Most fishes found in freshwater are either migratory, coming from or going to the sea to spawn - such as the tarpon (Megalops cyprinoides), barramundi (Lates calcarifer) - or are permanent inhabitants of freshwater habitats. In the second category, these fish belong to or are derived from marine families. Examples include fork-tailed catfishes (family Ariidae), gudgeons (family Cyprinidae), gobies (family Gobiidae), grunters (family Terapontidae) and jacks (family Carangidae).
The only fish considered not to have derived from marine ancestors is the bony tongue (Osteoglossiformes).1
A fish map of New GuineaFreshwater fishes living in the south of the island are generally different species to those in the north, unless they are capable of migrating through the sea. In general, southern rivers have a much higher diversity of fish species than northern rivers. 2
Where the fish live:3
- Blackwater streams
Catfishes (order Siluriformes), rainbowfishes (family Melanotaeniidae), gudgeons (family Cyprinidae) and gobies (family Gobiidae) are found here. These rivers are generally richer in fish fauna than the large, muddy rivers, and there are many fishing villages next to them.
- Lowland rivers
Turbid waters and silty or muddy bottoms make for poor aquatic vegetation and hence less fish life. Here we can find catfishes, which are common, along with marine visitors such as croakers (family Sciaenidae), silver biddies (family Gerreidae), ponyfishes (family Leiognathidae) and juvenile trevally (Caranx species).
- Floodplain lakes, swamps and backwaters
Cover huge areas with good quality water, rich in aquatic plants providing ample hiding places for juvenile fish. Common here are rainbow fishes, gobies, gudgeons and the ubiquitous catfishes.
- Upland tributaries
Very clear water, rapidly changing level and a general lack of aquatic plants. Common here are eel-tailed catfishes, rainbowfishes, hardyheads (Craterocephalus kailolae), grunters, gudgeons (especially the genera Oxyeleotris and Mogurnda) and gobies, many of the genus Glossogobius.
1 Coates, D. 1989. Review of Aquaculture and Freshwater Fisheries in Papua New Guinea - A report prepared for project PNG/85/001 Sepik River Fish Stock Enhancement Project. FAO. Field Document No. 1. PNG/85/001.
2 Coates, D. 1989. Review of Aquaculture and Freshwater Fisheries in Papua New Guinea - A report prepared for project PNG/85/001 Sepik River Fish Stock Enhancement Project. FAO. Field Document No. 1. PNG/85/001.
3 Muller, based on Allen.
4 Miller S. (Ed). 1994. Status of biodiversity in Papua New Guinea: Papua New Guinea Country Report on Biological Diversity. Waigani: The Department of Environment and Conservation, Conservation Resource Centre and the Africa Centre for Resources and Environment (ACRE); 67-95.
5 Swales, S. Undated. FISH AND FISHERIES OF THE FLY RIVER, PAPUA NEW GUINEA: Population Changes Associated with Natural and Anthropogenic Factors and Lessons to be Learned. World Fisheries Trust / IDRC /UNEP. 26 pp.