Do you like to eat salmon? If so, you’re not alone. European catfish, a large freshwater fish introduced into Europe for sport fishing, has also developed a taste for it. We wanted to know what happens when salmon and catfish meet in rivers that humans have changed (for instance: by building a power plant). We picked a big river with a power plant, the Garonne in South-West France, to address this question. With the help of video and acoustic cameras in a special waterway for fish around the power plant, as well as radio-transmitters attached to individual fish, we can confidently say that catfish prey on salmon in these altered parts of the river. In fact, they seem to even shift the time they’re active (from night time to more daylight hours) to increase their chances of catching salmon. And while salmon populations are declining in Europe, catfish seem to be doing better and better.