The isotopic analysis reported in the 1998 paper showed clearly that anadromous fish — fish that migrate between ocean and freshwater, like salmon — were a significant component of her diet.

This was established through carbon and nitrogen stable isotope ratios in her bone collagen, a technique that captures the average diet over several years of bone turnover.

The nitrogen isotope signature was particularly informative: high nitrogen values in bone collagen are characteristic of diets rich in animal protein, especially protein from aquatic species.

Salmon were present in the Snake River system during the terminal Pleistocene and through the early Holocene.

The river system eventually connects to the Columbia River and thence to the Pacific Ocean, and salmon would have made the same upstream migrations then that they make in modern rivers.