Fish-Tank Weed Polluted Lake

Press, Volume CV, Issue 30953, 8 January 1966, Page 1

Fish-Tank Weed Polluted Lake

(From Our Own Reporter) WELLINGTON, January 7. Tropical-fish owners who have emptied the contents of their fish tanks and bowls into the lakes about the centre of the North Island are believed by scientists to be responsible for the weed problem in many of the lakes.

Professor L. W. Tiller, assistant director of the Department of Scientific and Indus-

trial Research, said today that scientists were certain that in one area the weed problem had arisen from the emptying of a tropical-fish tank. “The whole problem almost certainly follows such action on the part of tropical-fish owners, who have introduced the varieties of what is commonly known as oxygen weed into the lakes.” Professor Tiller said it was likely to be some years before a permanent economical method of controlling the weed was found. The chemi.cal methods used so far had proved reasonably successful but the economics of them had yet to be proved. “The problem to which we want an answer is: ‘lf we get rid of this weed what will take its place?’ “We feel that the long term answer is biological control and hope that a biological control technique can be de-

veloped, but these sort of techniques are the ones that take a long time to pull <sff successfully.” Professor V. J. Chapman, of the Auckland University, had been experimenting with Chinese grass-eating carp.

It had been hoped they could live off the lake weed and at the same time keep it in check. But Professor Chapman’s experiments had apparently shown that the fish were difficult to rear on the weed and the mortality rate had been high, Professor Tiller said. Some of the lake weed, Professor Tiller said, was

rooted in the bottoms of the lakes. Other varieties floated about the lakes obtaining nutriment from the water. The inter-departmental committee established in March to consider the problem would meet for the second time early this year to review progress.

No meetings had been arranged since the inaugural one in March primarily because he himself had not been able to give more time to the problem, Professor Tiller said. Professor Chapman, because of his work at Auckland University, would be co-opted to the committee