|Conservation||The status of the knowledge of the freshwater fish fauna of New Guinea is good. A Field Guide to the Freshwater Fishes of New Guinea was published in 1991 (Allen, 1991) There are a range of threats to freshwater fishes in New Guinea. Lake Sentani and Lake Kutubu both have unique but threatened fish faunas. At Lake Sentani a rapidly increasing population has caused pollution and introduced species have impacted native fishes. The lake is also heavily fished and nearly all species are used for food. Oil deposits have been found near to the currently pristine Lake Kutubu there are plans to link Lake Kutubu by road to Mendi and the Highlands Highway and also to establish a township of 2000 on the lake shore. Both would be disastrous. Logging is another major general threat. It alters stream habitats and reduces shading and increases siltation. The problem is especially acute in Irian Jaya. Mining is another detrimental activity. The Ok Tedi copper and gold mine in western Papua New Guinea is situated on a major headwater stream of the Fly River. Silt and tailings effluent are dumped directly into the river. Both heavy metals and free cyanide are being released into the system. This has destroyed the Ok Tedi River, but the high runoff in the Fly River may help dilute the chemicals, giving a degree of protection downstream. There is an urgent need to conduct floral and faunal surveys throughout much of New Guinea. Many freshwater species occur in isolated lakes or small parts of single river systems. Economic concerns currently take priority over conservation issues. Educational and publicity campaigns amongst local people are essential to make them aware of the importance of their local environment. Contact: Dr Gerald R. Allen, Senior Curator, Western Australian Museum, Francis Street, Perth, Western Australia 6000, AUSTRALIA.|
|Geography and Climate||
Papua New Guinea forms the eastern half of New Guinea, the world's largest tropical island. It has a rugged geography, with steep mountain ranges leading down either to a narrow coastal fringe, or into major river floodplains with many lakes and swamps. Some areas receive up to 10 m rainfall per year, with an average of 2-4 m.
Ref. Fenwick, G.D. and D.S. Horning Jr., 1980
Although New Guinea can be broadly divided into major northern and southern faunal provinces, at least seven discrete sub-provinces are evident: 1. Western Islands. The four heavily forested , mountainous islands of Waigeo, Batanta, Salawati and Misool immediately west of the Vogelkop Peninsula; 2. Vogelkop Peninsula. This comprises the extreme western end of the mainland. It consists mainly of lowland forest and karst topography. It’s level of fish endemism is high.; 3. Great Northern. The largest province with several of New Guinea’s largest rivers including the Mamberamo, Sepik, Ramu and Markham. There are extensive lowland alluvial plains that periodically flood. There are numerous endemic species and two endemic genera; 4a. Eastern Papua: northern section. Isolated from other areas by the high central mountains. Very diverse with coastal plains, fjord-like inlets, forest-covered foothills and low mountains. Contains one endemic genus and several endemic species; 4b. Eastern Papua: southern section. The relatively narrow strip of south-eastern New Guinea wedged between the high central ranges to the north and east and the swamplands of the Purari River delta to the west. Includes Port Moresby. Habitat is similar to the northern section; 5. Great Southern. Similar in size to the Great Northern province this includes most of southern central New Guinea. Contains most extensive alluvial lowland plains in New Guinea composed of deposits from the Fly and Digul River systems. Most of the coast is fringed with mangroves with savannah and lowland swamps further inland. There is also extensive lowland rainforest. Has a number of endemic species as well as 33 shared with Australia; 6. Upper Purari - Kikori. Inland province with moderately high rainforested mountains and deep valleys in headwater areas of Fly, Strickland, Kikori and Purari Rivers. Isolation of areas has enhanced speciation. The fauna of Lake Kutubu is particularly noteworthy with 11 endemics out of a total of 13 species; 7. Aru Islands. Situated in the Arafura Sea. Formerly part of the land connection between New Guinea and Australia. Possible that a high level of endemism exists.
The major habitats for fish can be divided into the following seven categories:
Lowland rivers - The large lowland rivers (e.g., Fly, Sepik and Mamberamo) are generally slow flowing, though accelerated during flood periods from November to April. The water is highly turbid with a bottom of silt or mud. Aquatic vegetation is generally poor, with the exception of grasses and other terrestrial vegetation along the shore. Common fish are ariid catfishes and marine vagrants such as croakers, silver biddies, ponyfishes, and juvenile trevallies. The highland Wahgi River is similar.
Blackwater streams - These are small low-land tributaries of the major rivers, with dark tea-like color which is due to the presence of tannin, leached from rotting vegetation. Common fish include ariid catfishes, rainbows, garfishes, glassfishes, gudgeons, and gobies.
Floodplain lakes, swamps, and backwaters - In these side waters, water clarity is generally good, except when there is intensive flooding. This habitat is relatively rich in aquatic plants and offers good hiding places for juvenile fish. Common fishes include rainbows, gobies, gudgeons, and ariid catfishes.
Upland tributaries - This category includes a wide range of rivers, creeks, and rivulets in hilly to mountainous terrain, usually covered with dense rainforest. Aquatic plants are sparse or absent. The water is mostly clear, slow flowing, except during heavy rainfalls. Common fish are eel-tailed catfishes, rainbowfishes, hardyheads, mouth almighties, grunters, gudgeons and gobiids.
Upland lakes - Lake Kutubu in the Southern Highlands lies at an altitude of 800 m and has the riches lacustrine fauna with 13 species, of which 11 are endemic. Carp and trout have been stocked in other, smaller upland lakes.
Torrential mountain streams - Thes are characterised by extensive white water rapids and waterfalls, with a bottom of bolders, cobbles, and gravel. Very few species inhabit these waters.
Coastal streams - This category includes independant small creeks to medium-sized rivers in the coastal fringe and rainforest. Water clarity is usually good except during floods.
Ref. Fenwick, G.D. and D.S. Horning Jr., 1980