The existing records of previous rainbow trout stockings in highland streams are listed in the Appendix.
Apart from rainbow trout there have been a few attempts to stock other salmoniid trout species. Brown trout, Salmo trutta, were stocked in the 1950's in Eastern Highlands Province, Simbu Province, Western Highlands Province and Southern Highlands Province (West & Glucksman 1976). Furthermore, during village survey work in 1989, this project received the information that brown trout were introduced to Lake Kundik at Maramuni, Enga Province, in 1981. People from Maramuni believed that it reproduced in streams around the lake; but it was subject to a heavy fishing pressure and subsequently disappeared. The total number of introduced brown trout was very small, and there has been no record of this species establishing in Papua New Guinea.
In 1974, the Mendi Hatchery received a shipment of 50,000 eyed ova of the brook trout, Salvelinus fontinalis, from New South Wales. Hatching was not successful, and only 4000 fry were released in Margarima River (West & Glucksman 1976). There are no records of people catching brook trout, and the species probably did not establish.
It seems that only the rainbow trout has been able to establish in the highlands of Papua New Guinea.
The first introduction of rainbow trout took place in 1952, when Bulolo Gold Dredging Ltd imported 10,000 ova from New Zealand and subsequently stocked the hatched fry in Bulolo River (West & Glucksman 1976). The private importations and stockings continued until 1959, and in 1964 the Division of Fisheries was involved in stocking operations for the first time, when 2000 fry were released in Gumanch and Baiyer Rivers in Western Highlands (West & Glucksman 1976). These early stockings were mainly undertaken for sport fishing purposes, and they didn't significantly support a subsistence fishery at village level.
Since 1971 the introduction of trout has been based on fingerlings hatched and reared at two government operated hatcheries, the Mendi hatchery in Southern Highlands established in 1971 and the Keglsugl hatchery in Simbu Province established in 1979. These hatcheries were abandoned in 1986. Since then, the only recorded trout stocking occurred in March 1992 when 10,000 fingerlings were stocked in Weile Dam at the Porgera mining site, Enga Province (Kawei, personal communication). These fingerlings were bought from Nupaha Trout Farm at Goroka, Eastern Highlands (see later).
Large areas in the highlands have never been stocked with rainbow trout. Those include areas in Western Province, West Sepik Province and East Sepik Province. This study didn't cover those areas. However, there are probably many rivers there, where sustainable populations of rainbow trout could establish.
In addition to the recorded stockings listed in the Appendix, unrecorded stockings have occurred on a private as well as governmental basis. According to Sagom (1989), the hatchery at Mendi alone produced over 700,000 fingerlings in the period from 1971 to 1982, which is more than twice the total number of fingerlings listed here.
The first attempt at farming trout commercially in Papua New Guinea was the establishment of Kutuni Trout Farm at Goroka in 1970 (Coates 1989). It operated until 1984, but re-opened again in early 1989 as “Gana Trout Farm”. This re-opening was unsuccessful, and currently there are no fish farming activities at the Kutuni site.
In 1990 another trout farm was established at Goroka, the Nupaha Trout Farm, and this is currently the only trout farm in operation in Papua New Guinea.
There is considerable interest among the highlands people in trout farming; a fact that reflects the popularity of fish in the area. Unfortunately, trout farming is not a subsistence level activity; the fish is very demanding with regards to water quality, and food is very expensive.
A side-effect of the two farms at Goroka has been that unintentional stocking of streams adjacent to the farms have occurred by way of escaped fish. The present trout population in streams around Goroka may, partly, be a result of such escapes.
Despite the long history of rainbow trout in Papua New Guinea, very little information exists on the biology and ecology of this fish species under New Guinea conditions and the success and limitation of its introduction.
The only available data originate from a fisheries survey of the Kandep Lakes, Enga Province, undertaken in 1979, where rainbow trout were caught seven years after introduction and were believed to reproduce successfully (Wright 1980).