This close-up of the above image shows fish nests.  Rather large fish scrape the bottom clean with their stomachs and use it as a nest- even this close to the canoes

Close-up of the top-right nest shows what might be a fish entering it.

Close-up of the two nests on the lower left.

Scanned from the left-eye slide, on the right above.

Scanned from the right-eye slide, on the left above.