Anxiety takes a toll on people: they worry, they feel irritable, they avoid social gatherings\u2014like that upcoming New Year\u2019s Eve party. Juvenile salmon also experience stress when faced with unfamiliar situations, such as migrating out to sea where they\u2019ll encounter predators. While anti-anxiety medication helps countless humans function better in their daily lives, new research shows the drugs also make salmon less inhibited, which can have potentially devastating effects.<\/p>\n
In a study out of Sweden\u2019s Ume\u00e5 University, researchers show oxazepam\u2014a pharmaceutical prescribed to humans for the treatment of anxiety, alcohol withdrawal, and insomnia\u2014affects the downstream migratory behavior of Atlantic salmon. Exposing fish to anti-anxiety medication isn\u2019t something that only happens in scientific studies: when humans excrete drugs, some can end up in wastewater effluent and subsequently in sensitive habitats where salmon may get an unintended dose. The researchers found that when fish ingest oxazepam, it makes them migrate faster and farther\u2014potentially recklessly so.<\/p>\n
Leaving the freshwater nursery and heading out to sea is part of the salmon lifecycle, but landing in the big blue too soon can be risky. Fish may find ocean conditions unfavorable\u2014too cold, too dangerous, or lacking food, for example.<\/p>\n
Gustav Hellstr\u00f6m, a salmon biologist at Ume\u00e5 University and lead author on the study, says stress is probably an adaptive response as it may minimize unnecessary risk-taking and help maintain alertness.<\/p>\n
\u201cIf we interfere with the swimming behavior that\u2019s been adapted to that river, it\u2019s probably bad for the salmon. It would expose them to more risks,\u201d Hellstr\u00f6m says. \u201cThe migration behavior in itself is probably matched evolutionarily to different kinds of environmental factors.\u201d<\/p>\n
Hellstr\u00f6m and his colleagues studied how salmon respond to oxazepam in a large artificial stream and in a natural stream in Northern Sweden. In both environments, they found that fish treated with oxazepam migrated nearly twice as fast as sober salmon. Hellstr\u00f6m points out that the salmon in his study were given a low dose of the drug within the range of concentrations that have been found in effluent water.<\/p>\n
\u201cThe paper gives pretty strong evidence that anxiety and stress are a force that counterbalances foraging and migration,\u201d says Will Atlas<\/a>, a PhD candidate with the Hakai Institute* who wasn\u2019t involved in the research. \u201cI think we\u2019ve kind of known that for a long time in how we understand behavioral ecology, but this is a very tangible demonstration of it.\u201d<\/p>\n Atlas, who studies the biology of Pacific salmon and their ecosystems, says Pacific salmon would likely react to oxazepam the same way Atlantic salmon do. \u201cThere may be species-specific reactions, but I think the direction of the response would probably be the same,\u201d he says.<\/p>\n According to the World Health Organization<\/a>, the use of anti-anxiety drugs is projected to increase globally. As a result, the concentrations of oxazepam in aquatic environments near urban areas could more than double in the coming decades, according to a 2015 study<\/a>.<\/p>\n \u201cOur research group does not want to try to limit the prescriptions of drugs,\u201d Hellstr\u00f6m stresses. \u201cIt\u2019s really important to state that these drugs do a lot of good for people and reduce suffering.\u201d It\u2019s wastewater treatment that needs to be improved, he says.<\/p>\n The study does suggest one potentially promising application of the researchers\u2019 findings. Enhancing weak wild salmon populations with hatchery smolts is a fisheries management practice worldwide. However, the success of so-called enhancement stocking is generally low, in large part because of inadequate migration. The researchers suggest further exploring whether treating hatchery salmon with oxazepam, which the fish eventually eliminate from their bodies, could be beneficial.<\/p>\n The study also suggests a new way of understanding salmon migration. \u201cIt allows us to talk about cognitive and emotional dimensions in fish and that\u2019s really controversial,\u201d Hellstr\u00f6m says. \u201cMigration is almost always discussed in terms of environmental factors. This highlights that there is more to it than that.\u201d<\/p>\n