http://www.sciencemag.org/news/2020/08/tiny-fish-takes-its-predators-and-wins-transforming-baltic-coast

Though small, the three-spine stickleback has a big enough mouth to eat the young of its predators.

No bigger than a minnow, the three-spine stickleback may seem a puny player in the underwater world. But along the European coastline of the Baltic Sea, it has edged out its own predators—toothy pike and perch, fish that grow longer than your forearm. Records dating back 40 years show how the flamboyant little stickleback has shifted the ecosystem, thwarting efforts to restore the larger species favored by human fishers. “A little pelagic fish that many people ignore is having a dramatic ecological impact,” says Brad deYoung, an oceanographer at Memorial University who was not involved with the work.