Estuaries are places where fresh water from rivers mixes with salty water from the ocean. Why does this matter? This mixing creates dynamic, ever-changing conditions that fishes must navigate in order to survive. Environmental conditions can change yearly, seasonally, daily, and even hourly. Fishes use many di erent strategies to adjust to this wild variation. Some are picky and only use certain habitats. Others use many di erent kinds of habitats and move between them at di erent times of the year. Adults and juveniles might even live away from each other in di erent parts of the estuary. In this article, we describe some of the clever strategies that fishes use to survive in estuaries. We also consider how scientists uncover these clever strategies and what each of us can do to help protect the fishes of the San Francisco Estuary and elsewhere. kids. frontiersin. org September| Volume| Article|