Saturday, December 10, 2011

Cherax peknyi, Cherax Zebra, Cherax Tiger and Cherax Sp Papuana

A new species of crayfsh Cherax  (Cherax) peknyi  is described  from  the Fly River drainage, in the western province region of Papua New Guinea. This species differs from all others in its subgenus by the shape of the rostrum, and chelae, and in colouration. Cherax, new species, freshwater, crayfsh, Fly River, Papua New Guinea, Indonesia. Crayfish were collected at various locations in the Fly River catchment in 2005–2006, as part of a project aimed at developing techniques for aquaculture of indigenous species of Cherax. Techniques for sustainable aquaculture of Red-claw crayfish (Cherax quadricarinatus) were developed  in Queensland  in  the 1990s, and  it was hoped to adapt such techniques for similar species in Papua New Guinea.

Cherax peknyi are known to be present in the Fly River floodplain, and in the foothills of the mountains near the provincial capital of Kiunga. They are collected and eaten in all regions, particularly when the water level has receded during the dry season. The people knew of a crayfish with a soft red patch on  the claws of the males (as has Cherax quadricarinatus), but when we went collecting with them, they caught several species including the undescribed Cherax peknyi. Specimens were forwarded to Queensland Museum to ensure their presence was documented particularly important as some species are disappearing  from  the  Fly River  floodplain following the introduction of exotic predators such as the fish Anabas testudineus and Channa sp.

Specimens collected in Tamu Creek (a tributary of the Fly River in the Western Province of PNG) in 2006, were tentatively assigned as Cherax sp. “ papuana” by BH. We realised that these specimens perfectly matched  the species from the Merauke region introduced onto the German pet market as Cherax sp. “tiger” and Cherax sp.”zebra” in the year 2000, and which the senior author believed to be a new species. New Guinea has been the source for a highly lucrative trade in native fish from West Papua to Europe, in particular a number of rainbowfish species. The pretty colour patterns of this crayfish, and the ease with which it can be transported, makes it of particular interest to  the aquarium  trade. Crayfish collected from wild populations are supplied by wholesalers to the European, Japanese and USA pet markets. We here describe this distinctive crayfish as a new species, Cherax peknyi.


The Cherax peknyi were usually found in slow fowing, still water, in parts of southern New Guinea with pronounced wet and dry seasonality. The villagers traditionally collect these animals when the water levels are low during the dry season, as in most places the water fow is too fast in the wet season. Clarity of the water depends on the level of fooding and time. The Tamu River (near the West Papua border) is muddy during the flood season, becoming clear after the initial foods, and then becoming stagnant, with dark (tannin stained) water full of rotting leaves, and almost anaerobic (DO<1mg/L) in the dry season. The crayfsh live under logs and in crevices and holes in submerged timber. They also live in burrows in the clay in the banks of the river. Even when the water is very low in dissolved oxygen they live in all water depths and in their holes. No berried females were collected in the dry season suggesting that breeding is in the wet season.

Generally the habitat is in monsoon gallery forest, however they persist where habitat modification has been severe (clearing and siltation), and breed and maintain populations in small creeks around Kiunga (e.g. near  the Kiunga school). These modified creeks have moderate flow throughout the year, and are highly turbid (secchi <50mm), and DO >4mg/l. Water temperature in small streams around Kiunga gets as low as 18°C, and up  to 29°C. A few of  the creeks  in which  they occur dry out completely, so they probably are able to survive in moist conditions for a couple of months, in burrows or moist logs.

We did not collect crayfish in the swamps, and the villagers only fish for crayfish in rivers in the forest behind the swamps. No crayfish have been collected in the main Fly River channel which is heavily populated by Macrobrachium rosenbergii. In  the streams Cherax peknyi was sympatric with Cerax albertisii and Cerax quadricarinatus, which are also collected for food by  the  local people during the dry season.


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