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FACTSHEET Marine invaders New Zealand’s unique marine environment is increasingly under threat from unwanted foreign plants, animals and diseases. Already at least 148 marine invaders are found in New Zealand waters. More international shipping movements could increase our island nation’s vulnerability to introduced marine species. depend on the sea for their livelihoods and lifestyles. Marine invaders can significantly impact on marine ecosystems, seafood industries, human health and recreation. Eradication, control and management of marine invaders is both difficult and expensive, so greater biosecurity measures are needed to prevent the unintentional or deliberate arrival and spread of alien organisms. When undaria pinnatifida was first discovered in Wellington in 1987 no action was taken. It has since spread as far as Stewart Island and Gisborne. What are marine invaders? Marine invaders are foreign marine plants or animals that have been accidentally or intentionally spread to New Zealand’s marine environment. They can include microscopic organisms, starfish, shellfish, seaweed, crabs and fish. How do they get here? Nearly 90% of exotic marine organisms that have established in New Zealand since 1840 were transported by international shipping. Most aquatic hitch-hikers arrived in the last 40 years, usually attached to vessel hulls, or in ships’ ballast water, but they may be transported with seafood shipments and aquarium species imports. Invasive species are also spread by marine farming equipment, commercial fishing and boating. With little monitoring of the 2500 international ship visits to New Zealand each year, it could be only a matter of time before a potentially devastating marine invader arrives. Hull Fouling Researchers believe more than two-thirds of accidentally introduced organisms arrive attached to ships’ hulls and external structures and are then dislodged or reproduce in their new environment. Anti-fouling paints are designed to poison or discard marine stowaways during transit and foulings should be disposed of at landfill sites. Forest and Bird wants to see the adoption of stricter standards for hull cleaning and disposal. Ballast water Ballast water provides stability for large vessels (improving their safety and efficiency) but alien species sucked into tanks, from micro-organisms to schools of fish, can be discharged in foreign ports. While vessels are now required to exchange ballast water in mid-ocean, it is not always possible for safety reasons, and foreign species may still remain in the sediments. So Forest and Bird wants to see greater use of filters and heat treatments to lessen the risk of ships carrying undesirable cargo. What are the impacts of marine invaders? What marine invaders are potential threats? While not all exotic species arriving in New Zealand survive, Threats come from the ballast water stowaway Eurasian zebra overseas research suggests one in six introduced marine mussel clogging up the Great Lakes canal system, a comb species will establish itself and become a pest. Some marine jelly destroying the fisheries of the Black Sea and a tropical invaders are apparently harmless or nuisance species, but seaweed Caulerpa, smothering the seabed in the many are hardy and aggressive, changing the structure and Mediterranean and now in Australia. Another pest found in functioning of the ecosystems they invade. Australia is the northern Pacific seastar which has a ferocious appetite and can prise open and devour shellfish. The Chinese Invasive species compete for resources with native clam took just two years to spread throughout San Francisco species, changing the species composition and food web. Bay. The voracious predator green crab Invaders may also bring pathogens and eats bivalves and other crabs, threatening parasites that harm indigenous species, New Zealand’s unique commercially important species. while others interbreed with native More basic science is needed on native marine environment and species, reducing biodiversity. Most marine species and the distribution and aggressive invaders alter the marine ‘clean and green’ image impacts of introduced species and habitat to suit themselves. possible threats. need protecting from the Overseas, aquatic invasive species constant threat of marine clog lakes, waterways and coastal areas, What can be done? and adversely affect fisheries, water invaders and their often Forest and Bird wants a national pest supplies, irrigation, water treatment, strategy for marine invaders like Undaria irreversible impacts on the recreational activities and shipping. and a code of practice for all international natural environment, Invaders have replaced native marine vessels. This would ensure hulls are species and caused human health cleaned before leaving for another industries and recreation. country and that ships use ballast concerns from the build-up of toxins in treatment systems. A programme to fish and shellfish. monitor ports and identify risks was initiated in 2001, but marine biosecurity has received little funding compared to What marine invaders are land invader control. already here? Regional councils should include marine pest control Among the almost 150 known invaders is the Japan Sea measures in their pest management strategies. If detected brown seaweed Undaria. First discovered in Wellington early marine invaders can be removed, contained or controlled harbour in 1987, it is now found from Stewart Island to to prevent further spread, using pesticides, mechanical or Gisborne. The seaweed rapidly colonises areas to form biological control, or ecological manipulation. Early action dense forests which displace crayfish, paua and oysters before washing up on beaches to rot. While ‘the gorse of is needed before pests spread. the sea’ is being trialled as a commercial crop in the Marlborough Sounds, the government is trying to eradicate What can you do? the large kelp from Big Glory Bay on Stewart Island and • Keep a look out for new invaders and if you suspect Bluff before it spreads to Fiordland. anything, contact the Ministry of Fisheries Marine The Asian date mussel has now spread to the Hauraki Biosecurity hotline 0800 INVADERS (0800 468 233). Gulf and can form large colonies with as many as 3300 • Join Forest and Bird in its campaign to have New Zealand mussels per square metre. Another recent arrival is the uphold its international responsibilities to stop the spread toxic phytoplankton Gymnodinium catenatum which first of alien species. bloomed in Manukau harbour in May 2000. It has closed shellfish gathering areas and impacted on mussel farming. For more information contact: Forest and Bird Forest and Bird – www.forestandbird.org.nz P O Box 631, Wellington Ministry of Fisheries - www.fish.govt.nz ph 04-385 7374 Global Invasive Species Database – www.issg.org/database/ August 2002 fax 04-385 7373 www.forestandbird.org.nz