| Although
some marine pests can be suitable for harvest and be valuable,
for example, the Pacific oyster, others can have major
negative impacts. |
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| These
examples from overseas show how serious the impacts can
be: |
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 The
zebra mussel (Dreissena polymorpha) is a mussel that
forms dense mats that clog industrial water intakes
and discharge pipes. It invaded the Great Lakes in the
United States. It is estimated that it will cost $10
billion to manage it over 10 years.
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 The
comb jelly (Mnemiopsis leidyi) caused the collapse of
the fin fishing industry in the Black and Azov Seas
in Eastern Europe. Catch in Russia, the Ukraine, Bulgaria,
Turkey, and Romania fell from 250 000 tonnes to 30 000
tonnes.
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 The
northern Pacific seastar (Asterias amurensis) eats bivalves
such as mussels. It is spreading along Tasmania's coast.
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| How
marine pests are spread |
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Marine pests arrive in New Zealand's waters and move around
our coastal and marine environment in a number of ways.
They may be: |
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attached
to the external surface of vessels (for example, hulls),
structures such as oil rigs, animals such as turtles,
and wreckage and rubbish from ships; |
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contained
in ballast water. Ballast water is sea water that ships
carry for stability and then discharge when their cargo
is unloaded. Ballast water pumped into a ship in one port
contains organisms, larvae, and sometimes even whole fish; |
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transported
on fishing or marine farming equipment; |
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contained
in aquarium material; |
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introduced
deliberately. |
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| Marine
pests are most likely to arrive in busy ports and marinas.
They can spread rapidly into nearby communities or be
transported around the coast.
Over
2500 international vessels visit New Zealand each year
at over 20 ports. Up to 3 million tonnes of ballast
water is discharged in New Zealand each year.
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Marine pests already in New Zealand |
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At least 150 exotic marine species have already been introduced
to New Zealand. |
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Algal blooms |
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 The
toxic alga Gymnodinium catenatum is an example of an algal
bloom. It can causing paralytic shellfish poisoning (PSP)
in humans. PSP causes paralysis or death in severe cases.
G.
catenatum was first noticed in Manakau Harbour in May
2000. Since then, it has slowly spread north and south
along the west coast of the North Island, through Cook
Strait, and up the east coast of the North Island into
Wairarapa and Hawke Bay. When an algal bloom caused
by G. catenatum is present in an area, it is closed
to shellfish gathering because of the high levels of
toxins in the shellfish. So far, no one has died of
paralytic shellfish poisoning caused by G. catenatum.
Health protection officers at your local area health
board can tell you whether it is safe to eat shellfish
from your area.
G.
catenatum can damage the businesses that farm shellfish
in affected areas because when a bloom is present, farmers
are unable to harvest their shellfish. The Marlborough
Sounds is the main shellfish farming area in New Zealand.
The alga has not directly affected farms there because
it has only reached the outer part of the Sounds. However,
mussel farms in the Marlborough Sounds have been indirectly
affected because farmers are unable to collect baby
mussels (spat) to restock their farms. The traditional
collecting areas for spat are on Ninety Mile Beach in
Northland. This area is infected with G. catenatum,
and so if farmers brought infected spat to the Marlborough
Sounds, they might bring G. catenatum too. The shellfish
industry is developing ways of cleaning the spat and
looking for alternative sources of spat.
At
this stage, no one knows whether G. catenatum is native
to New Zealand but has not been noticed until recently
or it has been accidentally introduced to New Zealand.
For
more information, see:
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| Undaria
pinnatifida (Undaria) |
|
 Undaria
is an exotic seaweed. New Zealand's environmental conditions
suit it very well, and so it grows and spreads very
quickly here. It was first discovered in Wellington
Harbour in 1987. Since then, it has spread rapidly around
New Zealand and is now found from Gisborne to Stewart
Island. If we don't try to control it, undaria could
become widespread around the North and South Islands
and in more remote areas such as the Chatham Islands
and the sub-Antarctic islands. It has already changed
the natural character of many areas. We do not yet know
what effect undaria has on native ecosystems.
The
Government is doing a number of things to slow the spread
of undaria, such as:
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making
sure that boats and ships do not carry it to the Chatham
and sub-Antarctic islands; |
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teaching
boat and ship users how to avoid spreading it; |
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researching
ways to treat boats and ships to minimise the chance that
they could carry it. |
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For
more information, see:
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For more information click on any link below.
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