A buddy and I were walking along the shore by the ocean to get back to our boat, and came upon a row of wooden plugs in the ground, level with the surface. We had not seen them earlier as it was higher tide when we arrived. We followed the row of plugs and came to a defined bend in their layout. Finally got up on a tall rock and saw we had found one of two rows that converged into a vee or funnel. The whole arrangement covered 75 yards by 150 yards, next to a creek. Pulled up one plug and looked, it was sharpened like a stake on the bottom. (I put the plug back.)
Later went to an archaeology lecture put on by the Forest Service, and recognized we had found remains of a Tlingit indian fish trap. Originally these poles were high walls thatched with brush. The salmon got in at high tide and were trapped when the tide went out.
I told the archaeologist about our find, and marked it on a map. Later got a report. They radiocarbon dated it, several hundred years old, and the cuts on the poles were made with a stone axe. They said you can tell the tool was stone because the cuts are wavy, not straight.Apparently the salt water pickles the buried wood, and packed in the mud with no air, it does not decay.