Freshwater ecosystems are threatened by a wide range of anthropogenic infrastructure related to hydropower, irrigation, municipal withdrawals, and industrial cooling. Technology can be used to mitigate the loss of fish associated with such infrastructure by exploiting the sensory physiology of a species through stimuli designed to manipulate their natural behaviors (e.g., to attract or repel). Technologies used for behavioral guidance often incorporate light; however, previous studies investigating light devices have focused on mercury vapor bulbs and thus have been limited in their exploration of the broader light spectra. Innovations in light‐emitting diode (LED) technology provide opportunities for manipulating light spectra (i.e., color) as well as light‐pulse frequency. We tested the behavioral response of Largemouth Bass Micropterus salmoides under 16 different LED color and light‐pulse frequency combinations as well as in a control in which no light was emitted. Red, orange, yellow, and green were considered with four light‐pulse frequencies (0, 120, 300, and 600 pulses/min). Using a large shallow arena, lateral fish movement in response to the light treatments was examined. Regardless of color or light‐pulse frequency, fish were repelled by the light source. In contrast, when there was no light emitted, fish were evenly distributed throughout the arena. This work suggests that colored light accompanied with light‐pulse frequencies produced by LEDs can induce an avoidance response in Largemouth Bass.
All fish were caught and transported to the laboratory located on Lake Opinicon in large coolers supplied with fresh lake water. They were transferred to large acclimation tanks (2.6 m in diameter, water depth of 50 cm) and held for 24 h. A flow‐through system was used to provide a constant supply of aerated, fresh lake water to the holding tanks. Fish were also not fed during the study to avoid any confounding variables that could be related to differences in metabolic rate.
After approximately 24 h, each fish was tested for their response to light stimuli in an in‐lake experimental arena (Figrue 1) consisting of a converted enclosed boathouse slip (2.6 m × 6.0 m). Sources of natural sunlight were reduced by covering the windows and slip entrance. Additionally, an observation blind made of black plastic was used to prevent disturbance during testing. This blind consisted of two windows (30 cm × 30 cm) through which the fish were observed. The experimental arena was enclosed by walls that were covered in mesh to allow for water flow. This mesh also provided a barrier to debris and possible fish entry or escape. The water temperature during the experimental period followed the natural temperature fluctuations of the lake (mean = 23°C; range = 20–26°C) and was consistent with the holding tanks due to the flow‐through system design. The arena was separated into 1‐m zones to measure fish location as a behavioral response during the experiment. An LED device (model 521‐1045‐ND and LED type TITAN RGB Light Engine) with capabilities of displaying various spectra and light‐pulse frequencies was used. The light was put at the 0‐m line and a 2.6‐m × 1.0‐m acclimation box was placed between the 2‐ and 3‐m lines (Figure 1).
Each fish was independently presented with three randomly selected color or color and light‐pulse frequency combinations, consecutively displayed through a series of observational periods. Each observational period began with the removal of the acclimation box from the experimental arena as soon as the light device displayed one of the selected colors and light‐pulse frequencies. The fish's location relative to the LED device was recorded every 20 s for 5 min for a total of 15 observations per individual per trial. We considered the fish to be attracted to the light when it was within 2 m of the light, neutral when it was from 3 to 4 m from the light, and repulsed if it was from 5 to 6 m from the light. At the end of the observation period, the fish was dipnetted from the experimental arena with a rubberized fishing net (50 cm in diameter) and returned to the acclimation box (<10 s) for 10 min in preparation for the next selected color and light‐pulse frequency. Following the three consecutive behavioral tests, each fish was fin‐clipped (tip of the caudal fin) to ensure it was not retested and was then directly released into Lake Opinicon.