Fish are getting hooked on plastic that's making them "smaller, slower, and more stupid," say researchers behind a new study at Science. Scientists have long suspected that microplastics are dangerous, but "that has been very hard to determine until now, and that's why this is such a big paper," a scientist not involved with the study tells the BBC. Swedish researchers compared two tanks full of European perch: one with clean water, and one with high concentrations of polystyrene, a plastic pollutant. In the clean water, 96% of eggs hatched, with half surviving their first 24 hours. In the other tank, just 81% of eggs hatched—revealing smaller, less physically active fish, per the Washington Post—and all were eaten by predators in their first day.
Not only that, they also favored plastic as a food source in the same way that some humans favor fast food. "They all had access to zooplankton and yet they decided to just eat plastic," the lead author says. "It seems to be a chemical or physical cue that the plastic has." The fish "are basically fooled into thinking it's a high-energy resource that they need to eat a lot of." As a result, they stuff themselves but wind up with little or no energy. This could explain why juvenile perch and pike have been dying at increased rates in the Baltic Sea over the past 20 years. Researchers say they've recently found similar responses in pike, flounder, and coral reef damselfish exposed to microplastics, reports Reuters. If plastic has the same impact on all fish, it could have "profound effects" on ecosystems, they add. (Oysters are in danger, too.)