Figure 1.
Illustration of the bioinspired robotic fish and golden shiner: (a) computer-aided design of the bioinspired robotic fish connected to the two transparent Plexiglas rods and (b) picture of an experimental golden shiner.
(Online version in color).
Figure 2.
Schematic of the experimental setup (behavioral experiment): the bioinspired Red robot and an individual golden shiner swimming in a section of a Blazka-type water tunnel delimited by two plastic honeycombs.
Two webcams are placed above and laterally of the tunnel to record animal activity from two different perspectives. (Online version in color).
Figure 3.
Schematic of the experimental setup (hydrodynamics experiment): the bioinspired Red robot swimming in a section of a Blazka-type water tunnel delimited by two plastic honeycombs (not pictured).
A laser sheet oriented in the horizontal (x, y) perspective illuminates the seeded water in correspondence of the center of the bottom (a), middle (b), and top (c) compartments of the focal region, respectively. A camera placed below the tunnel films the area illuminated by the laser. (Online version in color).
Figure 4.
Top and Side views of the water tunnel with schematic illustration of the compartments forming the focal region.
A live fish is considered to actively interact with the bioinspired robotic fish when the x-coordinate of its center of mass is in the focal region, which extends four body lengths from the x-coordinate of the robotic fish center of mass along its longitudinal axis. The focal region is partitioned into front, B1, B2, B3, and B4 compartments from the Top view. The same region is partitioned into top, middle, and bottom compartments from the Side view.
Figure 5.
Time-resolved vorticity field measured in top (T), middle (M), and bottom (B) compartments of the Side view, respectively, with the robot tail-beat frequency set at 3 Hz.
The time interval (t) between frames is scaled with respect to the tail-beat period (T = 0.33 seconds) corresponding to the tail-beat frequency of 3 Hz. The initial time (t = 0) does not correspond to the same tail configuration, as PIV analyses were independently executed for the three compartments. For the first row (T) the tail-beat amplitude is −12, 3, 0, and −3 mm, for the second row (M) it is −10, −1, 3, and −5 mm, and for the third row (B) it is −3, −1, 8, and −10 mm (measured as the lateral transverse displacement at the caudal fin terminal with respect to the y-axis). Red structures represent counterclockwise vortices and blue structures represent clockwise vortices. The regions of observation correspond to the three compartments defined for the Side view identified in Figure 4. (Online version in color).
Figure 6.
Behavioral experiment: mean time spent by fish within the focal region in each experimental condition (note that the total acquisition time was five minutes for each trial).
Gray histograms represent the mean time spent in the vicinity of the Gray robot and red histograms represent the mean time spent in the vicinity of the Red robot. Means not sharing a common superscript are significantly different (Fisher's PLSD, p<0.05). (Online version in color).
Figure 7.
Behavioral experiment: mean time spent by fish in each compartment of the focal region across the experimental conditions (note that the total acquisition time was five minutes for each trial).
Histograms represent the mean time spent in the vicinity of the Gray robot (left) and the Red robot (right) with respect to both Top view (top) and Side view (bottom). Error bars refer to the standard error. Means not sharing a common superscript are significantly different (Fisher's PLSD, p<0.05).
Table 1.
Mean time spent by fish in each of the four one-body length compartments behind the robot (Top view) while in the middle compartment of the water column (Side view).