Effect of Turbidity on the Reaction Distance of Green Sunfish (Lepomis cyanellus) and Bluegill Sunfish (Lepomis macrochirus) in Columbus, Ohio
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Date
2022-05
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The Ohio State University
Abstract
Elevated turbidity (suspended particles) from organic (algae) and non-organic (sediment) sources in aquatic systems has become a problem of increasing concern globally as it alters the visual environment for fishes. Despite evidence for decreased visual detection thresholds in predator fish under turbid conditions, few studies investigate how this may affect predators with different visual abilities. We tested to see if two native predator centrarchid (sunfish) species that prefer clear or turbid waters react differently to changes in turbidity level. Bluegill (Lepomis macrochirus) are typically found in relatively clear waters, while Green Sunfish (Lepomis cyanellus) can be found across a wide variety of turbidity levels suggesting that they may have better vision or better utilize other sensory modes (e.g., chemoreception). Therefore, we expected Green Sunfish to have longer reaction distances (i.e., the maximum distance at which a fish reacted to a prey item) in turbid water compared to Bluegill. Fish were collected from the Olentangy River near the OSU Schiermeier Olentangy River Wetland Research Park and held in tanks at the outdoor mesocosm complex. We conducted foraging response trials to measure reaction distance under a clear control (< 5 NTU) and a sedimentary turbidity (20 NTU) treatment. Reaction distance (cm) was measured from recorded videos of trials. Fish weight (g) and total length (cm) were measured after trials. Due to logistical difficulties, we were only able to test Bluegill under the clear control treatment. Therefore, we tested for a difference in reaction distance between species in clear water and separately tested if reaction distance differed between turbid and clear treatments for Green Sunfish only. No significant difference in reaction distance to prey was found between species in clear water only or within Green Sunfish only between treatments. Additionally, fish length did not have a significant impact on reaction distance. It is possible that acclimation time to lab conditions was not sufficient or that the prey item used was not appropriate. While results showed no effect of turbidity on reaction distance in two common fish species, further study may be required to eliminate confounding variables so that significant conclusions may be drawn.
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Keywords
Reaction Distance, Anthropogenic Turbidity, Urban Watershed, Freshwater Sunfish, Foraging