Performance level and efficiency of two differing predator-avoidance strategies depend on nutritional state of the prey fish |
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Authors: | Volker Huckstorf Wolf-Christian Lewin Thomas Mehner Christian Wolter |
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Institution: | (1) Leibniz-Institute of Freshwater Ecology and Inland Fisheries, Department of Biology and Ecology of Fishes, POB 850 119, 12561 Berlin, Germany |
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Abstract: | Animal prey has developed a variety of behavioural strategies to avoid predation. Many fish species form shoals in the open
water or seek refuge in structurally complex habitats. Since anti-predator strategies bear costs and are energy-demanding,
we hypothesised that the nutritional state of prey should modify the performance level and efficiency of such strategies.
In aquaria either containing or lacking a structured refuge habitat, well-fed or food-deprived juvenile roach (Rutilus rutilus) were exposed to an open-water predator (pikeperch, Sander lucioperca). Controls were run without predators. In the presence of the predator, roach enhanced the performance of the anti-predator
strategy and increased the use of the refuge habitat whereby food-deprived roach were encountered more often in the structure
than well-fed roach. Nonetheless more starved than well-fed roach were fed upon by the predator. In the treatments offering
only open-water areas, roach always formed dense shoals in the presence of the predator. The shoal density, however, was lower
in starved roach. Starving fish in shoals experienced the highest predation mortality across all experimental treatments.
The experiment confirmed the plasticity of the anti-predator behaviour in roach and demonstrated that food deprivation diminished
the efficiency of shoaling more strongly than the efficiency of hiding. The findings may be relevant to spatial distribution
of prey and predator–prey interactions under natural conditions because when prey are confronted with phases of reduced resource
availability, flexible anti-predator strategies may lead to dynamic habitat use patterns. |
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