Protecting our aquatic biodiversity
On the lookout for marine pests
Recently introduced Asian paddle crab invades Waitemata Harbour
Minimising the impact of ballast water
Finned bio-invader surfaces in the Coromandel
Beware of the green invader
Pest fish in our freshwater
Biosecurity threats to geothermal streams
Potentially devastating foreign invaders
There are more than 150 exotic marine species already in our coastal waters, and at least one new species arrives every year, mostly on the hulls of visiting vessels. There is a very real potential for economic and environmental damage. We need to understand the impacts of these exotic invaders, and long-term dedicated effort is required to assess the risks and possible means of control.
NIWA has just established the National Centre for Aquatic Biodiversity & Biosecurity to help deal with these issues.
A NIWA survey of Auckland’s Waitemata Harbour in April this year uncovered large numbers of non-indigenous paddle crabs. The survey is the first major study of this newly introduced crab species to New Zealand waters.
This invasive crab first attracted scientific attention in November 2000 when two fishers caught them in their flounder nets in the Rangitoto channel near Auckland. They noticed that these paddle crabs had different markings, and were far more aggressive than the native paddle crabs.
This map shows the risk factor for discharge in the 12-mile Territorial Sea. Click to enlarge.
New Zealand’s coastal areas support a disproportionately large number of endemic marine species, and there is little doubt that they could be affected by the arrival of exotic organisms. New exotic species could also threaten marine shellfish and aquaculture in areas such as Foveaux Strait, Marlborough Sounds, and Tasman and Golden Bays.
The high-profile arrival of the seaweed Undaria pinnatifida to New Zealand was probably due to ballast water.
Acentrogobius pflaumii from Victoria Docks, Melbourne, Australia. (photo: Rudie Kuiter)
Another new goby species was recently discovered in our nets while sampling in Whangapoua Harbour, Coromandel. The goby did not match anything encountered before from estuaries throughout the northern North Island. Its most striking feature was the many iridescent blue spots along its sides, in contrast to native goby species.
Rudd ruined a trout fishery in a New Zealand lake, and may prevent the growth of plant seedlings.
Koi carp are prolific breeders and can ruin lakes by removing vegetation and increasing turbidity.
The European perch can reduce populations of small native fish in lakes (photo: Stephen Moore).
There is a growing awareness worldwide that some species of freshwater fish are serious pests which can damage both the biodiversity and quality of our aquatic environments.
Melanoides tuberculata collected from a stream near Taupo. (photo: B. Obrien)
The recent discovery of an alien snail, Melanoides tuberculata, in a geothermal stream near Taupo highlights the threat to geothermal habitats from tropical aquarium species.
Also known as “red-rimmed melania”, M. tuberculata originates from the Middle East and East Africa, but has invaded warm-water habitats in North and South America, Polynesia, and now New Zealand.
Caulerpa taxifolia. (photo: AIMS)
Caulerpa smothering the seabed in the Mediterranean. (photo: A. Meinesz)
Dubbed the “killer alga” and the “monster seaweed”, the green alga Caulerpa taxifolia has had sensational media coverage. It has even been reported to act like a “towering conquistador bullying coastal ecosystems”.
The problems began in 1984 when the seaweed was discovered growing in the sea immediately outside the Oceanographic Museum of Monaco.
The Mediterranean fanworm
The Mediterranean fanworm is a large, tube- building polychaete that has invaded sheltered harbours and bays in Western Australia, Victoria, Tasmania, New South Wales, and South Australia. It has a rapid growth rate and can form high-density beds, displacing other species and fouling boats and marine structures.
The European green crab
The European green crab has been introduced to the Atlantic coast of the US, California, Washington, southern Australia, and South Africa. It is a voracious predator with a broad diet, and can live in many estuarine environments.
Coastal marine environments are among the most invaded ecosystems in the world. The movement of species outside their natural range has dramatically changed native marine environments – and New Zealand is no exception. Over the past 100 years foreign species have become established in New Zealand waters at a rate of about one every 9 months. Not all of these species have become pests, but a few have caused significant problems for human health, native plant and animal species, and the fishing and aquaculture industry.
