Koura – Fresh Water Crayfish

Paranephrops planifrons – North island fresh water crayfish

Koura (fresh water crayfish) are common in the Tangihua’s

Koura live in the streams, lakes and ponds, and even in swamps in the Tangihua’s.

Koura prefer to 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.

Koura reach lengths of about 70 mm . Their first pair of legs are pincers used for both attack and defence,scavenging food and warding off predators or other koura. The other four pairs of well-developed walking legs are used for most movement, ; When alarmed, koura flick their tail forwards violently to propel themselves backwards at speed.

Feeding

Koura is a scavenger that feeds on leftovers that float by in the water or settle on the bottom; old leaves, small insects such as Invertebrates including aquatic snails , chironomids , and mayflies 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.
Koura are nocturnal, during daytime they find shelter under rocks, debris such as cans and bottles, and vegetation

Students find Koura fascinating, they are found in all the streams around the lodge

Advocate article quote –  At a school  camp
Around them, unseen, the daytime settled and the night life woke. They children heard a nearby morepork, a ruru, as they started out.
But then, on the way down the track back to the lodge, the real magic happened.
The children and their adults turned on torches for the shallow stream-crossing and there, illuminated in the silver light, were dozens of freshwater crayfish—koura —scampering about on the creek bed and its damp edges

Shed their shells

Koura like all crustaceans moult their exoskeletons in order to increase in size

Nocturnal

Koura are nocturnal, during daytime they find shelter under rocks, debris such as cans and bottles, and vegetation

Replace their limbs

When one limb is lost the koura will divert energy for overall growth to restoring the lost limb.

Reproduction

They can be sexed by looking at their underside: males have a pair of gonads that protrude from the base of the fourth pair of legs, while females have holes at the base of the second pair of legs.

The female carries between 20–200 eggs under the side flaps of her abdomen. They take 3–4 months to hatch. Over this time male sperm production corresponds with females reproductivity. Once hatched juvenile koura cling to their mother’s abdomen using their pincers to attach until they have reached a length of 4–10 mm. At this stage they resemble adult koura in appearance,

The total breeding length time from peak egg laying to the release of juveniles is estimated to be 28 weeks for the autumn–winter period and 19–20 weeks in spring–summer breeding groups.

Predators and cannibalism

Eels, and other Koura are the major aquatic predators . Other predators include rats, kingfishers, shags, stoats and kiwi.
Cannibalism in koura is most likely to occur when koura are sick or moulting. Cannibalism can be a greater problem in high density situations where competition for shelter and territory is greatest. Juvenile koura can be consumed whole by larger koura.

Threats and conservation

Although still common and not under threat they are preyed on by rats, possums ,cats and mustelids.

Good pest control will ensure their future.