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Learn about what cockles do for the ecosystem from scientist Stephen Wing

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ASSOC PROF STEPHEN WING Cockles play a very important role in the marine food web because they clean the water, and they make it so that phytoplankton don't bloom or become too abundant, and they keep the water from going eutrophic or full of phytoplankton.

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Young Ocean Explorers quiz: What do pipis and cockles do for the harbour? 

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Young Ocean Explorers quiz: What do pipis and cockles do for the harbour? 

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Young Ocean Explorers has been on a mission since 2012 to inspire kids to love our ocean - through entertaining education. We want to capture children's imaginations through great storytelling, bringing the beauty, awe and fascination of the ocean and its inhabitants alive.

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Getting muddy with cockles DOC Education resource  

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Getting muddy with cockles DOC Education resource  

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Find out about how scientists study cockles and what they look like, what they eat and how they live

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The impact of fresh water on cockles (Science Learning Hub) 

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The impact of fresh water on cockles (Science Learning Hub) 

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A scientist talks about the changes in salinity in Doubtful Sound due to a hydro-electric dam and the impact on cockles and the wider ecosystem

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In this video, Associate Professor Stephen Wing, from the University of Otago, discusses his research into the impact of freshwater on cockle populations in Fiordland.

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Cockles by Guardians of Pāuatahanui inlet 

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Cockles by Guardians of Pāuatahanui inlet 

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Information and photos about cockles

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Cockles " The Guardians of Pauatahanui Inlet

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Every three years the Guardians of the Pāuatahanui Inlet survey the cockles to see if their numbers are decreasing or growing, and if they're getting bigger, smaller, or staying the same. Perhaps your family has taken part in one of these surveys?

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Forest and Bird: Best fish guide: cockles 

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Forest and Bird: Best fish guide: cockles 

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How sustainable is it to eat cockles?

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"royal forest and bird protection society of new zealand"

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Cockles: Quick Facts Scientific name: Austrovenus stutchburyi Other names: hinangi, huangi, huuai, huangiangi tuangi (Maori), NZ littleneck clam (USA), clam, venus-shells, coque (Canada). Ranki

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Article about cockles by Science Learning Hub 

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Article about cockles by Science Learning Hub 

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Classification, habitat and adaptations

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Cockles are classified as bivalves within the phylum Mollusca. (Almost all shelled marine animals, as well as octopus and squid, are molluscs.)

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.

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.

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.

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.

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.

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Cockles are classified as bivalves within the phylum Mollusca. (Almost all shelled marine animals, as well as octopus and squid, are molluscs.)

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Description of cockles by Dunedin Aquarium

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From our Mm2 scientist series. Where do you find juvenile cockles?