About the exotic caulerpa threat in the Auckland region
Exotic caulerpa is the name for two closely related species of fast-growing, invasive seaweed that have been found in the parts of Hauraki Gulf, Bay of Islands, and Coromandel. Exotic caulerpa grows fast if conditions are favourable and smothers other forms of marine life, which means it can wreak havoc on our marine ecosystems and recreational waters.
We know that this pest gets spread over long distances on vessels and equipment. It’s been found around the Hauraki Gulf in popular anchorage locations.
That’s why a call has gone out to boaties from Auckland Council, Biosecurity New Zealand, iwi and neighbouring regions: help stop the spread of caulerpa by checking and cleaning your gear before you move, every time.
Boaties, fishers, and beachgoers – you can help contain the spread of exotic caulerpa if you:
- Avoid anchoring or disturbing the sea floor in infested areas. Anchors, chains and fishing/diving gear can break up caulerpa and pieces get snagged, accidentally moving it to new locations.
- Always check and clean gear: clean anchors, fishing gear, dive equipment, and any other gear when moving between regions.
- When at sea, check your anchor, chain and equipment for any attached seaweed. If you find any, bag it and bin it on-shore. If you can’t do this, return it to the waters it came from; do not move it to a new location.
If you see any unfamiliar seaweed, including exotic caulerpa, take a photo, record the location, and report it to MPI on 0800 80 99 66. - Respect Controlled Area Notices (CANs) and rāhui which are in place to protect vulnerable marine environments. As much as you can, avoid all locations where caulerpa has been found.
It is not possible to remove well-established, large infestations of exotic caulerpa with current tools. This makes it important that caulerpa is not spread to new locations. If we fail to contain this invasive weed we could lose more of the recreational areas we enjoy, or find them vastly changed. This pest has the ability to harm native marine habitats, affecting fish populations and overall marine health.
The message to all boaties is: make sure you know where you can safely anchor and fish before heading out. Throughout the summer, mainland champions and ambassadors will be stationed at places like boat ramps, marinas and out on the water to provide information and answer questions.
Frequently asked questions
Why is exotic caulerpa harmful?
Exotic caulerpa (Caulerpa brachypus and Caulerpa parvifolia) are fast-spreading seaweeds that have the potential to blanket the seafloor, potentially outcompeting native seaweeds and seagrass. This could disrupt vital marine habitats for fish, shellfish, and other marine life, leading to a decline in biodiversity and threatening the recreational fishing and diving opportunities New Zealanders cherish. The impacts are not only ecological. Consequences could include loss of recreational areas if infested areas are off-limits for anchoring, fishing and diving; loss of native marine habitats that affect fish populations and overall marine health; impacts on our aquaculture and tourism industries; and economic impacts.
Where has exotic caulerpa been found so far in Auckland?
Following nearly three years of surveillance, exotic caulerpa has been found in eight locations in the Hauraki Gulf, including much of the western side of Aotea Great Barrier Island.
- Mokohinau Islands
- Aotea Great Barrier Island
- Iris Shoal, Kawau Island
- Southern Kawau
- Rakino Island
- Waiheke Island
There has also been a small incursion in Omaha Cove/Leigh Harbour. This was found early, and successfully removed but surveillance continues. Outside of the Auckland region, it has been found at Fantail Bay and Ahuahu Great Mercury Island in the Coromandel, and Te Rāwhiti in the Bay of Islands.
What does exotic caulerpa look like?
There are a number of common seaweeds that appear similar to exotic caulerpa, including native caulerpa, the sea lettuce Ulva sp., and native seagrass. Exotic caulerpa (Caulerpa brachypus and Caulerpa parvifolia) are green seaweeds with leaves up to 10cm long and long runners with roots known as stolons. Unlike similar species, it has distinctive ‘oar shaped’ leaves.
What should I do if I find some outside of a known location – for example on a beach or when I pull up my anchor?
Please report your finding urgently to Ministry for Primary Industries, who will provide further instructions. Take a photo if possible, and record GPS co-ordinates. Authorities would rather receive a false alarm than miss the opportunity to investigate a potential incursion in its early stages. Call 0800 80 99 66.
Why focus on boats when caulerpa can travel in tides and currents?
While exotic caulerpa can spread via currents and waves, the reality is that vessels can take it to new places further and faster than natural dispersion. That is the reason why so much focus is placed on the checking and cleaning of equipment. Managing the spread, in combination with surveillance and rapid response, will help to contain exotic caulerpa and stop it spreading to new locations while future treatment/removal options are explored.
What else is being done?
There is a vast body of work underway involving councils, iwi and Biosecurity New Zealand. Some of the innovations developed in the first three years have included the use of wool benthic mats to smother caulerpa, removal with suction dredges, and even ultra-violet light. Projects have so far received more than $15m of government funding under the Accelerated Programme for caulerpa surveillance, management, and research, as well as significant regional investment by Auckland Council, Northland Regional Council and Iwi.
Websites
https://ourauckland.nz/stopthespread
https://www.biosecurity.govt.nz/caulerpa
