experiments, allowing them to see a predator, in this case a Jack Dempsey cichlid (Cichlasoma octofasciatum) and then measuring their response (in this case, the presence and length of time in which the fish remains immobile). 

The experiments were conducted in two adjacent tanks placed end-to-end (on their short sides). The angelfish were placed in one tank and the Jack Dempsey was placed in the other. An opaque divider separating the tanks was removed, and the responses of the angelfishes were recorded on a video camera for subsequent analysis. 

A control experiment was carried out in which the behaviour of the angelfish were observed and recorded under normal, stimulus-free conditions for 10 minutes.

The authors found that both the wild-caught and captive-bred angelfishes would freeze when they first saw the Jack Dempsey upon the removal of the partition, but that the wild-caught fish would freeze a little longer compared to the captive-bred fish. 

In subsequent encounters with the Jack Dempsey, the wild-caught angelfish would freeze for significantly shorter periods of time and resume normal behaviour significantly sooner.

Although these results seemed counterintuitive, as wild-caught fish are thought to be more cautious in the presence of predators, experiments conducted with other aquatic organisms (e.g. spiny lobsters) have produced similar results. 

This is hypothesised to be due to the captive-bred (and predator-naïve) individuals overreacting to the predator stimulus due to inexperience. It may also make more sense for the wild-caught fish to be bolder and spend less time freezing, as more time spent in refuge implies less time available for feeding or reproduction.

According to the authors, there are implications in conservation for the differences in behaviour between wild-caught and captive-bred fish. Given that captive-bred animals face a greater risk of being preyed upon, a realistic rearing environment that provides experience with natural threats is required if behavioural differences between captive-bred and wild-caught fish are to be avoided.

For more information, see the paper: El Balaa, R and G Blouin-Demers (2011) Anti-predatory behaviour of wild-caught vs captive-bred freshwater angelfish, Pterophyllum scalare. Journal of Applied Ichthyology doi: 10.1111/j.1439-0426.2011.01740.x