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The state of lakes/ponds at Cooks Beach – – needs resolution and action.

There seems to be an interminable number of processes that prevent any real progress and resolution.

This follows a previous article on the Cooks Beach ponds 31 October, 2023 Issue 1078.

There seems to be an interminable number of processes that prevent any real progress and resolution.

Background: When the lakes/ponds were established, they were intended as a storm water retention system which seems to work well. When the developers did the sub-division, the lakes/ponds were marketed as ‘lake front’. They are now called ‘passive recreation’ on the TCDC plan of the area. But the reality is these fresh water ponds or lakes are an eye sore and a health hazard.

For twenty years, diquat gel has been used by the council to clear the lakes of exotic weeds and green slime. Diquat gel acts as a desiccant. The leaves drop to the bottom but the plant doesn’t die at all, just the top leaves drop off.  Diquat gel has been approved. It is sprayed with a backpack. It hits the water, spreads out and then sinks. The Council decided not to do any more spraying because it wasn’t working. (It worked only temporarily three or four months of the year).

The leaves drop away out of sight, which means out of mind, but the rotting refuse comes back with a vengeance when the summer comes. That summer has come.


July 2022 – proposal – silver carp as a weed control measure

When the Council stopped doing the spraying, a representative group we will call the Cooks Beach action group (CB), went to the Council with a thoroughly researched proposal: Put Grass (silver) carp as a weed control measure (not Koi Carp) into those ponds.

The then Community Board and Councillors whole heartedly accepted the report and as a result, it was recommended to TCDC staff by the Council that they investigate the use of Grass(silver) Carp – the option proposed by the CB action group.

This meant the commissioning of a report from a consulting company in Auckland, who were reputedly experts in the field of freshwater lake contamination and the matter of grass (silver) carp. The consultants commenced on 22 October, 2023, the same month as a newly elected TCDC and Mercury Bay Community Board began their term of service.


Mechanical harvesting was another option mentioned by the Council in that period – a bit like mowing lawns – you keep on doing it. The cost of this is prohibitive and would have discouraged the Council.


Between October 22 and August 2023: Given what happened over the summer of 2023 with cyclones and storms, the CB action group backed off putting pressure on Council – too much storm damage to cope with, but they did make enquiries of the Council and were promised by TCDC they would receive a copy of the commissioned consultant’s report.

No further communication from Council until August 2023: The consultants’ report arrived in August. When the CB team knew the commissioned report was to be tabled, they asked if they could be present. They were denied this by a TCDC Manager, but when the team challenged it through a TCDC Councillor, they were given the right to attend. That’s how, on 6 September, two of the CB action group made a five-minute presentation to the Community Board meeting as part of the Public Forum segment.

Then at 10.00am, at the same meeting, Greg Roche and Brett Houston,(staff concerned with waterways management) came into the meeting and presented the consultant’s report to Council (the one that had been commissioned by the then Community Board, October 2022).

The CB presenters were allowed to sit and listen to the presentation, but they were not allowed to ask questions or speak or comment (even though they had initiated this process).

 The consultant’s report had the effect of ‘killing an ant with a sledge hammer.’

  • It had taken almost a year and to make matters worse, the report seemed to go in a totally misinformed direction. (This has been admitted to some extent by Greg Roche)
  • The only reference to grass (silver) carp which was the main reason for the commissioned report, was a half-page on page 50 of the report and it was the wrong kind of carp – it referred to koi carp, definitely an unwanted species and NOT the Grass (silver carp proposed by the CB action group).
  • There was no glossary on the Consultant’s report to substantiate their ‘research.’  Parts were a direct cut and paste off the internet. 
  • This was galling to the CB team when they were forbidden from commenting or asking questions on a matter where there was little experience and knowledge on the subject from the Community Board and TCDC Council members.
  • The cost of such a report would be expensive and that cost has not been made available. 
  • Thankfully, then Community Board member, Deli Connell, asked some pertinent questions – most of which could not be answered adequately. This raised so many red flags when her questions could not be answered by Greg Roche or Brett Houston. 
  • It seemed unbelievable to the CB team that the only DOC and MPI approved supplier of the grass (Silver) carp in New Zealand – Gray Jamieson, Director of NZ Waterways Restoration (NZWRA),) was not consulted – the one waterways restoration company that had been successful working with several NZ regional councils on the same problem as at Cooks Beach with the same solution the CB action group had recommended.
  • The CB team were not saying that Grass (silver) Carp are the only option, but they were asking the Council to seriously investigate it as an option. Their consultant’s report did not do this.


It seemed naïve and incompetent that the Council/Community Board would then, that day, vote to adopt the report. Adopting it was a mistake.


Next Steps: However, to keep things moving and communication open, the team invited Gray Jamieson of NZWRA and TCDC representatives and staff to come to a meeting with local Cooks Beach residents. That meeting occurred on Friday, 13 October,2023   

Gray Jamieson addressed the gathering about Grass (Silver) Carp and their suitability in similar settings around NZ. He reminded the group that silver carp are herbivores; eat the more nutritious leaves from the top down; do not breed; are saline sensitive so need keeping in with fences or they die in salt water if they escape; live a long time so are economical; do not eat the food source out or eat out the native plants. Mr Jamieson described how the carp transform these stagnated green slime pools by themselves.

It seemed like a successful meeting, and it was reported as such at a following Community Board meeting.

No action: However, the CB action group received an email from Council to the effect that there will be no more action at this time and that there is nothing to report.

A prompt email response from the CB team to this resulted in Deli Connell of TCDC asking Brett Houston to include this matter of the Grass (Silver)Carp in the Cooks Beach local committee’s agenda regarding flooding and stormwater issues. (TCDC has set up local committees to establish strategies to manage local storm water and flooding.)

October 2023:

Again, to maintain communication following the Cooks Beach meeting and the dismal email, the CB team arranged another meeting with TCDC to inspect the lake and try to get some clarity as to what Council’s thinking was particularly in respect to grass carp as a weed control measure. 

As they walked around the big lake, it was acknowledged things were in a very poor state and badly weeded over. It was agreed action would be taken but the tone was non-committal as to what that might be.

It was intimated that considering grass carp as a weed control measure had “neither been ruled in or ruled out… and there was further study required… to measure the downstream effects on marine life down the creek towards the Cooks Beach community hall…”  This comment was made despite the staff member being reminded of the fact that the carp would be contained and not make it to that point, plus would not survive there due to their low salinity tolerance. Let’s not forget the previous expensive and deficient consultant’s report commissioned and reported back by staff.

Another plan afoot – November 2023: Greg Roche confirmed that TCDC had engaged a Hamilton company to undertake an inspection. The company, Deep Dive Division, inspected the lake with two Scuba divers late November with a view to quoting the council for a weed clearance operation. The divers went down the big lake from the western end to the eastern end.

On 11 December, TCDC posted on its facebook page that a suction dredging operation for weed removal would take place from Wednesday, 13 December to Friday, 15 December ’23 by Deep Dive Division. The company duly arrived and set up its suction pump and hoses. Within minutes, the pump was clogged with weed and that was the end of that attempt to clear the weed. Yet another expensive undertaking with little regard for the opinion and research done by the CB team and now months without anything being achieved.

It is more than disappointing to note that, notwithstanding the fact that the company had been to inspect the lake prior, it should have been better prepared for the weed clearing task and brought the right equipment for the job.

The close of 2023: Staff responsible are now on annual leave – the CB ponds are with a counterpart in Thames who has little or no knowledge of the lake problems.

There has been no further comment or announcement as to what TCDC’s next plan is.

 As a consequence of the incompetent approach and lack of action by TCDC, continuous outlay of ratepayers’ money to no avail (and some perceived stubborn ideological objection to the use of grass carp), the residents undertook their own weed clearing operation on Friday, 29 December at the western end of the lake, which has by far the worst infestation.

Amongst the weed is horsetail, a pest weed requiring removal. This has been reported to Waikato Regional Council but nothing heard back from them as yet.   

Meanwhile several ponds and lakes in the Waikato region benefit from the deployment of grass (silver) carp in weed-infested ponds and lakes.


The weed issue is serious and needs to be addressed.

Caption: Weeds cleared from the west bank by 15 residents on 29 December 2023.