Photo / Project Kahurangi
Ask a room full of boaties, commercial operators and marina managers about marine biosecurity and you'll probably hear a range of opinions. For some it's common sense. Others question whether the investment is worthwhile.
The evidence shows marine pest spread isn't inevitable. The way vessels and marine infrastructure are managed can make a real difference. Here are some of the most common questions and concerns the ‘Clean Below? Good to Go’ team hears, and why they're worth another look.
Question: Is there scientific proof that pest species cause harm?
Answer: It’s easy to see the impact of a terrestrial pest - like gorse or aphids - on the world around us. It’s a little more challenging when it’s under water. Around the world, decades of research has shown that introduced marine species can damage native ecosystems, fisheries, aquaculture, infrastructure and local economies. Here in New Zealand, scientists have documented how introduced species can quickly change habitats, compete with native marine life and create significant long-term management costs.
Abe Growcott is Principal Adviser Aquatic Biosecurity Surveillance at the Ministry for Primary Industries (MPI). He says the most visible impacts of marine pests are that they can reach very high population densities in new locations resulting in competition for space and direct predation of native species.
“Marine pests have measurable ecological, economic and social consequences that are well documented by New Zealand research,” he says, noting significant financial burden on the aquaculture industry and impacts on tourism, communities and recreation where marine pests have become established - including Pacific oysters, the eyesore that is Australian droplet tunicate Eudistoma elongatum, and more recently, exotic caulerpa.
“We also have documented studies showing the direct financial losses to green-lipped mussel aquaculture of $11.4 per year in the Marlborough Sounds from invasive blue mussels and of $26.4m over a 24-year period from two marine pests (Sabella spallanzanii andStyela clava). The Pacific oyster has dramatically changed the shoreline in Manukau Harbour, making some areas much harder to access,” he says. “All this is before considering the cost of diseases such as ostreid herpesvirus, which can also spread within biofouling attached to boat hulls, and which has halved New Zealand's oyster production since it was detected in 2010.”
Question: Haven’t marine species always moved around naturally?
Marine pests and diseases do spread naturally through tides and currents. The problem is that boats move them much further, faster, and directly into places they may never otherwise reach.
Boat hulls and structures like pontoons provide ideal surfaces for many fouling organisms to settle, grow and hitch a ride to new locations.
Every new infestation creates another source population that can continue spreading.
The good news is there is often a small window of opportunity after a new arrival is detected. With vigilant surveillance and early detection, rapid action can successfully manage an incursion before it is able to reproduce and spread further.
Question: Is it good value for money?
Mediterranean fanworm (aka Sabella) provides a good example of why investment in early intervention matters and saves money in the long run.
Marine biosecurity specialists have repeatedly prevented Mediterranean fanworm from becoming established in new areas through surveillance, vessel inspections and rapid response. Whangapoua Harbour (east Coromandel Peninsula), Mangōnui Harbour and Tutukākā (both in Northland) are all examples where eradication has been achieved as a result of early intervention, and councils in Tauranga, Gisborne, Wellington, and Marlborough Sounds have successfully stopped fanworm in its tracks many times over. Marlborough District Council, for example, has dealt with 80 fanworm incursions since 2014.
These successes matter because where fanworm does become established, eradication becomes extremely difficult.
"If we do a good job of managing the pathways it travels on, spread isn't inevitable," says Danielle Kruger of Waikato Regional Council.
"It's far cheaper to prevent establishment and respond quickly to new detections than to allow a species to become widespread."
Question: What about marinas and structures?
Many boat owners ask why they should clean their hull if pests are already present on marina structures.
It’s a fair question and if it were practical to remove marine pests from every marina, port, and wharf structure around New Zealand, it would make a significant difference.
Researchers are actively working towards that goal. Projects such as the Marine Biosecurity Toolbox are investigating new technologies, including bubble curtains and other innovative control methods that may eventually provide practical, cost-effective management options for marinas.
Until those tools are available, the most effective approach is something we can actively do - to stop pests spreading to new locations.
"That's why we focus on both stopping the spread through pathways management, and finding and controlling pests like Mediterranean fanworm before it can get a foothold," says Cath Duthie – Manager Pest Management Programmes at Biosecurity New Zealand.
"Science is advancing rapidly, and future technologies can give us more options. In the meantime, preventing their spread remains our best defence."
Marine biosecurity is about slowing the spread, protecting iconic places like the Poor Knights Marine Reserve and the Abel Tasman coastal marine area from harm and buying time for science to develop better long-term solutions. By drawing the line now we can protect all of our interests - economic, recreational and environmental, well into the future.