Survey: New species causing imbalance

AN aquatic fauna survey conducted in the Ramu River catchments in Madang has found introduced fish species are responsible for the natural imbalance in the catchment area river system.
Ramu NiCo contracted Hydrobiology Company from Australia to undertake the aquatic fauna survey in the Ramu River catchments last November and December.
The study was to examine the status of fish and macrocrustacean fauna of sites in the vicinity of, and downstream of the Ramu project, in order to identify whether there was evidence the mine operation had impacted fish and macrocrustacean communities.
The aquatic fauna survey focused on the collection of fish and macrocrustacean diversity and abundance data and tissue metal data.
The data collected suggested that these catchment-wide changes in species composition and aquatic habitat quality were linked to and driven by the effects of introduced species in the system.
It said that had altered the natural balance of the aquatic ecosystem of the Ramu catchment.
The aquatic ecology of the system differs markedly from that before the introduction of exotic species into the Ramu catchment in 1997-98.
“Impacts to the aquatic ecology in the system, particularly at sites not located immediately downstream of the mine area may be primarily or wholly attributable to the establishment of exotic fish species in the Ramu catchment, rather than from any mine-derived impacts,” the report said.
“Monitoring was undertaken at 14 sites: Six upland stream and river sites, three off-river waterbody sites, and five main river channel sites, all of which had been sampled as part of previous baseline monitoring surveys. 
“Data was collected using sampling methods consistent with those used during earlier surveys.”