Marked growth in pipi and cockle populations
- Admin
- Sep 25
- 2 min read
In January and February 2025 Ōhiwa Harbour was again part of a regular survey that assesses the cockle and pipi populations across 11 northern North Island sites, including Cockle Bay, Kawakawa Bay (West), Mill Bay, Ōkahu Bay, Okoromai Bay, Otūmoetai (Tauranga Harbour), Pataua Estuary, Waiotahe Estuary, Whangapoua Harbour, and Whitianga Harbour.
According to Senior Scientist Dr Katrin Berkenbusch at Dragonfly, the company that undertakes the survey on behalf of Fisheries New Zealand, the latest survey showed that both pipi and cockle populations in the harbour were growing, however, that the bivalves were generally of a small size.
The New Zealand cockle (Austrovenus stutchburyi) or little neck clam is also commonly as Tuangi, an important taonga species. Tuangi can filter up to three litres of water per hour. So when tuangi are in high densities, this has a positive effect on water clarity.
The cockle population has grown since the last survey in 2023, with a notable increase in numbers and density. The population is mainly composed of medium-sized cockles, with only a few large individuals (i.e., larger than 30 mm shell length). The population fluctuates over time, but there is usually a good influx of new, young cockles, a process known as recruitment. A quarter of all cockles in 2025 were recruits, i.e., they were smaller than 15 mm shell length.
The pipi population has also grown markedly, with substantially more individuals and a higher density than in the previous survey in 2023. Similar to the cockles, large pipi (i.e., larger than 50 mm shell length) are rare. Almost half of the current pipi population is made up of new recruits (i.e., less than 20 mm shell length), indicating a large and recent recruitment event that has contributed to the overall population increase. The influx of these young pipi boosted the pipi population in 2025, from small population sizes in the three previous surveys.
Recognition of the potential impacts of human activities on northern cockle and pipi populations has led to the regular monitoring of their populations by Fisheries New Zealand. Initiated in the early 1990s in the Auckland region, the population surveys have been subsequently extended across the northern North Island area. Since the late 1990s, the use of largely consistent survey methods has provided extensive time-series data, particularly for cockle beds that are considered to be less temporary than some of the pipi beds.
The daily limit for both pipi and cockle remains at 150 per gatherer per day. As the latest survey indicates populations remain vulnerable to overexploitation.
Sources:
Berkenbusch, K.; Hill-Moana, T. (2025). Intertidal shellfish monitoring in the northern North Island region, 2024–25. New Zealand Fisheries Assessment Report 2025/27. 111 p.
Katrin Berkenbusch, Senior Scientist, Dragonfly, personal communication, 7 September 2025
NIWA, Tuangi. What does science tell us about New Zealand Cockles? NIWA Information Series, November 2021
https://niwa.co.nz/sites/default/files/FINAL Taonga Species_Tuangi LOW RES.pdf
