why fish cannot survive in polluted water
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Fish in lakes tainted with metals are losing their sense of smell, stoking concern among experts that the problem could devastate populations.
But if the fish can just get into cleaner water – even if they’ve been exposed to pollutants their whole life – they start sniffing things properly again, according to new research out of Canada.
Fish use their sense of smell to find mates and food, and to avoid getting eaten. It helps them navigate their often murky world, and it is necessary for their growth and survival. But when metals contact fish nostrils, the neurons shut down to protect the brain.
Metals already have been linked to impaired reproduction and growth in fish but now they are proving to be “covert toxics,” said Keith Tierney, a University of Alberta assistant professor who did not participate in the new study. “If you can’t smell food, or avoid predators, you’re more likely to die – simple as that.”
Greg Pyle, a professor at the University of Lethbridge in Alberta, said he suspects that impaired sense of smell “has meaningful and profound effects” on many fish species. It may be jeopardizing entire populations of fish, including some endangered species.
“We’ve tested everything from leeches to water fleas to several species of fish,” Pyle said. “Every species and every metal we’ve observed has had effects at low, environmentally relevant concentrations.”
Most contaminated lakes have a metallic mix, making it hard to tease out which pollutants are to blame.
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