Effects of Turbidity on the Vision and Behavior of Longear Sunfish

Fish are known to use vision in many essential behaviors, including foraging, intraspecific communication and predator avoidance. Turbidity is one of the many environmental factors potentially affecting vision quality. I examined the behavior of interacting conspecific fish in varying levels of turbidity to determine how this environmental variable affects vision and behavior. Experiments were designed to observe how longear sunfish, Lepomis megalotis, reacted to visual cues - in this case a conspecific fish in a glass jar - in the presence or absence of turbidity. My hypothesis is that sunfish will display territorial behavior when introduced to another fish of the same species, so long as it sees the other fish. These behaviors are hypothesized to decrease as turbidity increases and thus, visibility is compromised. A single sunfish was placed in a tank and allowed to acclimate for 30 minutes. Then, either an empty glass jar (negative control) or a jar containing a conspecific fish was added to the tank. Behaviors were then observed for 30 minutes in varying levels of turbidity. Turbidity was controlled using a circulation pump to stir sediment in the bottom of the tank and measured using a Secchi disk. Territorial behaviors such as bumping or head-butting the jar and circling near the other fish were observed when the fish interacted with a conspecific in non-turbid trials. Fish in turbidity with a conspecific behaved more similarly to fish in negative control trials (empty jar) than to fish in clear water with the presence of a conspecific. This suggests that fish do not react to conspecifics when exposed to turbidity, most likely because their vision is impaired. My findings suggest that visual impairment caused by turbidity alters the behavioral interactions between conspecifics. potentially affecting territorial distribution and mating habits