Media release from Eastern Fish & Game

Fish & Game Issues Angler Alert on Invasive Weed

Fish & Game is urging anglers to play their part in preventing the spread of an invasive weed discovered in Lake Waikaremoana in Te Urewera National Park.

The Department of Conservation found the oxygen weed (lagarosiphon) at Te Raoa Bay and has closed this bay to anglers and boaties – and is searching the rest of the lake for any further infestations.

The introduced freshwater weed causes problems for native plants and animals, along with recreational water users. The oxygen weed can smother and replace native vegetation, and reduce the oxygen supply for fish.

Eastern Region Fish & Game Officer Matt Osborne says the weed can be a serious issue for anglers if it gains a foothold and becomes established – even preventing shoreline fishing.

“Some of the surface-reaching weeds can be in water as deep as six metres, depending on water clarity. Waikaremoana is a very clear lake with very good water clarity, so shallow bays could be hard hit,” he says.

The oxygen weed has shown up several times before in Lake Waikaremoana, at Rosie Bay which has a boat ramp, and the latest infestation is across the lake in Te Raoa Bay where someone probably anchored, he says. However DOC has found Rosie Bay is clear on this occasion.

Fish & Game’s message to prevent the oxygen weed from spreading is the same for all users across all waterways – and the same for other weeds and pests – ‘Check, Clean, Dry.’

“Check your gear, equipment, boats and trailers and tow vehicles for any weed or other hangers on,” Matt says. Remove any weeds caught up and where possible give your equipment and craft time to dry so any weed fragments missed, can dry out and die.

He also advises removing bungs to drain and dry bilge areas. “Wash and disinfect your gear which keeps it clean and lasting longer.”

“Some invasive weeds pose a serious threat to the Rotorua lakes region,”Matt says, “especially with the water quality improvements which are happening.

“As the water becomes cleaner, and clearer, new weed invasions could make some areas unusable for swimming and angling. More light through the water column assists weed growth, and anglers would then find themselves regularly snagging weeds around the shoreline.”

The invasive weeds can be spread by just one fragment which breaks off the plant and it only takes only a very small amount of plant material dropped from a vessel or anchor to spark a new colony. This means that all boaties must be very careful to check trailers, anchors and anchoring systems.

Weed cordons put in place at Rotorua Lakes by Environment Bay of Plenty are playing their part in helping stop the spread of weed fragments, Mr Osborne says.

The cordons have been set up at boat ramps to trap weeds which boats and trailers sometimes bring with them from other waterways.

After launching from the ramp, boats may drop undetected weed but the weed cordon zones trap this material. The cordon areas are regularly sprayed with herbicide so that any weed strands caught are destroyed.

The weed cordons are a nice reminder to lake users of the risk – and to follow the CCD or “Check, Clean, Dry” routine.

ENDS

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