'Bad' biodiversity: Invasive alien species

Not all biodiversity is good for the ecosystem. One example are the freshwater stingrays found in Singapore's reservoir.
Growing to the size of 'dinner plates', barbed Motoro stingrays (Potamotrygon motoro) are breeding in Upper Seletar Reservoir, Grace Chua reports in the Straits Times today quoting a paper by authors from the Raffles Museum of Biodiversity Research.

Why are these exotic animals dangerous?

Originally from South America, these stingrays have venomous stings that can cause extreme pain and even death. Given the sport fishing, kayaking and boat rides that now happen in Upper Seletar Reservoir, the presence of such exotic introduced animals does not bode well for humans. These stingrays were likely to have been released into the reservoir by fish hobbyists.

Exotics are also seldom good our habitats. The impact is often so devastating that research results in Jan 10 considered invasive alien species one of the top three threats to life on this planet. The study showed that "although we are winning some battles in the fight against invasive species, current evidence suggests that we are losing the war.”

Why are invasive alien species bad?
Many invasive species are successful because they have no natural predators in their new environment. Meanwhile, predatory invasives such as the Motoro stingray, prey on native animals that have not evolved ways to hide or defend themselves. Non-predatory aliens can out-compete native animals for food, shelter and other necessities of life. Aliens may also introduce diseases to our native animals. By affecting the natural balance, aliens may upset and even destroy an ecosystem.

How do invasive alien species get introduced?
Many are unintended hitch-hikers on our modern transportation by boat, road and air. And via our imported food and plants. Others are intentionally introduced in misguided attempts to 'beautify' our parks or for commercial reasons (e.g., aquaculture). Yet many are intentionally released by pet owners and in Singapore, the religious practice of animal release.

What can be done once invasive alien species settle down?
Invasive alien species are very costly to control. The best way to tackle a potential invasive problem is early detection and stopping them from becoming permanently established.

Regarding the Motoro stingrays, Prof Peter Ng, one of the authors of the paper, said when alien species establish themselves, they cannot be eradicated overnight, 'so we need to be proactive and plan ahead'. In their paper, the scientists recommended fishing or trapping the rays, educating the public on the danger of releasing non-native species into the wild and teaching people how to avoid injuries.

According to the Straits Times report, since 2004, it has been illegal for pet shops to display and sell stingrays and other venomous fish or fish with spines, said the Agri-Food and Veterinary Authority (AVA). Shops caught selling such fish can be fined $100.

Unfortunately, the ban does not apply to fish farms, which import the fish for re-export. They are allowed to sell these fish to individual hobbyists who know how to handle them and are told not to release them into the environment, the AVA explained.

How many invasive alien species are found in Singapore?
The NParks Biodiversity Centre website has an inexhaustive list (pdf) of 67 species including 34 freshwater fishes. Also included among freshwater invasives are the Banded Bull Frog (Kaloula pulchra) and American Bullfrog (Lithobates catesbeianus). These are among the 'favourite' animals in religious animal release.

The freshwater invasives found here include these animals listed as 100 of the World’s Worst Invasive Alien Species: Red-eared Slider (Trachemys scripta elegans), Peacock Bass (Cichla orinocensis), Mosquitofish (Gambusia affinis), Mozambique Tilapia (Oreochromis mossambicus) and Guppy (Poecilia reticulata).

What can you do about invasive alien species?

• Do not release pets into our wild places. More about the impact of animal release.
• Do not grow plants which are known invasive alien species. Why not grow native plants instead?
  
• Learn and share what you know about invasive alien species.

“With sufficient funds and political will, invasive species can be controlled or eradicated. This will allow native species to be saved from extinction, but countries need to dramatically improve the way they deal with the problem.” says Dr Bill Jackson, IUCN’s Deputy Director General and Chairman of the Global Invasive Species Programme.

More links

• Invasive Alien Species in Singapore on the NParks Biodiversity Centre website.
• Stingrays breeding in Upper Seletar Non-native species with venomous sting likely released into reservoir by hobbyists, Grace Chua, Straits Times 25 Mar 10;
• "Stingers in a strange land: South American freshwater stingrays (Potamotrygonidae) in Singapore" by Heok Hee Ng, Heok Hui Tan, Darren C. J. Yeo and Peter K. L. Ng of the Raffles Museum of Biodiversity Research on SpringerLink
• Scary Aliens in Singapore a talk by Prof Peter Ng on invasive alien species on wild shores of singapore.
  
• “Global indicators of biological invasion: species numbers, biodiversity impact and policy responses” by the by the Global Invasive Species Programme (GISP).
• Global Trade Fuels Invasive Species livescience.com Yahoo News 11 Jan 10;
• More media articles on invasive alien species on the wildsingapore news blog.