Grass carp take up weed duty

By TONY GEE

KAIKOHE - The immediate future of shallow, weed-choked Lake Omapere in Northland is now literally in the mouths of 4000 grass carp released into the lake to control rampant oxygen weed.

A second batch of 2000 fish was released on Saturday and these will be followed by 4000 more during the next few days to make a total of 8000 adult carp in the 1200ha lake by the end of the week.

All fish are about 35cm long and weigh between 700g and 800g. Tens of thousands of smaller, nine-month-old fingerlings may also be released later in the year.

The initial release on Friday came after approval from Conservation Minister Sandra Lee.

It marked the culmination of years of sustained effort by members of the Lake Omapere Maori Trust Board and its agent, Orewa-based NZ Water Management director Gray Jamieson.

They maintain introduction of the voracious weed-eating carp is essential to control weed growth and algal bloom, which are threatening to turn the lake, just north of Kaikohe, into little more than a big stagnant pond.

"Those carp have got 45,000 tonnes of weed to eat so I hope they've started into it straight away," Mr Jamieson said after a lakeside ceremony and karakia (prayers) attended by more than 60 people, local kaumatua, lake board trustees and supporters.

The first carp into the lake arrived in a fish transporter from Wellington. The carp were raised by an Upper Hutt fish farming contractor.

Other carp are being trucked north from fish farms in Warkworth and Waipu in lower Northland.

Between them, the trust board, which owns the lake bed, and Mr Jamieson's company have put up $200,000 to pay for the 8000 adult fish now going into the lake. Up to $3 million more is needed, however, to pay for the overall cost of a wider lake restoration project, which will involve management by trustees and the National Institute of Water and Atmospheric Research (Niwa).

Mr Jamieson and the trustees are to meet conservation and Maori Affairs representatives in the next few days to discuss Government-linked funding options.

Included in the lake restoration project is the proposed release of tens of thousands of carp fingerlings, subject to the outcome of an application by trustees to the Ministry of Fisheries in Whangarei.

The final number of fingerlings involved will be recommended by Niwa.

There are also plans to farm adult carp in the lake as a source of income for local people.

Grass carp are said to be capable of eating their own body weight each day of aquatic vegetation.