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Description of how to find critters in your stream.

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How to find critters in a sandy or muddy-bottomed stream

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How to find critters in a sandy or muddy-bottomed stream

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A simple method for finding creepy crawlies!

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Another padlet all about kōura | Taupo for tomorrow

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Another padlet all about kōura | Taupo for tomorrow

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You will find even more resources about kōura here!

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Kākahi: What does science tell us about them?

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Kākahi: What does science tell us about them?

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Wow - these wee creatures are way more interesting than you'd expect! So much to find out about here - Kākahi would be a great creature to study for learning about life-cycles.

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What does science tell us about New Zealand freshwater mussels?

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Kōura: What does science tell us about them?

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Kōura: What does science tell us about them?

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This is a great place to start if you are interested in kōura!

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What does science tell us about New Zealand freshwater crayfish?

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Don't worry - it's tiny (about the size of a grain of rice) and sucks onto fish or other critters in the stream - not humans!

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Life Cycle of Kākahi | Aotearoa Lakes resource

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Life Cycle of Kākahi | Aotearoa Lakes resource

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Kākahi lifecycle |Aotearoa Lakes resource

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Kākahi infographic | Aotearoa Lakes resource

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Kākahi infographic | Aotearoa Lakes resource

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Find out more about Aotearoa Lakes here: nzlakes.org

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Freshwater mussels, known as Kākahi in New Zealand, are one of the most imperiled organisms on Earth and populations are declining globally with 70 percent of species considered at risk or threatened. This is including three species endemic to New Zealand. Echyridella menziesii is classified as declining, Echyridella aucklandica is considered nationally vulnerable, and Echyridella onekaka is naturally uncommon. These species are often geographically isolated and can only be found in a few locations which means they are likely to continue their decline if nothing is done to address the cause behind this imminent extinction.

Mussels are an important part of a lake ecosystem; as biofilters and bioturbators they filter out nutrients, algae, bacteria, and fine organic material which helps purify the water. They have the capacity to filter up to one liter per hour, and if present in large enough numbers, they can filter the entire volume of a small lake within days. They also oxygenate the sediment by moving it around which decreases anoxia and stems sediment nutrient remobilization. Aside from their ecological importance, these mussels were once a mahinga kai resource for many Māori, the shells were used as cutting utensils and to feed sick or abandoned infants.

Freshwater mussel population decline worldwide have been attributed to the loss of habitat associated with eutrophication and sedimentation as well as pollution. In Lake Rototoa (one of our project sites), the loss of native intermediate host fish through predation from invasive species is a significant contributor to their reduction in numbers. Unlike their marine counterparts, freshwater mussels cannot anchor themselves to a substrate. Instead, they bury themselves into the sediment which makes them vulnerable to increased sedimentation that can result from erosion in the catchment as well as from excessive organic matter like algal blooms. The fine silt clogs up their gills and suffocates them, leading to the death of many individuals. Aotearoa Lakes goal is to continue researching these vulnerable species to try and halt there decline.

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Kākahi - Freshwater Mussels - Aotearoa Lakes

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Freshwater mussels, known as Kākahi in New Zealand, are one of the most imperiled organisms on Earth and populations are declining globally with 70 percent of species considered at risk or threatened. This is including three species endemic to New Zealand. Echyridella menziesii is classified as declining, Echyridella aucklandica is considered nationally vulnerable, and Echyridella onekaka is naturally uncommon.

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When we think of our native freshwater mussels, "go-getter" may not be the first term that comes to mind.

In what is thought to be a world first, a new study is showing that native New Zealand kākahi behave in different ways according to their personalities.

Some take more risks, others wait until the coast is clear. Some rush around exploring their environment (the term "rush" is relative), others are content to wait for life to come to them.

Freshwater ecologist Amber McEwan of Masterton has undertaken a lot of work with various native freshwater species.

READ MORE:
* How your personality affects your pay packet
* Rare Kākahi (fresh water mussels) released in Wellington
* Giant extinct burrowing bat discovered in South Island
* Four types of drunks: Which one are you?

As part of her PhD research at Victoria University with Professor Jeff Shima, McEwan discovered, almost by accident, that kākahi exhibit different behavioral traits.

She was doing an experiment with around 80 tagged individuals in a tank and started to recognise something interesting.

"I started to notice that certain individuals were acting the same. I did some repeated trials looking at different types of activity and found that, yes, they were indeed exhibiting signs of individual personalities."

Unlike marine mussels, kākahi can move freely with the use of their muscular foot.

She saw that some were more bold and explorative while others more timid.

McEwan formulated an experiment where she could measure their activity to define their behavioural characteristics.

By watching how much they moved, how often they would extend their foot out of their shells and how deeply they would burrow in the substrate, she could collect data.

Giving the behavioural types labels such as "go-getters" or "just-lie-theres", McEwan was able to show how these personality types shaped their behaviour.

"Some of them were bolder than others, some of them were more active than others, some of them were just shy and cautious," McEwan said.

"One of the behaviours I looked at was probing propensity. Probing is the first step of burrowing. Putting their foot out is risky because it means that something could bite that soft tissue, but delaying probing is also risky, because it means they will be exposed to predators for longer."

The test of a definable personality is "consistent differences in behaviour through time or context" and by this definition McEwan believes the kākahi is showing these patterns across individuals.

"Then we say, ding, there's a personality. The data is indicative of different personalities which would be a world first demonstration for a bivalve."

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World first study shows native mussels have personalities

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When we think of our native freshwater mussels, "go-getter" may not be the first term that comes to mind. In what is thought to be a world first, a new study is showing that native New Zealand kākahi behave in different ways according to their personalities.

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Photo: Stella McQueen

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Kōura babies holding on to mum's abdomen

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Kōura babies holding on to mum's abdomen

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Photo: Anna Crowe

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The Kakahi is New Zealand's freshwater mussel! They are threatened and in decline, but are a vital filtering organism for our freshwater lakes and rivers.

The video below, by Bob Brown of Landcare Research, shows juvenile kakahi that are between 3 and 4 weeks old. They are now beginning to develop their brown periostracum (protective protein covering) of the adults.

DOC's endangered species ambassador Nicola Toki tells us all about these remarkable native creatures.

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Recent stories from Afternoons with Jesse Mulligan

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The Kakahi is New Zealand's freshwater mussel! They are threatened and in decline, but are a vital filtering organism for our freshwater lakes and rivers. The video below, by Bob Brown of Landcare Research, shows juvenile kakahi that are between 3 and 4 weeks old.

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Hudsonema alienum

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Photo by Jan Hamrsky

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Caddisfly: net-builder larva | Aoteapsyche

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Caddisfly: net-builder larva | Aoteapsyche

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Caddisfly net spun by free-living caddisfly

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Caddisfly net spun by free-living caddisfly

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Photo by Stella McQueen

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Marlborough's Freshwater Flora & Fauna | by Peter Hamill

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Marlborough's Freshwater Flora & Fauna | by Peter Hamill

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Marlborough's Freshwater Flora and FaunaSmall

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Macroinvertebrate monitoring is an important part of measuring stream health. There are numerous freshwater monitoring guides available. Check with your local regional council for resources and kits specific to your area.

Literacy links

'Wonderful Water' by Philippa Werry ( Connected 3 2004) describes a class investigation of two Wellington streams.

'The Water Wardens' by Alan Bagnall ( Connected 2 2002) tells how a class is inspired to adopt a nearby stream.

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Macroinvertebrate monitoring is an important part of measuring stream health. There are numerous freshwater monitoring guides available. Check with your local regional council for resources and kits specific to your area. 'Wonderful Water' by Philippa Werry ( Connected 3 2004) describes a class investigation of two Wellington streams. 'The Water Wardens' by Alan Bagnall ( Connected 2 2002) tells how a class is inspired to adopt a nearby stream.

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A Baby Dragonfly's Mouth Will Give You Nightmares | Deep Look

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This is such amazing footage of a dragonfly growing wings

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This is such amazing footage of a dragonfly growing wings

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Stunning Time-Lapse of a Dragonfly Growing Wings

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Aotearoa's largest freshwater insect species! This one is eating a mayfly.

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Identification charts in English and te reo Māori

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Identification charts in English and te reo Māori

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From Greater Wellington Regional Council website: http://www.gw.govt.nz/stream-health-assessment-kits-for-schools/

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High profile biodiversity efforts in this country focus on 'pin-up' species like kiwi and kakapo. "Sirocco" our trained touring show parrot certainly vouches for this.

However, there is a myriad of other species in decline that are just as deserving. Most New Zealanders are well aware of our freshwater mussel, a dark brown to black bivalve around 60-80mm long that inhabits the muddy margins of many of our watercourses and lakes, but few people know much more about them.

Dr Sue Clearwater, an ecotoxicologist with NIWA in Hamilton, has made it her job to wade around New Zealand and search out populations of our endemic mussel. Her passion for the creatures is nothing short of infectious, and my appreciation of the kakahi and desire to know more about them has risen dramatically as a result of Sue's three research visits to Golden Bay in as many years.

I've long known about the colony of kakahi that existed just out from the raupo at Kaihoka Lakes, as well as few other dune lakes within the Puponga Farm Park, and always made a point of wading out and showing them to my kids whenever we visited.

Some 12 years ago, Dr Mark Fenwick from NIWA rang to ask me for a few location pointers to help him find some kakahi, so I naturally told him of the lakes, but also took him to a private pond at Onekaka which I more recently heard was now chocka with mussels.

That man-made pond ended up supplying an entirely new species of freshwater mussel to science - Echyridella onekaka - which was formally identified in a paper by Mark Fenwick and Bruce Marshall to the Malacological Society of Australasia in 2006.

Big deal you may think, a new freshwater mussel, but until this point there was only two species identified in New Zealand, the common kakahi - Echyridella menziesii, widely distributed through North and South Islands, and the scarcer North Island-only species, (Echyridella aucklandica), which ranges only from Northland to Whanganui. Weirdly, isolated populations of Echyridella aucklandicaare also found in Lake Wairarapa and in Lake Hauroko, Southland - likely as a result of Maori transplanting them.

This relatively quiet "discovery" was the catalyst for Dr Sue Clearwater to get involved. Her overall goal is to understand how to more effectively restore taonga species in our freshwater systems. In Golden Bay, Sue has been wading through creeks and lakes, but also in particular the Onekaka catchment to establish the exact distribution of the new mussel species. Sophie Allen of the Working Waters Trust and others are pitching in to add more knowledge.

To look for them, Sue dons her waders and carries an underwater viewer, lugging along notepad, GPS and sampling bags, meticulously scouring creeks to find likely spots to investigate. She is excited that work done by local landowners and local biodiversity restoration groups appears to have helped return the stream habitat to a condition that favours local species such as the freshwater mussel.

She readily admits little is really known about these long-lived creatures - the oldest freshwater mussel found in this country so far has been 55 years of age - or what exactly makes them decline or thrive.

Explains Sue: "It's of concern that only geriatric populations remain in many of our rivers and streams. In some of our shallow nutrient-laden lakes mussels have died out completely, whereas in Lake Taupo and the Rotorua Lakes they are still well represented. Just last month, a NIWA team sampled a stream on the outskirts of Auckland that had patches of 2000 mussels per square metre. I've seen dense populations in the Waikato Hydro Lakes too. But the younger ones are absent in many locations. Juvenile mussels are very sensitive to contaminants, copper and ammonia for instance, and the number of those pollutants has increased in the past few decades."

Sue is quick to point out that you can't jump to conclusions; "Worldwide, there's around 860 species of freshwater mussels and we know from overseas research that populations are invariably skewed towards adults. What the juveniles get up to after their larvae stage is still a bit of a mystery because fresh water mussels have the most an amazing reproduction strategy."

Sue pulls out her laptop and plays me a five-minute underwater video from the United States, which surprisingly starts with a mother freshwater mussel in a stream suddenly lurching to grab the snout of a passing small fish which it clamps shut for nearly a minute until it is "sedated" by partial suffocation.

Unlike marine mussels which spray their eggs and sperm out into the ocean currents for fertilisation, mother kakahi inhale passing sperm through their siphons, keeping the eggs in specialised brood chambers in their gills. When the time comes for the sand grain-size larvae (called glochidia) to leave home, the mussel in this case conveniently catches a host fish which it then "sneezes" over with parasitic larvae while the fish gasps for breath. There is no struggle during the minute-or so process, and finally the dopey looking fish swims off, larvae firmly attached to it.

Admittedly this is one of the more spectacular methods freshwater mussels use to infest fish with their larvae - the majority of mussels (including the kiwi species) simply broadcast their larvae, sometimes using lures to bring host fish in close enough for attachment.

"We don't really know what happens to those juvenile kakahi after they drop off their host fish because you never see any, presumably they live in habitats yet to be discovered," Sue says. "The smallest juveniles we come across are perfectly formed young mussels around 15 - 20mm, and that's not often."

Also known to Maori as kaeo, ngaeo and koaru, waikakahi and torewai, freshwater mussels were a valuable food to Maori, easily obtainable when many other food sources were out of season, and were often fed to the infirm, infants and elderly.

They also used to dry them and eat them like gum, and some Maori still like to collect these particular mahinga kai and cook up a feed. An early Women's Division cookbook features a recipe for them, but any further European culinary mention to them is virtually non-existent.

The freshwater mussel's ability to filter-feed water is impressive. One study in South Otago's Lake Tuakitoto worked out that the resident kakahi population there filters the entire volume of the lake every 32 hours, leading to speculation that kakahi could be used to clean up lakes polluted with algae and sediment. The trouble is, anecdotal evidence is pointing to a gradual decline in freshwater mussel numbers, so finding enough critters to do the cleanup job may be difficult.

Sue says: "The important thing now is finding out more about kakahi so we can develop our conservation strategy. They are an integral part of our freshwater ecosystems, it'd be a real tragedy to lose them."

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Unlocking secrets to saving our native freshwater mussels

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High profile biodiversity efforts in this country focus on 'pin-up' species like kiwi and kakapo. "Sirocco" our trained touring show parrot certainly vouches for this. However, there is a myriad of other species in decline that are just as deserving.

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Zealandia has just welcomed its latest arrivals - 200 kākahi or freshwater mussels.

While they are not the most glamorous species to make a new home in the predator-proof fenced sanctuary in the heart of Wellington city, staff and iwi are excited about the role the kākahi will play in cleaning up the waters of the Kaiwharawhara Stream.

Kākahi or freshwater mussels were once a staple food for Māori, who used their shells for cutting hair or as kite rattles.

Today, kākahi are considered more threatened than kokāko.

On a sunny but very windy winter's day, I joined an enthusiastic crowd on a mission to collect 150 kākahi for a translocation to Zealandia, Te Māra a Tāne. The group included Taranaki Whānui whānau, along with Greater Wellington Regional Council and Zealandia staff.

We were at Lake Kohangapiripiri, one of the two Parangarahu lakes on the eastern side of the entrance to Wellington Harbour. They are part of the rohe of Taranaki Whānui.

The previous day, Ngāti Kahungunu had helped collect a further 50 mussels from Wairarapa Moana in their rohe.

Ngahuia Wright, from Taranaki Whānui, was at the translocation with her daughter Harmony, her sister Ada and nieces Perzia-Rose and Ryah-Jane. Ngahuia says her family are descendants of Tohu Kākahi of Parihaka.

They brought with them five new flax kete, which Naghuia said had been specially woven by her mother Sharon Wright and her Roopu Raranga, or weaving group.

Ngahuia says the kete were traditionally used as food baskets, that could hold different kinds of kai, or food. She explained that the kete with large holes were designed to hold larger mussels, and allow water to freely flow in and out, while the smaller weave could hold smaller mussels.

Although kākahi were once an important staple food for iwi, Taranaki Whānui trustee Holden Hohaia said they had not been part of his life growing up, and he had only begun to learn about them since Zealandia had initiated the translocation.

Holden was one of half a dozen brave people who donned wetsuits and ventured into the waist-deep lake to collect the mussels.

Freshwater biologist Amber McEwan is studying kākahi and will be monitoring the success of the translocation for her PhD research at Victoria University of Wellington.

She explained that unlike marine mussels, which attach themselves to rocks, freshwater mussels live partly submerged in soft mud. She said the best way to find them was to feel for them with your foot, and then bend down to pick them up.

Amber says there are three species of freshwater mussel in New Zealand, and the translocation involves two of these.

She says that kākahi were once widespread. "They used to be just about everywhere. You'd find huge beds in lakes and rivers."

These days, kākahi are far less common, and although they are still reasonably widespread the concern is that many populations are comprised of old large mussels and there are no young mussels. A mussel can live up to 50 years, and their decline is due in part to degraded freshwater habitats and in part to the loss of a critical part of the mussel's life cycle.

Amber says that all freshwater mussels "have this really amazing life cycle, where they need fish in order to complete [it]."

"So the mum kākahi will brood her babies internally, and then when she's ready she'll sneeze them out of shell into the water," says Amber. "Then these little glochidia - these little animals that have grabbing hooks - they'll grab those hooks onto a passing fish."

The young mussels are using the fish almost as a bus, a way of getting moved to a new destination. After a couple of weeks of riding their fish 'bus' they transform into a miniature kākahi and drop off to settle in a new patch of mud away from their parents.

The problem for the kākahi is that major declines in native fish populations make it difficult for the glocidia to complete that vital first stage of their development.

For kākahi, says Amber, a fish "is a critical bus. If it's not there, you die."

Freshwater mussels are considered to be important ecosystem engineers. Studies have shown that a single mussel can filter more than a litre of water in an hour, so a whole bed of mussels can play an important role in keeping a waterway clean.

Paul Atkins, CEO at Zealandia, says the introduction of kākahi to Zealandia's upper dam, Roto Mahanga, which is the headwaters of the Kaiwharawhara Stream, is part of a catchment-wide ' sanctuary to sea ' conservation project.

Amber is attaching tiny microchips to the mussels' shells, and will be monitoring their survival and breeding success over the next few years.
Dragonflies at Lake Kohangapiripiri
Earlier this year, Our Changing World featured a story about dragonflies and damselflies living at Lake Kohangapiripiri.

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Zealandia has just welcomed its latest arrivals - 200 kākahi or freshwater mussels. While they are not the most glamorous species to make a new home in the predator-proof fenced sanctuary in the heart of Wellington city, staff and iwi are excited about the role the kākahi will play in cleaning up the waters of the Kaiwharawhara Stream.

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On Gordian Worms_by Stella McQueen via Facebook

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Check out these cute baby kakahi under the microscope at 3 - 4 weeks old!

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Check out these cute baby kakahi under the microscope at 3 - 4 weeks old!

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This is really cool!

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Sticky. Stretchy. Waterproof. The Amazing Underwater Tape of the Caddisfly | Deep Look

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How to tell whether a kōura is male or female

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How to tell whether a kōura is male or female

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gender determination of koura_NIWA technical paper

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trending trending
Steam rises off Broken River. Mayflies emerge from their larval stage as winged adults, forming dense clouds, and the water surface boils with feeding trout. Such a sight is the dream of every fisherman, the image that propels them out of bed at 5 am. So it is also for a special type of arachnid, New Zealand's fishing spiders. They prey on the mayflies, as well as many other aquatic insects, and are well-adapted to take advantage of such an abundant food supply, provided they stay out of reach of the hungry trout.

New Zealand has 1158 described species of spiders, of which some 95 per cent aren't found anywhere else. The number of species expands to around 2000 when undescribed species are included. However, when it comes to catching prey in a riparian environment, one spider is unmatched. While orb web spiders fabricate large webs, and cursorial spider species live under rocks and logs close to the river's edge, it is only fishing spiders ( Dolomedes spp.) that hunt directly on the water surface rather than having to wait for aquatic insects to appear on land.

Mainland New Zealand has two widespread species of fishing spider which grow up to 7 cm across, including their thickset legs. Dolomedes aquaticus is an open riverbank specialist that lives under rocks, generally within 5 m of unforested rivers. The other mainland species, currently undescribed and known only as Dolomedes III, also live under rocks close to rivers but in forested catchments. Both species have yellow stripes down either side of their head region (cephalothorax) characteristic of endemic Dolomedes species, but are coloured to suit their respective environments- D. aquaticus is a greywacke colour while D. III is painted with a mottled camouflage pattern. The Chatham Islands host a third particularly large species of the Dolomedes genus while on the mainland a fourth species, D. minor, is not dependant on rivers and creates characteristic dense white nursery webs on shrubs. Fishing spiders are relatively common and distinctive, but few people other than keen fishermen will have encountered them.

My first fieldtrip to observe fishing spiders was early in the summer of 2003 with my supervisor Angus McIntosh from Canterbury University. It was dusk when we arrived at the Cass River in the Canterbury high country, just east of Arthur's Pass. With the light fading we put on our head torches and the hunt for the hunter began. Through the swarm of moths and aquatic insects orbiting my lamp I began to see clusters of light, mere pinpricks low down near the waters edge. As it turned out, D. aquaticus is not that hard to spot at night-reflections from the spiders' eight eyes give them away almost immediately.

At night they appear in characteristic fishing pose: back legs anchored to a rock on the riverbank with the rest of their body floating on the water surface, front legs outstretched, waiting, listening.

Fishing spiders use the water surface as other spiders use a web, feeling with their feet for vibrations created by potential prey such as aquatic insects. While web-building spiders must distinguish between vibrations caused by trapped insects and those caused by wind or detritus, fishing spiders have to discern signals caused by wind or leaves falling into the river from that caused by prey; all above the background noise created by water swirling around rocks. They achieve this feat of sensory perception using an array of very sensitive vibration receptors, some of which are long hairs (tricho-bothria) on their legs and feet.

Experiments on related species in America showed that blinding a fishing spider had little effect on its ability to find and attack prey, leading scientists to conclude that its sense of touch is more important than vision. In contrast, removing or tampering with the spiders' vibration sensing organs significantly reduced the spiders' ability to capture prey, effectively turning them into sitting ducks for potential predators, such as those trout.

But in normal circumstances the fishing spider can detect tiny differences in the frequency of surface wave vibrations and in the number of waves produced. A leaf hitting the water creates a single vibration event, while a struggling insect creates more erratic wave patterns for a longer period. Fishing spiders are also able to determine the distance and angle to the source of vibrations by the subtle differences in amplitude and frequency of the waves created, in the same way that we can locate another person speaking in a crowded room.

Once they have detected the presence of, say, a struggling insect, some fishing spiders take a very direct approach to capturing it, dashing across the water surface and snaring their dinner before it can free itself from the surface tension. Several overseas Dolomedes species even use silk draglines, a bit like a drag-racer's parachute, to prevent them overshooting their target. D. III, the New Zealand forest fishing spider, has been known to employ such direct tactics.

Further anecdotal evidence of the fishing prowess of these spiders comes from a closely related species in North America, where a gentleman in the 1880s reportedly observed a spider leaping into his pond, dragging his prize goldfish from the water and subsequently devouring it on the bank. D. aquaticus, in general, shows a more sedate approach to capturing prey, often waiting for insects to touch its legs or to fly within range before a rapid lunge ensures that the spider won't go hungry.

To be able to fish from the water surface these spiders must be able to walk on water. They generally weigh less than a gram and are covered with hydrophobic (literally water-hating) hairs that repel the water and leave the spider dry. However, an interested PhD student might decide to interfere with the laws of physics-the simple addition of a drop of detergent is enough to disrupt the surface tension and the spider sinks instantly, the rules of its world suddenly broken. While water-walking is not unique to fishing spiders, they are the only documented species in New Zealand that use it as part of their hunting repertoire.

The fishing spider's diet is mainly aquatic insect prey, but it is also an opportunistic feeder that will eat almost anything that comes wriggling its way. On my first fieldtrip I discovered the fun of hand feeding them. I caught a large moth and offered it, struggling in my fingers, to a relatively small juvenile fishing spider. The spider daintily took it, moved itself to dry land and proceeded to eat. I watched this process for almost half an hour; fascinated by the way the spider stood on the tips of its articulated legs and deftly manoeuvred the moth with its mouthparts. She then delicately cleaned all her legs, passing each between her fangs; carefully scraping them clean before wiping each front leg over her eyes. Finally satisfied with her dinner and ablutions she returned to the water's edge to see what other insects the river would deliver.

Like most New Zealand invertebrates, Dolomedes are nocturnal, feeding between dusk and dawn when most of their avian predators sleep. Lizards, which live in similar rocky habitats, are also likely to prey on the spiders. There have been records of fishing spiders eaten by young dragonflies, moreporks and bitterns. There is even an account of several being fought over by baby goldfinches in the nest.

This species is also vulnerable to a parasitic wasp (family Pompiliidae), that stings the unfortunate spider, paralysing it before dragging it off to its nest so it can lay a single egg in its abdomen. When they hatch, the wasp larvae eat the still-living spider from the inside out. On more than one occasion I have watched as parasitic wasps carried off my field specimens.

But D. aquaticus has developed an effective and dramatic means of escape; pulling themselves through the filmy surface tension, they magically disappear-which isn't particularly helpful if you are trying to study them. For a while I was perplexed as to how they vanished beneath my poised capturing container, but one night near Porters Pass a large female was waiting at the water's edge for her dinner to float past when my torchlight startled her. Instead of making for the shore as I expected, she ran under the rock she was fishing from and disappeared underwater. In the light of my torch I could see the silvery outline of air trapped in the hairs on her body. Fishing spiders can remain underwater breathing this air supply through a specialised "booklung" structure on the underside of their abdomen for half an hour. This air layer makes them very buoyant and they must hang onto a rock to remain underwater; if they lose their grip they pop to the surface like a cork, perfectly dry and ready for action. This underwater escape technique is not perfect however. One overseas account reports a parasitic wasp crawling underwater to sting and retrieve a hiding fishing spider, a tremendous effort as the spider is often several times larger than the wasp.

Researchers in New York have documented alternative escape responses of a North American relative called D. triton using an elaborate and bizarre methodology. They freeze-dried frogs, coated them in latex and launched them at unsuspecting fishing spiders, videotaping the jump escape responses. The scientists concluded that the spiders were warned of the frog's attack by increased air rushing past their vibration sensors and that these escape jumps more than often saved them from becoming a frog's dinner.

But birds, trout, lizards, parasitic wasps and freeze-dried frogs notwithstanding, Dolomedes can be their own worst enemies. Male fishing spiders have it especially tough as the female is often larger and can choose to overpower and eat him once she has mated. As males can't detect that a female has mated, some unfortunate victims will be lured in by a hungry female under the false pretence of sex. Scientists suggest that in certain circumstances it can even be beneficial to the males' offspring for their mother to make a meal of their father. In this way she receives a large feed that will help produce more or larger spiderlings, increasing their survival chances and passing on the dead male's genes.

Female fishing spiders aren't the only individuals with cannibalistic tendencies. Spiders eat their own kind, as this results both in a large meal and less competition for shared food resources. Dolomedes just need to be careful that they take on an individual smaller or weaker than themselves as the tables are easily turned with the would-be diner often becoming the dinner. Hunger can increase a spider's willingness to take a risk, even with larger spiders.

During the course of my PhD I conducted cannibalism experiments with D. aquaticus in the backyard of my flat that involved 16 children's paddling pools full of spiders at different densities and with different amounts of aquatic insects as food. My flatmates weren't terribly impressed, but I gathered some interesting data. Spiders that were crowded together were more cannibalistic and food availability had only a minor effect on rates of cannibalism.

One of the last pieces of research I conducted for my thesis highlighted how well-adapted fishing spiders are to their riverine habitat. This can be both a huge advantage and a limitation. Fishing spiders depend on rivers for their food and habitat, and as a water source. But what happens if the river dries? Initially the spiders are likely to benefit from a smorgasbord of insect prey trapped in the shrinking pools. Those insects that can, like several mayfly species, escape by becoming adults, which make easy targets for the fishing spiders aggregating around the drying pools. But the feast doesn't last long.

On one of my last fieldtrips I was out on a sunny day, so hot that I could almost see the river drying before my eyes; a slender tongue of water gradually retreating upstream. Left behind were the fishing spiders too slow to chase the water front. These animals can survive for a short time without the river, but eventually die either from dehydration or lack of food. I still remember the sad sight of a large female making a dash across the hot rocks trying to reach the retreating water, to no avail.

The fate of the fishing spider is intricately linked to the flow of its natal river. And as long as it contains water, they are one of the best-adapted invertebrates to make use of this food resource and habitat.

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The secret life of fishing spiders Steam rises off Broken River. May­flies emerge from their larval stage as winged adults, forming dense clouds, and the water surface boils with feeding trout. Such a sight is the dream of every fisherman, the image that propels them out of bed at 5 am.

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The importance of kōura; how to restore kōura; tau kōura (traditional Māori method for harvesting and monitoring kōura) and more!

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Shell-like skin

Kōura has a hard shell-like skin so it is a crustacean, one of the large group of animals, the arthropods, so-called because their legs and bodies are protected by a jointed hard but flexible body covering.

This covering eventually gets too small for the growing animal. It then splits and is left behind, while the new skin underneath hardens. This is called moulting.

Species

There are two species of kōura found only in New Zealand. In the east and south of the South Island and on Stewart Island they are larger (about 80 mm long) and have very hairy pincers.

But kōura in the North Island and in Marlborough, Nelson and the West Coast of the South Island are slightly smaller (about 70 mm long) and have less hairy pincers.

It lives in fresh water such as streams, lakes and ponds, and even in swamps. Kōura shelter between stones on gravelly bottoms but they can burrow into muddy bottoms, and will burrow well down into swamps that dry out over summer, to wait until the water returns.

Survival

Kōura need oxygen like all living animals and plants which they get from the water through their gills, under the thorax where the legs join the body. Water is sucked in, pumped forwards over the gills and out through the mouth. If the gills get clogged they can back-pump to flush out any debris.

Kōura use their four pairs of walking legs to get around quite quickly - they do not crawl as their common name, 'crawly', suggests. They also have a sort of reverse gear, to shoot back into shelter when alarmed, by flicking their tail forwards violently. Their first pair of legs, their pincers, are used mainly for catching food, for fighting with invaders, or for waving menacingly at intruders. They can give a painful nip, so be careful.

Kōura is a scavenger that feeds on leftovers that float by in the water or settle on the bottom; old leaves, small insects are favourites. It does not go hunting for its food. Once food is caught in the pincers it is torn up, pushed into its mouth to be ground up and separated by a filter system that lets only fine pieces pass through to the small stomach to be digested.

Large trout love koura and so do shags.

Kōura/freshwater crayfish

Reproduction

Female kōura produce eggs between April and December, and most in May and June. She carries the berry-like eggs, between 20 to 200, under the side flaps of her abdomen, when she is said to be 'in berry'. Small kōura hatch about 3 to 4 months later, looking exactly like their parents in miniature. They cling to their mothers with their pincers until they are nearly 4 mm long, around December of their first year. By their fourth year they are 20 mm long and become adults.

Threats

Crayfish populations are decreasing in some areas as they are subject to habitat modification and land intensification.

Predation by introduced species has also played a role as has harvest for human consumption in some places. They are listed as a threatened species and their populations are in gradual decline.

You can help

Kōura/freshwater crayfish

Kōura have a special part to play in our freshwater lakes and streams. They are native animals and recycle some of the leftover materials by their scavenging, therefore helping to clean up our streams and lakes in their own small way.

As they are so slow growing and many do not reach adulthood, there are never too many. It pays to take care of them and put the ones we catch back where we found them.

Fence off your waterways or ponds from stock and plant native vegetation along the edge of waters.

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Kōura has a hard shell-like skin so it is a crustacean, one of the large group of animals, the arthropods, so-called because their legs and bodies are protected by a jointed hard but flexible body covering. This covering eventually gets too small for the growing animal.

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Common name: Freshwater crayfish
Scientific names: Paranephrops planifrons and Paranephrops zealandicus
Māori names: includes kōura and kēwai

About this species

There are two species of kōura in New Zealand, both belonging to the family Parastacidae. Paranephrops planifrons is found in the North Island and in the northwest of the South Island and Paranephrops zealandicus is distributed along the eastern side of the South island and on Stewart Island. P. planifrons is separated from P. zealandicus by the Southern Alps.

Traditional knowledge

Kōura are a valued mahinga kai species and considered a delicacy by Māori. In the past they were a staple food item, and prized in some areas for their use as a bartering tool. The Te Arawa and Taupō lakes were considered the most productive kōura fisheries in New Zealand. In the past, the kōura fishery was actively managed by a combination of rāhui (where all fishing was halted in a particular area for a specified period of time, or where limits were placed on the use of particular methods) and ownership rights (based on ancestral fishing grounds). Occasional releases of kōura were made into waterways to boost populations and selective harvesting (e.g., return of gravid females to the lake) ensured the long term viability of the populations.

Impacts on kōura

Catchment land use

Kōura are found in native forest, exotic forest, and pastoral waterways, but very rarely in urban streams because of chemical pollution, increased flood flows from stormwater inputs, and degradation of habitat. Kōura densities can be lower in pasture streams compared to native forest streams. Kōura tend to live longer in native forest streams because of cooler water, but grow faster in pasture streams with warmer water temperatures and more abundant invertebrate food.

Water quality

Kōura survival can be affected by high water temperatures, particularly for the southern species, P. zealandicus, where survival in laboratory experiments decreased as constant water temperatures exceeded 16ºC, with 50% survival at 21ºC after 12 weeks. The northern species, P. planifrons, can tolerate higher temperatures, but optimum temperatures are likely to be less than 23ºC. Kōura are rare in low calcium waters such as Lake Tikitapu, and kōura ( P. zealandicus) survival in laboratory tests increased with water calcium concentrations above 10 mg/L. Kōura in lakes can be affected by periods of anoxia, e.g., they are now absent from Lake Okaro as this lake has no oxygen in its bottom waters during summer. Kōura may also be affected by pollutants such as heavy metals or by toxins from cyanobacterial blooms.

Habitat

Habitat cover (e.g., large wood, undercut banks, cobbles, and boulders) is extremely important as it provides shelter from predation and cannibalism. Kōura prefer pools and areas of slow or no flow. Deep habitat (pools in streams) may act as a refuge from terrestrial predators and collect leaves and other foods. At times of heavy flooding, forested streams with stable habitat from riparian vegetation (e.g., stable banks, tree roots, and pools) provide a better refuge for kōura populations than pasture streams dominated by unstable cover items such as cobbles and macrophytes.

Introduced predators

Crayfish are vulnerable to predation from introduced species that they have not evolved with (e.g., trout, catfish, and perch). Kōura make up a large proportion of catfish diet in Lake Taupō (up to 80% in some areas). Anecdotally, the introduction of perch to a Northland lake has dramatically decreased crayfish populations. In some South Island streams, brown trout were the main factor affecting kōura abundance, particularly for kōura sized 7-20 mm.

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There are two species of kōura in New Zealand, both belonging to the family Parastacidae. Paranephrops planifrons is found in the North Island and in the northwest of the South Island and Paranephrops zealandicus is distributed along the eastern side of the South island and on Stewart Island. P.

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Tau kōura: freshwater crayfish traditional fishing method

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Tau kōura: freshwater crayfish traditional fishing method

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Historically, kōura (freshwater crayfish) was an important food for Māori, who harvested large numbers for consumption and trading. Today, kōura is considered a taonga species by Te Arawa iwi (the tangata whenua of Rotorua), that supports important mahinga kai (customary food gathering) activities on some Te Arawa lakes. Historical anecdotal evidence from iwi reflects a declining trend in kōura abundance in these lakes.

We compare tau kōura, a traditional fishing method for harvesting kōura, with more conventional fishing methods as a way of monitoring kōura abundance in the Te Arawa lakes. Limited information on kōura abundance and ecology makes it difficult for iwi and others to manage kōura in the lakes.

We classified Tau kōura: freshwater crayfish traditional fishing method as supporting information.

Key findings

Anecdotal evidence suggests kōura abundance in the Te Arawa lakes has been declining, which affects important mahinga kai activities on the lakes.

Some environmental factors are causing the decline of kōura abundance, including the introduction of exotic fish and plant species, and reduced concentrations of dissolved oxygen in the bottom waters of the lakes due to eutrophication (algae growth stimulated by nutrients).

Tau kōura was found to be a more effective monitoring technique for kōura in the Te Arawa lakes compared with conventional methods such as baited traps.

Tau kōura has an advantage over conventional monitoring methods because it samples all kōura size classes, generally has a higher catch per unit effort, can be used in murky waters at a wide range of depths, and does not require expensive equipment or specialised expertise compared with other sampling methods (eg scuba diving).

Tau kōura is currently practised only in the Te Arawa lakes.

Figure 1 A traditional tau kōura
Source: Kusabs and Quinn, 2009

Note: The traditional tau kōura comprises the surface float line (tauhu) attached at one end to a surface-reaching pole (tumu) and a float (poito) at the other held in place by an anchor (punga). From the poito, drop lines (pekapeka) reach to the lakebed with fern bundles attached.

Definition and methodology

There is limited published biological information on kōura in lakes. The lack of quantitative data on kōura abundance and ecology makes it difficult for iwi and others to manage lake-dwelling kōura. Until recently, the main reason for this lack was the absence of suitable representative sampling methods (Kusabs & Quinn, 2009).

The tau kōura method is an effective fishing method that is also useful for monitoring kōura abundance in lakes. The tau kōura is still used by Ngati Pikiao at Lake Rotoiti and nearby lakes. Te Arawa/Ngati Tuwharetoa and NIWA have developed a protocol for using the tau kōura for monitoring kōura (NIWA, nd).

The traditional Te Arawa fishing method (tau kōura) involves resting bundles of bracken fern fronds on the lakebed for kōura to take refuge in, then retrieving the bundles into a canoe to harvest the kōura. To harvest the kōura, the fern bundles are lifted onto a net of woven flax (the korapa, shaped like a large tennis racket without the handle) to prevent them escaping as they are lifted out of the water. Today, the same concepts as traditional tau kōura are applied but are made of modern materials. The traditional bracken fern bundles are attached by synthetic ropes to a bottom-line of copper wire anchored at both ends to large weights, and the kōrapa is made of plastic mesh.

Tau kōura is a method developed by iwi - who have tāngata whenua rights and ability to harvest kōura and want to monitor the state of kōura populations in their waterways (Tri-Linear, 2016). It is inexpensive and avoids safety issues associated with diving, although there are some safety concerns with the small boat handling required. Compared with other monitoring methods, tau kōura captures a wider range of kōura sizes and sexes in both shallow and deep waters. It can be used in difficult weather conditions, in murky waters, at any depth, and does not require expensive equipment (Kusabs & Quinn, 2009).

Data quality

We classified Tau kōura: freshwater crayfish traditional fishing method as supporting information.

Topic

Classification

Relevance

Accuracy

Customary use and mahinga kai

Supporting information

Partial

Medium

See Data quality information for more detail.

References

Kusabs, IA, & Quinn, JM (2009). Use of a traditional Maori harvesting method, the tau koura, for monitoring koura (freshwater crayfish, Paranephrops planifrons) in Lake Rotoiti, North Island, New Zealand. New Zealand Journal of Marine and Freshwater Research, 43, 713-722. Retrieved from www.niwa.co.nz.

NIWA (nd). Tau koura sample collection and processing protocol. Retrieved 28 October 2016 from www.niwa.co.nz

Tri-Linear (2016). Te Arawa Lakes Trust Fresh Water Management Project Six Monthly Report 1 January to 30 June 2016. Retrieved from www.mfe.govt.nz.

Published 27 April 2017

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Tau kōura: freshwater crayfish traditional fishing method

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Historically, kōura (freshwater crayfish) was an important food for Māori, who harvested large numbers for consumption and trading. Today, kōura is considered a taonga species by Te Arawa iwi (the tangata whenua of Rotorua), that supports important mahinga kai (customary food gathering) activities on some Te Arawa lakes.

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Extra information if you want to know more!

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Extra information if you want to know more!

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Freshwater invertebrate species checklists

These checklists provide an up-to-date listing of all known species in certain invertebrate groups.

Macroinvertebrate ID guides

A Guide to Mature Larvae of Psilochorema (Hydrobiosidae) - a Lucid-based Identification Key

Acari (mites) families (PDF 1.9 MB)

Acari (mites) major groups (PDF 1.2 MB)

Amphipoda (PDF 1.1 MB)

Coleoptera (beetles) families, adults (PDF 1.1 MB)

Coleoptera (beetles) families, larvae (PDF 1.1 MB)

Coleoptera (beetles), family Dytiscidae, adults (PDF 2.1 MB)

Coleoptera (beetles), family Dytiscidae, larvae (PDF 1 MB)

Coleoptera (beetles), family Hydrophilidae, adults (PDF 1.1 MB)

Coleoptera (beetles), family Hydrophilidae, larvae (PDF 411 KB)

Diptera (true-flies), Chironomidae (non-biting midges) (PDF 222 KB)

Diptera (true-flies), non-Chironomidae (PDF 438 KB)

Ephemeroptera (mayflies), family Leptophlebiidae (PDF 543 KB)

Isopoda (PDF 1.3 MB)

Mollusca (snails and clams) (PDF 1.7 MB)

Oligochaete (PDF 390 KB)

Planktonic Cladocera (PDF 389 KB)

Planktonic Copepoda (PDF 2.1 MB)

Plecoptera (stoneflies) (PDF 543 KB)

Trichoptera (cased caddisflies) (PDF 561 KB)

Trichoptera (caddisflies), family Hydrobiosidae (PDF 151 KB)

Trichoptera (caddisflies), other free-living caddisflies (PDF 429 KB)

Find out more about the conservation status of New Zealand phreatoicid isopods

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Freshwater invertebrate species checklists These checklists provide an up-to-date listing of all known species in certain invertebrate groups.

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Online identification guide | Manaaki Whenua Landcare Research

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Online identification guide | Manaaki Whenua Landcare Research

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Mill Flat, by Anna Crowe

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Mill Flat, by Anna Crowe

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Despite appearances, this is not a mutant tree wētā. The coils emerging from the rear of the wētā belong to one or more Gordian (or horsehair) worms. Bug expert Dr Phil Sirvid explains the bizarre behaviour of this parasitic worm and why this specimen is a tour favourite.
A tour favourite

We don't have any information about where this particular specimen came from, but we do know it has been part of our collection for at least 50 years.

It's not the only specimen we have like this, but it's a lovely example of its kind - if lovely is the right word to use! We often show it when we are doing behind the scenes tours and it never fails to get a reaction, particularly when people hear the story behind what they're seeing.

What has happened to this weta?

This is a tree wētā ( Hemideina sp.) with one or more Gordian worms emerging from its rear end. The worm is probably a species called Parachordodes diblastus (previously known as Gordionus diblastus) as tree wētā species are its preferred hosts. Other wētā species are infected by other kinds of Gordian worms.

Gordian worms

Gordian worms, also called horsehair worms, belong to a phylum of animals call Nematomorpha.

While the adults are free-living worm-like creatures that live in freshwater, they all have a larval stage that enters a host (usually an insect) and grows and develops inside it.

The larvae absorb nutrients and as you can see from the picture, can grow to a great length that is somehow packed tightly into the host's body cavity.

How larvae get inside a wētā is still uncertain. George Poinar, a world authority on these animals, has suggested that it may happen when a wētā feeds on the dead body of an infected intermediate host (i.e. another species that may contain larvae but that the larvae doesn't develop in). However, we also know that wētā sometimes drink from free-standing water sources and that may be another way for the larvae to enter.

Leaving its host

If all this is sounding weird and perhaps a little horrifying, there is more to come!

After about a year, the adult worm is ready to emerge. It triggers something in the host's brain that makes it seek out water, which is where these worms live and reproduce. Quite how it creates this drive to find water is a mystery, but that's going to be the last thing the wētā ever does. If the wētā doesn't drown, the emergence of the worm will be fatal.

Who needs the Alien movies when we have creatures like this in real life?

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The body as a nursery: a wētā's grim end | Te Papa's Blog

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Despite appearances, this is not a mutant tree wētā. The coils emerging from the rear of the wētā belong to one or more Gordian (or horsehair) worms. Bug expert Dr Phil Sirvid explains the bizarre behaviour of this parasitic worm and why this specimen is a tour favourite.Read more

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Despite appearances, this is not a mutant tree wētā. The coils emerging from the rear of the wētā belong to one or more Gordian (or horsehair) worms. Bug expert Dr Phil Sirvid explains the bizarre behaviour of this parasitic worm and why this specimen is a tour favourite.
A tour favourite

We don't have any information about where this particular specimen came from, but we do know it has been part of our collection for at least 50 years.

It's not the only specimen we have like this, but it's a lovely example of its kind - if lovely is the right word to use! We often show it when we are doing behind the scenes tours and it never fails to get a reaction, particularly when people hear the story behind what they're seeing.

What has happened to this weta?

This is a tree wētā ( Hemideina sp.) with one or more Gordian worms emerging from its rear end. The worm is probably a species called Parachordodes diblastus (previously known as Gordionus diblastus) as tree wētā species are its preferred hosts. Other wētā species are infected by other kinds of Gordian worms.

Gordian worms

Gordian worms, also called horsehair worms, belong to a phylum of animals call Nematomorpha.

While the adults are free-living worm-like creatures that live in freshwater, they all have a larval stage that enters a host (usually an insect) and grows and develops inside it.

The larvae absorb nutrients and as you can see from the picture, can grow to a great length that is somehow packed tightly into the host's body cavity.

How larvae get inside a wētā is still uncertain. George Poinar, a world authority on these animals, has suggested that it may happen when a wētā feeds on the dead body of an infected intermediate host (i.e. another species that may contain larvae but that the larvae doesn't develop in). However, we also know that wētā sometimes drink from free-standing water sources and that may be another way for the larvae to enter.

Leaving its host

If all this is sounding weird and perhaps a little horrifying, there is more to come!

After about a year, the adult worm is ready to emerge. It triggers something in the host's brain that makes it seek out water, which is where these worms live and reproduce. Quite how it creates this drive to find water is a mystery, but that's going to be the last thing the wētā ever does. If the wētā doesn't drown, the emergence of the worm will be fatal.

Who needs the Alien movies when we have creatures like this in real life?

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The body as a nursery: a wētā's grim end | Te Papa's Blog

# data[].attributes.attachment_link.description
Despite appearances, this is not a mutant tree wētā. The coils emerging from the rear of the wētā belong to one or more Gordian (or horsehair) worms. Bug expert Dr Phil Sirvid explains the bizarre behaviour of this parasitic worm and why this specimen is a tour favourite.Read more

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Uropetala chiltoni