Humans are killing the oldest fish in the sea, a new study suggests. That is likely altering ocean food webs and making populations of many important species eaten by people less stable and resilient.

In one of the first studies of its kind, a team of fish experts used models and fish-catch data to analyze 63 major fish populations around the United States and Europe, from Atlantic cod and Greenland halibut to rockfish, hake, grouper, and sole. They found significant declines in the oldest fish in nearly 80 percent of the populations. In roughly one-third, the number of older fish had declined by more than 90 percent.

It didn't matter whether the species were long-lived yelloweye rockfish, which can survive