Investigating the effects of light colour on fish assemblages observed at night via baited video

Video systems, such as baited remote underwater video stations (BRUVS) are potentially useful for assessing fish assemblages at night. They can be used to assess fish behavior, as well as provide estimates of abundance and diversity. One of the challenges of using a visual medium at night is having adequate illumination and minimizing the potential biases each light source may have. Our study compared two light colors, red and blue, within a range of habitats to further quantify the effects of light color on fish assemblages recorded at night. Red was selected as it is theorized to be below the threshold of visibility for many fish species due to its fast retention in the water column, whereas blue was chosen because previous studies have suggested that it provides a bigger area of illumination without reflection issues caused by white light, thus making identification easier. The study was conducted in seagrass, bare substrate, shipwrecks, and in a range of protection levels, providing insights into how the effects of light color are influenced by these factors. The results from our study will allow for more informed decision-making with regards to light color and the effect it has on fish as-mblages observed. Our study found some differences in the assemblages observed between light colors along with differences in how the light interacted with the water turbidity. Overall, it was found that use of BRUVS was a suitable method for assessing fish assemblages at night with multiple species seen from both light colors.