Thousands of paua were washed up dead and dying on Kaka Point beaches last week.
Residents contacted the newspaper on Thursday after discovering the shellfish and other marine animals piled up on the shore after a heavy tide.
The "natural phenomenon" had occurred previously in 2016 and 2013, although Kaka Point residents said it "has never been this bad".
When contacted, marine experts and government agencies, including the Ministry for Primary Industries (MPI), said they were aware of the situation.
"The cause of the wash-up is not yet known, but is likely due to natural events," MPI fisheries compliance regional manager Garreth Jay said, adding that MPI had taken samples for testing.