A couple of weeks ago I got the opportunity to go and have a wander around a stream near a friends house. After poking at various insects and other creepy crawlies, it occurred to me to have a look in the water and see if I could find anything a bit different than the usual insects I find. It just so happens that I found this fellow (click images for full sized picture..theoretically anyway):
This fellow is a freshwater crayfish, one of two species in New Zealand Paranephrops zealandicus, or more commonly known as the Southern Koura. The other species, rather boringly enough, is simply called the Northern Koura (Paranephrops planifrons) and is rather similar to the Southern Koura, but is often of a smaller size. Moving some rocks around revealed something moving about in the water and closer inspection revealed several Koura wandering about. Catching them was a little tricky, as they are extremely fast and stirring up sediments makes life much harder, but in the end I succeeded (for SCIENCE!). Once ready for his photoshoot this guy* was rather happy for the most part to sit up for the camera and have his photograph taken, but there was one rather dramatc incident towards the late afternoon.
As you can see, naturalism can be a dangerous hobby, as the little crayfish grabbed my thumb and squeezed with all his crayfishy might. I can assure you, that really did hurt and it actually took me a while to get him off my thumb. Other than that, numerous pictures were taken and good times were had by all.
Once finished with his exciting photoshoot, he was released back into the stream to do whatever it is he spends time doing, most likely hiding under rocks during the day to surface at night to feed on small critters and algae. You’ll notice growths on the animals head and claws in all of the photos, which I figure is either the direct result of their feeding habits on algae (just getting some stuck on) or growths that provide some degree of camouflage. Unfortunately though, Koura are becoming harder to find in New Zealand as introduced aquatic predators (namely trout) and pollution of their natural habitat takes its toll. Unlike many species of freshwater crayfish, New Zealand Koura have no marine phase in their lifecycle, so once they go extinct they are unfortunately unable to re-colonise an area they have been removed from.
*I will immediately concede I’m no expert on determining the sex of freshwater crayfish. He didn’t have any eggs, which would be the obvious giveaway.
The crayfish is cool and all, but how do you determine they’re sex?
The easiest way I know of, which can depend on the time of year is looking on the underside of the crayfish for eggs, which indicates a female (they carry them under the tail). I’m not sure if Koura have any sexual dimorphism, like males having bigger claws or being of a considerably larger size (Deep sea crayfish have bigger males than females). One way may be to look at the swimmerets (structures underneath the tail, called pleopods) as male Koura may have much bigger sized swimmerets than females.
Another way is to look for a sperm duct, which on males runs down several sements, while females have an opening on their underside (though spotting it may be difficult as these critters don’t appreciate being turned over, as I quickly discovered when it assaulted my thumb).
Is it possible to keep the crayfish in a fishtank as pets? If so, what to feed them and what do they need to survive.
It could be possible, though I’m not sure if this would be recommended. I do know that they normally eat small invertebrates (often found on the underside of rocks in a stream) and I believe algae growths on rock surfaces as well. Assuming that the water was filtered and kept oxygenated (possibly even flowing somewhat), they might be fairly happy in captivity.
It wouldn’t be the most loving of pets as the second photo shows, but could be possible.
Hi Jim,
We have some land in Central Otago and went armed with xmas ham to see if we had a KOURA population, 5mins later about 25 large ones and 30 odd small ones in 2 mtrs of river.
Hi, do you eat yoghurt?
I have one in a tank, they are easy to look after, easier than other fish even. just give it a rocky subtrate and some things to hide under and it will build its own habitat. i suggest putting a rock with algae on it into the tank and adding live insects like boatmen. they can also eat food scraps like chicken and beef (though its probably not too good for them) so keep that to a minimum. frozen bloodworms are an excellent food source but remember they dont eat very much, so feeding a quarter of the cube every couple of days would be good. and a must is aeration and filtration, i suggest a fountain filter with the turnover rate turned quite far down. hopefully i could be of some help
BJ,
How long have you cultured this little fella for? I am interested in attempting reproductive research of the Koura in order to possibly start a stock enhancement project in the north.
Any info would be much appreciated.
Im looking at Koura too as part of my diploma, I would be interested in how your project has gone. Im more looking at stocking density, but any enhanced information would be most helpful cheers