New research shows that the oldest fish can decline dramatically in fished populations, even when fisheries are sustainable. Old fish declined in 97% of populations when compared to an unfished state, and in about a third of populations, old fish declined by more than 90%. These changes reduce the diversity of fished populations, which can lead to lower stability. Reducing the impact of fishing on old fish would require marine reserves, rotational harvesting, or slot limits that prohibit fishing on all but a narrow range of fish ages. The work by SAFS postdoc Lewis Barnett and professors Trevor Branch and Timothy Essington, together with Anthony Ranasinghe, appeared in Current Biology. and was featured in National Geographic News.