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What are toheroa and where can you find them?
Toheroa (Paphies ventricosa) are large surf clams endemic to Aotearoa.
Toheroa are also known by other names such as moeone, taiwhatiwhati, tohemanga, roroa, and tupehokura according to iwi dialect.
Toheroa are found in the intertidal zone of sandy and surf-exposed beaches in the North and South Islands of Aotearoa.
These toheroa habitats are often associated with freshwater streams and seeps.
Major populations of toheroa are mostly found on west and south facing beaches in Northland, Wellington and Southland.
Historically, smaller populations of toheroa were also found along the east coast of the North Island, many of which are said to have been translocated from west coast beaches.
Toheroa can grow to over 150 mm and can live for 20 years!
Did you know?
Endemic means that these species are only found in Aotearoa.
Other surf clam species
Toheroa are part of the Paphies family which includes three other types of surf clams.
All of these species look similar and it is easy to mistake toheroa for tuatua. Here are some ways you might be able to tell toheroa and tuatua apart.
- How big is it?
An adult toheroa can become twice as big as a tuatua. - Look at the shell
Toheroa shells are rounder, gape at one end and have a lump at the base. Tuatua shells are fully closed, have a sharper edge, and the base of the shell is quite flat.
It is important to be able to identify different surf clams to ensure toheroa are not being mistakenly harvested as tuatua.
What do toheroa eat?
Toheroa are filter feeders which means they obtain all their food by straining it from the water. They are also generalists, feeding on a variety of food.
Toheroa feed on phytoplankton (microscopic plants) and organic matter in the water. This is obtained by inhaling seawater through the inhalant siphon. The top of the inhalant siphon has a network of tentacles which acts as a filter to prevent large particles from being inhaled.
Phytoplankton and organic matter inhaled into the toheroa are then sorted in the alimentary canal with any excess food or waste expelled by the exhalant siphon (see - Toheroa Anatomy).
Toheroa life cycle
Toheroa move up and down the shore during their different life stages.
1. Spawning
Adult toheroa are broadcast
spawners which means they
release their sperm and eggs
externally into seawater. Spawning
events usually occur in spring
and summer, but it can vary
depending on location. The timing
of spawning events also appears to
follow environmental cues such as
full and new moon phases.
2. Larvae
The larvae of toheroa are planktonic (drift in the water). The larval phase of northern toheroa is around three weeks whereas for southern toheroa it can be up to seven weeks. The duration of this phase varies depending on temperature and feed. Larvae that settle on suitable beach habitat in the surf zone will transform (undergo metamorphosis) into juvenile toheroa
3. Juveniles
Juvenile toheroa will settle in the surf zone with a length of up to 2 mm. They are collected in wave fronts and carried up the beach where they form a band near the high-water mark. Juvenile toheroa will then burrow 1-2 cm beneath the sand
4. Adult
As toheroa grow larger, they will move down the shore toward low water. Although larger toheroa become more exposed to the surf they can dig down to 20 cm beneath the sand allowing them to maintain their position on the
lower shores.
Toheroa anatomy
The anatomy of toheroa is similar to many other surf clams and includes:
Foot
The muscular foot helps toheroa to move around and burrow quickly into the sand.
Siphons
Toheroa have two long and extendable siphons. As filter feeders these are how they ‘eat’ - the inhalant siphon inhales the seawater and the exhalant siphon expels it.
Shell
The hard outer shell helps provide protection from predation, drying out, and physical damage, but interestingly it does not fully close. The wedge shape of the shell also helps it to burrow quickly!
Gills
The gills play an important role in filtering seawater to obtain oxygen, as well as plant material and organic matter.
Adductor muscle
This muscle allows the toheroa to open and close its shell.
Retractor Muscle
Retractors pull the foot back into the shell before it closes, or, when digging, pull the clam toward an expanded foot anchored in the sand.
Alimentary canal
This is where phytoplankton and organic matter is separated
What are the threats?
There are a wide range of threats which may impact toheroa, including:
- Harvesting - Harvesting toheroa is restricted and monitored to support toheroa management as harvesting can negatively impact its recovery.
- Driving - Driving over toheroa beds can cause juvenile toheroa to float to the surface, which makes them vulnerable to being directly crushed, drying out, or being predated by birds.
- Changes in habitat - Toheroa like sandy habitats with freshwater nearby which means changes in water quality and beach sediment could all negatively impact toheroa.
- Climate change - Climate change can lead to changes in currents, sea temperature and pH which can impact toheroa populations and affect shell formation.
How can we help toheroa?
Toheroa were once abundant in Aotearoa but numbers of toheroa have drastically dropped.
Some ways we can help our toheroa populations include:
Protect and restore toheroa habitats.
Avoid driving over toheroa beds.
Minimise disturbances to toheroa populations.
Follow toheroa regulations in your area.
Learn more about the toheroa.
Did you know?
Canned toheroa soup was so popular no one could keep up with demand even though it was a strange khaki green colour!
The recent history of toheroa
Toheroa were once abundant on west and south coast beaches of Aotearoa.
1890s - Toheroa canneries were established in Northland, Wellington, and Southland.
1900s - Commercial and recreational harvesting of toheroa was intensive, with Northland beaches producing an average of 20 tonnes of canned toheroa per year from 1928-1969.
1940 - A record 77 tonnes of canned toheroa from Northland was produced in a single year.
1969 - All commercial harvesting of toheroa ceased as toheroa populations around the country declined.
1971 - Recreational harvesting of toheroa was being prohibited in Aotearoa from 1971-1980. The final open day was in 1993 at Oreti Beach in the South Island. Before this, all recreational harvesting ceased in 1980 with the final open seasons at Ripiro (Dargaville), Te Waewae Bay and Oreti.
Current day - Although intense harvesting has long been prohibited, toheroa populations have not yet recovered indicating there could be environmental factors impacting their recovery.
