A 100-year simulation of individuals reveals the opposing forces that fisheries and natural selection play in sockeye salmon in Bristol Bay, Alaska. Natural selection favored the production of longer salmon, but also produced differences between the body type of salmon spawning in shallow streams (where body depth declined) and those spawning in the beaches of large lakes (where body depth increased). On the other hand, fisheries tended to catch larger salmon on average, creating selective pressure towards shorter fish. In addition, natural selection was able to maintain locally adapted populations of salmon in streams and creeks even in the face of fishing and considerable genetic flow among the two salmon populations. The research by former SAFS PhD student Jocelyn Lin, SAFS professors Lorenz Hauser and Ray Hilborn, and Jeffrey Hard of the Northwest Fisheries Science Center, NOAA, appears in the open-access journal Ecosphere.