Ballast water exchange

Ships carry ballast water for stability. Ballast water pumped into a ship in one port will contain organisms from that port. These can include microscopic organisms, larval stages of organisms, and even whole fish. When the ballast water is discharged, those organisms escape and may establish themselves in the new environment. A large ship might discharge as much as 50 000 tonnes of ballast water.

The Import Health Standard for Ballast Water is the government document that describes what ships and boats must do when they enter New Zealand waters. It says that ships and boats containing ballast water collected at a foreign port cannot discharge it into New Zealand waters unless:

It is safer for boats to exchange their ballast water in mid-ocean because the organisms they pick up are less likely to survive when discharged in New Zealand's coastal waters. This is because they are not suited to warmer, shallower coastal water. However, exchanging the ballast water only partly reduces the risk as some of the water from the foreign port will remain in the ballast tanks.

The Import Health Standard names Tasmania and the port at Melbourne, Australia, as "higher risk areas" because of the presence of the northern Pacific sea star. Ballast water from designated high-risk areas may not be discharged into New Zealand waters under any circumstances. Fisheries officers take extra care to make sure that ships from these areas exchange their ballast water in mid-ocean before they discharge it in port.

Scientists are researching a treatment system for ballast water. They have found that heat treatment effectively kills most organisms in ballast water. They are also investigating ultraviolet radiation, filtration, and chemical treatments.

Hull fouling and cleaning

Organisms can grow on the external areas of boats. This is known as "fouling". If a boat carrying fouling organisms arrives in New Zealand, the organisms may be knocked off or scraped off deliberately when a hull is cleaned. They may then breed in New Zealand waters. This threat is significant - it has been estimated that over 69 percent of the exotic marine species now in New Zealand arrived here on vessel hulls.

The Ministry of Fisheries is developing guidelines to ensure that when ships are cleaned, fouling organisms are not washed back into the sea. These controls are designed to ensure that the fouling organisms are contained, treated, and properly disposed of to reduce the chance of spores or fragments finding their way back into our coastal waters.

More information:
Information about hull cleaning for vessels arriving in New Zealand

Surveillance

We are establishing a surveillance programme that will focus on high-risk coastal areas, including ports and marinas. It will be the first of its kind in the world. It consists of three elements.

Invasion response

If a new species arrives in New Zealand, we will first try to assess what kind of risk it might pose to our environment. Eradication of introduced marine species is very difficult, and it may be better to try to control the species' spread rather than eliminate it completely.

How to help us

If you have seen anything that you think may be an exotic species to New Zealand waters, we want to hear from you!

What to do

If you think you've seen a new exotic marine pest, please collect a sample of the organism(s).

To preserve your sample (except if it is a seaweed), place it in a plastic bag and freeze it.

If your sample is seaweed, liberally spread salt over the plant, leave it overnight, drain off the liquid, spread salt over the plant again, and pack it in a plastic bag. If you need assistance we're ready to help you.

Please contact us

Phone toll free 0800 INVADERS (0800 468 233)

Email biosecurity@fish.govt.nz or comms@fish.govt.nz

Website www.fish.govt.nz