Scientists have provided evidence supporting what many anglers have known for years – taking water from rivers has a negative impact on fish quality. The new knowledge, based on 15 years of research led by the Cawthron Institute, has global implications for irrigation and hydro-electric development, and recreational fishing.
Project leader and Cawthron Institute freshwater fisheries scientist Dr John Hayes says a river acts like a conveyor belt delivering drifting food to waiting fish. “We’ve shown that as flow declines, the diminished power and transport capacity of a river results in less drifting food. A new computer model that our team developed predicts that this translates to fewer, or more slowly growing, fish.”
Dr Hays says the insights from the model are a caution to regional councils and the public to be more careful when allocating water – in New Zealand, regional councils may need to revise minimum flows upward and water allocation limits downward.
Fish & Game’s Chief Executive Bryce Jonson says Cawthron are to be applauded for producing such sound, world-leading scientific research. Mr Johnson says the government needs to heed the research findings and bring in stronger water management rules and reconsider its support for intensive farming and irrigation. “At the moment, the government is pouring hundreds of millions of dollars into irrigation as a subsidy for intensive farming and ignoring the impact this is having on the environment and fish, including native species.”
“It is ludicrous that irrigators now want to take water from rivers and use it to replenish aquifers that have been over exploited. All this has a huge impact on the environment,” says Johnson.
“This report should be a wake-up call for the government. It has huge implications for tourism, farming and hydro-electric development and greater recognition needs to be given to freshwater fisheries,” Johnson concluded.
Neil Deans, technical policy adviser to the Minister for the Environment, says up-to-date technical information is vital for policy development, and such research can help inform water resource management.
“The quality of Dr Hayes’ and his collaborators’ research is internationally recognised, If we are going to set limits, then they should be effective in meeting community aspirations and as up-to-date as they can be.”
“This has implications for both environmental protection and for the allocation of water and its quality,” said Deans.
Go to the Cawthron Institutes’ project specific webpage to find the full story:
Listen to Dr Hayes speaking on Radio NZ: