Carp popular for weed-clogged lakes
For those willing to tackle the red tape and front up with some serious cash, using grass carp to clear up weed clogged lakes and ponds may be a good option.
Popular Brick Bay winery, restaurant and sculpture trail at Sandspit has applied to the Department of Conservation to release grass carp in their five ponds.
With Department of Conservation approval needed, grass carp have been used in lakes and ponds including dune lake Kereta, and council storm water lakes like Maygrove in Orewa. Surprisingly, at least five golf clubs in the area use them.
‘‘We get around three applications a year in the northern area,’’ DOC Senior Biodiversity Ranger at Warkworth Thelma Wilson says.
New Zealand Waterways Restoration in Warkworth are the only grass carp breeders, and owner Gray Jamieson says an increasing interest in the fish for weed control among farmers, lifestylers and local councils, along with supplying stock for aquaculture is behind a new $2 million facility in the Hawkes Bay.
Riparian planting, replacing exotic plants with natives around the course, Omaha Golf Club course manager Corey Willcox also wanted to get away from the use of chemical sprays for weeds.
After a big algal bloom, the club applied to DOC and now has grass carp in three lakes.
While very unlikely to breed,
‘‘Trying to ensure they can't escape during floods is one of the biggest considerations’’
Thelma Wilson
escapees can live for 20 years.
Also eating native plants, DOC has concerns escapees could damage sensitive freshwater ecologies, so trying to ensure they can’t escape during floods is a big consideration, Wilson says.
One carp, washed out of a Matakana Valley property, took up residence near the Matakana wharf. Though not able to survive in seawater they can tolerate some brackish water and the fish was periodically seen for months after, she says.
Wilson is concerned fish have been stolen from ponds, sold illegally, and released into ponds and lakes Doc hasn’t vetted.
Critical of the strict requirements in DOC’s application process, Jamieson says the high cost of getting hold of the fish legally is likely driving the black market.
The application process costs around $2500.