New Zealand Freshwater Crayfish - KOURA Stream life New Zealand Freshwater Crayfish - KOURA

By Lachie Bowker, Class 5P

Introduction I want to study Freshwater Crayfish known in Maori as “Koura”. I studied 3 streams. In all 3 streams Eels and other animals such as snails were seen, lots of plants were seen but Koura were not observed. I have caught Koura in Lake Taupo so I know some exist. Are they being hunted and eaten by predators in the streams such as Eels? Is their food source running out? Are the streams no longer a healthy place for them to live?

Questions What do they eat? Where do they go in the daytime? Why aren’t they found in all streams? What predators do they have? Where can they be found? Are they endangered?

Scientific Name Kingdom: Animalia Phylum: Arthropoda Subphylum: Crustacea Class: Malacostracea Order: Decapoda Family: Parastacidae Genus: Paranephrops

Description These are photos of some Koura. North Island Koura and South Island are different sizes South Island koura grow to 80mm long North Island koura grow to 70mm long

Food Chain Koura eat both animals and plants so are omnivores. They eat snails and insects. They have lots of enemies! Their predators in water include eels, perch, catfish, trout. Some of these aren’t native to New Zealand. They also have lots of land based enemies which is strange because Koura live only in water.

Food Chain Continued... Some of their land enemies are rats, kingfishers, shags, scaup, stouts and kiwis. Humans also eat Koura so we are a predator! So koura have enemies in water, on land and even birds eat them. Koura also eat their own species! This is called cannibalism. Isn’t it strange that they eat each other when they have so many enemies?

Adaptive Features Antannae Eyes Pincers Koura use Antannae to feel around the stream. They can also be used to poke enemies Eyes The eyes of Koura are on short stems and can be moved around in all directions Pincers Pincers are used to scare enemies and grab their prey. If a Koura looses a pincer it will grow back during their next molting cycle.

Habitat Koura live in rocks, tree roots or in holes in the bank during day time. Koura move to shallow water and on the surface during periods of darkness. They move to deeper water during daylight hours. In shallow water it would be easier for nocturnal enemies to eat them such as kiwis and rats.

Is Their Population Shrinking? The department of conservation lists Koura as a threatened specie as their population is declining. Some people think this is because the streams are now polluted more than they used to be due to farming. Also there are lots of predators that eat Koura and some of these are not native to New Zealand. Trout eat a lot of Koura and Trout were brought to New Zealand by the English. Eels and Trout eat a lot of the same food as Koura so maybe there isn’t enough food for them all. Human Beings also catch and eat a lot of Koura! Koura was like a treat for the Maori’s. We caught and ate some at Lake Taupo last year.

Conclusion I started this project trying to answer some questions about Koura. I went to 3 streams to look at the natural habitat of Koura but I did not see any Koura in the streams. After researching Koura on the internet I found out that they are now listed as a threatened specie by the department of conservation. This means they might one day not exist as a specie. The reasons for this include 1. some streams are now polluted and aren’t healthy homes for Koura 2. The food they eat is being eaten by other animals in streams like eels and trout. And 3. Koura have lots and lots of enemies who like to eat them such as eels, trout, kingfisher birds, HUMAN BEINGS and Kiwis.

Video of Me and My brother investigating a stream Here is a video of my brother Mason and I looking for Koura at Battle Hill Park stream in Pauhatanui. We saw Eels, snails and lots of plants and caught a baby Eel in our net but we didn’t find at Koura.

Photos

Photos

Bibliography http://www.doc.govt.nz/nature/native-animals/invertebrates/crayfish-koura/ http://animals.pawnation.com/crayfish-adaptations-5605.html http://terranature.org/koura.htm http://en.wikipedia.org/wiki/Paranephrops