Drugged Fish Can Act Aggressively in Nature
February 21st, 2013 // 5:31 pm @ jmpickett
In the latest indication that traces of pharmaceuticals floating through rivers and streams can be problematic, scientists have discovered that tiny amounts of the oxazepam anti-anxiety drug can cause perch to become aggressive, anti-social and overactive. The fish are also prone to gobble up other fish more quickly. And the end result is that these behavioral changes could ultimately upset the dynamics of the marine environment.
“We looked at just one benzodiazepine-type drug but there are many others out there, and they probably all have the same effects on fish and other vertebrates. So we may be underestimating what is happening in nature,†Tomas Brodin, one of Umea University researchers from Sweden who conducted the study, tells the BBC. The study was published in Science and discussed last week at the annual meeting of the American Association for the Advancement of Science (here is the abstract).
The researchers initially found concentrations of oxazepam in perch taken from a river in Sweden that was up to six times higher in their muscle tissue than in the river. This was seen as troubling, since fish store chemicals in muscle tissue. So the researchers raised juvenile perch under three different conditions — one with twice the level of oxazepam than was found in the river, one with 500 times the level and a group with no drug – and ran a test to gauge the effects of exposure to the medicine.
The perch exposed to to high levels of oxazepam displayed the changed behaviors and the researchers maintain these could jeopardize populations of perch, which lives in both fresh and brackish water. There is also a ripple effect. For instance, more aggressive feeding by perch on zooplankton could reduce the numbers of these tiny creatures. And the Associated Press notes that, since zooplankton feed on algae, this could cause algae to grow uncontrollably and disrupt marine life.
This is not the only instance in which traces of a prescription drug has yielded a change in a type of fish. A study in 2009 found that tiny concentrations of antidepressants made fathead minnows more vulnerable to predators. In a study published last year, a team of researchers discovered that fish show autism-like gene expression after exposure to water containing antidepressants (read here). And a 2011 study indicated that active pharmaceutical ingredients were linked to changes in sexual characteristics of wild gudgeon in a river in France (see this).
The larger issue, of course, is the effect of pharmaceuticals in extremely low concentrations, which are measured in parts per billion and have been discovered in waterways in the US, Europe and elsewhere. An AP investigation in 2008 found that the drinking water of at least 51 million Americans carries low concentrations of many common drugs (back story here).
The disclosure led to congressional hearings, legislation and additional water testing, but as the AP notes, there are no mandatory US limits on pharmaceuticals in waterways. Meanwhile, the AP writes, the researchers say better methods are needed for removing drugs from water at treatment plants and unused drugs should be brought to take-back programs, instead of being flushed down the toilet.
However, as we have noted previously, this is a contentious issue. Last year, the trade groups for brand-name and generic drugmakers in the US filed a lawsuit against a California county that passed an ordinace requiring them to pay for the disposal of unused and expired prescription medicines. The ordinance, which seeks to lower county expenses, is the first of its kind in the country
