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Set Nemo free in the ocean? Think twice: invasive fish species harm local ecosystems

PUBLISHED : Saturday, 14 July, 2018, 2:03pm
UPDATED : Saturday, 14 July, 2018, 6:46pm

Invasive fish species pose a problem to our dams, lakes, and rivers, but not much attention is given to addressing the issue (“More action urged on potentially invasive alien wildlife in Hong Kong”, March 24). Piranhas, African catfish, pirarucu (Arapaima gigas), peacock bass and tilapia, to name a few, are all found in abundance in waterways, and some are bred in ponds for aquaculture projects.

Lately, news has surfaced of the discovery of two new foreign predatory fish known as the eartheater and the black ghost knifefish. Experts warn about the devastating implications these aquatic nuisance species have on waterways and aquatic life.

Ecosystems around the world have been dramatically altered as fish species are introduced, whether for commercial fishing stock or the aquarium trade.

Humans are experts at helping species move from their native habitat into new territory. The new habitat may suit the invader fish so well that the results are catastrophic for local species. They are able to multiply at a very rapid rate and, in the absence of a predator, are wiping out many of our native river species.

Reversing the damage is challenging and at times unsuccessful. Prevention is the key to avoiding invasive threats to native aquatic ecosystems.

Watch: Invasion of the giant goldfish

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Species are transported around the world to fish farms, and when they escape, they become naturalised in many areas, causing damage to native species and habitats. Recreational fishing is also to blame for the spread of invasive species. Exotic fish, marine plants, invertebrates, and corals are used for aquariums and are inadvertently released in streams and waterways when tanks are cleaned or the fish have become unmanageable.

It may seem humane to set Nemo free in the ocean, but such impulses pose an enormous threat to native ecosystems. Even something as seemingly harmless as a goldfish can disrupt local food chains. Invasive species feed on fish eggs and small invertebrates, rooting up plants while swimming and releasing nutrients that trigger excess algal growth.

Certain freshwater fish species used for recreational angling are released into rivers, dams and lakes without an environmental impact assessment or monitoring, for the sole purpose of providing enjoyment for anglers. This practice has become so widespread that people often think that some of the invasive species are actually native ones.

Watch: How Hong Kong is decimating its fish stocks

Invasive species and global warming ‘a deadly duo’

At a UN conference on invasive species in Norway in 1996, experts from 80 countries concluded that “invasive species were a major threat to biodiversity conservation and probably the greatest threat after habitat destruction”.

Management of invasive fish species requires urgent attention and Friends of the Earth Malaysia calls on government fisheries departments to:

  • enforce the law in dealing with those found to be importing, selling and keeping alien predator fish;
  • halt the introduction of invasive species solely for the pursuit of recreation; and
  • ban aquarium shops and fish farms from importing invasive species that are a direct threat to native aquatic ecosystems.

Community participation, education, and awareness are critical to prevention to halt the spread of invasive species.

S. M. Mohd Idris, president, Friends of the Earth Malaysia