Fish Space Use and Behavior in an Aquarium: The Use of Microhabitats as Enrichment

Environmental enrichment is an important tool to maintain the health and well-being of animals in human care, but studies of environmental enrichment for fish in human care have lagged behind those of land animals. To broaden our understanding of environmental enrichment in fish, we conducted a study at the Ridges to Rivers Exhibit at the Tennessee Aquarium in which we assessed whether the inclusion of three microhabitats-a Plunge Pool, a Riffle, and a Run-within the exhibit could function as a form of environmental enrichment. We quantified (1) microhabitat space use of tangerine darters (Percina aurantiaca), (2) microhabitat space use of all fish species, and (3) tangerine darter behavior in each microhabitat. If microhabitats function as a form of environmental enrichment, we expected tangerine darters and all fish to utilize the microhabitats in a nonrandom manner and for tangerine darter behavior to vary in relation to microhabitat. As expected, fish used microhabitats nonrandomly. Tangerine darters were more likely to utilize the Riffle and Run microhabitats, which is primarily where tangerine darters are located in the wild, whereas all fish were on average more likely to utilize the Plunge Pool and Run. Tangerine darters most frequently engaged in stationary and swimming behaviors, particularly in the Riffle microhabitat, which is characteristic of tangerine darters in the wild. These results suggest that the inclusion of microhabitats within a tank influences behavior in a manner that is consistent with natural conditions. As such, the inclusion of microhabitats in aquaria likely functions as environmental enrichment by providing habitat choice. Such habitat choice could improve the welfare of stream fish in human care and elicit behaviors that occur in the wild.