More than 50 species of fish have been found to consume plastic trash at sea. This is bad news, not only for fish but potentially also for humans who rely on fish for sustenance. Fish don't usually die as a direct result of feeding on the enormous quantities of plastic trash floating in the oceans. But that doesn't mean it's not harmful for them. Some negative effects that scientists have discovered when fish consume plastic include reduced activity rates and weakened schooling behavior, as well as compromised liver function. Most distressingly for people, toxic compounds that are associated with plastic transfer to and bioaccumulate in fish tissues. This is troubling because these substances could further bioaccumulate in people who consume fish that have eaten plastic. Plastic trash poses a serious threat to marine animals, but we are still trying to understand why animals eat it. Typically, research has concluded that marine animals visually mistake plastic for food. While this may be true, the full story is probably more complex. For example, colleagues at the University of California at Davis and I showed in a recent study that plastic debris may smell attractive to marine organisms. That's a problem, because if plastic looks and smells interesting to fish, it will be very hard for them to discern that it is not food.