Thu 17 June 2004
Hui to hear effects of pollution on fish
The findings of a major health study of fish in New Zealand's largest river will be presented at a hui on Friday. The
study reveals that some native fish are struggling to cope with the effects of intensive development, but that
conditions are helping at least one pest fish species to thrive. Landcare Research and Forest Research scientists, with
the support of Tainui, are completing what is probably the most ambitious fish health study ever conducted in New
Zealand.
Over the course of three years, they studied fish in five rivers in Canterbury, Wellington, the Bay of Plenty, and
Waikato. They measured the reproductive health of fish, a significant indicator of how fish respond to pollution and
other types of stressors. This approach is at the forefront of research overseas, and is a first for New Zealand.
The Waikato River study results are of particular importance, not only because of its size, but because it receives a
range of effluents from industry, agriculture and town sewage. It is also neighboured by a thermal power plant.
The study was also very important to Tainui because of their role as kaitiaki or environmental guardians. The team of
scientists, led by Drs Louis Tremblay (Landcare Research) and Mike van den Heuvel (Forest Research), studied three fish
species: the native common bully, which lives in nearly all New Zealand streams; the native eel or tuna, a taonga for
M*ori; and an introduced pest species: the brown bullhead catfish.
This range of species provided an overall indication of the health of fish populations in the Waikato River."We examined
the sexual hormone levels in blood, the males' gonads, and the number of eggs the females had, and the age structure of
the population," Dr Tremblay says. "The biological and chemical characteristics we found indicated exposure to a range
of metals and organic compounds at a number of the effluent discharge sites.
One site on the river showed indications of a lack of successful reproduction in common bullies and brown bullhead
catfish. "There was little evidence of cumulative damage along the river, partly because of its length and the fact that
it ranges from placid to fast-flowing. However, there were clear signs of eel overexploitation in the lower Waikato
River.
"Probably the most unexpected and interesting finding was that increased temperature (thermal pollution) appears to
increase populations of catfish * a pest species * most likely to the detriment of the native species."Dr Tremblay says
Landcare Research and Forest Research are working with Tainui, local authorities and industry to seek solutions to
pollution, and help prevent contaminants from having unpleasant effects. "This project is a good example of interested
parties working together to address environmental issues."
The hui has been organised by the Tainui Environmental Unit, Landcare Research, Forest Research and the University of
Waikato. It will be attended by representatives of local councils, industry and science providers from universities and
crown research institutes.
There will also be presentations from other groups researching the Waikato River, and group discussions on sustainable
environmental management of the river.Media are welcome to attend the hui at Te Kauhaunganui Chambers in Hopuhopu, 15
kilometres north of Hamilton city, 9.30am * 3.00pm.
ENDS