Laboratory studies of predator–prey encounters in turbulent environments: effects of changes in orientation and field of view

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Small polystyrene particles were used to represent aquatic micro-organisms on millimeter scales, assuming small or negligible self-induced motions. A large number of such particles were released in turbulent flows that were generated in a controlled laboratory experiment, where the turbulence parameters were reproducible and could be kept constant over extended times. These polystyrene particles are tracked by video techniques. The available database allows estimates of the equivalents of planktonic contact rates in the turbulent flow. The results are expressed in terms of average prey fluxes. Scaling laws for the average contact rates for different turbulence intensities and for varying ranges of interception of the predators and also for different forms of the fields of view were analyzed, using two models for the orientation with respect to the flow. Irrespective of orientation and shape of the volume of interception, the scaling with the turbulence intensity is weak, while the variations with the range of perception are significant. The scaling laws obtained by this procedure have universal validity, and they are applicable also for conditions in nature. The sole restriction is that the range of predator perception is within the universal subrange.

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