Summer Series 5: Cockles and Pipis, alive, alive-oh

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Pipi – fritter away your summer

Over the long hot summer many kiwis will be digging deep in the sand for pipi. These yummy shellfish live buried in the sand and are free at the beach!

They are distributed around the New Zealand coastline, including the Chatham Islands and, further afield, the Auckland Islands. They are most plentiful in sheltered beaches, bays, and estuaries. They are tolerant of moderate wave action, and occur at depths of up to seven metres.

Pipi can range in colour from white to a straw colour, they have an oblong shape shell with rounded ends, and a foot that they use to burrow. In fact, if you swim with your eyes open in the water, they can be seen moving through the water column – hovering or floating.

"The interesting thing about pipi is that they can make a mucus thread that makes them more buoyant and enables them to float in the water column. They stick out their mucus thread and off they go, travelling along with the current, – they can only go as fast as the water," says NIWA marine ecologist Dr Vonda Cummings.

"You find pipi packed together in dense patches, in fast flowing water in estuaries," says Dr Cummings. 

They like exposed areas, for example, a sandbank in the middle of an estuary or near the estuary's mouth. They can be found just below the surface on sandy flats, sometimes in such vast numbers that shells can be found forced into different shapes by the pressure of the shell beside it.

Baby pipi can be found further up in the estuaries.

In a spot that really suits them there can be over 1000 pipi per square metre.

They are closely related to tuatua and toheroa; they look similar, are a similar size. The way pipi can be distinguished is that they have a hinge in the middle of their shell.

Pipi can be eaten raw; straight from the shell, tossed on an open fire or barbecue until their shells open, or cooked in a variety of ways. Fritters are a favourite!

The daily pipi limit is 150 per person and only larger pipi should be taken. There is no minimum legal size for pipi, although fishers favour larger pipi, greater than 60 mm long. Pipi are available for harvest year-round, so there is no apparent seasonality in the fishery. They are commercially harvested. 

Traditional Māori ate vast quantities of pipi. Centuries-old midden heaps are filled with shells, and are prominent features on pa sites.

Shellfish have been an important part of the Māori diet since the first peoples arrived in New Zealand. Many hapu would travel around their area in a seasonal rotation harvesting the various sources of kai.

Pipi are still a favourite of Māori and Pakeha.

To find out more visit www.fish.govt.nz

Cockles – the heart of summer

The hazy days of summer are here, and for many that means digging for cockles. This heart-shaped food is free at the beach! Cockles are shellfish that live just below the surface of the sand. They are sub tidal, found up to ten metres deep, and are common all around New Zealand.

Many New Zealanders have memories of collecting shellfish from the beach in summertime. Digging in the sand with two hands, to catch them. Maybe eating a few live ones, from the bucket. 

Cockles have plump, round, hard, heart-shaped shells with ridges which run across and downwards. "If it's nice clean sand the shells are often lighter in colour," says NIWA marine ecologist Dr Vonda Cummings.

Cockles are a shallow-burrowing shellfish, found on protected beaches, and enclosed shores around the North and South Islands, Stewart Island, and the Chatham Islands. They are found in a variety of sediment types, but prefer sediments that are predominantly sand, with little mud content. They are also common in eelgrass.

They burrow using their foot, and feed on plankton filtered from the surrounding water. Cockles are capable of 'jumping' by bending and straightening their foot.

They are prized as culinary delicacies. Tasty when steamed open, they can be cooked with linguine, onions, and garlic in a white wine sauce.

Because cockles filter large amounts of water they can accumulate toxins from phytoplankton or bacteria in the surrounding water. It is important that they be collected only from unpolluted sites, especially as they can be eaten raw. Unsafe areas are usually sign posted – check with regional council.

Cockle growth is slower in the higher tidal ranges and in high-density beds. Interestingly, significant increases in growth rates have been observed for cockles remaining in areas that have been thinned out by harvesting. Growth rate is related to the amount of food they can take in. The larger ones are closer to the low tide mark. So don't be afraid to get your feet wet if you're looking for bigger ones.

Recreational fishers like relatively large cockles, but sometimes take cockles less than 30 mm long. 35 mm is a reasonably sized adult. The South Island cockles grow even bigger.

The daily bag limit is 150 per person per day, except for Auckland and the Coromandel where it is 50 per person per day.

Hungry beach goers are not their only threat. Birds, whelks, and crabs also eat them. Sediments shifted during storms or strong tides can smother cockles. At NIWA, past research has investigated the effects of increasing sediment inputs, for example from land erosion, to coastal waters on some of New Zealand's important shellfish species.

To find out more visit www.fish.govt.nz

Species Fact File: Cockles

Common names: Cockle, NZ little neck clams

Māori name: Tuangi, Tuaki is used by Ngai Tahu in the South Island

Scientific name: Austrovenus stutchburyi

Type: Bivalve

Family: Veneridae

Size: 51–62 mm

Diet: Phytoplankton

Reproduction: The sexes are separate, male and female, and the sex ratio is balanced.

Maturity appears to be a function of size rather than age, with sexual maturity occurring at a size of about 18 mm shell length.

Spawning extends over spring and summer, and fertilisation is followed by a planktonic larval stage lasting about 3 weeks.

Things you need to know: The daily bag limit is 150 per person per day, except for Auckland and the Coromandel where it is 50 per person per day.

Something strange: Barnacles often grow on cockles, and bits of algae may attach to them on a sandy beach where there isn't much substrate for the algae to settle on to.

About Vonda Cummings

Dr Vonda Cummings is a NIWA marine ecologist whose research interests include studying the impact of ocean acidification on shellfish.

She also looks at the interactions between different species, what species you find where and why, and what influences the different communities in different places. 

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Pipi in the sand Photo. Credit: Sarah Hailes

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Pipi in hand. Credit: Sarah Hailes

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Cockles. Credit: NIWA