15.30 Fuzzy fish?

Drugs used to treat anxiety persist in wastewater effluent, resulting in relatively high concentrations of these drugs in our rivers and streams. A regional commercial fishing business wants to better understand the effects of these drugs on fish. They hire researchers who expose fish to various levels of an anxiety drug in a laboratory setting and observe their behavior. In one study, researchers considered the effects of three doses of oxazepam on the behaviour of the European perch.¹¹ Twenty-five perch were each assigned to doses of 0, 1.8, or 910 micrograms per liter of water . Each fish was first observed prior to treatment and then observed seven days after treatment. The following table summarizes the results for activity (number of swimming bouts greater than 0.25 cm during 10 minutes).