Drugs to treat anxiety in people may alter the behaviour of fish when the chemicals are flushed into rivers, according to scientists. Swedish researchers found that European perch exposed to tiny concentrations of a drug became less sociable, ate more and became more adventurous – all changes in behaviour that could have unexpected ecological impacts on fish populations.
When scientists at Umeå University in Sweden screened rivers for pharmaceuticals they found that a drug for treating anxiety, called oxazepam, was accumulating in fish. Many drugs and other synthetic chemicals used by humans in everything from pesticides to cosmetics can pass through waste water treatment and end up in wildlife, potentially accumulating to toxic levels.
But until now scientists had never studied the behavioural impacts of small quantities of contaminants. Tomas Brodin led a team that mimicked in the lab the concentrations of oxazepam found in the wild – around a microgram per kilogram of fish body weight – and watched for changes in how bold, sociable and active the fish were.
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