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German wasp | Vespula germanica

German wasp

Vespula germanica

Coral bush | Ardisia crenata

Coral bush

Ardisia crenata

Purple loosestrife | Lythrum salicaria

Purple loosestrife

Lythrum salicaria

Pom pom weed | Campuloclinium macrocephalum

Pom pom weed

Campuloclinium macrocephalum

Canarybird bush | Crotalaria agatiflora

Canarybird bush

Crotalaria agatiflora

Peanut butter cassia | Senna didymobotrya

Peanut butter cassia

Senna didymobotrya

Rubber vine | Cryptostegia grandiflora

Rubber vine

Cryptostegia grandiflora

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Environmental Programmes

In order to tackle our country’s socio-economic challenges, the government adopted the Outcomes based approach to improve government performance and providing focus on service delivery. find out more

Japanese oyster

Crassostrea gigas

Common name:

Japanese oyster

Scientific name:

Crassostrea gigas

Alternative common names:

Pacific oyster, Miyagi oyster. 

The Japanese oyster is native to the Pacific coast of Asia. It has been introduced to many parts of the world for aquacultural and ecological purposes. Introducing the species in vast quantities throughout the world has had a negative effect, and it is now considered an invasive species. 

Additional Info

  • Where does this species come from?

    Japan and Southeast Asia.

    What is its invasive status in South Africa?

    NEMBA Category 2.

    Where in South Africa is it a problem?

    Western Cape, Eastern Cape and Northern Cape.

    How does it spread?

    Its swimming stage, its capacity to survive in various environmental conditions and its ability to colonise new areas facilitate the dispersion of the species along coastal areas. The aggressive manner in which it spreads is detrimental to ecosystems.

    Why is it a problem?

    These oysters are generally impossible to contain if environmental conditions are suitable. Their planktonic eggs and larvae facilitate natural dispersal, and this, in combination with high fecundity, allows for rapid population. In some areas it has become the dominant oyster species, displacing indigenous species.

    What does it look like?

    Description: It is a cupped oyster species with a curved lower shell (which attaches to the substratum) and a flat upper shell. Its shell is elongated, with a maximum length of 400mm (average length 150-200mm), and it has at least one abductor scar, which is purple. No radial threads are present and valve margins generally show no colouration, with margins normally undulating. Habitat: The preferred habitat is a firm substrate, such as rocks, other shells or debris, although they can also be found on mud and sand. Breeding: They are protandrous hermaphrodites, meaning they are able to change gender (usually from male to female, although the reverse is also possible). When resources, such as food and space, are abundant, the sex ratio is skewed towards females, with males predominant when resources become scarce. The development of mature eggs and sperm takes place when the environmental conditions are appropriate for breeding, with a water temperature of approximately 16-34°C. An average female produces 50-200 million eggs in a single broadcast spawning event.

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General News Updates

2019 National Symposium on Biological Invasio…

26-02-2019

This is your invitation to South Africa's 2019 National Symposium on Biological Invasions. The convention is hosted by the Centre for Invasion Biology (CIB), University of Stellenbosch, and the Biolo... Read more

2019 Invasive Species Training

22-01-2019

During the past five years (2014-2018), ISSA invasive species trainers have trained 4 000 in the identification of invasive species and laws pertaining to invasive species across South Africa.  ... Read more

Alien Grass Working Group

04-09-2018

Who are we? The South African National Alien Grass Working Group was jointly initiated by the South African Biodiversity Institute (SANBI) and the Centre for Excellence in Invasion Biology (C·I·B) in... Read more

Permits for planting indigenous Cynodon?

01-03-2018

On 16 February, 2018, South Africa's Department of Environmental Affairs issued amendments to the regulations and lists relating to the National List of Invasive Species.  Updates to the draft&n... Read more

Invasive species training 2018 dates released

28-02-2018

Interested in invasive species?  How much do you know about NEMBA invasive species compliance for landowners and organs of state? The South African Green Industries Council (SAGIC) have released... Read more

Communications post for Africa advertised

25-01-2018

The Nature Conservancy has advertised a brand new post:  Communications Manager, Africa Region. Knowledge of invasive species and water would be an asset in this post. See details below:    Job Titl... Read more