Effects of Daily Forced Exercise on Anxiety of Zebrafish (Danio rerio) Living in Impoverished Environments

The purpose of this research was to investigate the effects of daily forced exercise on the anxiety of zebrafish (Danio rerio) living in structurally-impoverished and structurally-enriched environments. Previous research shows that environmental enrichment decreases anxiety whereas living in an impoverished environment increases anxiety. Zebrafish were randomly assigned to the following aquarium tank environments: Group 1 lived with brown gravel and 3 green plastic plants (enriched environment), and Group 2 lived in a barren tank (impoverished environment). Twenty days later, fish received daily exercise or no exercise (control group) for another 14 days. Fish in the exercise group were forced to swim against a current generated in a glass tube by a submersible water pump. Fish in the non-exercised group were treated in an identical manner each day, but the water pump was off. Behavioral tracking software was used to test the anxiety of fish for 10 minutes using two well-established, reliable behavioral tests. We hypothesized the following: fish living in impoverished environments would display more anxiety than fish living in enriched environments, and the anxiety of fish living in impoverished environments would be reduced or prevented by daily, forced exercise.