Antisocial fish from psychotropic drugs in rivers

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Psychopharmaceutical residues in rivers make fish braver and anti-social

The residues of psychotropic drugs enter our rivers with the wastewater and can even lead to sustainable changes in behavior of fish and other aquatic organisms, even in the smallest doses, according to scientists from Umeå University in Sweden in the scientific journal Science. The animals react "strangely even with low concentrations of the medication in the rivers, which indicates that the psychotropic drugs can influence the behavior of the fish and the ecology even in small doses," write the researchers led by Tomas Brodin from Umeå University.

According to the Swedish scientists, "Hundreds of different medicinal products are able to slip through conventional sewage treatment plants and can then be found in our waters." Researchers at Umeå University explained that "the many medicines in rivers and streams have an impact on the behavior of aquatic life". From earlier studies it was already known that "high concentrations of drug residues in the water have an impact on aquatic life". The Swedish researchers have now been able to demonstrate that even very dilute concentrations of psychotropic drugs lead to serious behavioral changes in fish - they became braver, but at the same time showed less socially beneficial (partially anti-social) behavior.

Residues of the drug oxazepam in the waters According to the Swedish scientists, "a few years ago, the psychoactive drug oxazepam (group of the diazepam) was detected in water samples from the river Fyris, which flows through Uppsala - the fourth largest city in Sweden" . Oxazepam is "a class of medication that makes neurons less excitable and slower," the researchers report. The transmission of signals in the brain is inhibited. Psychoactive drugs based on oxazepam are an “essential” ingredient in the treatment of panic attacks and other serious anxiety disorders, the Swedish scientists write. The contamination of the waters with such medication is "not a particular Swedish problem," continued the main author Tomas Brodin. Since the psychopharmaceuticals accumulate in the tissue of the fish over time, even low concentrations should be critically assessed in the long term. According to the researchers, the "concentrations of oxazepam found in perch from the Fyris River were up to six times higher in the muscle tissue of the fish than in the water," report Brodin and colleagues.

Fish under the influence of psychotropic drugs show significant changes in behavior As part of its current study, the research team at Umeå University examined the effects of the residues of psychotropic drugs in the aquatic environment on the organism of fish. They tested this on three different groups of juvenile perch (young perch fish). One group was raised in an aquarium with twice the oxazepam concentration as in the Fyris River, another with 500 times the concentration and the third in water free of drug residues. The scientists observed “three striking changes in the behavior of the perches that were exposed to oxazepam.” For example, the perches discarded their behavior as “schooling fish” due to the psychotropic drugs. This "social behavior, which keeps the schools of fish together and protects them from predators", declined significantly under the influence of the medication and the fish instead swam solo more often, write Brodin and colleagues.

Increased risk appetite under the influence of medication Secondly, a significantly increased risk appetite was observed in fish that were exposed to very high concentrations of psychotropic drugs. The perches became more courageous and dared "than their sober peers to venture into new surroundings through a flap in the aquarium", the Swedish research team found. The third noticeable behavior change, according to the scientists, concerned the nutritional behavior of the fish. Both groups under the influence of psychotropic drugs showed a much more greedy eating behavior, but also proved to be more efficient feed procurers or better hunters of water fleas.

In the course of their study, the scientists were unable to clarify unambiguously the consequences of the behavior changes in perch, which influence the behavior changes due to psychopharmaceutical residues have on the fish in their natural environment. Both positive and negative effects are conceivable here. For example, the greed of the fish could drastically decimate the water fleas, which could threaten an algae bloom that deprives the water of oxygen and, in the worst case, would result in the death of the fish, write Brodin and colleagues. On the other hand, "the more efficient procurement of feed may also lead to the fish population growing faster". However, the more courageous behavior, as well as the stronger tendency to go it alone, can also lead to the fish falling prey to predators more often. This strongly depends on whether the perches are the largest predatory fish in their area, according to Brodin and colleagues.

Reduction of drug residues in water demanded Your study shows how urgent it is to improve wastewater treatment, the Swedish researchers emphasized. Because comparable behavior changes as with the perches can also be expected with other fish. In addition, the residues of medicinal products increasingly reach humans through drinking water. Here, for example, a study by Jacobs University Bremen on pollution of drinking water in Berlin in 2010 had shown that there were sometimes alarming contaminations with the gadolinium MRI contrast agent. This contrast medium could also be used as an indicator of drinking water pollution with other medicinal products, the Bremen researchers reported a good two years ago and referred to possible health risks for the population. (fp)

Also read:
Significant pollution of the fish
Antibiotic detected in feed
High-fat fish prevents diabetes and heart disease

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