The team sifted through all known sites older than 7,000 years for reports of fish. Ten sites were identified, all from the middle Tanana basin, where the Tanana River runs through before connecting to the larger Yukon River. Eight sites had materials available for study, with seven dating from the Younger Dryas ~11,650 to 12,900 years old.

A total of 1,110 fish specimens were identified, all of them Actinopterygii (ray-finned fishes). Of these, 627 (56%) could be identified to a taxonomic level. Identified fish included salmon (34%), burbot (58%), whitefish (7%), and northern pike (<1%).

All of these fish are still caught today in the Tanana and northern North America. The authors note an absence of grayling, char and longnose suckers, despite those fish currently inhabiting the river. Also interesting, all identified fish before 11,800 years ago are freshwater fish, which might hint at a connection to environmental climate change associated with the Younger Dryas event.

The Younger Dryas is a climate-driven extinction event. The planet was leaving a prolonged ice age, continental glaciers were receding, and humans and megafauna were expanding into new territories. Then suddenly, a climactic shift thrust temperatures back into an ice age in the Northern Hemisphere.