In this case they have carbon dated wooden equipment for fish farming and know due to geological factors when the lake could support fish, though of course the fish might have gotten there first somehow. I thought this was interesting because it predates agriculture in the same area.

How did wooden equipment not whither away in 7000 years?

Humans were shaping their environments to produce food long before they plowed fields. Hunter-gatherers didn't just hunt and gather willy-nilly, picking up whatever they found, oblivious to how it got there.