Pill To Gill | Mood Drugs In Waterways, Alter Fish Behaviour, Study Finds

Mood-changing drugs enter waterways, affect fish, study finds

Courtesy of Umeå University, Science and World Science staff

      Some medicines that end up in the world’s wa­ter­ways af­ter be­ing used are af­fect­ing fish be­hav­ior, ac­cord­ing to a new stu­dy.

Tomas Brodin of Swe­den’s Umeå Uni­vers­ity and col­leagues found that wild Eu­ro­pe­an perch ate faster, be­came bolder and acted less so­cial af­ter ex­po­sure to an anxiety-moderating drug known as Ox­aze­pam.

Perch. (Courtesy Ben       Christensen)

      Residues of the drug of­ten wind up in nat­u­ral aquat­ic sys­tems af­ter peo­ple con­sume it, the re­search­ers said. They’re ex­cret­ed, flushed down the toi­let, trea­ted at wastewa­ter treat­ment plants, and end up in the wa­ter un­changed.

Brodin and col­leagues dosed wild perch with amounts of Ox­aze­pam equiv­a­lent to those found in Swe­den’s riv­ers and streams. Their re­sults, they said, sug­gested that even small amounts of the drug can al­ter the be­hav­ior and for­ag­ing ra­tes of these fish. 

“Nor­mally, perch are shy and hunt in schools. This is a known stra­tegy for sur­viv­al and growth. But those who swim in Ox­aze­pam be­came con­sid­erably bold­er,” said Brodin, lead au­thor of the re­port, pub­lished in the Feb. 15 is­sue of the jour­nal Sci­ence. The af­fect­ed fish left their schools to seek food on their own, a be­hav­ior that can be risky, he ex­plained; they al­so ate more quick­ly.

“We’re now go­ing to ex­am­ine what con­se­quenc­es this might have. In wa­ters where fish beg­in to eat more ef­fi­cient­ly, this can af­fect the com­po­si­tion of spe­cies, for ex­am­ple, and ultima­tely lead to un­ex­pected ef­fects, such as in­creased risk of al­gal bloom­ing,” said Brodin.

“The so­lu­tion to the prob­lem is not to stop med­i­cat­ing ill peo­ple but to try to de­vel­op sew­age treat­ment plants that can cap­ture en­vi­ron­men­tally haz­ard­ous drugs,” added en­vi­ron­men­tal chem­ist Jerk­er Fick, a co-au­thor of the stu­dy.

The sci­en­tists added that the find­ings should be seen as a point­er about what might be un­der­way in many wa­ters around the world, though full­er stud­ies are re­quired be­fore any far-reach­ing con­clu­sions can be drawn.

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