| 33 Northland Regional Council: Bio Security T T Kelly Deeks Invasive seaweed theatens marine life Photo: Cawthron Institute “There are lots of challenges with this because although we have many tools available to address land-based biosecurity threats, we don’t have many good tools for working in the sea.” REGIONAL DEVELOPMENT New Zealand is now battling invasive exotic caulerpa seaweeds at multiple locations around the upper North Island, with its spread and its associated impacts posing a very real threat to our marine life and our recreational, commercial, and cultural activities. Exotic caulerpa was first found in Blind Bay, Great Barrier Island in 2021 and has since been found at Ahuahu Great Mercury Island, Te Rāwhiti Inlet in Northland, Kawau Island, Waiheke Island, Mokohinau Islands, Rakino Island, and Fantail Bay, Coromandel Peninsula. Exotic caulerpa spreads rapidly and forms large underwater meadows, competing with other species for space, and upsetting the balance of local ecosystems. Biosecurity New Zealand, mana whenua, regional councils, and the Department of Conservation have all been making a comprehensive effort to understand this pest, prevent its spread, and have even explored ways to remove it. Cawthron Institute is helping Northland Regional Council with its response. Team leader invasion ecology and management Dr Ian Davidson says the response, essentially led by the Ministry for Primary Industries, included an initial delimitation plan with Biosecurity New Zealand establishing an interactive map identifying all areas of New Zealand exotic caulerpa can be found, and then enacting an exclusion zone on fishing and boating in these areas to prevent further spread by people and boats before trying to reduce its footprint. “There are lots of challenges with this because although we have many tools available to address land-based biosecurity threats, we don’t have many good tools for working in the sea,” Ian says. “We’ve been working with Northland Regional Council and local hapu on new advancements, including a New Zealand-first suction dredging machine which is now on trial at Omākiwi Cove in the Bay of Islands. “Built by Johnson Brothers, this machine is mechanically harvesting exotic caulerpa from the sea floor and removing it from the system and if successful, we’ll be able to use it at other sites throughout New Zealand for this pest and other similar ones.” Ian says the exotic caulerpa response has been taken up strongly and enthusiastically by several stakeholders. Meanwhile everyone working or relaxing in our coastal waters can help stop the spread of exotic caulerpa. This pest is spread easily by vessel equipment such as anchors and anchor chains, and on other marine equipment such as dive gear and fishing lines. So before moving to a new location out on the water, always check the anchor and gear and if seaweed is found, it should be bagged and disposed of on shore. Mariners can also help by following the legal restrictions on anchoring and fishing in place at Aotea Great Barrier Island, Ahuahu Great Mercury Island, and Te Rāwhiti Inlet in the Bay of Islands. “We’re looking at long-term management and if we can develop the tools a bit better and delay the spread, we’ll be in a pretty good space.” Exotic caulerpa spreads rapidly and forms large underwater meadows Bookings & enquiries please phone: Steph 0800 FLIPPER or 07 308 2001 or txt 027 2444 964 diveworks@xtra.co.nz | www.diveworks-charters.com Dolphin and Seal Encounters • Whale Island Tours • Fishing Trips Proudly working with the Northland Regional Council to remove Caulerpa • Northland-based marine construction company specialising in Dredging, Wharfs, Jetties, Floating Structures and Tug & Barge Operations. • Green field turn key solutions: Concept – Design – Resource Consent – Construction JOHNSON BROS – MARINE CONSTRUCTION info@johnsonbros.co.nz 021 798 525 | www.johnsonbros.co.nz commercialdivespecialists.co.nz 021 731 775 PROUDLY SUPPLYING DIVE TEAMS FOR MARINE BIOSECURITY WORK
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