The pipi beds in the Ngunguru River are closed after their population has collapsed.
The cockle, cousin of the pipi, is not doing well in that river either.
Last May, thousands of Ngunguru pipi died, and no one knows why.
It's an obvious factor in the pipi decline, measured through Ministry of Primary Industries surveys, which 10 years ago, found about 50 pipi per square metre.
The pipi were 5cm or bigger.