The dead shellfish, mostly cockles, were found on the shoreline at the entrance to the Okura River estuary at the northern end of the marine reserve.
DOC manages the marine reserve and is working with the Ministry of Primary Industries (MPI) and Auckland Council to try and establish what caused the shellfish to die.
MPI are testing dead shellfish from the estuary to determine if they have been infected by a disease.
Auckland Council monitors the condition of the marine environment across the region. The council is pulling together data it has gathered for the area to help the investigation and is looking to gather extra seawater samples from the Okura River Estuary.
“We don’t know why the shellfish have died so we’re working with MPI and Auckland Council to try and establish the cause of death,” says DOC Auckland Mainland Operations Manager Kirsty Prior.