Fishes that exploit current-swept habitats commonly encounter the wakes behind multiple bluff bodies. To better understand how these wakes can repel or attract fishes, we studied the flow across multiple cylinders with both CFD and live fish experiments at Re=10,000. Our first set of experiments consists of 7 cylinders arranged in a single row in the streamwise direction. We analyze configurations in the co-shedding regime, i.e. for spacing larger than 1.9D, where D = cylinder diameter. We determined the optimal cylinder configurations that generates the most peaked velocity spectrum, for which the flow field consists of a coherent Kármán vortex street with a dominant vortex shedding frequency. These configurations consist of equally spaced cylinders, with spacing close to the wavelength of a vortex street shed from one single cylinder (2D). In a second set of experiments, cylinders are arranged in multiple rows. We determined the optimal cylinder configurations by varying both Lx (streamwise) and Ly (spanwise). We found a distinct range (1.9 < Lx/D < 2.2 and 3.3 < Ly/D < 3.5, where D = cylinder diameter) of cylinder spacings that generate coherent vortices. If Ly/D > 3.5, there is no interaction between vortices and each cylinder row behaves as an individual row. If Ly/D <2.2, increased mixing will disturb the flow field. Trout (n=15, 5-9 cm total length) swimming at Re=10,000 avoid wakes where upstream cylinders (1.9 cm diameter) interact destructively with downstream cylinders (velocity = 52 cm s^-1). These arrangements produce weaker, more widely spaced and less-organized vortices that discourage Kármán gaiting. Rainbow trout hold station behind cylinder arrangements that promote the strongest vortex coherence across a range of flow speeds (50-90 cm s ^-1). These findings suggest that certain arrangements of bluff bodies are more conducive to optimizing energy expenditure and migration than others.