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.

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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.

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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