Cockles
Cockles are classified as bivalves within the phylum Mollusca. (Almost all shelled marine animals, as well as octopus and squid, are molluscs.)
Harvesting cockles
Cockles have been a popular food item for people since early Māori settlement.
The New Zealand cockle, also known as tuaki or tuangi, is endemic to New Zealand’s coastal areas. They are not endangered, although there are some concerns about the commercial harvesting of the species.
| Scientific classification | |
|---|---|
Kingdom | Animalia |
Phylum | Mollusca |
Class | Bivalvia |
Order | Veneroidea |
Family | Veneridae |
Genus | Austrovenus |
Species | Stutchburyi |
Habitat
New Zealand cockles live in sheltered coastal areas around the North and South Islands, Stewart Island and the Chatham Islands. Cockles’ preferred habitat is within the soft mud and fine sand in subtidal areas. They favour sediments that have a larger grain size and commonly live in sand flats and beds of eelgrass. In some areas, they have been found at water depths of 20 metres but they generally prefer shallower habitats. Cockles also live in estuaries and can tolerate some changes in salinity.
Cockles are filter feeders and are normally sessile, remaining in the same spot and feeding on microscopic plankton that are floating in the water column. However, both adults and juveniles are able to move to more favourable habitats when required.
Label the cockle/tuangi
Use this interactive to label parts of a cockle/tuangi. Drag and drop the text labels onto the boxes next to the diagram. Selecting or hovering over a box will highlight each area in the diagram. If you hover your mouse over the text labels there is more information.
If you want to redo an answer, click on the box and the answer will go back to the top so you can move it to another box. If you want to check your answers, use the Reset incorrect button. This will reset incorrect answers only. When you are happy with your selection, use the Check answers button to check them. Use Reset all to practise again from the start.
Adaptations
The New Zealand cockle is well adapted to its sandy, sheltered habitat. They have a sturdy, heavy shell that provides protection from physical damage, predators and drying out. Cockles normally burrow 2–3 centimetres into the sand. However, they live in a tidal environment, and if waves or currents dislodge them, their shell protects them from damage as they tumble around in the water. Their soft flesh is also protected from many predators by the sturdy shell (although it is not always enough to stop the prying beaks and sharp pincers of birds and crabs that like to eat them!). Drying out is a daily danger for animals that live in tidal environments. A cockle’s shell is able to hold a reservoir of water to sustain it when the tide is out.
Impact of freshwater on cockles
In this video Associate Professor Stephen Wing discusses his research into the impact of freshwater from a hydroelectric plant on cockle populations in Fiordland.
Select here to view point of interest, video transcript and copyright information.
Cockles: a popular food source
Cockles are not only a favourite food source for birds and crabs. They have been a popular item for people since early Māori settlement, and cockle shells have been found in middens throughout the country. Recreational harvesting is still widespread, and many people consider cockles a delicacy. Cockles are also commercially harvested in a number of locations including Whangārei Harbour, Golden Bay and Otago Peninsula. Cockles can be harvested all year round, and New Zealand manages the harvest with strict quotas. In 2008/2009, the total allowable commercial catch (TACC) was set at 3,214 metric tonnes.
The role of cockles in the ecosystem
Cockles are filter feeders, and they may accumulate toxins, bacteria and viruses present in the surrounding environment. This has important implications for harvesting, and cockles should only be eaten if they are taken from unpolluted areas. It also means that cockles have the potential to act as environmental indicators and to help gauge the health of an ecosystem.
New Zealand cockles (Austrovenus stutchburyi)
Austrovenus stutchburyi, common names are tuaki, tuangi or New Zealand cockle, and they are widespread in sediments ranging from soft mud to soft, silty sand across New Zealand harbours and estuaries from the mean tide level to low tide. These bivalve molluscs are endemic to Aotearoa New Zealand and play a vital role in marine ecosystems.
In their role as filter feeders, cockles also provide an important link in the food web between the primary producers, such as phytoplankton, and smaller carnivores, such as birds, crabs and rock lobsters. Cockles also provide another important food web service – when they are filtering the water, they help prevent blooms of phytoplankton that reduce oxygen availability for fish and many other species.
Related content
Discover more about tuaki and explore food and resource-gathering traditions practised by Ngāi Tahu whānau in Te Waipounamu, this is part of the Mahinga kai – natural resources that sustain life interactive.
Explore marine webs further in this article and interactive.
Activity idea
The activity Labelling a cockle/tuangi uses the interactive Label the cockle/tuangi to explore some of the structures of this common marine bivalve. The activity provides an excellent opportunity to discuss structural adaptations.
Useful link
Visit the Te Ara website to learn more about cockles and other shellfish in New Zealand.
