Preventing the Introduction of Invasive Species
Boaties Can Help Stop The Spread of Marine Pests In New Zealand
May 31, 2009
The movement of large commercial vessels is considered to be the main source of introductions of invasive and harmful marine species to marine waters. This includes transportation on the antifoul of the ships' hulls and also introduction through the discharge of ballast water. But recreational boats are considered to play a significant role in the spread once the introduction of the invasive species has been made.
There are merchant shipping acts which help to manage the discharging of ballast water and the cleanliness of commercial ship hulls. However, recreational boats are not subject to such regulations. Voluntary support is really the only way to achieve some ground against these invasive species taking over marine environments.
Introduced Pest Species in New Zealand
There are some key introduced species which are a significant issue for New Zealand's aquatic ecosystems.
- Didymo (Didymosphenia geminata): Didymo, also known as "rock snot" was found in late 2004 in the Lower Waiau River in Southland. It is an invasive freshwater alga found in rivers and lakes. Didymo is spread easily via boats, kayaks and other vessels used in rivers and lakes. To date it has not been found in the North Island. Didymo can clog up waterways and smoother native plants.
- Sea Squirt (Styela clava):The sea squirt is now widely spread throughout the Hauraki Gulf and has also been found in Lyttelton Harbour and in Tutukaka marina in Northland. The sea squirt competes for space and food with native and aquaculture species (e.g., mussels, oysters). It can also be a nuisance by fouling marine farming lines, vessel hulls, and other structures.
- Undaria (Undaria pinnatifida): The Asian seaweed was first found in Wellington Harbour in 1987. It has now spread throughout New Zealand, although because it is spread via vessel hulls, it is mainly confined to harbours, ports and aquaculture areas. Efforts to control and eradicate Undaria have been ongoing throughout the country.
- Didemnum (Didemnum vexillum): Didemum, also known as Whangamata Sea Squirt, has established itself in Whangamata and Tauranga in the North Island and in the Marlborough Sounds in the South Island. It is a yellowish colonising sea squirt that is generally found on artificial structures like pilings, boat hulls and mooring lines. It is a particular threat to the aquaculture industry.
Code of Practice to Minimise and Help Prevent the Spread of Introduced Marine Species
A voluntary Code of Practice has been developed by the Sir Peter Blake Trust to help recreational boaties reduce the spread of these invasive pests in marine and freshwater systems.
- Use the most effective, legally approved anti-fouling paints.
- Apply extra anti-foulings to key areas such as rudder trailing edges, stern tube outlets and propellers.
- Avoid scrubbing off underwater hull surfaces in-water. Shore-based facilities have proper collection points which do not allow anti-fouling residues or fouling organisms to be released back into the water.
- Keep anchors and chain clean. Keep the chain locker clean and free of mud and weed.
- If undertaking an international voyage, sailing make sure that it has been thoroughly cleaned before heading off.
- Avoid discharging any bilge-water in a different location from where it was taken up.
- If trailing small boats by road to other places avoid transferring any water, especially bilge water.
- If there is a known risk of contamination, sponge over the boat with a disinfectant such as paracetic acid after washing. Make sure the trailer is included in the cleaning.
The role recreational boaties play in spreading invasive marine species in New Zealand is significant. Implementing the Code of Practice will help keep the harbours, lakes and oceans clean and pest-free.
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