Does Artificial Light at Night Alter the Subsequent Diurnal Behavior of a Teleost Fish?

Artificial light at night (ALAN) is one of the fastest growing anthropogenic disturbances to animals across many ecosystems, yet little is known about how ALAN influences fish and aquatic ecosystems. Our current understanding of the effects of ALAN on fish behavior and physiology tend to be based on research conducted during night, with comparatively little research on whether ALAN influences subsequent behavior during diurnal periods. We used wild-caught Bluegill Lepomis macrochirus as a model to assess whether ALAN of differing intensities comparable to what would be experienced in the wild near human-altered landscapes (i.e., 0.5 lux, 4 lux, 9 lux) alters subsequent diurnal behavior relative to controls (i.e., dark, 0 lux). We assessed a number of behavioral traits in a laboratory setting known to relate to performance and fitness in wild teleost fish including exploration, activity levels, space usage, and risk aversion. Exploration behavior, space use, and risk-taking behaviors were similar among treatments. Only locomotor activity differed among treatments with Bluegill in the 0.5 and 9 lux treatments swimming significantly less than controls after being exposed to ALAN overnight. This difference in behavior was found at light intensities commonly found at waterways today and thus may already be affecting fish communities and aquatic ecosystems.